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Sample records for brayton cycle improving

  1. Performance improvement options for the supercritical carbon dioxide brayton cycle

    International Nuclear Information System (INIS)

    The supercritical carbon dioxide (S-CO2) Brayton cycle is under development at Argonne National Laboratory as an advanced power conversion technology for Sodium-Cooled Fast Reactors (SFRs) as well as other Generation IV advanced reactors as an alternative to the traditional Rankine steam cycle. For SFRs, the S-CO2 Brayton cycle eliminates the need to consider sodium-water reactions in the licensing and safety evaluation, reduces the capital cost of the SFR plant, and increases the SFR plant efficiency. Even though the S-CO2 cycle has been under development for some time and optimal sets of operating parameters have been determined, those earlier development and optimization studies have largely been directed at applications to other systems such as gas-cooled reactors which have higher operating temperatures than SFRs. In addition, little analysis has been carried out to investigate cycle configurations deviating from the selected 'recompression' S-CO2 cycle configuration. In this work, several possible ways to improve S-CO2 cycle performance for SFR applications have been identified and analyzed. One set of options incorporates optimization approaches investigated previously, such as variations in the maximum and minimum cycle pressure and minimum cycle temperature, as well as a tradeoff between the component sizes and the cycle performance. In addition, the present investigation also covers options which have received little or no attention in the previous studies. Specific options include a 'multiple-recompression' cycle configuration, intercooling and reheating, as well as liquid-phase CO2 compression (pumping) either by CO2 condensation or by a direct transition from the supercritical to the liquid phase. Some of the options considered did not improve the cycle efficiency as could be anticipated beforehand. Those options include: a double recompression cycle, intercooling between the compressor stages, and reheating between the turbine stages. Analyses carried

  2. A treatment of thermal efficiency improvement in the Brayton cycle

    International Nuclear Information System (INIS)

    So far, as the working fluid for power-generating plants, mainly water and air (combustion gas) have been used. In this study, in regeneration and isothermal compression processes being considered as the means for the efficiency improvement in Brayton cycle, the investigation of equivalent graphical presentation method with T-S diagrams, the introduction of the new characteristic number expressing the possibility of thermal efficiency improvement by regeneration, and the investigation of the effect of the difference of working fluid on thermal efficiency were carried out. Next, as the cycle approximately realizing isothermal compression process with condensation process, the super-critical pressure cycle with liquid phase compression was rated, and four working fluids, NH3, SO2, CO2 and H2O were examined as perfect gas and real gas. The advantage of CO2 regeneration for the thermal efficiency improvement was clarified by using the dimensionless characteristic number. The graphical presentation of effective work, the thermal efficiency improvement by regeneration, the thermal efficiency improvement by making compression process isothermal, the effect on thermal efficiency due to various factors and working fluids, the characteristic number by regeneration, and the application to real working fluids are reported. (Kako, I.)

  3. Improvement of supercritical CO2 Brayton cycle using binary gas mixture

    International Nuclear Information System (INIS)

    A Sodium-cooled Fast Reactor (SFR) is one of the strongest candidates for the next generation nuclear reactor. However, the conventional design of a SFR concept with an indirect Rankine cycle is inevitably subjected to a sodium-water reaction. To prevent hazardous situation caused by sodium-water reaction, the SFR with Brayton cycle using Supercritical Carbon dioxide (S-CO2 cycle) as a working fluid can be an alternative approach. The S-CO2 Brayton cycle is more sensitive to the critical point of working fluids than other Brayton cycles. This is because compressor work significantly decreases at slightly above the critical point due to high density near the boundary between the supercritical state and the subcritical state. For this reason, the minimum temperature and pressure of cycle are just above the CO2 critical point. The critical point acts as a limitation of the lowest operating condition of the cycle. In general, lowering the rejection temperature of a thermodynamic cycle increases the efficiency and thus, changing the critical point of CO2 can result in an improvement of the total cycle efficiency with the same cycle layout. Modifying the critical point of the working fluid can be done by adding other gases to CO2. The direction and range of the CO2 critical point variation depends on the mixed component and its amount. In particular, chemical reactivity of the gas mixture itself and the gas mixture with sodium at high temperatures are of interest. To modify the critical point of the working fluid, several gases were chosen as candidates by which chemical stability with sodium within the interested range of cycle operating condition was assured: CO2 was mixed with N2, O2, He, Ar and Xe. To evaluate the effect of shifting the critical point and changes in the properties of the S-CO2 Brayton cycle, a supercritical Brayton cycle analysis code connected with the REFPROP program from the NIST was developed. The developed code is for evaluating simple

  4. Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving VHTR Efficiency and Testing Material Compatibility - Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Chang H. Oh

    2006-06-01

    Generation IV reactors will need to be intrinsically safe, having a proliferation-resistant fuel cycle and several advantages relative to existing light water reactor (LWR). They, however, must still overcome certain technical issues and the cost barrier before it can be built in the U.S. The establishment of a nuclear power cost goal of 3.3 cents/kWh is desirable in order to compete with fossil combined-cycle, gas turbine power generation. This goal requires approximately a 30 percent reduction in power cost for stateof-the-art nuclear plants. It has been demonstrated that this large cost differential can be overcome only by technology improvements that lead to a combination of better efficiency and more compatible reactor materials. The objectives of this research are (1) to develop a supercritical carbon dioxide Brayton cycle in the secondary power conversion side that can be applied to the Very-High-Temperature Gas-Cooled Reactor (VHTR), (2) to improve the plant net efficiency by using the carbon dioxide Brayton cycle, and (3) to test material compatibility at high temperatures and pressures. The reduced volumetric flow rate of carbon dioxide due to higher density compared to helium will reduce compression work, which eventually increase plant net efficiency.

  5. Examination of the performance of an unconventional combination of Rankine, Brayton, and Inverse Brayton cycles

    Energy Technology Data Exchange (ETDEWEB)

    Alabdoadaim, M.; Agnew, B.; Potts, I. [University of Newcastle-upon-Tyne (United Kingdom). School of Mechanics and Systems Engineering

    2006-07-01

    The study presented in this article examined the thermodynamic performance of a proposed system constructed from Brayton, inverse Brayton, and steam Rankine cycles. The theoretical examination was performed by varying the Brayton cycle pressure ratio for different values of inlet pressure and expansion pressures of the inverse Brayton cycle and for different ratios of the inverse Brayton power turbine mass flow to the gas generator mass flow. The results indicated that for the three values of mass flow ratio examined, better performance could be achieved when the proposed system is operated at high Brayton cycle pressure ratio (high maximum system temperature and the highest value of inverse Brayton cycle expansion pressure). It was revealed that in the case of the mass flow equal to 0.25, the proposed system achieved the highest value of Brayton cycle pressure ratio and attained a maximum thermal efficiency of 57.7 per cent. (author)

  6. Back Work Ratio of Brayton Cycle

    Directory of Open Access Journals (Sweden)

    Malaver de la Fuente M.

    2010-07-01

    Full Text Available This paper analizes the existing relation between temperatures, back work ratio and net work of Brayton cycle, a cycle that describes gas turbine engines performance. The application of computational soft ware helps to show the influence of back work ratio or coupling ratio, compressor and turbine in let temperatures in an ideal thermodynamical cycle. The results lead to deduce that the maximum value reached in back work ratio will depend on the ranges of maximum and minimal temperatures of Brayton cycle.

  7. Binary Brayton cycle with two isothermal processes

    International Nuclear Information System (INIS)

    Highlights: • This paper presents binary Brayton cycle with two isothermal processes. • Different parameters affecting the cycle performance have been studied. • The present cycle is a promising cycle for future power generation. - Abstract: The literature introduced isothermal concept and binary Brayton cycle as two promising methods used to enhance the performance of the gas turbine. Consequently, this work presents a cycle based on the blending of the two methods. This cycle is composed of gas turbine topping cycle with isothermal combustion and air turbine bottoming cycle with isothermal heating. Different parameters affecting the cycle performance have been studied. Simulations demonstrate that the present cycle achieves drastic enhancement in performance. The cycle merits justify its potential utilization for future power generation

  8. Advanced Supercritical Carbon Dioxide Brayton Cycle Development

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark [Univ. of Wisconsin, Madison, WI (United States); Sienicki, James [Argonne National Lab. (ANL), Argonne, IL (United States); Moisseytsev, Anton [Argonne National Lab. (ANL), Argonne, IL (United States); Nellis, Gregory [Univ. of Wisconsin, Madison, WI (United States); Klein, Sanford [Univ. of Wisconsin, Madison, WI (United States)

    2015-10-21

    Fluids operating in the supercritical state have promising characteristics for future high efficiency power cycles. In order to develop power cycles using supercritical fluids, it is necessary to understand the flow characteristics of fluids under both supercritical and two-phase conditions. In this study, a Computational Fluid Dynamic (CFD) methodology was developed for supercritical fluids flowing through complex geometries. A real fluid property module was implemented to provide properties for different supercritical fluids. However, in each simulation case, there is only one species of fluid. As a result, the fluid property module provides properties for either supercritical CO2 (S-CO2) or supercritical water (SCW). The Homogeneous Equilibrium Model (HEM) was employed to model the two-phase flow. HEM assumes two phases have same velocity, pressure, and temperature, making it only applicable for the dilute dispersed two-phase flow situation. Three example geometries, including orifices, labyrinth seals, and valves, were used to validate this methodology with experimental data. For the first geometry, S-CO2 and SCW flowing through orifices were simulated and compared with experimental data. The maximum difference between the mass flow rate predictions and experimental measurements is less than 5%. This is a significant improvement as previous works can only guarantee 10% error. In this research, several efforts were made to help this improvement. First, an accurate real fluid module was used to provide properties. Second, the upstream condition was determined by pressure and density, which determines supercritical states more precise than using pressure and temperature. For the second geometry, the flow through labyrinth seals was studied. After a successful validation, parametric studies were performed to study geometric effects on the leakage rate. Based on these parametric studies, an optimum design strategy for the see

  9. Multi-objective optimization of combined Brayton and inverse Brayton cycles using advanced optimization algorithms

    Science.gov (United States)

    Venkata Rao, R.; Patel, Vivek

    2012-08-01

    This study explores the use of teaching-learning-based optimization (TLBO) and artificial bee colony (ABC) algorithms for determining the optimum operating conditions of combined Brayton and inverse Brayton cycles. Maximization of thermal efficiency and specific work of the system are considered as the objective functions and are treated simultaneously for multi-objective optimization. Upper cycle pressure ratio and bottom cycle expansion pressure of the system are considered as design variables for the multi-objective optimization. An application example is presented to demonstrate the effectiveness and accuracy of the proposed algorithms. The results of optimization using the proposed algorithms are validated by comparing with those obtained by using the genetic algorithm (GA) and particle swarm optimization (PSO) on the same example. Improvement in the results is obtained by the proposed algorithms. The results of effect of variation of the algorithm parameters on the convergence and fitness values of the objective functions are reported.

  10. Systems Analyses of Advanced Brayton Cycles

    Energy Technology Data Exchange (ETDEWEB)

    A.D. Rao; D.J. Francuz; J.D. Maclay; J. Brouwer; A. Verma; M. Li; G.S. Samuelsen

    2008-09-30

    The main objective is to identify and assess advanced improvements to the Brayton Cycle (such as but not limited to firing temperature, pressure ratio, combustion techniques, intercooling, fuel or combustion air augmentation, enhanced blade cooling schemes) that will lead to significant performance improvements in coal based power systems. This assessment is conducted in the context of conceptual design studies (systems studies) that advance state-of-art Brayton cycles and result in coal based efficiencies equivalent to 65% + on natural gas basis (LHV), or approximately an 8% reduction in heat rate of an IGCC plant utilizing the H class steam cooled gas turbine. H class gas turbines are commercially offered by General Electric and Mitsubishi for natural gas based combined cycle applications with 60% efficiency (LHV) and it is expected that such machine will be offered for syngas applications within the next 10 years. The studies are being sufficiently detailed so that third parties will be able to validate portions or all of the studies. The designs and system studies are based on plants for near zero emissions (including CO{sub 2}). Also included in this program is the performance evaluation of other advanced technologies such as advanced compression concepts and the fuel cell based combined cycle. The objective of the fuel cell based combined cycle task is to identify the desired performance characteristics and design basis for a gas turbine that will be integrated with an SOFC in Integrated Gasification Fuel Cell (IGFC) applications. The goal is the conceptualization of near zero emission (including CO{sub 2} capture) integrated gasification power plants producing electricity as the principle product. The capability of such plants to coproduce H{sub 2} is qualitatively addressed. Since a total systems solution is critical to establishing a plant configuration worthy of a comprehensive market interest, a baseline IGCC plant scheme is developed and used to study

  11. Quantum Brayton cycle with coupled systems as working substance

    Science.gov (United States)

    Huang, X. L.; Wang, L. C.; Yi, X. X.

    2013-01-01

    We explore the quantum version of the Brayton cycle with a composite system as the working substance. The actual Brayton cycle consists of two adiabatic and two isobaric processes. Two pressures can be defined in our isobaric process; one corresponds to the external magnetic field (characterized by Fx) exerted on the system, while the other corresponds to the coupling constant between the subsystems (characterized by Fy). As a consequence, we can define two types of quantum Brayton cycle for the composite system. We find that the subsystem experiences a quantum Brayton cycle in one quantum Brayton cycle (characterized by Fx), whereas the subsystem's cycle is quantum Otto cycle in another Brayton cycle (characterized by Fy). The efficiency for the composite system equals to that for the subsystem in both cases, but the work done by the total system is usually larger than the sum of the work done by the two subsystems. The other interesting finding is that for the cycle characterized by Fy, the subsystem can be a refrigerator, while the total system is a heat engine. The result in this paper can be generalized to a quantum Brayton cycle with a general coupled system as the working substance.

  12. Thermodynamic Optimization of Supercritical CO2 Brayton Cycles

    International Nuclear Information System (INIS)

    The supercritical CO2 Brayton cycle has been studied for nuclear applications, mainly for one of the alternative power conversion systems of the sodium cooled fast reactor, since 1960's. Although the supercritical CO2 Brayton cycle has not been expected to show higher efficiency at lower turbine inlet temperature over the conventional steam Rankine cycle, the higher density of supercritical CO2 like a liquid in the supercritical region could reduce turbo-machinery sizes, and the potential problem of sodium-water reaction with the sodium cooled fast reactor might be solved with the use of CO2 instead of water. The supercritical CO2 recompression Brayton cycle was proposed for the better thermodynamic efficiency than for the simple supercritical CO2 Brayton cycle. Thus this paper presents the efficiencies of the supercritical CO2 recompression Brayton cycle along with several decision variables for the thermodynamic optimization of the supercritical CO2 recompression Brayton cycle. The analytic results in this study show that the system efficiency reaches its maximum value at a compressor outlet pressure of 200 bars and a recycle fraction of 30 %, and the lower minimum temperature approach at the two heat exchangers shows higher system efficiency as expected

  13. Thermodynamic Optimization of Supercritical CO{sub 2} Brayton Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Rhim, Dong-Ryul; Park, Sung-Ho; Kim, Su-Hyun; Yeom, Choong-Sub [Institute for Advanced Engineering, Yongin (Korea, Republic of)

    2015-05-15

    The supercritical CO{sub 2} Brayton cycle has been studied for nuclear applications, mainly for one of the alternative power conversion systems of the sodium cooled fast reactor, since 1960's. Although the supercritical CO{sub 2} Brayton cycle has not been expected to show higher efficiency at lower turbine inlet temperature over the conventional steam Rankine cycle, the higher density of supercritical CO{sub 2} like a liquid in the supercritical region could reduce turbo-machinery sizes, and the potential problem of sodium-water reaction with the sodium cooled fast reactor might be solved with the use of CO{sub 2} instead of water. The supercritical CO{sub 2} recompression Brayton cycle was proposed for the better thermodynamic efficiency than for the simple supercritical CO{sub 2} Brayton cycle. Thus this paper presents the efficiencies of the supercritical CO{sub 2} recompression Brayton cycle along with several decision variables for the thermodynamic optimization of the supercritical CO{sub 2} recompression Brayton cycle. The analytic results in this study show that the system efficiency reaches its maximum value at a compressor outlet pressure of 200 bars and a recycle fraction of 30 %, and the lower minimum temperature approach at the two heat exchangers shows higher system efficiency as expected.

  14. Performance comparison of different supercritical carbon dioxide Brayton cycles integrated with a solar power tower

    International Nuclear Information System (INIS)

    In this study, a thermodynamic comparison of five supercritical carbon dioxide Brayton cycles integrated with a solar power tower was conducted. The Brayton cycles analyzed were simple Brayton cycle, regenerative Brayton cycle, recompression Brayton cycle, pre-compression Brayton cycle, and split expansion Brayton cycle. A complete mathematical code was developed to carry out the analysis. A heliostat field layout was generated and then optimized on an annual basis using the differential evolution method, which is an evolutionary algorithm. The heliostat field was optimized for optical performance and then integrated with the supercritical CO2 Brayton cycles. Using the results of the optimization, a comparison of net power outputs and thermal efficiencies for these cycles was performed. The findings demonstrated that the highest thermal efficiency was achieved using the recompression Brayton cycle, at June noontime. The maximum integrated system thermal efficiency using this cycle was 40% while the maximum thermal efficiency of this cycle alone was 52%. The regenerative Brayton cycle, although simpler in configuration, shows comparable performance to the recompression Brayton cycle. This analysis was carried out for Dhahran, Saudi Arabia. - Highlights: • The heliostat field of the solar power tower optimized and its optical efficiency identified. • Performance of the solar power tower integrated with five sCO2 Brayton Cycles was assessed. • Recompression supercritical CO2 Brayton cycle has the best performance. • The regenerative supercritical CO2 Brayton cycle has the second best performance

  15. Back work ratio of Brayton cycle; La relacion de trabajo de retroceso de un ciclo Brayton

    Energy Technology Data Exchange (ETDEWEB)

    Malaver de la Fuente, M. [Universidad Maritima del Caribe (Venezuela)]. E-mail: mmf_umc@hotmail.com

    2010-07-15

    This paper analyzes the existing relation between temperatures, back work ratio and net work of Brayton cycle, a cycle that describes gas turbine engines performance. The application of computational software helps to show the influence of back work ratio or coupling ratio, compressor and turbine inlet temperatures in an ideal thermodynamical cycle. The results lead to deduce that the maximum value reached in back work ratio will depend on the ranges of maximum and minimal temperatures of Brayton cycle. [Spanish] En este articulo se estudia la relacion que existe entre las temperaturas, la relacion de trabajo de retroceso y el trabajo neto en el ciclo Brayton, que es el ciclo ideal que describe el comportamiento de los motores de turbina de gas. La aplicacion de programas computarizados ayuda a mostrar la influencia de la relacion de trabajo de retroceso o relacion de acoplamiento, la temperatura de entrada al compresor y la temperatura de entrada a la turbina en este ciclo termodinamico ideal. Los resultados obtenidos permiten deducir que el valor maximo que alcanza la relacion de trabajo de retroceso dependera de los limites de temperatura maxima y minima impuestos en el ciclo Brayton.

  16. Power enhancement of the Brayton cycle by steam utilization

    Science.gov (United States)

    Jesionek, Krzysztof; Chrzczonowski, Andrzej; Ziółkowski, Paweł; Badur, Janusz

    2012-09-01

    The paper presents thermodynamic analysis of the gas-steam unit of the 65 MWe combined heat and power station. Numerical analyses of the station was performed for the nominal operation conditions determining the Brayton and combined cycle. Furthermore, steam utilization for the gas turbine propulsion in the Cheng cycle was analysed. In the considered modernization, steam generated in the heat recovery steam generator unit is directed into the gas turbine combustion chamber, resulting in the Brayton cycle power increase. Computational flow mechanics codes were used in the analysis of the thermodynamic and operational parameters of the unit.

  17. Optimization of the performance characteristics in an irreversible regeneration magnetic Brayton refrigeration cycle

    Science.gov (United States)

    Wang, Hao; Wu, GuoXing

    2012-02-01

    A model of the irreversible regenerative Brayton refrigeration cycle working with paramagnetic materials is established, in which the regeneration problem in two constant-magnetic field processes and the irreversibility in two adiabatic processes are considered synthetically. Expressions for the COP, cooling rate, power input, the minimum ratio of the two magnetic fields, etc., are derived. It is found that the influence of the irreversibility and the regeneration on the main performance parameters of the magnetic Brayton refrigerator is remarkable. It is important that we have obtained several optimal criteria, which may provide some theoretical basis for the optimal design and operation of the Brayton refrigerator. The results obtained in the paper can provide some new theoretical information for the optimal design and performance improvement of real Brayton refrigerators.

  18. Preliminary design of the supercritical CO2 Brayton cycle energy conversion system

    International Nuclear Information System (INIS)

    The supercritical CO2 Brayton cycle energy conversion system is presented as a promising alternative to the present Rankine cycle. The principal advantage of the S-CO2 gas is a good efficiency at a modest temperature and a compact size of its components. The S-CO2 Brayton cycle coupled to a SFR also excludes the possibilities of a SWR (Sodium-Water Reaction) which is a major safety-related event, so that the safety of a SFR can be improved. KAERI is conducting a feasibility study for the supercritical carbon dioxide (S-CO2) Brayton cycle power conversion system coupled to KALIMER(Korea Advanced LIquid MEtal Reactor). The purpose of this research is to develop S-CO2 Brayton cycle energy conversion systems and evaluate their performance when they are coupled to advanced nuclear reactor concepts of the type under investigation in the Generation IV Nuclear Energy Systems. This paper contains the research overview of the S-CO2 Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system

  19. Combined-Brayton cycle, space nuclear power systems

    International Nuclear Information System (INIS)

    Because it is a widely recognized dynamic space conversion system, the Brayton cycle has been studied in France since several years, especially within the framework of a limited space program. A recuperated cycle of 20 to 30 kWe has been considered so far. However, possible applications could evolve and the need for an extended, diversified utilization of the Brayton cycle could appear. So, for Lunar or Mars bases which would accept large radiators and can benefit from a certain gravity level, combined cycle systems could be proposed. Following a reference to past works on space combined cycles, a possible association of a Brayton cycle with a thermoionic reactor is presented. The power level of a 'Topaz-2' type space nuclear system can be boosted from 8 kWe to around 36 to 53 kWe, at the expense of a large radiator of course. Furthermore, combined Brayton-Rankine, organic (toluene) or steam, cycles can pave the way to a simpler gas-cooled, particle bed reactor concept. A particular arrangement of HeXe heater and boiler or steam generator in series is proposed. It makes it possible to lower the reactor inlet temperature, which is quite adequate for the use of light water as moderator. Oustanding net efficiencies of 25.8 to 27.6 per cent, given the reactor temperature profile, are obtained. Consequences on the reactor design are mentioned

  20. Nuclear reactor closed Brayton cycle space power conversion systems

    International Nuclear Information System (INIS)

    This paper presents the past history, present status and future prospects for closed Brayton cycle power conversion systems to be used in space when requirements have been established. Since there is a classic lack of coordination between advanced technology and its perceived need that can be strongly affected by associated factors, recommendations will be made to assist in the current situation. 4 refs

  1. The role of real gas Brayton cycles for the use of liquid natural gas physical exergy

    International Nuclear Information System (INIS)

    When using the cooling capacity of LNG several thermodynamic schemes are proposable employing conventional and non conventional conversion cycles. All conventional systems make use of organic working fluids such as methane or propane in series of Rankine cycles used in a cascading mode. A simpler system is available, using a single cycle and a single fluid in a Brayton cycle. However ordinary Brayton cycles exhibit a modest efficiency. Resorting to Brayton cycles with strong real gas effects (which is possible selecting the base parameters of pressure and temperature in the vicinity of the critical point) improves considerable cycle performance. Since the level of cold in a LNG flow is thermodynamically predetermined, working fluids must be selected with a critical point which fit the LNG thermal capacity, i.e. some 5-15 C higher than the usual LNG temperature which is around -160 oC. Nitrogen was found as the best fluid to exploit real gas effects with efficiencies above 63% while perfect gas cycles give efficiencies around 56%. However, in real gas cycles the cooling capacity of LNG is only partially exploited: a better exploitation is obtained from perfect gas cycles or for more complex cascading Rankine cycle. Selecting working fluids with a higher critical temperature than nitrogen, as for example argon, the efficiency decreases to 58% respect to 63% for nitrogen, but the utilization of the cold of LNG improves from 0.30 MW/(kg/s) to 0.75 MW/(kg/s). Obviously as heat rejection temperature increases a larger fraction of cold in the LNG flow can be utilized. Combined cycles making use of a gas turbine offer also a good performance. The merits of real gas effect Brayton cycles also in this case remains evident. Finally, it is theoretically possible to use real gas effect Brayton cycles at low temperatures, which are typical of waste heat (say 100-150 oC: in this case cycle efficiency remain good, but power obtainable from a unit flow of LNG is modest. - Research

  2. Operation and analysis of a supercritical CO2 Brayton cycle.

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven Alan; Radel, Ross F.; Vernon, Milton E.; Pickard, Paul S.; Rochau, Gary Eugene

    2010-09-01

    Sandia National Laboratories is investigating advanced Brayton cycles using supercritical working fluids for use with solar, nuclear or fossil heat sources. The focus of this work has been on the supercritical CO{sub 2} cycle (S-CO2) which has the potential for high efficiency in the temperature range of interest for these heat sources, and is also very compact, with the potential for lower capital costs. The first step in the development of these advanced cycles was the construction of a small scale Brayton cycle loop, funded by the Laboratory Directed Research & Development program, to study the key issue of compression near the critical point of CO{sub 2}. This document outlines the design of the small scale loop, describes the major components, presents models of system performance, including losses, leakage, windage, compressor performance, and flow map predictions, and finally describes the experimental results that have been generated.

  3. Modeling and Simulation of a Desiccant Assisted Brayton Refrigeration Cycle

    OpenAIRE

    Nobrega, Carlos E.L.; Sphaier, Leandro Alcoforado

    2012-01-01

    The phase-out of CFCs has shed a new light over natural refrigerants, which have null global warming potentials. Air would be a natural choice, and although the Brayton cycle usually exhibits a lower coefficient of performance when compared to vapor-compression systems of same capacity, it has been considered in applications other than aircraft cooling. These include gas separation, food processing and preservation, refrigerated containers and train air-conditioning. Price perspectives in the...

  4. Supercritical Carbon Dioxide Brayton Cycle Energy Conversion System

    International Nuclear Information System (INIS)

    This report contains the description of the S-CO2 Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For system development, a computer code was developed to calculate heat balance of 100% power operation condition. Based on the computer code, the S-CO2 Brayton cycle energy conversion system was constructed for the KALIMER-600. Using the developed turbomachinery models, the off-design characteristics and the sensitivities of the S-CO2 turbomachinery were investigated. For the development of PCHE models, a one-dimensional analysis computer code was developed to evaluate the performance of the PCHE. Possible control schemes for power control in the KALIMER-600 S-CO2 Brayton cycle were investigated by using the MARS code. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na/CO2 boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO2 gas. The long term behavior of a Na/CO2 boundary failure event and its consequences which lead to a system pressure transient were evaluated

  5. Supercritical Carbon Dioxide Brayton Cycle Energy Conversion System

    Energy Technology Data Exchange (ETDEWEB)

    Cha, Jae Eun; Kim, S. O.; Seong, S. H.; Eoh, J. H.; Lee, T. H.; Choi, S. K.; Han, J. W.; Bae, S. W

    2007-12-15

    This report contains the description of the S-CO{sub 2} Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For system development, a computer code was developed to calculate heat balance of 100% power operation condition. Based on the computer code, the S-CO{sub 2} Brayton cycle energy conversion system was constructed for the KALIMER-600. Using the developed turbomachinery models, the off-design characteristics and the sensitivities of the S-CO{sub 2} turbomachinery were investigated. For the development of PCHE models, a one-dimensional analysis computer code was developed to evaluate the performance of the PCHE. Possible control schemes for power control in the KALIMER-600 S-CO{sub 2} Brayton cycle were investigated by using the MARS code. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na/CO{sub 2} boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO{sub 2} gas. The long term behavior of a Na/CO{sub 2} boundary failure event and its consequences which lead to a system pressure transient were evaluated.

  6. Thermodynamic Modeling for Open Combined Regenerative Brayton and Inverse Brayton Cycles with Regeneration before the Inverse Cycle

    Directory of Open Access Journals (Sweden)

    Lingen Chen

    2012-01-01

    Full Text Available A thermodynamic model of an open combined regenerative Brayton and inverse Brayton cycles with regeneration before the inverse cycle is established in this paper by using thermodynamic optimization theory. The flow processes of the working fluid with the pressure drops and the size constraint of the real power plant are modeled. There are 13 flow resistances encountered by the working fluid stream for the cycle model. Four of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining nine flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, regenerator inlet and outlet, combustion chamber inlet and outlet, turbine outlet of the top cycle, turbine outlet of the bottom cycle, heat exchanger inlet, and compressor inlet of the bottom cycle. These resistances associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle, and control the air flow rate, the net power output and the thermal efficiency. The analytical formulae about the power output, efficiency and other coefficients are derived with 13 pressure drop losses. It is found that the combined cycle with regenerator can reach higher thermal efficiency but smaller power output than those of the base combined cycle at small compressor inlet relative pressure drop of the top cycle.

  7. Applications of Brayton Cycle technology to space power

    International Nuclear Information System (INIS)

    The Closed Brayton (CBC) power conversion cycle can be used with a wide range of heat sources for space power applications. These heat source include solar concentrator, radioisotope, and reactor. With a solar concentrator, a solar dynamic ground demonstration test using existing Brayton components is being assembled for testing at NASA Lewis Research Center (LeRC). This 2-kWe system has a turbine inlet temperature of 1,015 K and is a complete end-to-end simulation of the Space Station Freedom solar dynamic design. With a radioisotope heat source, a 1-kWe Dynamic Isotope Power System (DIPS) is under development using an existing turbo alternator compressor (TAC) for testing at the same NASA-LeRC facility. This DIPS unit is being developed as a replacement to Radioisotopic Thermoelectric Generators (RTGs) to conserve the Pu-238 supply for interplanetary exploration. With a reactor heat source, many studies have been performed coupling the SP-100 reactor with a Brayton power conversion cycle. Applications for this reactor/CBC system include global communications satellites and electric propulsion for interplanetary exploration

  8. Closed Brayton cycle power conversion systems for nuclear reactors :

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven A.; Lipinski, Ronald J.; Vernon, Milton E.; Sanchez, Travis

    2006-04-01

    This report describes the results of a Sandia National Laboratories internally funded research program to study the coupling of nuclear reactors to gas dynamic Brayton power conversion systems. The research focused on developing integrated dynamic system models, fabricating a 10-30 kWe closed loop Brayton cycle, and validating these models by operating the Brayton test-loop. The work tasks were performed in three major areas. First, the system equations and dynamic models for reactors and Closed Brayton Cycle (CBC) systems were developed and implemented in SIMULINKTM. Within this effort, both steady state and dynamic system models for all the components (turbines, compressors, reactors, ducting, alternators, heat exchangers, and space based radiators) were developed and assembled into complete systems for gas cooled reactors, liquid metal reactors, and electrically heated simulators. Various control modules that use proportional-integral-differential (PID) feedback loops for the reactor and the power-conversion shaft speed were also developed and implemented. The simulation code is called RPCSIM (Reactor Power and Control Simulator). In the second task an open cycle commercially available Capstone C30 micro-turbine power generator was modified to provide a small inexpensive closed Brayton cycle test loop called the Sandia Brayton test-Loop (SBL-30). The Capstone gas-turbine unit housing was modified to permit the attachment of an electrical heater and a water cooled chiller to form a closed loop. The Capstone turbine, compressor, and alternator were used without modification. The Capstone systems nominal operating point is 1150 K turbine inlet temperature at 96,000 rpm. The annular recuperator and portions of the Capstone control system (inverter) and starter system also were reused. The rotational speed of the turbo-machinery is controlled by adjusting the alternator load by using the electrical grid as the load bank. The SBL-30 test loop was operated at

  9. A Brayton cycle solar dynamic heat receiver for space

    Science.gov (United States)

    Sedgwick, L. M.; Nordwall, H. L.; Kaufmann, K. J.; Johnson, S. D.

    1989-01-01

    The detailed design of a heat receiver developed to meet the requirements of the Space Station Freedom, which will be assembled and operated in low earth orbit beginning in the mid-1990's, is described. The heat receiver supplies thermal energy to a nominal 25-kW closed-Brayton-cycle power conversion unit. The receiver employs an integral thermal energy storage system utilizing the latent heat of a eutectic-salt phase-change mixture to store energy for eclipse operation. The salt is contained within a felt metal matrix which enhances heat transfer and controls the salt void distribution during solidification.

  10. Super-critical carbon dioxide based brayton cycle for Indian High Temperature Reactors

    International Nuclear Information System (INIS)

    The most effective way to improve economic competitiveness of NPPs is to enhance its efficiency which has remained static at around 33% since the first commercial LWR came into operation. New generation reactor designs including the six Gen-IV reactor concepts aim to increase the NPPs efficiency to almost 50%. This is proposed to be achieved by high temperature designs using Brayton cycle based power conversion systems. World over, Super-critical Carbon dioxide Brayton Cycle (SCBC) for power generation is an important R and D area. High efficiency SCBC power conversion system is proposed as power conversion system for Indian Molten Salt Breeder Reactor (IMSBR) and Innovative High Temperature Reactor (IHTR). This section provides the details regarding design and development of SCBC for these reactors. (author)

  11. Simulation of CO2 Brayton Cycle for Engine Exhaust Heat Recovery under Various Operating Loads

    Institute of Scientific and Technical Information of China (English)

    舒歌群; 张承宇; 田华; 高媛媛; 李团兵; 仇荣赓

    2015-01-01

    A bottoming cycle system based on CO2 Brayton cycle is proposed to recover the engine exhaust heat. Its performance is compared with the conventional air Brayton cycle under five typical engine conditions. The results show that CO2 Brayton cycle proves to be superior to the air Brayton cycle in terms of the system net output power, thermal efficiency and recovery efficiency. In most cases, the recovery efficiency of CO2 Brayton cycle can be higher than 9%and the system has a better performance at the engine’s high operating load. The thermal efficiency can be as large as 24.83%under 100%operating load, accordingly, the net output power of 14.86 kW is obtained.

  12. Cold startup and low temperature performance of the Brayton cycle electrical subsystem

    Science.gov (United States)

    Vrancik, J. E.; Bainbridge, R. C.

    1971-01-01

    Cold performance tests and startup tests were conducted on the Brayton-cycle inverter, motor-driven pump, dc supply, speed control with parasitic load resistor and the Brayton control system. These tests were performed with the components in a vacuum and mounted on coldplates. A temperature range of ?25 to -50 C was used for the tests. No failures occurred, and component performance gave no indication that there would be any problem with the safe operation of the Brayton power generating system.

  13. Gas Foil Bearing Technology Advancements for Closed Brayton Cycle Turbines

    Science.gov (United States)

    Howard, Samuel A.; Bruckner, Robert J.; DellaCorte, Christopher; Radil, Kevin C.

    2007-01-01

    Closed Brayton Cycle (CBC) turbine systems are under consideration for future space electric power generation. CBC turbines convert thermal energy from a nuclear reactor, or other heat source, to electrical power using a closed-loop cycle. The operating fluid in the closed-loop is commonly a high pressure inert gas mixture that cannot tolerate contamination. One source of potential contamination in a system such as this is the lubricant used in the turbomachine bearings. Gas Foil Bearings (GFB) represent a bearing technology that eliminates the possibility of contamination by using the working fluid as the lubricant. Thus, foil bearings are well suited to application in space power CBC turbine systems. NASA Glenn Research Center is actively researching GFB technology for use in these CBC power turbines. A power loss model has been developed, and the effects of a very high ambient pressure, start-up torque, and misalignment, have been observed and are reported here.

  14. Sensitivity study on nitrogen Brayton cycle coupled with a small ultra-long cycle fast reactor

    International Nuclear Information System (INIS)

    The main characteristics of UCFR are constant neutron flux and power density. They move their positions every moment at constant speed along with axial position of fuel rod for 60 years. Simultaneously with the development of the reactors, a new power conversion system has been considered. To solve existing issues of vigorous sodium-water reaction in SFR with steam power cycle, many researchers suggested a closed Brayton cycle as an alternative technique for SFR power conversion system. Many inactive gases are selected as a working fluid in Brayton power cycle, mainly supercritical CO2 (S-CO2). However, S-CO2 still has potential for reaction with sodium. CO2-sodium reaction produces solid product, which has possibility to have an auto ignition reaction around 600 .deg. C. Thus, instead of S-CO2, CEA in France has developed nitrogen power cycle for ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration). In addition to inactive characteristic of nitrogen with sodium, its thermal and physical similarity with air enables to easily adopt to existing air Brayton cycle technology. In this study, for an optimized power conversion system for UCFR, a nitrogen Brayton cycle was analyzed in thermodynamic aspect. Based on subchannel analysis data of UCFR-100, a parametric study for thermal performance of nitrogen Brayton cycle was achieved. The system maximum pressure significantly affects to the overall efficiency of cycle, while other parameters show little effects. Little differences of the overall efficiencies for all cases between three stages (BOC, MOC, EOC) indicate that the power cycle of UCFR-100 maintains its performance during the operation

  15. Thermo-economic performance of HTGR Brayton power cycles

    International Nuclear Information System (INIS)

    High temperature reached in High and Very High Temperature Reactors (VHTRs) results in thermal efficiencies substantially higher than those of actual nuclear power plants. A number of studies mainly driven by achieving optimum thermal performance have explored several layout. However, economic assessments of cycle power configurations for innovative systems, although necessarily uncertain at this time, may bring valuable information in relative terms concerning power cycle optimization. This paper investigates the thermal and economic performance direct Brayton cycles. Based on the available parameters and settings of different designs of HTGR power plants (GTHTR-300 and PBMR) and using the first and second laws of thermodynamics, the effects of compressor inter-cooling and of the compressor-turbine arrangement (i.e., single vs. multiple axes) on thermal efficiency have been estimated. The economic analysis has been based on the El-Sayed methodology and on the indirect derivation of the reactor capital investment. The results of the study suggest that a 1-axis inter-cooled power cycle has a similar thermal performance to the 3-axes one (around 50%) and, what's more, it is substantially less taxed. A sensitivity study allowed assessing the potential impact of optimizing several variables on cycle performance. Further than that, the cycle components costs have been estimated and compared. (authors)

  16. Solar/gas Brayton/Rankine cycle heat pump assessment

    Science.gov (United States)

    Rousseau, J.; Liu, A. Y.

    1982-05-01

    A 10-ton gas-fired heat pump is currently under development at AiResearch under joint DOE and GRI sponsorship. This heat pump features a highly efficient, recuperated, subatmospheric Brayton-cycle engine which drives the centrifugal compressor of a reversible vapor compression heat pump. The investigations under this program were concerned initially with the integration of this machine with a parabolic dish-type solar collector. Computer models were developed to accurately describe the performance of the heat pump packaged in this fashion. The study determined that (1) only a small portion (20 to 50 percent) of the available solar energy could be used because of a fundamental mismatch between the heating and cooling demand and the availability of solar energy, and (2) the simple pay back period, by comparison to the baseline non-solar gas-fired heat pump, was unacceptable (15 to 36 years).

  17. Calculation principles of humid air in a reversed Brayton cycle

    Energy Technology Data Exchange (ETDEWEB)

    Backman, J. [Lappeenranta Univ. of Technology (Finland). Dept. of Energy Technology

    1997-12-31

    The article presents a calculation method for reversed Brayton cycle that uses humid air as working medium. The reversed Brayton cycle can be employed as an air dryer, a heat pump or a refrigerating machine. In this research the use of humid air as a working fluid has an environmental advantage, as well. In this method especially the expansion process in the turbine is important because of the condensation of the water vapour in the humid air. This physical phenomena can have significant effects on the level of performance of the application. The expansion process differs physically from the compression process, when the water vapour in the humid air begins to condensate. In the thermodynamic equilibrium of the flow, the water vapour pressure in humid air cannot exceed the pressure of saturated water vapour in corresponding temperature. Expansion calculation during operation around the saturation zone is based on a quasistatic expansion, in which the system after the turbine is in thermodynamical equilibrium. The state parameters are at every moment defined by the equation of state, and there is no supercooling in the vapour. Following simplifications are used in the calculations: The system is assumed to be adiabatic. This means that there is no heat transfer to the surroundings. This is a common practice, when the temperature differences are moderate as here; The power of the cooling is omitted. The cooling construction is very dependent on the machine and the distribution of the losses; The flow is assumed to be one-dimensional, steady-state and homogenous. The water vapour condensing in the turbine can cause errors, but the errors are mainly included in the efficiency calculation. (author) 11 refs.

  18. Parametric Investigation and Thermoeconomic Optimization of a Combined Cycle for Recovering the Waste Heat from Nuclear Closed Brayton Cycle

    Directory of Open Access Journals (Sweden)

    Lihuang Luo

    2016-01-01

    Full Text Available A combined cycle that combines AWM cycle with a nuclear closed Brayton cycle is proposed to recover the waste heat rejected from the precooler of a nuclear closed Brayton cycle in this paper. The detailed thermodynamic and economic analyses are carried out for the combined cycle. The effects of several important parameters, such as the absorber pressure, the turbine inlet pressure, the turbine inlet temperature, the ammonia mass fraction, and the ambient temperature, are investigated. The combined cycle performance is also optimized based on a multiobjective function. Compared with the closed Brayton cycle, the optimized power output and overall efficiency of the combined cycle are higher by 2.41% and 2.43%, respectively. The optimized LEC of the combined cycle is 0.73% lower than that of the closed Brayton cycle.

  19. Automatic Control Strategy Development for the Supercritical CO2 Brayton Cycle for LFR Autonomous Load Following

    International Nuclear Information System (INIS)

    The supercritical carbon dioxide (S-CO2) Brayton cycle is a promising advanced alternative to the Rankine saturated steam cycle and ideal gas Brayton cycle for the energy converters of specific reactor concepts belonging to the U.S. Department of Energy Generation IV Nuclear Energy Systems Initiative. A new plant dynamics analysis computer code has been developed for simulation of the S-CO2 Brayton cycle coupled to an autonomous Lead-Cooled Fast Reactor (LFR). The plant dynamics code was used to develop an automatic control strategy for the whole plant in response to changes in the demand from the electrical grid. The specific features of the S-CO2 Brayton cycle that result in limitations on the control range and speed of specific control mechanisms are discussed. Calculations of whole-plant responses to plant operational transients involving step and continuous changes in grid demand are demonstrated. (authors)

  20. Assessing the potential of hybrid fossil–solar thermal plants for energy policy making: Brayton cycles

    International Nuclear Information System (INIS)

    This paper proposes a first study in-depth of solar–fossil hybridization from a general perspective. It develops a set of useful parameters for analyzing and comparing hybrid plants, it studies the case of hybridizing Brayton cycles with current solar technologies and shows a tentative extrapolation of the results to integrated combined cycle systems (ISCSS). In particular, three points have been analyzed: the technical requirements for solar technologies to be hybridized with Brayton cycles, the temperatures and pressures at which hybridization would produce maximum power per unit of fossil fuel, and their mapping to current solar technologies and Brayton cycles. Major conclusions are that a hybrid plant works in optimum conditions which are not equal to those of the solar or power blocks considered independently, and that hybridizing at the Brayton cycle of a combined cycle could be energetically advantageous. -- Highlights: •We model a generic solar–fossil hybrid Brayton cycle. •We calculate the operating conditions for maximum ratio power/fuel consumption. •Best hybrid plant conditions are not the same as solar or power blocks separately. •We study potential for hybridization with current solar technologies. •Hybridization at the Brayton in a combined cycle may achieve high power/fuel ratio

  1. Exergy analyses of an endoreversible closed regenerative Brayton cycle CCHP plant

    OpenAIRE

    Bo Yang, Lingen Chen, Fengrui Sun

    2014-01-01

    An endoreversible closed regenerative Brayton cycle CCHP (combined cooling, heating and power) plant coupled to constant-temperature heat reservoirs is presented using finite time thermodynamics (FTT). The CCHP plant includes an endoreversible closed regenerative Brayton cycle, an endoreversible four-heat-reservoir absorption refrigerator and a heat recovery device of thermal consumer. The heat-resistance losses in the hot-, cold-, thermal consumer-, generator-, condenser-, evaporator- and ab...

  2. Brayton-Cycle Baseload Power Tower CSP System

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Bruce

    2013-12-31

    The primary objectives of Phase 2 of this Project were: 1. Engineer, fabricate, and conduct preliminary testing on a low-pressure, air-heating solar receiver capable of powering a microturbine system to produce 300kWe while the sun is shining while simultaneously storing enough energy thermally to power the system for up to 13 hours thereafter. 2. Cycle-test a high-temperature super alloy, Haynes HR214, to determine its efficacy for the system’s high-temperature heat exchanger. 3. Engineer the thermal energy storage system This Phase 2 followed Wilson’s Phase 1, which primarily was an engineering feasibility study to determine a practical and innovative approach to a full Brayton-cycle system configuration that could meet DOE’s targets. Below is a summary table of the DOE targets with Wilson’s Phase 1 Project results. The results showed that a Brayton system with an innovative (low pressure) solar receiver with ~13 hours of dry (i.e., not phase change materials or molten salts but rather firebrick, stone, or ceramics) has the potential to meet or exceed DOE targets. Such systems would consist of pre-engineered, standardized, factory-produced modules to minimize on-site costs while driving down costs through mass production. System sizes most carefully analyzed were in the range of 300 kWe to 2 MWe. Such systems would also use off-the-shelf towers, blowers, piping, microturbine packages, and heliostats. Per DOE’s instructions, LCOEs are based on the elevation and DNI levels of Daggett, CA, for a 100 MWe power plant following 2 GWe of factory production of the various system components. Success criteria DOE targets Wilson system LCOE DOE’s gas price $6.75/MBtu 9 cents/kWh 7.7 cents/kWh LCOE Current gas price $4.71/MBtu NA 6.9 cents/kWh Capacity factor 75% (6500hr) 75-100% Solar fraction 85% (5585hr) >5585hr Receiver cost $170/kWe $50/kWe Thermal storage cost $20/kWhth $13/kWhth Heliostat cost $120/m2 $89.8/m2

  3. Concept definition study of small Brayton cycle engines for dispersed solar electric power systems

    Science.gov (United States)

    Six, L. D.; Ashe, T. L.; Dobler, F. X.; Elkins, R. T.

    1980-01-01

    Three first-generation Brayton cycle engine types were studied for solar application: a near-term open cycle (configuration A), a near-term closed cycle (configuration B), and a longer-term open cycle (configuration C). A parametric performance analysis was carried out to select engine designs for the three configurations. The interface requirements for the Brayton cycle engine/generator and solar receivers were determined. A technology assessment was then carried out to define production costs, durability, and growth potential for the selected engine types.

  4. Volatile organic compound recovery by Brayton cycle Heat Pump

    International Nuclear Information System (INIS)

    Organic solvent emissions from industrial processes are a major source of volatile organic compounds (VOCs). VOCs contribute to the formation of photochemical ozone, a major component of smog. Over 90 percent of the organic solvents used in industry are emitted. Not only does this represent a significant source of air pollution, but it also represents a waste of energy resources. A pound of solvent requires an average of 23,000 Btu of energy to produce, in the form of the feedstock and processing energy expenditures. In 1988, the total amount of solvents emitted in the United States was over 4 billion pounds and represent 100 trillion Btu in energy loss. In the mid-1970's, the 3M Company began developing the Brayton Cycle Heat Pump for solvent recovery (BCSRHP). In 1979, the US Department of Energy (DOE) began a project to fabricate and install a BCSRHP in a 3M plant in Hutchinson, Minnesota. DOE has continued sponsoring the development of a large BCSRHP system with 3M, and NUCON International (NUCON). In 1989 DOE and NUCON, with cosponsorship from the Electric Power Research Institute and Southern California Edison Company began development of a small-scale system for use by small emitters. To obtain data for design of the small-scale system, a small, mobile pilot plant was built by NUCON. Between 1990 and 1991, the pilot plant was demonstrated at four industrial sites in Southern California. The operation of the pilot plant was continuously monitored during the demonstrations, and its ability to remove VOCS, utility consumption and other operating characteristics were recorded and its performance quantified

  5. Optimization of Brayton cycles for low-to-moderate grade thermal energy sources

    International Nuclear Information System (INIS)

    Future electricity generation will involve low or moderate temperature technologies. In such a scenario, optimisation of thermodynamic cycles will be a key task. This work presents a systematic analysis to find the operating regime where Brayton cycles reach the highest efficiency, using real substances and given heat source and sink temperatures. Several configurations using fluids close to its critical point at the compressor inlet are considered. Irreversibility sources are carefully analysed, as well as the type of working fluid. The analysis is performed by means of a theoretical approach to obtain some trends, which are afterwards validated with real gases. Results show that the efficiency and the specific work improve if the compressor inlet is close to the critical point. Furthermore, these cycles are less sensitive to pressure drops and politropic efficiencies than those working with ideal gases. The above features are more evident when the ratio of heat source and heat sink temperatures is low. The selection of the gas becomes a fundamental issue in this quest. Critical temperature should be close to ambient temperature, low critical pressure is advisable and the R/cp factor measured at the ideal gas condition should be low to further enhance the efficiency. - Highlights: • Performance analysis of Brayton cycles with the compressor inlet close to the critical point. • Cycles are not very sensitive to pressure drops and isentropic efficiencies of the compressor. • Gas selection becomes important, regarding the critical pressure and temperature as well as the kind of fluid. • R/cp factor measured at the ideal gas condition should be as low as possible

  6. Exergy analyses of an endoreversible closed regenerative Brayton cycle CCHP plant

    Directory of Open Access Journals (Sweden)

    Bo Yang, Lingen Chen, Yanlin Ge, Fengrui Sun

    2014-01-01

    Full Text Available An endoreversible closed regenerative Brayton cycle CCHP (combined cooling, heating and power plant coupled to constant-temperature heat reservoirs is presented using finite time thermodynamics (FTT. The CCHP plant includes an endoreversible closed regenerative Brayton cycle, an endoreversible four-heat-reservoir absorption refrigerator and a heat recovery device of thermal consumer. The heat-resistance losses in the hot-, cold-, thermal consumer-, generator-, condenser-, evaporator- and absorber-side heat exchangers and regenerator are considered. The performance of the CCHP plant is studied from the exergetic perspective, and the analytical formulae about exergy output rate and exergy efficiency are derived. Through numerical calculations, the pressure ratio of regenerative Brayton cycle is optimized, the effects of heat conductance of regenerator and ratio of heat demanded by the thermal consumer to power output on dimensionless exergy output rate and exergy efficiency are analyzed.

  7. Operational Curves for HTGR's Coupled to Closed Brayton Cycle Power Conversion Systems

    International Nuclear Information System (INIS)

    Gas Cooled Reactors (GCR) that drive Closed Brayton Cycle (CBC) systems are being evaluated by the Department of Energy (DOE) Next Generation Program for high-efficiency electricity generation. This paper describes the operational performance of measured and predicted closed Brayton cycles. The measured results were obtained from an electrically driven closed Brayton cycle test loop that Sandia fabricated and has operating within the laboratories. The predicted behavior is based on integrated dynamic system models that are capable of predicting both the transient and steady state behavior of reactor driven Brayton cycle systems. Sandia contracted Barber Nichols Corporation to modify a Capstone C30 open-cycle Brayton engine so that it could be operated in a closed loop. We are currently operating the test loop to validate the models and to study control issues. Operation of the test-loop and developing the system models has allowed Sandia to develop and validate a set of tools and models that are being used to determine how nuclear reactors operate with gas turbine power conversion systems. Both measured and modeled operational performance curves will be presented to show how the electrical load (or power generated) varies as a function of shaft speed for various turbine inlet temperatures and for a fixed fill gas inventory. The measured and modeled behavior of the test loop both reveal the non-linear nature of the reactor and Brayton cycle loop because for a fixed electrical load there are two shaft speeds that can produce this steady-state power. Closer examination of the system of equations shows that only one of these steady-state solutions is dynamically stable. An active electronic control system will be required to operate at the more efficient but dynamically unstable point, and some means of controlling the flow via inventory control or bypass flow valves will also be required. (authors)

  8. Computational analysis of supercritical CO2 Brayton cycle power conversion system for fusion reactor

    International Nuclear Information System (INIS)

    Highlights: ► Computational analysis of S-CO2 Brayton cycle power conversion system. ► Validation of numerical model with literature data. ► Recompression S-CO2 Brayton cycle thermal efficiency of 42.44%. ► Reheating concept to enhance the cycle thermal efficiency. ► Higher efficiency achieved by the proposed concept. - Abstract: The Optimized Supercritical Cycle Analysis (OSCA) code is being developed to analyze the design of a supercritical carbon dioxide (S-CO2) driven Brayton cycle for a fusion reactor as part of the Modular Optimal Balance Integral System (MOBIS). This system is based on a recompression Brayton cycle. S-CO2 is adopted as the working fluid for MOBIS because of its easy availability, high density and low chemical reactivity. The reheating concept is introduced to enhance the cycle thermal efficiency. The helium-cooled lithium lead model AB of DEMO fusion reactor is used as reference in this paper.

  9. Exergy Analysis and Second Law Efficiency of a Regenerative Brayton Cycle with Isothermal Heat Addition

    Directory of Open Access Journals (Sweden)

    Naser M. Jubeh

    2005-07-01

    Full Text Available Abstract: The effect of two heat additions, rather than one, in a gas turbine engine is analyzed from the second law of thermodynamics point of view. A regenerative Brayton cycle model is used for this study, and compared with other models of Brayton cycle. All fluid friction losses in the compressor and turbine are quantified by an isentropic efficiency term. The effect of pressure ratio, turbine inlet temperature, ambient temperature, altitude, and altitude with variable ambient temperature on irreversibility "exergy destroyed" and second law efficiency was investigated and compared for all models. The results are given graphically with the appropriate discussion and conclusion.

  10. Comparison of various Brayton cycles for a Sodium-cooled Fast Reactor

    International Nuclear Information System (INIS)

    The nuclear energy is considered as one of the most realistic energy sources for both reducing the carbon dioxide emission and attaining sufficient and stable electricity supply for economy development. As a part of the nuclear energy development, many countries around the world are focusing on the next generation reactor development. One of the next generation reactors that is seriously being considered is the Sodium-cooled Fast Reactor (SFR). However, current SFR design faces the difficulty in public acceptance due to the potential threat from sodium-water reaction (SWR) when the current conventional steam Rankine cycle is utilized as a power conversion system for SFR. To substitute the violent sodium-water reaction with milder or no reaction, several Brayton cycle concepts including the S-CO2 cycle, helium cycle and nitrogen cycle are considered by many research organizations. This paper discusses these Brayton cycles'performance for SFR application compared to the current steam Rankine cycle

  11. Thermodynamic analysis of the double Brayton cycle with the use of oxy combustion and capture of CO2

    Science.gov (United States)

    Ziółkowski, Paweł; Zakrzewski, Witold; Kaczmarczyk, Oktawia; Badur, Janusz

    2013-06-01

    In this paper, thermodynamic analysis of a proposed innovative double Brayton cycle with the use of oxy combustion and capture of CO2, is presented. For that purpose, the computation flow mechanics (CFM) approach has been developed. The double Brayton cycle (DBC) consists of primary Brayton and secondary inverse Brayton cycle. Inversion means that the role of the compressor and the gas turbine is changed and firstly we have expansion before compression. Additionally, the workingfluid in the DBC with the use of oxy combustion and CO2 capture contains a great amount of H2O and CO2, and the condensation process of steam (H2O) overlaps in negative pressure conditions. The analysis has been done for variants values of the compression ratio, which determines the lowest pressure in the double Brayton cycle.

  12. Development and validation of models for simulation of supercritical carbon dioxide Brayton cycles and application to self-propelling heat removal systems in boiling water reactors

    OpenAIRE

    Venker, Jeanne

    2015-01-01

    The objective of the current work was to develop a model that is able to describe the transient behavior of supercritical carbon dioxide (sCO2) Brayton cycles, to be applied to self-propelling residual heat removal systems in boiling water reactors. The developed model has been implemented into the thermohydraulic system code ATHLET. By means of this improved ATHLET version, novel residual heat removal systems, which are based on closed sCO2 Brayton cycles, can be assessed as a retrofit measu...

  13. NASA 30,000 hour test demonstration of closed Brayton cycle reliability

    Science.gov (United States)

    Mccormick, J. E.; Dunn, J. H.

    1977-01-01

    Four Brayton rotating units (BRU) developed by an American company were tested in connection with studies concerning the feasibility to use closed Brayton power conversion systems for space applications. The rotating assembly operates at a speed of 36,000 rpm and consists of a radial outflow compressor, a four-pole Rice alternator/motor, and a radial inflow turbine. The cycle working fluid consists of a mixture of helium and xenon. After 20,000 hours of operation, there was no apparent wear on failure mode to prevent attainment of the 5-year BRU design life objective.

  14. Brayton-Cycle Heat Recovery System Characterization Program. Glass-furnace facility test plan

    Energy Technology Data Exchange (ETDEWEB)

    1980-08-29

    The test plan for development of a system to recover waste heat and produce electricity and preheated combustion air from the exhaust gases of an industrial glass furnace is described. The approach is to use a subatmospheric turbocompressor in a Brayton-cycle system. The operational furnace test requirements, the operational furnace environment, and the facility design approach are discussed. (MCW)

  15. Influence of irreversible losses on the performance of a two-stage magnetic Brayton refrigeration cycle

    International Nuclear Information System (INIS)

    The general performance characteristics of a two-stage magnetic Brayton refrigeration cycle consisting of three constant magnetic fields and three irreversible adiabatic processes are investigated. Based on the thermodynamic properties of a magnetic material and the irreversible cycle model of a two-stage Brayton refrigerator, expressions for the cooling load and coefficient of performance of the refrigeration system are derived. The influence of the finite-rate heat transfer in the heat exchange processes, irreversibilities in the three adiabatic processes, ratios of two magnetic fields in the three constant magnetic field processes, and heat leak losses between two heat reservoirs on the performance of the two-stage magnetic Brayton refrigeration cycle are analyzed in detail. Some important performance curves, which can reveal the general characteristics of the refrigeration system, are presented and the maximum values of cooling load and coefficient of performance are numerically calculated. The optimal choices and matches of other parameters at the maximum cooling load or the maximum coefficient of performance are discussed and the optimally operating regions of some important parameters in the refrigeration system are determined. The results obtained here are compared with those derived from other models of the magnetic Brayton refrigeration cycles, and consequently, the advantage of an inter-cooled process is expounded.

  16. Techno-economic studies of environmentally friendly Brayton cycles in the petrochemical industry

    OpenAIRE

    Nkoi, Barinyima

    2014-01-01

    Brayton cycles are open gas turbine cycles extensively used in aviation and industrial applications because of their advantageous volume and weight characteristics. With the bulk of waste exhaust heat and engine emissions associated, there is need to be mindful of environmentally-friendliness of these engine cycles, not compromising good technical performance, and economic viability. This research considers assessment of power plants in helicopters, and aeroderivative ind...

  17. Optimal analysis on the performance of an irreversible harmonic quantum Brayton refrigeration cycle.

    Science.gov (United States)

    Lin, Bihong; Chen, Jincan

    2003-11-01

    An irreversible model of a quantum refrigeration cycle working with many noninteracting harmonic oscillators is established. The refrigeration cycle consists of two adiabatic and two constant-frequency processes. The general performance characteristics of the cycle are investigated, based on the quantum master equation and the semigroup approach. The expressions for several important performance parameters such as the coefficient of performance, cooling rate, power input, and rate of entropy production are derived. By using numerical solutions, the cooling rate of the refrigeration cycle subject to finite cycle duration is optimized. The maximum cooling rate and the corresponding parameters are calculated numerically. The optimal region of the coefficient of performance and the optimal ranges of temperatures of the working substance and times spent on the two constant-frequency processes are determined. Moreover, the optimal performance of the cycle in the high-temperature limit is compared with that of a classical Brayton refrigerator working with an ideal gas. The results obtained here show that in the high-temperature limit a harmonic quantum Brayton cycle may be equivalent to a classical Brayton cycle. PMID:14682856

  18. Analysis of Superimposed Elementary Thermodynamic Cycles: from the Brayton-Joule to Advanced Mixed (Auto-Combined Cycles

    Directory of Open Access Journals (Sweden)

    Giovanni Manente

    2009-09-01

    Full Text Available

    The need for efficiency improvement in energy conversion systems leads to a stricter functional integration among system components. This results in structures of increasing complexity, the high performance of which are often difficult to be understood easily. To make the comprehension of these structures easier, a new approach is followed in this paper, consisting in their representation as partial or total superimposition of elementary thermodynamic cycles. Although system performance cannot, in general, be evaluated as the sum of the performance of the separate thermodynamic cycles, this kind of representation and analysis can be of great help in understanding directions of development followed in the literature for the construction of advanced energy systems, and could suggest new potential directions of work. The evolution from the simple Brayton-Joule cycle to the so called “mixed” cycles, in which heat at the turbine discharge is exploited using internal heat sinks only without using a separate bottoming section, is used to demonstrate the potentiality of the approach. Mixed cycles are named here "auto-combined cycles” to highlight the combination of different (gas and steam cycles within the same system components.

    • This paper is an updated version of a paper published in the ECOS'08 proceedings. 

  19. Preliminary Design of S-CO{sub 2} Brayton Cycle for KAIST Micro Modular Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Seong Gu; Kim, Min Gil; Bae, Seong Jun; Lee, Jeong Ik [Korea Advanced Institue of Science and Technology, Daejeon (Korea, Republic of)

    2013-10-15

    This paper suggests a complete modular reactor with an innovative concept of reactor cooling by using a supercritical carbon dioxide directly. Authors propose the supercritical CO{sub 2} Brayton cycle (S-CO{sub 2} cycle) as a power conversion system to achieve small volume of power conversion unit (PCU) and to contain the core and PCU in one vessel for the full modularization. This study suggests a conceptual design of small modular reactor including PCU which is named as KAIST Micro Modular Reactor (MMR). As a part of ongoing research of conceptual design of KAIST MMR, preliminary design of power generation cycle was performed in this study. Since the targets of MMR are full modularization of a reactor system with S-CO{sub 2} coolant, authors selected a simple recuperated S-CO{sub 2} Brayton cycle as a power conversion system for KAIST MMR. The size of components of the S-CO{sub 2} cycle is much smaller than existing helium Brayton cycle and steam Rankine cycle, and whole power conversion system can be contained with core and safety system in one containment vessel. From the investigation of the power conversion cycle, recompressing recuperated cycle showed higher efficiency than the simple recuperated cycle. However the volume of heat exchanger for recompressing cycle is too large so more space will be occupied by heat exchanger in the recompressing cycle than the simple recuperated cycle. Thus, authors consider that the simple recuperated cycle is more suitable for MMR. More research for the KAIST MMR will be followed in the future and detailed information of reactor core and safety system will be developed down the road. More refined cycle layout and design of turbomachinery and heat exchanger will be performed in the future study.

  20. Investigation on the performance of the supercritical Brayton cycle with CO2-based binary mixture as working fluid for an energy transportation system of a nuclear reactor

    International Nuclear Information System (INIS)

    In this study, the performance of a SBC (supercritical gas Brayton cycle) using CO2-based binary mixtures as the working fluids have been studied. Based on the thermodynamic analyses, an in-house code has been developed to determine the cycle efficiency and the amounts of heat transfer in the HTR (high temperature recuperator) and the LTR (low temperature recuperator) with different CO2/additive gas ratios. Several gases are selected as potential additives, including O2, He, Ar, Kr, butane and cyclohexane. Compared with the Brayton cycle with pure S–CO2 (supercritical carbon dioxide) as the working fluid, it is found that both CO2–He and CO2–Kr mixtures can improve the thermodynamic performances of the SBC by increasing the cycle efficiency and decreasing the amounts of heat transfer in the HTR and LTR. For the cycles with the pure S–CO2 mixture, CO2–butane mixture and CO2–cyclohexane mixture as the working fluids, the cycle efficiencies decrease with increasing main compressor inlet temperature. However, when the main compressor inlet temperature is above the critical temperature of pure CO2, the cycle efficiencies of the cycles with CO2–butane mixture and CO2–cyclohexane mixture are higher than that of the cycle with pure CO2 as the working fluid. For the cycles with CO2-based binary mixtures and pure S–CO2 as the working fluids, the higher reactor outlet temperature always results into higher cycle efficiencies and larger amount of heat transfer in the HTR and smaller amount of heat transfer in the LTR. - Highlights: • The Brayton cycle performance with different mixtures as working fluids is studied. • Thermodynamic analysis is carried out to evaluate cycle efficiency and heat transfer in HTR and LTR. • The optimum working parameters of the Brayton cycle is proposed to improve working performance

  1. Optimum criteria of an irreversible quantum Brayton refrigeration cycle with an ideal Bose gas

    International Nuclear Information System (INIS)

    An irreversible cycle model of the quantum Brayton refrigeration cycle is established, in which finite-time processes and irreversibility in the two adiabatic processes are taken into account. On the basis of the thermodynamic properties of an ideal Bose gas, by using the optimal control-theory, the mathematical expressions for several important performance parameters, such as the coefficient of performance, power input and cooling load, are derived and some important performance parameters, e.g., the temperatures of the working substance at several important state-points, are optimized. By means of numerical predictions, the optimal performance characteristic curves of a Bose-Brayton refrigeration cycle are obtained and analyzed. Furthermore, some optimal operating regions including those for the cooling load, coefficient of performance and the temperatures of the cyclic working substance at the two important state-points are determined and evaluated. Finally, several special cases are discussed in detail

  2. Features of supercritical carbon dioxide Brayton cycle coupled with reactor

    International Nuclear Information System (INIS)

    In order to obtain acceptable cycle efficiency, current helium gas turbine power cycle technology needs high cycle temperature which means that the cycle needs high core-out temperature. The technology has high requirements on reactor structure and fuel elements materials, and also on turbine manufacture. While utilizing CO2 as cycle working fluid, it can guarantee to lower the cycle temperature and turbo machine Janume but achieve the same cycle efficiency, so as to enhance the safety and economy of reactor. According to the laws of thermodynamics, a calculation model of supercritical CO2 power cycle was established to analyze the feature, and the decisive parameters of the cycle and also investigate the effect of each parameter on the cycle efficiency in detail were obtained. The results show that supercritical CO2 power cycle can achieve quite satisfied efficiency at a lower cycle highest temperature than helium cycle, and CO2 is a promising working fluid. (authors)

  3. Neon turbo-Brayton cycle refrigerator for HTS power machines

    Science.gov (United States)

    Hirai, Hirokazu; Hirokawa, M.; Yoshida, Shigeru; Nara, N.; Ozaki, S.; Hayashi, H.; Okamoto, H.; Shiohara, Y.

    2012-06-01

    We developed a prototype turbo-Brayton refrigerator whose working fluid is neon gas. The refrigerator is designed for a HTS (High Temperature Superconducting) power transformer and its cooling power is more than 2 kW at 65 K. The refrigerator has a turboexpander and a turbo-compressor, which utilize magnetic bearings. These rotational machines have no rubbing parts and no oil-components. Those make a long maintenance interval of the refrigerator. The refrigerator is very compact because our newly developed turbo-compressor is volumetrically smaller than a displacement type compressor in same operating specification. Another feature of the refrigerator is a wide range operation capability for various heat-loads. Cooling power is controlled by the input-power of the turbo-compressor instead of the conventional method of using an electric heater. The rotational speed of the compressor motor is adjusted by an inverter. This system is expected to be more efficient. We show design details, specification and cooling test results of the new refrigerator in this paper.

  4. Supercritical carbon dioxide Brayton power conversion cycle for battery optimized reactor integral system

    International Nuclear Information System (INIS)

    Supercritical carbon dioxide (SCO2) promises a high power conversion efficiency of the recompression Brayton cycle due to its excellent compressibility reducing the compression work at the bottom of the cycle and to a higher density than helium or steam decreasing the component size. The SCO2 Brayton cycle efficiency as high as 45% furnishes small sized nuclear reactors with economical benefits on the plant construction and maintenance. A 23 MWth lead-cooled Battery Optimized Reactor Integral System (BORIS) is being developed as an ultra-long-life, versatile-purpose, fast-spectrum reactor. BORIS is coupled to the SCO2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO2 Brayton cycle of BORIS consists of a 16 MW turbine, a 32 MW high temperature recuperator, a 14 MW low temperature recuperator, an 11 MW precooler and 2 and 2.8 MW compressors. Entering six heat exchangers between primary and secondary system at 19.9 MPa and 663 K, the SCO2 leaves the heat exchangers at 19.9 MPa and 823 K. The promising secondary system efficiency of 45% was calculated by a theoretical method in which the main parameters include pressure, temperature, heater power, the turbine's, recuperators' and compressors' efficiencies, and the flow split ratio of SCO2 going out from the low temperature recuperator. Development of Modular Optimized Brayton Integral System (MOBIS) is being devised as the SCO2 Brayton cycle energy conversion cycle for BORIS. MOBIS consists of Loop Operating Brayton Optimization Study (LOBOS) for experimental Brayton cycle loop and Gas Advanced Turbine Operation Study (GATOS) for the SCO2 turbine. Liquid-metal Energy Exchanger Integral System (LEXIS) serves to couple BORIS and MOBIS. LEXIS comprises Physical Aspect Thermal Operation System (PATOS) for SCO2 thermal hydraulic characteristics, Shell-and-tube Overall Layout Optimization Study (SOLOS) for shell-and-tube heat exchanger, Printed-circuit Overall

  5. A review of test results on solar thermal power modules with dish-mounted Stirling and Brayton cycle engines

    Science.gov (United States)

    Jaffe, Leonard D.

    1988-01-01

    This paper presents results of development tests of various solar thermal parabolic dish modules and assemblies that used dish-mounted Brayton or Stirling cycle engines for production of electric power. These tests indicate that early modules achieve net efficiencies up to 29 percent in converting sunlight to electricity, as delivered to the grid. Various equipment deficiencies were observed and a number of malfunctions occurred. The performance measurements, as well as the malfunctions and other test experience, provided information that should be of value in developing systems with improved performance and reduced maintenance.

  6. Brayton cycle conversion and additional French investigations on space nuclear power systems

    International Nuclear Information System (INIS)

    The French studies on space nuclear power systems were relatively active the past six years. It was anticipated that 20-kWe should have to be supplied to a spacecraft as soon as in 2005 and a reference near term liquid metal-cooled reactor using available terrestrial technologies as much as possible was mainly investigated. A Brayton cycle heat conversion has been adopted from the beginning and it remains considered. Because first applications are delayed, more attractive concepts can be contemplated. The basic idea is to take advantage of the Brayton cycle specific properties and for instance to use them for the temperature conditioning of the moderator of a thermal spectrum reactor. At first, the utilization of ZrH was thought mandatory, but recent proposals have prompted to use the conventional, effective light water material for that purpose. A gas cycle high pressure (HP) derivation technique makes it possible to maintain water within an adequate temperature range. A Brayton cycle adaptation and an example of a gas-cooled, particle bed fuel elements, H2O moderated reactor are briefly described. Key comparison data are given. Such concepts should be attractive from fuel inventory, mass, radition shielding and control points of view

  7. Supercritical CO2 Brayton Cycle Energy Conversion System Coupled with SFR

    International Nuclear Information System (INIS)

    This report contains the description of the S-CO2 Brayton cycle coupled to KALIMER-600 as an alternative energy conversion system. For a system development, a computer code was developed to calculate heat balance of normal operation condition. Based on the computer code, the S-CO2 Brayton cycle energy conversion system was constructed for the KALIMER-600. Computer codes were developed to analysis for the S-CO2 turbomachinery. Based on the design codes, the design parameters were prepared to configure the KALIMER-600 S-CO2 turbomachinery models. A one-dimensional analysis computer code was developed to evaluate the performance of the previous PCHE heat exchangers and a design data for the typical type PCHE was produced. In parallel with the PCHE-type heat exchanger design, an airfoil shape fin PCHE heat exchanger was newly designed. The new design concept was evaluated by three-dimensional CFD analyses. Possible control schemes for power control in the KALIMER-600 S-CO2 Brayton cycle were investigated by using the MARS code. The MMS-LMR code was also developed to analyze the transient phenomena in a SFR with a supercritical CO2 Brayton cycle to develop the control logic. Simple power reduction and recovery event was selected and analyzed for the transient calculation. For the evaluation of Na-CO2 boundary failure event, a computer was developed to simulate the complex thermodynamic behaviors coupled with the chemical reaction between liquid sodium and CO2 gas. The long term behavior of a Na-CO2 boundary failure event and its consequences which lead to a system pressure transient were evaluated

  8. Preheating of fluid in a supercritical Brayton cycle power generation system at cold startup

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven A.; Fuller, Robert L.

    2016-07-12

    Various technologies pertaining to causing fluid in a supercritical Brayton cycle power generation system to flow in a desired direction at cold startup of the system are described herein. A sensor is positioned at an inlet of a turbine, wherein the sensor is configured to output sensed temperatures of fluid at the inlet of the turbine. If the sensed temperature surpasses a predefined threshold, at least one operating parameter of the power generation system is altered.

  9. Coupling a Supercritical Carbon Dioxide Brayton Cycle to a Helium-Cooled Reactor.

    Energy Technology Data Exchange (ETDEWEB)

    Middleton, Bobby [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pasch, James Jay [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Kruizenga, Alan Michael [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Walker, Matthew [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2016-01-01

    This report outlines the thermodynamics of a supercritical carbon dioxide (sCO2) recompression closed Brayton cycle (RCBC) coupled to a Helium-cooled nuclear reactor. The baseline reactor design for the study is the AREVA High Temperature Gas-Cooled Reactor (HTGR). Using the AREVA HTGR nominal operating parameters, an initial thermodynamic study was performed using Sandia's deterministic RCBC analysis program. Utilizing the output of the RCBC thermodynamic analysis, preliminary values of reactor power and of Helium flow rate through the reactor were calculated in Sandia's HelCO2 code. Some research regarding materials requirements was then conducted to determine aspects of corrosion related to both Helium and to sCO2 , as well as some mechanical considerations for pressures and temperatures that will be seen by the piping and other components. This analysis resulted in a list of materials-related research items that need to be conducted in the future. A short assessment of dry heat rejection advantages of sCO2> Brayton cycles was also included. This assessment lists some items that should be investigated in the future to better understand how sCO2 Brayton cycles and nuclear can maximally contribute to optimizing the water efficiency of carbon free power generation

  10. Brayton cycle conversion system and temperature conditioning of small space nuclear reactors

    International Nuclear Information System (INIS)

    A companion paper (Carre et al. 1989) presented at this symposium gives an overview of the French preliminary studies on space nuclear power systems in progress within the framework of a three-year (1986-1989) program. Other papers (Proust et al. 1988, Tilliette et al. 1988, Tilliette IECEC 1988) supplement the information on this activity. Low power levels of about 20-KWe and both liquid metal- and gas-cooled reactors are concerned. The Brayton cycle is currently selected as the conversion subsystem. Critical issues like safety, reliability, radiation shielding and reactor concept and technology have to be addressed more and more carefully and relevant temperature conditions are crucial. It is shown in this paper that the Brayton cycle can offer a valuable flexibility which allows the desired thermal environment. For instance, it is possible to significantly decrease the reactor inlet temperature and consequently, also given an adequate design, to favourably put forward convenient solutions for the lateral and axial bottom reflector, the shadow shield, the control drums drives and safety rods actuators and penetrations as well as for the possibility of using efficient moderator materials like metal hydrides (ZrH or 7LiH), which is worth being investigated as far as low power levels are concerned. Examples of Brayton cycle conversion subsystems and possible reactor arrangements are presented for both gas-cooled and liquid metal (NaK or Na)-cooled reactor heat sources. The study follows up the research described by Thilliette (1988, IECEC)

  11. The Brayton Cycle heat pump for solvent recovery and pollution control

    International Nuclear Information System (INIS)

    The Brayton Cycle heat pump technology for the recovery of solvent and prevention of emissions is relatively new. Like most new technologies, it is a combination of older concepts, ideas and types of processes put together in a unique way. As a result, proven equipment enables achievement of extremely low condensing temperatures at relatively low cost. The Brayton Cycle is a thermodynamic principle. It was used first for a turbine engine, but more recently it has been used for a variety of other kinds of processes including refrigeration. A great variety of methods are used for emission control including adsorption, direct condensation, absorption in a fluid, and incineration or destruction. The Brayton Cycle technology actually fits into two of these categories, adsorption and direct condensation. Since it is a refrigeration process, it can be used to condense solvents from a solvent-laden air stream. The advantage of this particular process over other refrigeration methods is that lower temperatures can be achieved more easily. In fact, temperatures as low as -150 degrees F have been used to recover solvents in this manner. That happens to be the freezing point of methylene chloride which is a very volatile compound. High recovery efficiencies can be obtained for a whole variety of organic materials. 8 figs., 1 tab

  12. Progress in investigating Brayton cycle conversion systems for future French Ariane 5 space power applications

    International Nuclear Information System (INIS)

    The present consideration of performance capabilities and system design requirements for a Brayton cycle conversion system usable by future Ariane 5 launch vehicle applications gives attention to such a power system's matching to available radiator concepts and dimensions, the use of direct or indirect waste heat transfer to the radiator and of simple or intercooled cycles, as well the consequences of gas cycle selection on reactor technology. The results presented are expected to be useful in the optimization of a 20-30 kW(e) system employing a liquid metal-cooled nuclear reactor in conjunction with a gas turbine energy conversion system. 10 references

  13. Analysis of a 115MW, 3 shaft, helium Brayton cycle

    International Nuclear Information System (INIS)

    This research theme is originated from a development project that is going on in South Africa, for the design and construction of a closed cycle gas turbine plant using gas-cooled reactor as the heat source to generate 115 MW of electricity. South African Power utility company, Eskorn, promotes this developmental work through its subsidiary called PBMR (Pebble Bed Modular Reactor). Some of the attractive features of this plant are the inherent and passive safety features, modular geometry, small evacuation area, small infrastructure requirements for the installation and running of the plant, small construction time, quick starting and stopping and also low operational cost. This exercise is looking at the operational aspects of a closed cycle gas turbine, the finding of which will have a direct input towards the successful development and commissioning of the plant. A thorough understanding of the fluid dynamics in this three-shaft system and its transient performance analysis were the two main objectives of this research work. A computer programme called GTSI, developed by a previous Cranfield University research student, has been used in this as a base programme for the performance analysis. Some modifications were done on this programme to improve its control abilities. The areas covered in the performance analysis are Start-up, Shutdown and Load ramping. A detailed literature survey has been conducted to learn from the helium Turbo machinery experiences, though it is very limited. A critical analysis on the design philosophy of the PBMR is also carried out as part of this research work. The performance analysis has shown the advantage, disadvantage and impact of various power modulation methods suggested for the PBMR. It has tracked the effect of the operations of the various valves included in the PBMR design. The start-up using a hot gas injection has been analysed in detail and a successful start region has been mapped. A start-up procedure is also written

  14. Nuclear reactor closed Brayton cycle power conversion system optimization trends for extra-terrestrial applications

    International Nuclear Information System (INIS)

    Extra-terrestrial exploration and development missions of the next century will require reliable, low-mass power generation modules of 100 kWe and more. These modules will be required to support both fixed-base and manned rover/explorer power needs. Low insolation levels at and beyond Mars and long periods of darkness on the moon make solar conversion less desirable for surface missions. For these missions, a closed Brayton cycle energy conversion system coupled with a reactor heat source is a very attractive approach. The authors conducted parametric studies to assess optimized system design trends for nuclear-Brayton systems as a function of operating environment and user requirements. The inherent design flexibility of the closed Brayton cycle energy conversion system permits ready adaptation of the system to future design constraints. This paper describes a dramatic contrast between system designs requiring man-rated shielding. The paper also considers the ramification of using indigenous materials to provide reactor shielding for a fixed-base power source

  15. Design Development Analyses in Support of a Heatpipe-Brayton Cycle Heat Exchanger

    Science.gov (United States)

    Steeve, Brian E.; Kapernick, Richard J.

    2004-01-01

    One of the power systems under consideration for nuclear electric propulsion or as a planetary surface power source is a heatpipe-cooled reactor coupled to a Brayton cycle. In this system, power is transferred from the heatpipes to the Brayton gas via a heat exchanger attached to the heatpipes. This paper discusses the fluid, thermal and structural analyses that were performed in support of the design of the heat exchanger to be tested in the SAFE-100 experimental program at the Marshall Space Flight Center: An important consideration throughout the design development of the heat exchanger w its capability to be utilized for higher power and temperature applications. This paper also discusses this aspect of the design and presents designs for specific applications that are under consideration.

  16. Finite-thermal reservoir effects on ecologically optimized closed regenerative Joule-Brayton power cycles

    Energy Technology Data Exchange (ETDEWEB)

    Khaliq, A. [Jamia Millia Islamia, New Delhi (India). Dept. of Mechanical Engineering

    2006-07-01

    A finite-time thermodynamic analysis based on a new kind of optimization criterion has been carried out for an endoreversible and regenerative Joule-Brayton power cycle coupled with variable temperature thermal reservoirs. The optimal performance and design parameters that maximize the ecological function are investigated. In this context, the optimal temperatures of the working fluid, the optimum power output, the optimum thermal efficiency, and the optimum second-law efficiency are determined in terms of technical parameters. Results are reported for the effect of regeneration, hot-cold temperature ratio, and the number of heat transfer units in hot and cold exchangers on the optimal performance parameters. The power and efficiency at maximum ecological function are found to be less than the maximum power and Curzon-Ahlborn efficiency. Power output increases significantly with increasing hot-cold side temperature ratio. However, it slightly increased as the number of heat transfer units in the regenerator increases. The optimization of ecological function leads to the improvement in exergetic efficiency and thermal efficiency, especially for low hot-cold side temperature ratios. Moreover, the thermal efficiency at maximum ecological function is less than the average of the finite time or maximum power efficiency and reversible Carnot efficiency. (author)

  17. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Nuclear Space Power Systems: A Feasibility Assessment

    Science.gov (United States)

    Barrett, Michael J.; Johnson, Paul K.

    2004-01-01

    The feasibility of using carbon-carbon recuperators in closed-Brayton-cycle (CBC) nuclear space power conversion systems (PCS) was assessed. Recuperator performance expectations were forecast based on projected thermodynamic cycle state values for a planetary mission. Resulting thermal performance, mass and volume for a plate-fin carbon-carbon recuperator were estimated and quantitatively compared with values for a conventional offset-strip-fin metallic design. Material compatibility issues regarding carbon-carbon surfaces exposed to the working fluid in the CBC PCS were also discussed.

  18. Restrictions on linear heat capacities from Joule-Brayton maximum-work cycle efficiency.

    Science.gov (United States)

    Angulo-Brown, F; Gonzalez-Ayala, Julian; Arias-Hernandez, L A

    2014-02-01

    This paper discusses the possibility of using the Joule-Brayton cycle to determine the accessible value range for the coefficients a and b of the heat capacity at constant pressure C(p), expressed as C(p) = a + bT (with T the absolute temperature) by using the Carnot theorem. This is made for several gases which operate as the working fluids. Moreover, the landmark role of the Curzon-Ahlborn efficiency for this type of cycle is established. PMID:25353449

  19. Supercritical Carbon Dioxide Brayton Power Conversion Cycle Design for Optimized Battery-Type Integral Reactor System

    International Nuclear Information System (INIS)

    Supercritical carbon dioxide (SCO2) promises a high power conversion efficiency of the recompression Brayton cycle due to its excellent compressibility reducing the compression work at the bottom of the cycle and to a higher density than helium or steam decreasing the component size. Therefore, the high SCO2 Brayton cycle efficiency as high as 45 % furnishes small sized nuclear reactors with economical benefits on the plant construction and maintenance. A 23 MWth BORIS (Battery Optimized Reactor Integral System) is being developed as a multipurpose reactor. BORIS, an integral-type optimized fast reactor with an ultra long life core, is coupled to the SCO2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO2 Brayton cycle of BORIS consists of a 16 MW turbine, a 32 MW high temperature recuperator, a 14 MW low temperature recuperator, an 11 MW pre-cooler and 2 and 2.8 MW compressors. Entering six heat exchangers between primary and secondary system at 19.9 MPa and 663 K, the SCO2 leaves the heat exchangers at 19.9 MPa and 823 K. The promising secondary system efficiency of 45 % was calculated by a theoretical method in which the main parameters include pressure, temperature, heater power, the turbine's, recuperators' and compressors' efficiencies, and the flow split ratio of SCO2 going out from the low temperature recuperator. Test loop SOLOS (Shell-and-tube Overall Layout Optimization Study) is utilized to develop advanced techniques needed to adopt the shell-and-tube type heat exchanger in the secondary loop of BORIS by studying the SCO2 behavior from both thermal and hydrodynamic points of view. Concurrently, a computational fluid dynamics (CFD) code analysis is being conducted to develop an optimal analytical method of the SCO2 turbine efficiency having the parameters of flow characteristics of SCO2 passing through buckets of the turbine. These simultaneous experimental and analytical methods for designing

  20. Thermal analysis on N2 and S-CO2 Brayton cycle for the energy conversion system of small scale ultra-long cycle fast reactor

    International Nuclear Information System (INIS)

    An ultra-long cycle fast reactor (UCFR) is one of the SFR designs operating in a long cycle without refueling. The operational mechanism of long cycle fast reactor is once-through fuel cycle through breed and burn system. The benefits of long cycle fast reactor include capital/operation cost reductions, low proliferation risk, and the interim storage of light water reactor (LWR) spent fuel. For the power conversion system of next generation nuclear reactor, Brayton cycle has been mainly considered. Brayton cycle not only increases overall thermal efficiency in corresponding temperature range of GenIV reactors, but also solves sodium-water reaction issues. As a working fluid in Brayton cycle, many inactive gases are selected. For the power conversion system of next generation nuclear reactor, Brayton cycle has been mainly considered. Among the candidates for working fluid in Brayton power cycle, S-CO2 and N2 are analyzed in thermal aspect. For the major parameters including maximum system pressure, isentropic efficiencies of compressor and turbine, and pinch point, S-CO2 cycle shows the highest thermal performance. However, N2 cycle without intermediate loop gives comparable thermal performance, if high pressure around 70 bar and high isentropic efficiency of each component are maintained

  1. Investigation of alternative layouts for the supercritical carbon dioxide Brayton cycle for a sodium-cooled fast reactor

    International Nuclear Information System (INIS)

    Analyses of supercritical carbon dioxide (S-CO2) Brayton cycle performance have largely settled on the recompression supercritical cycle (or Feher cycle) incorporating a flow split between the main compressor downstream of heat rejection, a recompressing compressor providing direct compression without heat rejection, and high and low temperature recuperators to raise the effectiveness of recuperation and the cycle efficiency. Alternative cycle layouts have been previously examined by Angelino (Politecnico, Milan), by MIT (Dostal, Hejzlar, and Driscoll), and possibly others but not for sodium-cooled fast reactors (SFRs) operating at relatively low core outlet temperature. Thus, the present authors could not be sure that the recompression cycle is an optimal arrangement for application to the SFR. To ensure that an advantageous alternative layout has not been overlooked, several alternative cycle layouts have been investigated for a S-CO2 Brayton cycle coupled to the Advanced Burner Test Reactor (ABTR) SFR preconceptual design having a 510 deg. C core outlet temperature and a 470 deg. C turbine inlet temperature to determine if they provide any benefit in cycle performance (e.g., enhanced cycle efficiency). No such benefits were identified, consistent with the previous examinations, such that attention was devoted to optimizing the recompression supercritical cycle. The effects of optimizing the cycle minimum temperature and pressure are investigated including minimum temperatures and/or pressures below the critical values. It is found that improvements in the cycle efficiency of 1% or greater relative to previous analyses which arbitrarily fixed the minimum temperature and pressure can be realized through an optimal choice of the combination of the minimum cycle temperature and pressure (e.g., for a fixed minimum temperature there is an optimal minimum pressure). However, this leads to a requirement for a larger cooler for heat rejection which may impact the

  2. Supercritical CO2 Brayton power cycles for DEMO fusion reactor based on Helium Cooled Lithium Lead blanket

    International Nuclear Information System (INIS)

    Fusion energy is one of the most promising solutions to the world energy supply. This paper presents an exploratory analysis of the suitability of supercritical CO2 Brayton power cycles (S-CO2) for low-temperature divertor fusion reactors cooled by helium (as defined by EFDA). Integration of three thermal sources (i.e., blanket, divertor and vacuum vessel) has been studied through proposing and analyzing a number of alternative layouts, achieving an improvement on power production higher than 5% over the baseline case, which entails to a gross efficiency (before self-consumptions) higher than 42%. In spite of this achievement, the assessment of power consumption for the circulating heat transfer fluids results in a penalty of 20% in the electricity production. Once the most suitable layout has been selected an optimization process has been conducted to adjust the key parameters to balance performance and size, achieving an electrical efficiency (electricity without taking into account auxiliary consumptions due to operation of the fusion reactor) higher than 33% and a reduction in overall size of heat exchangers of 1/3. Some relevant conclusions can be drawn from the present work: the potential of S-CO2 cycles as suitable converters of thermal energy to power in fusion reactors; the significance of a suitable integration of thermal sources to maximize power output; the high penalty of pumping power; and the convenience of identifying the key components of the layout as a way to optimize the whole cycle performance. - Highlights: • Supercritical CO2 Brayton cycles have been proposed for BoP of HCLL fusion reactor. • Low temperature sources have been successfully integrated with high temperature ones. • Optimization of thermal sources integration improves 5% the electricity production. • Assessment of pumping power with sources and sink loops results on 20% of gross power. • Matching of key parameters has conducted to 1/3 of reduction in heat exchangers

  3. A four-year investigation of Brayton cycle systems for future French space power applications

    International Nuclear Information System (INIS)

    Within the framework of a joint program initiated in 1983 by the two French Government Agencies C.N.E.S. (Centre National d'Etudes Spatiales) and C.E.A. (Commissariat a l'Energie Atomique), in order to study space nuclear power systems for future ARIANE 5 applications, extensive investigations have dealt with the Brayton cycle, which has been selected as the energy conversion system. Several aspects can be mentioned in this field: matching of the power system to the available radiator dimensions up to 200 kWe, direct or indirect waste heat transfer to the radiator, the use of a recuperator, recent work on moderate (25 kWe) power levels, simulation studies related to various operating conditions, and general system optimization. A limited experimental program is starting on some crucial technology areas including a first contract to the Industry concerning the turbogenerator. Particular attention is being paid to the significance of the adoption of a Brayton cycle for space applications involving a nuclear heat source, which can be either a liquid-metal-cooled or a gas-cooled reactor. For a gas-cooled reactor, direct-cycle system, the relevance to the reactor technology and the concept for moderator thermal conditioning is particularly addressed

  4. Closed Brayton Cycle Power Conversion Unit for Fission Surface Power Phase I Final Report

    Science.gov (United States)

    Fuller, Robert L.

    2010-01-01

    A Closed Brayton cycle power conversion system has been developed to support the NASA fission surface power program. The goal is to provide electricity from a small nuclear reactor heat source for surface power production for lunar and Mars environments. The selected media for a heat source is NaK 78 with water as a cooling source. The closed Brayton cycle power was selected to be 12 kWe output from the generator terminals. A heat source NaK temperature of 850 K plus or minus 25 K was selected. The cold source water was selected at 375 K plus or minus 25 K. A vacuum radiation environment of 200 K is specified for environmental operation. The major components of the system are the power converter, the power controller, and the top level data acquisition and control unit. The power converter with associated sensors resides in the vacuum radiation environment. The power controller and data acquisition system reside in an ambient laboratory environment. Signals and power are supplied across the pressure boundary electrically with hermetic connectors installed on the vacuum vessel. System level analyses were performed on working fluids, cycle design parameters, heater and cooling temperatures, and heat exchanger options that best meet the needs of the power converter specification. The goal is to provide a cost effective system that has high thermal-to-electric efficiency in a compact, lightweight package.

  5. Scaling considerations for a multi-megawatt class supercritical CO2 brayton cycle and commercialization.

    Energy Technology Data Exchange (ETDEWEB)

    Fleming, Darryn D.; Holschuh, Thomas Vernon,; Conboy, Thomas M.; Pasch, James Jay; Wright, Steven Alan; Rochau, Gary Eugene; Fuller, Robert Lynn [Barber-Nichols, Inc., Arvada, CO

    2013-11-01

    Small-scale supercritical CO2 demonstration loops are successful at identifying the important technical issues that one must face in order to scale up to larger power levels. The Sandia National Laboratories supercritical CO2 Brayton cycle test loops are identifying technical needs to scale the technology to commercial power levels such as 10 MWe. The small size of the Sandia 1 MWth loop has demonstration of the split flow loop efficiency and effectiveness of the Printed Circuit Heat Exchangers (PCHXs) leading to the design of a fully recuperated, split flow, supercritical CO2 Brayton cycle demonstration system. However, there were many problems that were encountered, such as high rotational speeds in the units. Additionally, the turbomachinery in the test loops need to identify issues concerning the bearings, seals, thermal boundaries, and motor controller problems in order to be proved a reliable power source in the 300 kWe range. Although these issues were anticipated in smaller demonstration units, commercially scaled hardware would eliminate these problems caused by high rotational speeds at small scale. The economic viability and development of the future scalable 10 MWe solely depends on the interest of DOE and private industry. The Intellectual Property collected by Sandia proves that the ~10 MWe supercritical CO2 power conversion loop to be very beneficial when coupled to a 20 MWth heat source (either solar, geothermal, fossil, or nuclear). This paper will identify a commercialization plan, as well as, a roadmap from the simple 1 MWth supercritical CO2 development loop to a power producing 10 MWe supercritical CO2 Brayton loop.

  6. Modeling the small-scale dish-mounted solar thermal Brayton cycle

    Science.gov (United States)

    Le Roux, Willem G.; Meyer, Josua P.

    2016-05-01

    The small-scale dish-mounted solar thermal Brayton cycle (STBC) makes use of a sun-tracking dish reflector, solar receiver, recuperator and micro-turbine to generate power in the range of 1-20 kW. The modeling of such a system, using a turbocharger as micro-turbine, is required so that optimisation and further development of an experimental setup can be done. As a validation, an analytical model of the small-scale STBC in Matlab, where the net power output is determined from an exergy analysis, is compared with Flownex, an integrated systems CFD code. A 4.8 m diameter parabolic dish with open-cavity tubular receiver and plate-type counterflow recuperator is considered, based on previous work. A dish optical error of 10 mrad, a tracking error of 1° and a receiver aperture area of 0.25 m × 0.25 m are considered. Since the recuperator operates at a very high average temperature, the recuperator is modeled using an updated ɛ-NTU method which takes heat loss to the environment into consideration. Compressor and turbine maps from standard off-the-shelf Garrett turbochargers are used. The results show that for the calculation of the steady-state temperatures and pressures, there is good comparison between the Matlab and Flownex results (within 8%) except for the recuperator outlet temperature, which is due to the use of different ɛ-NTU methods. With the use of Matlab and Flownex, it is shown that the small-scale open STBC with an existing off-the-shelf turbocharger could generate a positive net power output with solar-to-mechanical efficiency of up to 12%, with much room for improvement.

  7. Preliminary market analysis for Brayton cycle heat recovery system characterization program. Subtask 5. 2 of phase I program plan

    Energy Technology Data Exchange (ETDEWEB)

    1980-08-31

    The purpose of the task is to determine the market potential of the Brayton-cycle Subatmospheric System (SAS), especially as applied to the glass processing industry. Areas which impact the sales of the Brayton-cycle systems examined are: market size; opportunities for waste heat system installation (furnace rebuild and repair); pollution control on glass furnaces; equipment costs; equipment performance; and market growth potential. Supporting data were compiled for the glass industry inventory and are presented in Appendix A. Emission control techniques in the glass industry are discussed in Appendix B. (MCW)

  8. Exergetic efficiency optimization for an irreversible heat pump working on reversed Brayton cycle

    Indian Academy of Sciences (India)

    Yuehong Bi; Lingen Chen; Fengrui Sun

    2010-03-01

    This paper deals with the performance analysis and optimization for irreversible heat pumps working on reversed Brayton cycle with constant-temperature heat reservoirs by taking exergetic efficiency as the optimization objective combining exergy concept with finite-time thermodynamics (FTT). Exergetic efficiency is defined as the ratio of rate of exergy output to rate of exergy input of the system. The irreversibilities considered in the system include heat resistance losses in the hot- and cold-side heat exchangers and non-isentropic losses in the compression and expansion processes. The analytical formulas of the heating load, coefficient of performance (COP) and exergetic efficiency for the heat pumps are derived. The results are compared with those obtained for the traditional heating load and coefficient of performance objectives. The influences of the pressure ratio of the compressor, the allocation of heat exchanger inventory, the temperature ratio of two reservoirs, the effectiveness of the hot- and cold-side heat exchangers and regenerator, the efficiencies of the compressor and expander, the ratio of hot-side heat reservoir temperature to ambient temperature, the total heat exchanger inventory, and the heat capacity rate of the working fluid on the exergetic efficiency of the heat pumps are analysed by numerical calculations. The results show that the exergetic efficiency optimization is an important and effective criterion for the evaluation of an irreversible heat pump working on reversed Brayton cycle.

  9. Conceptual Design of S-CO2 Brayton Cycle Radial Turbomachinery for KAIST Micro Modular Reactor

    International Nuclear Information System (INIS)

    KAIST proposed a new SMR design, which utilizes S-CO2 as the working fluid. It was named as KAIST MMR. Compared with existing SMR concepts, KAIST MMR has advantages of achieving smaller volume of power conversion unit (PCU) and containing the core and PCU in one vessel for the complete modularization. Authors noticed that the compressor and turbine assumed performances of KAIST MMR were conservatively selected previously. Thus, this paper tries to address the best estimate values of each turbomachinery in 10MWe class KAIST MMR. The turbomachinery size of the S-CO2 cycle is smaller than helium Brayton cycle and steam Rankine cycle. The suggested SMR concept adopts passive cooling system by using air. This method can cool reactor without external electricity supply. Small size and more flexible installation in the inland area will be necessary characteristics for the future nuclear application in the water limited region. KAIST MMR meets all these requirements by utilizing S-CO2 as a working fluid. This paper presents the work for further increasing the system performance by estimating the component efficiency more realistically. The cycle layout adopted for the application is S-CO2 recuperated Brayton cycle. The best efficiency of compressor and turbine was evaluated to be 84.94% and 90.94%, respectively. By using KAIST in-house code, thermal efficiency and net output were increased to 35.81% and 12.45MWe, respectively, for the same core thermal power. More refined cycle layout and suitable turbomachinery design will be performed in the near future

  10. Carbon-Carbon Recuperators in Closed-Brayton-Cycle Space Power Systems

    Science.gov (United States)

    Barrett, Michael J.; Johnson, Paul K.; Naples, Andrew G.

    2006-01-01

    The feasibility of using carbon-carbon (C-C) recuperators in conceptual closed-Brayton-cycle space power conversion systems was assessed. Recuperator performance expectations were forecast based on notional thermodynamic cycle state values for potential planetary missions. Resulting thermal performance, mass and volume for plate-fin C-C recuperators were estimated and quantitatively compared with values for conventional offset-strip-fin metallic designs. Mass savings of 30 to 60 percent were projected for C-C recuperators with effectiveness greater than 0.9 and thermal loads from 25 to 1400 kWt. The smaller thermal loads corresponded with lower mass savings; however, 60 percent savings were forecast for all loads above 300 kWt. System-related material challenges and compatibility issues were also discussed.

  11. Brayton cycle conversion and additional French investigations on space nuclear power systems

    International Nuclear Information System (INIS)

    French activities in the field of space nuclear power systems have proceeded in anticipation that spacecraft would require such systems for the provision of 20 kW(e) by the year 2005. A liquid metal-cooled reactor patterned on well tested terrestrial technologies has been investigated which employs a Brayton-cycle heat-conversion system in such a way as to allow temperature conditioning of the moderator for a thermal-spectrum reactor. A high pressure gas cycle derivation technique makes it possible to maintain water within the requisite temperature range. The concept thus evolved is attractive in light of fuel inventory, mass, radiation shielding, and control points considerations. 7 refs

  12. Creep Property Characterization of Potential Brayton Cycle Impeller and Duct Materials

    Science.gov (United States)

    Gabb, Timothy P.; Gayda, John; Garg, Anita

    2007-01-01

    Cast superalloys have potential applications in space as impellers within closed-loop Brayton cycle nuclear power generation systems. Likewise wrought superalloys are good candidates for ducts and heat exchangers transporting the inert working gas in a Brayton-based power plant. Two cast superalloys, Mar-M247LC and IN792, and a NASA GRC powder metallurgy superalloy, LSHR, have been screened to compare their respective capabilities for impeller applications. Mar-M247LC has been selected for additional long term evaluations. Initial tests in helium indicate this inert environment may debit long term creep resistance of this alloy. Several wrought superalloys including Hastelloy® X, Inconel® 617, Inconel® 740, Nimonic® 263, Incoloy® MA956, and Haynes 230 are also being screened to compare their capabilities for duct applications. Haynes 230 has been selected for additional long term evaluations. Initial tests in helium are just underway for this alloy. These proposed applications would require sufficient strength and creep resistance for long term service at temperatures up to 1200 K, with service times to 100,000 h or more. Therefore, long term microstructural stability is also being screened.

  13. Creep Property Characterization of Potential Brayton Cycle Impeller and Duct Materials

    Science.gov (United States)

    Gabb, Timothy P.; Gayda, john; Garg, Anita

    2007-01-01

    Cast superalloys have potential applications in space as impellers within closed-loop Brayton cycle nuclear power generation systems. Likewise wrought superalloys are good candidates for ducts and heat exchangers transporting the inert working gas in a Brayton-based power plant. Two cast superalloys, Mar-M247LC and IN792, and a NASA GRC powder metallurgy superalloy, LSHR, have been screened to compare their respective capabilities for impeller applications. Mar-M247LC has been selected for additional long term evaluations. Initial tests in helium indicate this inert environment may debit long term creep resistance of this alloy. Several wrought superalloys including Hastelloy(Registered TradeMark) X, Inconel(Registered TradeMark) 617, Inconel(Registered TradeMark) 740, Nimonic(Registered TradeMark) 263, Incoloy(Registered TradeMark) MA956, and Haynes 230 are also being screened to compare their capabilities for duct applications. Haynes 230 has been selected for additional long term evaluations. Initial tests in helium are just underway for this alloy. These proposed applications would require sufficient strength and creep resistance for long term service at temperatures up to 1200 K, with service times to 100,000 h or more. Therefore, long term microstructural stability is also being screened.

  14. Tensile and Creep Property Characterization of Potential Brayton Cycle Impeller and Duct Materials

    Science.gov (United States)

    Gabb, Timothy P.; Gayda, John

    2006-01-01

    This paper represents a status report documenting the work on creep of superalloys performed under Project Prometheus. Cast superalloys have potential applications in space as impellers within closed-loop Brayton cycle nuclear power generation systems. Likewise wrought superalloys are good candidates for ducts and heat exchangers transporting the inert working gas in a Brayton-based power plant. Two cast superalloys, Mar-M247LC and IN792, and a NASA GRC powder metallurgy superalloy, LSHR, are being screened to compare their respective capabilities for impeller applications. Several wrought superalloys including Hastelloy X, (Haynes International, Inc., Kokomo, IN), Inconel 617, Inconel 740, Nimonic 263, and Incoloy MA956 (Special Metals Corporation, Huntington, WV) are also being screened to compare their capabilities for duct applications. These proposed applications would require sufficient strength and creep resistance for long term service at temperatures up to 1200 K, with service times to 100,000 h or more. Conventional tensile and creep tests were performed at temperatures up to 1200 K on specimens extracted from the materials. Initial microstructure evaluations were also undertaken.

  15. Thermal hydraulic feasibility of supercritical carbon dioxide Brayton cycle power conversion for the KALIMER-150 sodium-cooled fast reactor

    International Nuclear Information System (INIS)

    One possible approach to achieving a significant reduction in the overnight and operating costs of a sodium-cooled fast reactor is to replace the traditional Rankine steam cycle with an advanced power converter that consists of a gas turbine Brayton cycle that utilizes supercritical carbon dioxide (S-CO2) as the working fluid. A joint project between Argonne National Laboratory and the Korea Atomic Energy Research Institute has been initiated to investigate the thermal-hydraulic feasibility of coupling the S-CO2 Brayton cycle to the KALIMAR-150 sodium-cooled fast reactor conceptual design. As an initial step in investigating the system aspects of coupling the reactor to the S-CO2 Brayton cycle, the case is investigated in which the intermediate heat transfer loop is eliminated in order to achieve additional cost reductions. The main objectives are to determine the potential gain in plant efficiency and to estimate the size of the key Brayton cycle components. A S-CO2 Brayton cycle efficiency of 43.2% is calculated. Accounting for primary pump power and other in-house loads, a net plant efficiency of 40.8% is obtained, compared to 38.2% for the current (Rankine cycle) plant. If higher Na temperatures could be accommodated, then a 1% gain in plant efficiency could be obtained for each 20degC incremental increase in sodium core outlet temperature. Further investigation of the thermal sizing of the Na/S-Co2 heat exchanger is also carried out; parametric sensitivity studies are performed for the case in which the intermediate heat transport system is retained as well as the case in which it is eliminated. (author)

  16. Dynamic response simulation for high temperature gas-cooled reactor with indirect closed Brayton cycle

    International Nuclear Information System (INIS)

    A transient simulation program is developed in order to study dynamic characteristics of high temperature gas-cooled reactor with indirect closed Brayton cycle. After the brief introduction to such a plant, detailed mathematical models for important installations are described in the paper. By inducing step positive reactivity into the reactor, it looks like that the powers of turbo machine installations have a different growth rate accompanied with small increase of reactor power. Furthermore, this paper shows the temperature changes of reactor and heat exchangers. For the heat exchangers of the whole secondary loop, the pressure changes behave quite differently for those three sections divided by turbine, low pressure compressor and high pressure compressor. For all these equipments, the simulation program gives reasonable results and is in accordance with dynamic characteristics of their own. (authors)

  17. Heat exchanger optimization of a closed Brayton cycle for nuclear space propulsion

    Energy Technology Data Exchange (ETDEWEB)

    Ribeiro, Guilherme B.; Guimaraes, Lamartine N.F.; Braz Filho, Francisco A., E-mail: gbribeiro@ieav.cta.br, E-mail: guimarae@ieav.cta.br, E-mail: braz@ieav.cta.br [Instituto de Estudos Avancados (IEAV), Sao Jose dos Campos, SP (Brazil). Divisao de Energia Nuclear

    2015-07-01

    Nuclear power systems turned to space electric propulsion differs strongly from usual ground-based power systems regarding the importance of overall size and weight. For propulsion power systems, weight and efficiency are essential drivers that should be managed during conception phase. Considering that, this paper aims the development of a thermal model of a closed Brayton cycle that applies the thermal conductance of heat exchangers in order to predict the energy conversion performance. The centrifugal-flow turbine and compressor characterization were achieved using algebraic equations from literature data. The binary mixture of He-Xe with molecular weight of 40 g/mole is applied and the impact of heat exchanger optimization in thermodynamic irreversibilities is evaluated in this paper. (author)

  18. Heat exchanger optimization of a closed Brayton cycle for nuclear space propulsion

    International Nuclear Information System (INIS)

    Nuclear power systems turned to space electric propulsion differs strongly from usual ground-based power systems regarding the importance of overall size and weight. For propulsion power systems, weight and efficiency are essential drivers that should be managed during conception phase. Considering that, this paper aims the development of a thermal model of a closed Brayton cycle that applies the thermal conductance of heat exchangers in order to predict the energy conversion performance. The centrifugal-flow turbine and compressor characterization were achieved using algebraic equations from literature data. The binary mixture of He-Xe with molecular weight of 40 g/mole is applied and the impact of heat exchanger optimization in thermodynamic irreversibilities is evaluated in this paper. (author)

  19. Thermodynamic analysis of a Brayton cycle and Rankine cycle arranged in series exploiting the cold exergy of LNG (liquefied natural gas)

    International Nuclear Information System (INIS)

    The LNG (liquefied natural gas) regasification process is a source of cold exergy capable of being exploited to improve the efficiency of energy conversion. This paper presents a novel power plant consisting of a combination of a CBC (closed Brayton cycle) with a SRC (steam Rankine cycle), arranged in series with regard to the power source, while exploiting the cold exergy available in the regasification process of LNG. The power plant is fuelled by a combustion system of natural gas where the flue gases firstly yield heat to the CBC, then to the SRC and finally to the combustion air by means of a heat recovery process. The LNG cold exergy is exploited to cool the He used in the CBC to cryogenic temperatures at the compressor inlet as well as for generating electric power through direct expansion. The power plant is thermodynamically modelled and simulated using EES (Engineering Equation Solver). An energy and exergy analysis is carried out to evaluate the effect of some key parameters on the efficiency such as the temperature at the compressor inlet, the compression ratio, the temperature at the CBC turbine inlet and the LNG pressure during the regasification process. The outcome is a high efficiency power plant. - Highlights: • A closed Brayton cycle and a steam Rankine cycle arranged in series. • Exploitation of LNG cold exergy to increase power plant efficiency. • Thermodynamic analysis to evaluate the effect of the key parameters on the efficiency. • Energy and exergy efficiency of the power plant is respectively 56.72% and 55.09%. • The exergy available in the LNG represents 20.34% of the fuel exergy

  20. Enhanced arrangement for recuperators in supercritical CO2 Brayton power cycle for energy conversion in fusion reactors

    International Nuclear Information System (INIS)

    Highlights: •We propose an enhanced power conversion system layout for a Model C fusion reactor. •Proposed layout is based on a modified recompression supercritical CO2 Brayton cycle. •New arrangement in recuperators regards to classical cycle is used. •High efficiency is achieved, comparable with the best obtained in complex solutions. -- Abstract: A domestic research program called TECNOFUS was launched in Spain in 2009 to support technological developments related to a dual coolant breeding blanket concept for fusion reactors. This concept of blanket uses Helium (300 °C/400 °C) to cool part of it and a liquid metal (480 °C/700 °C) to cool the rest; it also includes high temperature (700 °C/800 °C) and medium temperature (566 °C/700 °C) Helium cooling circuits for divertor. This paper proposes a new layout of the classical recompression supercritical CO2 Brayton cycle which replaces one of the recuperators (the one with the highest temperature) by another which by-passes the low temperature blanket source. This arrangement allows reaching high turbine inlet temperatures (around 600 °C) with medium pressures (around 225 bar) and achieving high cycle efficiencies (close to 46.5%). So, the proposed cycle reveals as a promising design because it integrates all the available thermal sources in a compact layout achieving high efficiencies with the usual parameters prescribed in classical recompression supercritical CO2 Brayton cycles

  1. Use of Multiple Reheat Helium Brayton Cycles to Eliminate the Intermediate Heat Transfer Loop for Advanced Loop Type SFRs

    Energy Technology Data Exchange (ETDEWEB)

    Haihua Zhao; Hongbin Zhang; Samuel E. Bays

    2009-05-01

    The sodium intermediate heat transfer loop is used in existing sodium cooled fast reactor (SFR) plant design as a necessary safety measure to separate the radioactive primary loop sodium from the water of the steam Rankine power cycle. However, the intermediate heat transfer loop significantly increases the SFR plant cost and decreases the plant reliability due to the relatively high possibility of sodium leakage. A previous study shows that helium Brayton cycles with multiple reheat and intercooling for SFRs with reactor outlet temperature in the range of 510°C to 650°C can achieve thermal efficiencies comparable to or higher than steam cycles or recently proposed supercritical CO2 cycles. Use of inert helium as the power conversion working fluid provides major advantages over steam or CO2 by removing the requirement for safety systems to prevent and mitigate the sodium-water or sodium-CO2 reactions. A helium Brayton cycle power conversion system therefore makes the elimination of the intermediate heat transfer loop possible. This paper presents a pre-conceptual design of multiple reheat helium Brayton cycle for an advanced loop type SFR. This design widely refers the new horizontal shaft distributed PBMR helium power conversion design features. For a loop type SFR with reactor outlet temperature 550°C, the design achieves 42.4% thermal efficiency with favorable power density comparing with high temperature gas cooled reactors.

  2. Innovative biomass to power conversion systems based on cascaded supercritical CO2 Brayton cycles

    International Nuclear Information System (INIS)

    In the small to medium power range the main technologies for the conversion of biomass sources into electricity are based either on reciprocating internal combustion or organic Rankine cycle engines. Relatively low energy conversion efficiencies are obtained in both systems due to the thermodynamic losses in the conversion of biomass into syngas in the former, and to the high temperature difference in the heat transfer between combustion gases and working fluid in the latter. The aim of this paper is to demonstrate that higher efficiencies in the conversion of biomass sources into electricity can be obtained using systems based on the supercritical closed CO2 Brayton cycles (s-CO2). The s-CO2 system analysed here includes two cascaded supercritical CO2 cycles which enable to overcome the intrinsic limitation of the single cycle in the effective utilization of the whole heat available from flue gases. Both part-flow and simple supercritical CO2 cycle configurations are considered and four boiler arrangements are investigated to explore the thermodynamic performance of such systems. These power plant configurations, which were never explored in the literature for biomass conversion into electricity, are demonstrated here to be viable options to increase the energy conversion efficiency of small-to-medium biomass fired power plants. Results of the optimization procedure show that a maximum biomass to electricity conversion efficiency of 36% can be achieved using the cascaded configuration including a part flow topping cycle, which is approximately 10%-points higher than that of the existing biomass power plants in the small to medium power range. - Highlights: • Supercritical CO2 cycles are proposed for biomass to electricity conversion. • Four boiler design options are considered. • High total system efficiency is due to the part-flow cascaded configuration. • The efficiency is higher than that of other small/medium size alternative systems

  3. Acacia: A small scale power plant with pebble bed cartridge reactor and indirect Brayton cycle

    International Nuclear Information System (INIS)

    For markets other than large-scale electricity production a 60 MWth, 23 MWe (max.) nuclear plant design with an indirect Brayton cycle is proposed for application on the short to medium term. The reactor will be cooled by helium, whereas for the secondary cycle nitrogen is proposed as a heat carrier. In this way, a conventional air based gas turbine can be applied, while at the same time excluding the scenario of air ingress in the reactor core through a heat exchanger leak. Two variations of cycle design will be discussed: co-generation and maximized electricity production. The cogeneration mode will be elaborated for the application of seawater desalination. The reactor core geometry is annular with a central graphite reflector region, creating an optimal location for burnable poison. Optimization calculations on burnable poison distribution show that burnup of fuel and poison are balancing each other into a fairly constant reactivity behaviour during the entire core lifetime. Also, the two most important safety transient scenarios for pebble bed reactors, Pressurised and Depressurised Loss Of Forced Cooling, will be discussed. It will be shown that the maximum fuel temperatures will stay below the level where fuel damage starts for any point in time. (author)

  4. Application of exergetic sustainability index to a nano-scale irreversible Brayton cycle operating with ideal Bose and Fermi gasses

    International Nuclear Information System (INIS)

    Highlights: • An irreversible Brayton cycle operating quantum gasses is considered. • Exergetic sustainability index is derived for nano-scale cycles. • Nano-scale effects are considered. • Calculation are conducted for irreversible cycles. • Numerical results are presented and discussed. - Abstract: In this study, a nano-scale irreversible Brayton cycle operating with quantum gasses including Bose and Fermi gasses is researched. Developments in the nano-technology cause searching the nano-scale machines including thermal systems to be unavoidable. Thermodynamic analysis of a nano-scale irreversible Brayton cycle operating with Bose and Fermi gasses was performed (especially using exergetic sustainability index). In addition, thermodynamic analysis involving classical evaluation parameters such as work output, exergy output, entropy generation, energy and exergy efficiencies were conducted. Results are submitted numerically and finally some useful recommendations were conducted. Some important results are: entropy generation and exergetic sustainability index are affected mostly for Bose gas and power output and exergy output are affected mostly for the Fermi gas by x. At the high temperature conditions, work output and entropy generation have high values comparing with other degeneracy conditions

  5. Application of exergetic sustainability index to a nano-scale irreversible Brayton cycle operating with ideal Bose and Fermi gasses

    Energy Technology Data Exchange (ETDEWEB)

    Açıkkalp, Emin, E-mail: eacikkalp@gmail.com [Department of Mechanical and Manufacturing Engineering, Engineering Faculty, Bilecik S.E. University, Bilecik (Turkey); Caner, Necmettin [Department of Chemistry, Faculty of Arts and Sciences, Eskisehir Osmangazi University, Eskisehir (Turkey)

    2015-09-25

    Highlights: • An irreversible Brayton cycle operating quantum gasses is considered. • Exergetic sustainability index is derived for nano-scale cycles. • Nano-scale effects are considered. • Calculation are conducted for irreversible cycles. • Numerical results are presented and discussed. - Abstract: In this study, a nano-scale irreversible Brayton cycle operating with quantum gasses including Bose and Fermi gasses is researched. Developments in the nano-technology cause searching the nano-scale machines including thermal systems to be unavoidable. Thermodynamic analysis of a nano-scale irreversible Brayton cycle operating with Bose and Fermi gasses was performed (especially using exergetic sustainability index). In addition, thermodynamic analysis involving classical evaluation parameters such as work output, exergy output, entropy generation, energy and exergy efficiencies were conducted. Results are submitted numerically and finally some useful recommendations were conducted. Some important results are: entropy generation and exergetic sustainability index are affected mostly for Bose gas and power output and exergy output are affected mostly for the Fermi gas by x. At the high temperature conditions, work output and entropy generation have high values comparing with other degeneracy conditions.

  6. Nuclear Air-Brayton Combined Cycle Power Conversion Design, Physical Performance Estimation and Economic Assessment

    Science.gov (United States)

    Andreades, Charalampos

    The combination of an increased demand for electricity for economic development in parallel with the widespread push for adoption of renewable energy sources and the trend toward liberalized markets has placed a tremendous amount of stress on generators, system operators, and consumers. Non-guaranteed cost recovery, intermittent capacity, and highly volatile market prices are all part of new electricity grids. In order to try and remediate some of these effects, this dissertation proposes and studies the design and performance, both physical and economic, of a novel power conversion system, the Nuclear Air-Brayton Combined Cycle (NACC). The NACC is a power conversion system that takes a conventional industrial frame type gas turbine, modifies it to accept external nuclear heat at 670°C, while also maintaining its ability to co-fire with natural gas to increase temperature and power output at a very quick ramp rate. The NACC addresses the above issues by allowing the generator to gain extra revenue through the provision of ancillary services in addition to energy payments, the grid operator to have a highly flexible source of capacity to back up intermittent renewable energy sources, and the consumer to possibly see less volatile electricity prices and a reduced probability of black/brown outs. This dissertation is split into six sections that delve into specific design and economic issues related to the NACC. The first section describes the basic design and modifications necessary to create a functional externally heated gas turbine, sets a baseline design based upon the GE 7FB, and estimates its physical performance under nominal conditions. The second section explores the off-nominal performance of the NACC and characterizes its startup and shutdown sequences, along with some of its safety measures. The third section deals with the power ramp rate estimation of the NACC, a key performance parameter in a renewable-heavy grid that needs flexible capacity. The

  7. A Mass Computation Model for Lightweight Brayton Cycle Regenerator Heat Exchangers

    Science.gov (United States)

    Juhasz, Albert J.

    2010-01-01

    Based on a theoretical analysis of convective heat transfer across large internal surface areas, this paper discusses the design implications for generating lightweight gas-gas heat exchanger designs by packaging such areas into compact three-dimensional shapes. Allowances are made for hot and cold inlet and outlet headers for assembly of completed regenerator (or recuperator) heat exchanger units into closed cycle gas turbine flow ducting. Surface area and resulting volume and mass requirements are computed for a range of heat exchanger effectiveness values and internal heat transfer coefficients. Benefit cost curves show the effect of increasing heat exchanger effectiveness on Brayton cycle thermodynamic efficiency on the plus side, while also illustrating the cost in heat exchanger required surface area, volume, and mass requirements as effectiveness is increased. The equations derived for counterflow and crossflow configurations show that as effectiveness values approach unity, or 100 percent, the required surface area, and hence heat exchanger volume and mass tend toward infinity, since the implication is that heat is transferred at a zero temperature difference. To verify the dimensional accuracy of the regenerator mass computational procedure, calculation of a regenerator specific mass, that is, heat exchanger weight per unit working fluid mass flow, is performed in both English and SI units. Identical numerical values for the specific mass parameter, whether expressed in lb/(lb/sec) or kg/ (kg/sec), show the dimensional consistency of overall results.

  8. High Temperature Fusion Reactor Cooling Using Brayton Cycle Based Partial Energy Conversion

    Science.gov (United States)

    Juhasz, Albert J.; Sawicki, Jerzy T.

    2003-01-01

    For some future space power systems using high temperature nuclear heat sources most of the output energy will be used in other than electrical form, and only a fraction of the total thermal energy generated will need to be converted to electrical work. The paper describes the conceptual design of such a partial energy conversion system, consisting of a high temperature fusion reactor operating in series with a high temperature radiator and in parallel with dual closed cycle gas turbine (CCGT) power systems, also referred to as closed Brayton cycle (CBC) systems, which are supplied with a fraction of the reactor thermal energy for conversion to electric power. Most of the fusion reactor's output is in the form of charged plasma which is expanded through a magnetic nozzle of the interplanetary propulsion system. Reactor heat energy is ducted to the high temperature series radiator utilizing the electric power generated to drive a helium gas circulation fan. In addition to discussing the thermodynamic aspects of the system design the authors include a brief overview of the gas turbine and fan rotor-dynamics and proposed bearing support technology along with performance characteristics of the three phase AC electric power generator and fan drive motor.

  9. Development of the ANL plant dynamics code and control strategies for the supercritical carbon dioxide Brayton cycle and code validation with data from the Sandia small-scale supercritical carbon dioxide Brayton cycle test loop

    International Nuclear Information System (INIS)

    Significant progress has been made in the ongoing development of the Argonne National Laboratory (ANL) Plant Dynamics Code (PDC), the ongoing investigation and development of control strategies, and the analysis of system transient behavior for supercritical carbon dioxide (S-CO2) Brayton cycles. Several code modifications have been introduced during FY2011 to extend the range of applicability of the PDC and to improve its calculational stability and speed. A new and innovative approach was developed to couple the Plant Dynamics Code for S-CO2 cycle calculations with SAS4A/SASSYS-1 Liquid Metal Reactor Code System calculations for the transient system level behavior on the reactor side of a Sodium-Cooled Fast Reactor (SFR) or Lead-Cooled Fast Reactor (LFR). The new code system allows use of the full capabilities of both codes such that whole-plant transients can now be simulated without additional user interaction. Several other code modifications, including the introduction of compressor surge control, a new approach for determining the solution time step for efficient computational speed, an updated treatment of S-CO2 cycle flow mergers and splits, a modified enthalpy equation to improve the treatment of negative flow, and a revised solution of the reactor heat exchanger (RHX) equations coupling the S-CO2 cycle to the reactor, were introduced to the PDC in FY2011. All of these modifications have improved the code computational stability and computational speed, while not significantly affecting the results of transient calculations. The improved PDC was used to continue the investigation of S-CO2 cycle control and transient behavior. The coupled PDC-SAS4A/SASSYS-1 code capability was used to study the dynamic characteristics of a S-CO2 cycle coupled to a SFR plant. Cycle control was investigated in terms of the ability of the cycle to respond to a linear reduction in the electrical grid demand from 100% to 0% at a rate of 5%/minute. It was determined that

  10. Development of the ANL plant dynamics code and control strategies for the supercritical carbon dioxide Brayton cycle and code validation with data from the Sandia small-scale supercritical carbon dioxide Brayton cycle test loop.

    Energy Technology Data Exchange (ETDEWEB)

    Moisseytsev, A.; Sienicki, J. J. (Nuclear Engineering Division)

    2011-11-07

    Significant progress has been made in the ongoing development of the Argonne National Laboratory (ANL) Plant Dynamics Code (PDC), the ongoing investigation and development of control strategies, and the analysis of system transient behavior for supercritical carbon dioxide (S-CO{sub 2}) Brayton cycles. Several code modifications have been introduced during FY2011 to extend the range of applicability of the PDC and to improve its calculational stability and speed. A new and innovative approach was developed to couple the Plant Dynamics Code for S-CO{sub 2} cycle calculations with SAS4A/SASSYS-1 Liquid Metal Reactor Code System calculations for the transient system level behavior on the reactor side of a Sodium-Cooled Fast Reactor (SFR) or Lead-Cooled Fast Reactor (LFR). The new code system allows use of the full capabilities of both codes such that whole-plant transients can now be simulated without additional user interaction. Several other code modifications, including the introduction of compressor surge control, a new approach for determining the solution time step for efficient computational speed, an updated treatment of S-CO{sub 2} cycle flow mergers and splits, a modified enthalpy equation to improve the treatment of negative flow, and a revised solution of the reactor heat exchanger (RHX) equations coupling the S-CO{sub 2} cycle to the reactor, were introduced to the PDC in FY2011. All of these modifications have improved the code computational stability and computational speed, while not significantly affecting the results of transient calculations. The improved PDC was used to continue the investigation of S-CO{sub 2} cycle control and transient behavior. The coupled PDC-SAS4A/SASSYS-1 code capability was used to study the dynamic characteristics of a S-CO{sub 2} cycle coupled to a SFR plant. Cycle control was investigated in terms of the ability of the cycle to respond to a linear reduction in the electrical grid demand from 100% to 0% at a rate of 5

  11. Use of RELAP5-3D for Dynamic Analysis of a Closed-Loop Brayton Cycle Coupled To a Nuclear Reactor

    International Nuclear Information System (INIS)

    This paper describes results of a dynamic system model for a pair of closed Brayton-cycle (CBC) loops running in parallel that are connected to a nuclear gas reactor. The model assumes direct coupling between the reactor and the Brayton-cycle loops. The RELAP5-3D (version 2.4.1) computer program was used to perform the analysis. Few reactors have ever been coupled to closed Brayton-cycle systems. As such their behavior under dynamically varying loads, startup and shut down conditions, and requirements for safe and autonomous operation are largely unknown. The model described in this paper represents the reactor, turbine, compressor, recuperator, heat rejection system and alternator. The initial results of the model indicate stable operation of the reactor-driven Brayton-cycle system. However, for analysts with mostly pressurized water reactor experience, the Brayton cycle loops coupled to a gas-cooled reactor also indicate some counter-intuitive behavior for the complete coupled system. This model has provided crucial information in evaluating the reactor design and would have been further developed for use in developing procedures for safe start up, shut down, safe-standby, and other autonomous operating modes had the plant development cycle been completed

  12. Transient analysis of an FHR coupled to a helium Brayton power cycle

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Minghui [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Kim, In Hun [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Sun, Xiaodong [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Christensen, Richard [The Ohio State Univ., Columbus, OH (United States). Nuclear Engineering Program; Utgikar, Vivek [Univ. of Idaho, Idaho Falls, ID (United States); Sabharwall, Piyush [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-08-01

    The Fluoride salt-cooled High-temperature Reactor (FHR) features a passive decay heat removal system and a high-efficiency Brayton cycle for electricity generation. It typically employs an intermediate loop, consisting of an intermediate heat exchanger (IHX) and a secondary heat exchanger (SHX), to couple the primary system with the power conversion unit (PCU). In this study, a preliminary dynamic system model is developed to simulate transient characteristics of a prototypic 20-MWth Fluoride salt-cooled High-temperature Test Reactor (FHTR). The model consists of a series of differential conservation equations that are numerically solved using the MATLAB platform. For the reactor, a point neutron kinetics model is adopted. For the IHX and SHX, a fluted tube heat exchanger and an offset strip-fin heat exchanger are selected, respectively. Detailed geometric parameters of each component in the FHTR are determined based on the FHTR nominal steady-state operating conditions. Three initiating events are simulated in this study, including a positive reactivity insertion, a step increase in the mass flow rate of the PCU helium flow, and a step increase in the PCU helium inlet temperature to the SHX. The simulation results show that the reactor has inherent safety features for those three simulated scenarios. It is observed that the increase in the temperatures of the fuel pebbles and primary coolant is mitigated by the decrease in the reactor power due to negative temperature feedbacks. The results also indicate that the intermediate loop with the two heat exchangers plays a significant role in the transient progression of the integral reactor system.

  13. An Experimental Programme to Evaluate the Feasibility of Jet Compressors for Closed Brayton Cycle MPD Systems

    International Nuclear Information System (INIS)

    The application of jet compressors to closed Brayton cycle MPD systems has been suggested previously. In the present paper the feasibility of jet compression for MPD systems is investigated and some preliminary test results from a single-stage jet compressor loop are given. Thepurposeoftheexperimentalprogrammeis, (1) to simulate the operation of a jet compressor under conditions comparable to those of an actual MPD plant, and (2) to study the physics of momentum transfer of two high velocity gas (or vapour) streams of very different molecular weights. A jet compressor in which both gases mix at equal forward velocity has the same theoretical compression ratio as a reversible engine. The upper limit for the compression ratio achievable for a given set of input parameters (stagnation properties of both gases) can be calculated from purely thermodynamic principles. The expressions for the performance of an ideal jet compressor were applied to two typical high temperature MPD cycles. The overall cycle efficiency is somewhat lower than obtainable with rotating machinery, but acceptable for special applications. In the experimental programme a single-stage test facility was designed and operated. The driving gas was caesium vapour, the driven gas helium. In the design of the system the objective was to simulate the temperatures, pressures and working media of an MPD plant on a small scale. The facility is capable of handling up to 12 g/sec of the primary stream (caesium) and up to 2.5 g of the secondary stream (helium). The caesium is fed by a diaphragm pump into a refractory metal boiler at a pressure of up to 8.0 atmospheres and then superheated to approximately 1700°K. The superheated vapour expands in a supersonic nozzle and transfers part of its momentum to the low temperature helium stream. The helium is circulated in a closed loop which is equipped with a throttle valve to simulate the pressure drop which would occur in an MPD generator. During some preliminary

  14. Optimization performance and thermodynamic analysis of an irreversible nano scale Brayton cycle operating with Maxwell–Boltzmann gas

    International Nuclear Information System (INIS)

    Highlights: • Performance analysis of irreversible nano scale Brayton cycle operating with Maxwell–Boltzmann gas is studied. • Multi-objective optimization approach is carried out for performance optimization. • 3 decision-making methods are employed to select final answers. - Abstract: In last decades, nano technology developed. Since, nano scale thermal cycles will be possibly employed in the near future. In this research, a nano scale irreversible Brayton cycle is investigated thermodynamically for optimizing the performance of the aforementioned cycle. Ideal Maxwell–Boltzmann gas is employed as a working fluid in the system. In this paper, two scenarios are employed in the multi-objective optimization process; however, the outcomes of each of the scenarios are evaluated independently. In the first scenario, in order to maximize the dimensionless Maximum available work and energy efficiency of the system, multi-objective optimization algorithms is employed. Furthermore, in the second scenario, two objective functions comprising the dimensionless Maximum available work and the dimensionless Ecological function are maximized concurrently via employing multi objective optimization algorithms. The multi objective evolutionary approaches on the basis of non-dominated sorting genetic algorithm method are employed in this paper. Decision making is done via three methods including linear programming techniques for multidimensional analysis of preference and Technique for order of preference by similarity to ideal solution and Bellman–Zadeh. Finally, error analysis is implemented on the results obtained from each scenario

  15. Development of 0.5-5 W, 10K Reverse Brayton Cycle Cryocoolers - Phase II Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Doty, F. D.; Boman, A.; Arnold, S.; Spitzmesser, J. B.; Jones, D.; McCree, D.; Hacker, L. J.

    2001-10-15

    Miniature cryocoolers for the 8-30 K range are needed to provide 0.5-5 w of cooling to high sensitivity detectors (for long-wave-length IR, magnetism, mm-wave, X-ray, dark matter, and possibly y-ray detection) while maintaining low mass, ultra-low vibration, and good efficiency. This project presents a new approach to eliminating the problems normally encountered in efforts to build low-vibration, fieldable, miniature cryocoolers. Using the reverse Brayton Cycle (RBC), the approach applies and expands on existing spinner technology previously used only in Nuclear Magnetic Resonance (NMR) probes.

  16. The efficiency of an open-cavity tubular solar receiver for a small-scale solar thermal Brayton cycle

    International Nuclear Information System (INIS)

    Highlights: • Results show efficiencies of a low-cost stainless steel tubular cavity receiver. • Optimum ratio of 0.0035 is found for receiver aperture area to concentrator area. • Smaller receiver tube and higher mass flow rate increase receiver efficiency. • Larger tube and smaller mass flow rate increase second law efficiency. • Large-tube receiver performs better in the small-scale solar thermal Brayton cycle. - Abstract: The first law and second law efficiencies are determined for a stainless steel closed-tube open rectangular cavity solar receiver. It is to be used in a small-scale solar thermal Brayton cycle using a micro-turbine with low compressor pressure ratios. There are many different variables at play to model the air temperature increase of the air running through such a receiver. These variables include concentrator shape, concentrator diameter, concentrator rim angle, concentrator reflectivity, concentrator optical error, solar tracking error, receiver aperture area, receiver material, effect of wind, receiver tube diameter, inlet temperature and mass flow rate through the receiver. All these variables are considered in this paper. The Brayton cycle requires very high receiver surface temperatures in order to be successful. These high temperatures, however, have many disadvantages in terms of heat loss from the receiver, especially radiation heat loss. With the help of ray-tracing software, SolTrace, and receiver modelling techniques, an optimum receiver-to-concentrator-area ratio of A′ ≈ 0.0035 was found for a concentrator with 45° rim angle, 10 mrad optical error and 1° tracking error. A method to determine the temperature profile and net heat transfer rate along the length of the receiver tube is presented. Receiver efficiencies are shown in terms of mass flow rate, receiver tube diameter, pressure drop, maximum receiver surface temperature and inlet temperature of the working fluid. For a 4.8 m diameter parabolic dish, the

  17. Performance characteristics of an irreversible regenerative magnetic Brayton refrigeration cycle using Gd0.74Tb0.26 as the working substance

    Science.gov (United States)

    Diguet, Gildas; Lin, Guoxing; Chen, Jincan

    2012-10-01

    The cycle model of an irreversible regenerative magnetic Brayton refrigerator using Gd0.74Tb0.26 as the working substance is established. Based on the experimental characteristics of iso-field heat capacities of the material Gd0.74Tb0.26 at 0 T and 2 T, the corresponding iso-field entropies are calculated and the thermodynamic performance of an irreversible regenerative magnetic Brayton refrigeration cycle is investigated. The effects of the irreversibilities in the two adiabatic processes and non-perfect regenerative process of the magnetic Brayton refrigeration cycle on the cooling quantity, the heat quantity released to the hot reservoir, the net cooling quantity and the coefficient of performance are discussed in detail. Some significant results are obtained.

  18. Simulation of operational an accidental behaviour of modular high temperature reactors with Brayton cycle Power Conversion Unit

    International Nuclear Information System (INIS)

    The present work analyses and investigates the behaviour of a High Temperature Reactor (HTR) with a Pebble Bed core connected to a Brayton cycle Power Conversion Unit (PCU) during operational and accident conditions. The modelling of a complete circuit including both the PCU and the Pebble Bed Reactor has been performed with the commercial thermal-fluid analysis simulation code Flownex. Flownex has been developed for High Temperature Pebble Bed Reactor applications, and has been exten-sively validated against other codes. As the reactor core model incorporated in Flownex is a simplified model based on 0D point kinetics, the extended 1D WKIND core model was implemented in the analysis calculations using a special coupling methodology. This study introduces a new sub-routine which enables the cou-pling of the WKIND reactor core model to the Flownex PCU model via an external interface. The interface facilitates the data exchange between the two codes, allowing for necessary manipulations and synchronisation of the coupled codes. By doing so, the 1D diffusion equation solution implemented in WKIND core model replaces the point kinetics model implemented in Flownex. This replacement allows for a detailed accurate solution even for very fast transients, through the treatment of the space-dependent heat conduction from the graphite matrix to helium. Flownex component models have been validated against the experimental results of the 50 MWel direct helium turbine facility Energieversorgung Oberhausen (EVO II). This provided the opportunity to validate Flownex calculations against experimental data derived from a large-scale helium Brayton cycle installation. Small differences observed in the results could be explained. Based upon steady state and transient analysis it is concluded that Flownex models simulate accurately the behaviour of the components integrated in the EVO II plant. Such models could be applied to analyse the transient behaviour of the total system of the

  19. An isotope heat source integrated with a 7 kW/e/ to 25 kW/e/ Brayton cycle space power supply.

    Science.gov (United States)

    Ryan, R. L.; Graham, J. W.; Coombs, M. G.; Bloomfield, H. S.

    1972-01-01

    The power system described is intended for applications in a manned space mission. The Isotope Reentry Vehicle (IRV) developed is considered together with the Heat Source (HS), the Heat Source Heat Exchanger and the Brayton Cycle Power Conversion Module. Other subjects discussed include the IRV/Brayton cycle spacecraft integration concept, abort and deorbit mechanization, emergency cooling methods, and crew shielding requirements. Mounting and integration for the IRV is to a large degree controlled by nuclear safety requirements. Another major factor in the installation concept is the type of emergency cooling or passive heat dump mode used in rejection of HS energy.

  20. Optimum performance of the small-scale open and direct solar thermal Brayton cycle at various environmental conditions and constraints

    International Nuclear Information System (INIS)

    The Brayton cycle's heat source can be obtained from solar energy instead of the combustion of fuel. The irreversibilities of the open and direct solar thermal Brayton cycle with recuperator are mainly due to heat transfer across a finite temperature difference and fluid friction, which limit the net power output of such a system. In this work, the method of total entropy generation minimisation is applied to optimise the geometries of the receiver and recuperator at various steady-state weather conditions. For each steady-state weather condition, the optimum turbine operating point is also found. The authors specifically investigate the effect of wind and solar irradiance on the maximum net power output of the system. The effects of other conditions and constraints, on the maximum net power output, are also investigated. These include concentrator error, concentrator reflectivity and maximum allowable surface temperature of the receiver. Results show how changed solar beam irradiance and wind speed affect the system net power output and optimum operating point of the micro-turbine. A dish concentrator with fixed focal length, an off-the-shelf micro-turbine and a modified cavity receiver is considered. -- Highlights: ► An off-the-shelf micro-turbine and a modified cavity receiver are considered. ► We investigate the optimum operating point of micro-turbine in various situations. ► Optimum mass flow rate and exhaust temperature increase with beam irradiance. ► Optimum exhaust temperature increases as wind speed increases.

  1. Ecological Optimization and Parametric Study of an Irreversible Regenerative Modified Brayton Cycle with Isothermal Heat Addition

    OpenAIRE

    Vivek Tiwari; Subhash Chandra Kaushik; Sudhir Kumar Tyagi

    2003-01-01

    Abstract: An ecological optimization along with a detailed parametric study of an irreversible regenerative Brayton heat engine with isothermal heat addition have been carried out with external as well as internal irreversibilities. The ecological function is defined as the power output minus the power loss (irreversibility) which is ambient temperature times the entropy generation rate. The external irreversibility is due to finite temperature difference between the heat engine and the exter...

  2. Conceptual Design of S-CO{sub 2} Brayton Cycle Radial Turbomachinery for KAIST Micro Modular Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seongkuk; Kim, Seong Gu; Lee, Jekyoung; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-05-15

    KAIST proposed a new SMR design, which utilizes S-CO{sub 2} as the working fluid. It was named as KAIST MMR. Compared with existing SMR concepts, KAIST MMR has advantages of achieving smaller volume of power conversion unit (PCU) and containing the core and PCU in one vessel for the complete modularization. Authors noticed that the compressor and turbine assumed performances of KAIST MMR were conservatively selected previously. Thus, this paper tries to address the best estimate values of each turbomachinery in 10MWe class KAIST MMR. The turbomachinery size of the S-CO{sub 2} cycle is smaller than helium Brayton cycle and steam Rankine cycle. The suggested SMR concept adopts passive cooling system by using air. This method can cool reactor without external electricity supply. Small size and more flexible installation in the inland area will be necessary characteristics for the future nuclear application in the water limited region. KAIST MMR meets all these requirements by utilizing S-CO{sub 2} as a working fluid. This paper presents the work for further increasing the system performance by estimating the component efficiency more realistically. The cycle layout adopted for the application is S-CO{sub 2} recuperated Brayton cycle. The best efficiency of compressor and turbine was evaluated to be 84.94% and 90.94%, respectively. By using KAIST in-house code, thermal efficiency and net output were increased to 35.81% and 12.45MWe, respectively, for the same core thermal power. More refined cycle layout and suitable turbomachinery design will be performed in the near future.

  3. Preliminary design of a Brayton cycle as a standalone Decay Heat Removal system for the Gas-cooled Fast Reactor

    International Nuclear Information System (INIS)

    This paper reports a preliminary design study of a Brayton cycle which would be a dedicated, standalone Decay Heat Removal (DHR) loop of the Gas-cooled Fast Reactor (GFR). In comparison to the DHR reference strategy developed during the GFR pre-conceptual design phase (which was completed by the CEA at the end of 2007), the salient feature of this alternative device would be to combine the energetic autonomy of the natural convection process - which is foreseen for operation at high and medium pressures - to the efficiency of the forced convection process which is foreseen for operation down to very low pressures. An analytical model, the so-called 'Brayton scoping' model, is described in the paper. This is based on simplified thermodynamical and aerodynamical equations and was developed to highlight design choices. First simulations of the proposed device's performance during loss-of-coolant-accident (LOCA) transients have been performed using the CATHARE code, and these are also reported. Analysis of the simulation results are consistent with the first insights obtained from usage of the 'Brayton scoping' model, e.g. the turbomachine accelerates during the depressurization process to tend towards a steady rotational speed value which is inversely proportional to the pressure. For small break LOCA events, the device operates successfully as regards its safety function and delivers to the core a relatively unperturbed cooling mass flowrate as a function of pressure change. However, further studies are required for medium to large break sizes, since certain stability concerns have been met in such cases. For example, an unexpected turbomachine stoppage was induced during the transients, resulting in loss of the necessary core cooling mass flow. (author)

  4. Motor starting a Brayton cycle power conversion system using a static inverter

    Science.gov (United States)

    Curreri, J. S.; Edkin, R. A.; Kruchowy, R.

    1973-01-01

    The power conversion module of a 2- to 15-kWe Brayton engine was motor started using a three-phase, 400-hertz static inverter as the power source. Motor-static tests were conducted for initial gas loop pressures of 10, 14, and 17 N/sq cm (15, 20, and 25 psia) over a range of initial turbine inlet temperatures from 366 to 550 K (200 to 530 F). The data are presented to show the effects of temperature and pressure on the motor-start characteristics of the rotating unit. Electrical characteristics during motoring are also discussed.

  5. Detailed analysis of the effect of the turbine and compressor isentropic efficiency on the thermal and exergy efficiency of a Brayton cycle

    Directory of Open Access Journals (Sweden)

    Živić Marija

    2014-01-01

    Full Text Available Energy and exergy analysis of a Brayton cycle with an ideal gas is given. The irreversibility of the adiabatic processes in turbine and compressor is taken into account through their isentropic efficiencies. The net work per cycle, the thermal efficiency and the two exergy efficiencies are expressed as functions of the four dimensionless variables: the isentropic efficiencies of turbine and compressor, the pressure ratio, and the temperature ratio. It is shown that the maximal values of the net work per cycle, the thermal and the exergy efficiency are achieved when the isentropic efficiencies and temperature ratio are as high as possible, while the different values of pressure ratio that maximize the net work per cycle, the thermal and the exergy efficiencies exist. These pressure ratios increase with the increase of the temperature ratio and the isentropic efficiency of compressor and turbine. The increase of the turbine isentropic efficiency has a greater impact on the increase of the net work per cycle and the thermal efficiency of a Brayton cycle than the same increase of compressor isentropic efficiency. Finally, two goal functions are proposed for thermodynamic optimization of a Brayton cycle for given values of the temperature ratio and the compressor and turbine isentropic efficiencies. The first maximizes the sum of the net work per cycle and thermal efficiency while the second the net work per cycle and exergy efficiency. In both cases the optimal pressure ratio is closer to the pressure ratio that maximizes the net work per cycle.

  6. Operating conditions of an open and direct solar thermal Brayton cycle with optimised cavity receiver and recuperator

    International Nuclear Information System (INIS)

    The small-scale open and direct solar thermal Brayton cycle with recuperator has several advantages, including low cost, low operation and maintenance costs and it is highly recommended. The main disadvantages of this cycle are the pressure losses in the recuperator and receiver, turbomachine efficiencies and recuperator effectiveness, which limit the net power output of such a system. The irreversibilities of the solar thermal Brayton cycle are mainly due to heat transfer across a finite temperature difference and fluid friction. In this paper, thermodynamic optimisation is applied to concentrate on these disadvantages in order to optimise the receiver and recuperator and to maximise the net power output of the system at various steady-state conditions, limited to various constraints. The effects of wind, receiver inclination, rim angle, atmospheric temperature and pressure, recuperator height, solar irradiance and concentration ratio on the optimum geometries and performance were investigated. The dynamic trajectory optimisation method was applied. Operating points of a standard micro-turbine operating at its highest compressor efficiency and a parabolic dish concentrator diameter of 16 m were considered. The optimum geometries, minimum irreversibility rates and maximum receiver surface temperatures of the optimised systems are shown. For an environment with specific conditions and constraints, there exists an optimum receiver and recuperator geometry so that the system produces maximum net power output. -- Highlights: → Optimum geometries exist such that the system produces maximum net power output. → Optimum operating conditions are shown. → Minimum irreversibility rates and minimum entropy generation rates are shown. → Net power output was described in terms of total entropy generation rate. → Effects such as wind, recuperator height and irradiance were investigated.

  7. Transient Accident Analysis of a Supercritical Carbon Dioxide Brayton Cycle Energy Converter Coupled to an Autonomous Lead-Cooled Fast Reactor

    International Nuclear Information System (INIS)

    The Supercritical Carbon Dioxide (S-CO2) Brayton Cycle is a promising advanced alternative to the Rankine saturated steam cycle and recuperated gas Brayton cycle for the energy converters of specific reactor concepts belonging to the U.S. Department of Energy Generation IV Nuclear Energy Systems Initiative. A new plant dynamics analysis computer code has been developed for simulation of the S-CO2 Brayton cycle coupled to an autonomous, natural circulation Lead-Cooled Fast Reactor (LFR). The plant dynamics code was used to simulate the whole-plant response to accident conditions. The specific design features of the reactor concept influencing passive safety are discussed and accident scenarios are identified for analysis. Results of calculations of the whole-plant response to loss-of-heat sink, loss-of-load, and pipe break accidents are demonstrated. The passive safety performance of the reactor concept is confirmed by the results of the plant dynamics code calculations for the selected accident scenarios. (authors)

  8. Integrated solar thermal Brayton cycles with either one or two regenerative heat exchangers for maximum power output

    International Nuclear Information System (INIS)

    The main objective of this paper is to optimise the open-air solar-thermal Brayton cycle by considering the implementation of the second law of thermodynamics and how it relates to the design of the heat exchanging components within it. These components included one or more regenerators (in the form of cross-flow heat exchangers) and the receiver of a parabolic dish concentrator where the system heat was absorbed. The generation of entropy was considered as it was associated with the destruction of exergy or available work. The dimensions of some components were used to optimise the cycles under investigation. EGM (Entropy Generation Minimisation) was employed to optimise the system parameters by considering their influence on the total generation of entropy (destruction of exergy). Various assumptions and constraints were considered and discussed. The total entropy generation rate and irreversibilities were determined by considering the individual components and ducts of the system, as well as their respective inlet and outlet conditions. The major system parameters were evaluated as functions of the mass flow rate to allow for a proper discussion of the system performance. The performances of both systems were investigated, and characteristics were listed for both. Finally, a comparison is made to shed light on the differences in performance. - Highlights: • Implementation of the second law of thermodynamics. • Design of heat exchanging and collecting equipment. • Utilisation of Entropy Generation Minimization. • Presentation of a multi-objective optimization. • Raise efficiency with more regeneration

  9. System Mass Variation and Entropy Generation in 100-kWe Closed-Brayton-Cycle Space Power Systems

    Science.gov (United States)

    Barrett, Michael J.; Reid, Bryan M.

    2004-02-01

    State-of-the-art closed-Brayton-cycle (CBC) space power systems were modeled to study performance trends in a trade space characteristic of interplanetary orbiters. For working-fluid molar masses of 48.6, 39.9 and 11.9 kg/kmol, peak system pressures of 1.38 and 3.0 MPa and compressor pressure ratios ranging from 1.6 to 2.4, total system masses were estimated. System mass increased as peak operating pressure increased for all compressor pressure ratios and molar mass values examined. Minimum mass point comparison between 72% He at 1.38 MPa peak and 94% He at 3.0 MPa peak showed an increase in system mass of 14%. Converter flow loop entropy generation rates were calculated for 1.38 and 3.0 MPa peak pressure cases. Physical system behavior was approximated using a pedigreed NASA-Glenn modeling code, Closed Cycle Engine Program (CCEP), which included realistic performance prediction for heat exchangers, radiators and turbomachinery.

  10. Off-design performance prediction of Radial Compressor of Supercritical CO2 Brayton Cycle for KAIST Micro Modular Reactor

    International Nuclear Information System (INIS)

    KAIST research team suggested a new concept of SMR, which utilizes S-CO2 as the operating fluid and coolant. It was named as KAIST MMR(Micro Modular Reactor). Compared with existing SMR concepts, this reactor has advantages of achieving smaller volume of power conversion unit (PCU) containing the core and PCU in one vessel for the complete modularization passive air-cooling system more flexible installation in the inland area. In previous study, performance of turbomachinery in PCU was considered only on-design. But, off-design performances of each component can affect not only PCU but also the core because this reactor adopts the direct S-CO2 loop in GFR. Nuclear system is applied by relatively conservative criteria of safety. Thus, off-design performances of each component should be considered in order to be more realistic reactor. The suggested turbomachinery size of the S-CO2 cycle is relatively smaller than those of helium Brayton cycle and steam Rankine cycle. Performance analysis of compressor is conducted by KAIST-TMD in case of on-design and off-design. Compressor efficiency in on-design conditions is obtained 84.51 %. But compressor performance in off-design conditions decreases certainly. This means that more heat than existing prediction is rejected by air-cooling system. KAIST-TMD will be verified with more experiment data for providing the results of more accurate analysis. Also, this code will be modified to couple with safety analysis codes and S-CO2 cycle analysis codes in the future. Furthermore, authors will consider aerodynamic performance analysis and various losses for more realization

  11. Design of automatic startup and shutdown logic for a Brayton-cycle 2- to 15-kilowatt engine

    Science.gov (United States)

    Vrancik, J. E.; Bainbridge, R. C.

    1975-01-01

    The NASA Lewis Research Center is conducting a closed-Brayton-cycle power conversion system technology program in which a complete power system (engine) has been designed and demonstrated. This report discusses the design of automatic startup and shutdown logic circuits as a modification to the control system presently used in this demonstration engine. This modification was primarily intended to make starting the engine as simple and safe as possible and to allow the engine to be run unattended. In the modified configuration the engine is started by turning the control console power on and pushing the start button after preheating the gas loop. No other operator action is required to effect a complete startup. Shutdown, if one is required, is also effected by a simple stop button. The automatic startup and shutdown of the engine have been successfully and purposefully demonstrated more than 50 times at the Lewis Research Center during 10,000 hours of unattended operation. The net effect of this modification is an engine that can be safely started and stopped by relatively untrained personnel. The approach lends itself directly to remote unattended operation.

  12. Reactor dynamics and stability analysis of a burst-mode gas core reactor, Brayton cycle space power system

    International Nuclear Information System (INIS)

    Reactor dynamics and system stability studies are performed on a conceptual burst-mode gaseous core reactor space nuclear power system. This concept operates on a closed Brayton cycle in the burst mode (on the order of 100-MW output for a few thousand seconds) using a disk magnetohydrodynamic generator for energy conversion. The fuel is a gaseous mixture of UF4 or UF6 and helium. Nonlinear dynamic analysis is performed using circulating-fuel, point-reactor-kinetics equations along with thermodynamic, lumped-parameter heat transfer and one-dimensional isentropic flow equations. The gaseous nature of the fuel plus the fact that the fuel is circulating lead to dynamic behavior that is quite different from that of conventional solid-core systems. For the transients examined, Doppler fuel temperature and moderator temperature feedbacks are insignificant when compared with reactivity feedback associated with fuel gas density variations. The gaseous fuel density power coefficient of reactivity is capable of rapidly stabilizing the system, within a few seconds, even when large positive reactivity insertions are imposed; however, because of the strength of this feedback, standard external reactivity insertions alone are inadequate to bring about significant power level changes during normal reactor operation. Additional methods of reactivity control, such as changes in the gaseous of fuel mass flow rate or core inlet pressure, are required to achieve desired power level control. Finally, linear stability analysis gives results that are qualitatively in agreement with the nonlinear analysis

  13. Performance optimization of quantum Brayton refrigeration cycle working with spin systems

    International Nuclear Information System (INIS)

    The new model of a quantum refrigeration cycle composed of two adiabatic and two isomagnetic field processes is established. The working substance in the cycle consists of many non-interacting spin-1/2 systems. The performance of the cycle is investigated, based on the quantum master equation and semi-group approach. The general expressions of several important performance parameters, such as the coefficient of performance, cooling rate and power input, are given. It is found that the coefficient of performance of this cycle is a close analogue of the classical Carnot-cycle. Some performance characteristic curves relating the cooling rate, the coefficient of performance and power input are plotted. Further, for high temperatures, the optimal relations between the cooling rate and the coefficient of performance are analyzed in detail

  14. Supercritical Carbon Dioxide Brayton Cycle for SFR Applications: Optimization, Transient Analysis, and Control

    International Nuclear Information System (INIS)

    A Plant Dynamics Code (PDC) has been under development at Argonne National Laboratory for several years to investigate steady-state and transient performance and behavior of the S-CO2 cycle as an alternative power converter for advanced SFRs. The code was specifically developed to address unique features of the S-CO2 cycle, including operation near the critical point and the effect of properties variation on the design and transient behavior of turbomachinery and heat exchangers. A coupling approach between PDC and SAS4A/SASSYS-1 Liquid Metal Reactor Code System has been implemented to allow simultaneous investigation of transient behavior of liquid metal-cooled reactors and S-CO2 cycle balance-of-plants. PDC has been used to optimize the S-CO2 cycle design and to develop a control strategy. It has been demonstrated that with the proposed control systems the cycle can be effectively and stably operated over the entire range of grid loads and for decay heat removal. (author)

  15. Thermal Assessment of Very High Temperature Reactors: Direct and Indirect Brayton Power Cycles

    International Nuclear Information System (INIS)

    Search for a sustainable energy supply system has driven nuclear engineering towards what has been termed Generation IV. One of the main objectives of these innovative nuclear designs is to reach a high thermal efficiency in their power cycles. This way a substantial fuel saving and waste reduction is achieved, which would enhance competitiveness of the nuclear kWh. This paper investigates the thermal performance of helium-cooled power cycles based on the characteristic working parameters of Very High Temperature Reactor systems both at present and at the near future. Direct (C(IC)2HTRTX) and indirect (C(IC)2(IHX)TX) cycle baselines have been modelled and both have shown an excellent thermal performance ( with thermal efficiencies near or even higher than 50%). Enhancement of associated technology would increase thermal performance (i.e., and wnet) of both cycles drastically. The analysis of the results indicate that from the thermal performance standpoint, the cycle C(IC)2HTRTX would be a better option. However, when advances in associated technologies are considered, the efficiency gap between the two baselines analyzed become smaller. In no case net power turned out to be a differential feature between the layouts. (authors)

  16. Investigation of plant control strategies for the supercritical C02Brayton cycle for a sodium-cooled fast reactor using the plant dynamics code

    International Nuclear Information System (INIS)

    The development of a control strategy for the supercritical CO2 (S-CO2) Brayton cycle has been extended to the investigation of alternate control strategies for a Sodium-Cooled Fast Reactor (SFR) nuclear power plant incorporating a S-CO2 Brayton cycle power converter. The SFR assumed is the 400 MWe (1000 MWt) ABR-1000 preconceptual design incorporating metallic fuel. Three alternative idealized schemes for controlling the reactor side of the plant in combination with the existing automatic control strategy for the S-CO2 Brayton cycle are explored using the ANL Plant Dynamics Code together with the SAS4A/SASSYS-1 Liquid Metal Reactor (LMR) Analysis Code System coupled together using the iterative coupling formulation previously developed and implemented into the Plant Dynamics Code. The first option assumes that the reactor side can be ideally controlled through movement of control rods and changing the speeds of both the primary and intermediate coolant system sodium pumps such that the intermediate sodium flow rate and inlet temperature to the sodium-to-CO2 heat exchanger (RHX) remain unvarying while the intermediate sodium outlet temperature changes as the load demand from the electric grid changes and the S-CO2 cycle conditions adjust according to the S-CO2 cycle control strategy. For this option, the reactor plant follows an assumed change in load demand from 100 to 0 % nominal at 5 % reduction per minute in a suitable fashion. The second option allows the reactor core power and primary and intermediate coolant system sodium pump flow rates to change autonomously in response to the strong reactivity feedbacks of the metallic fueled core and assumed constant pump torques representing unchanging output from the pump electric motors. The plant behavior to the assumed load demand reduction is surprising close to that calculated for the first option. The only negative result observed is a slight increase in the intermediate inlet sodium temperatures by about 10 C

  17. SP-100 reactor with Brayton conversion for lunar surface applications

    International Nuclear Information System (INIS)

    Examined here is the potential for integrating Brayton-cycle power conversion with the SP-100 reactor for lunar surface power system applications. Two designs were characterized and modeled. The first design integrates a 100-kWe SP-100 Brayton power system with a lunar lander. This system is intended to meet early lunar mission power needs while minimizing on-site installation requirements. Man-rated radiation protection is provided by an integral multilayer, cylindrical lithium hydride/tungsten (LiH/W) shield encircling the reactor vessel. Design emphasis is on ease of deployment, safety, and reliability, while utilizing relatively near-term technology. The second design combines Brayton conversion with the SP-100 reactor in a erectable 550-kWe powerplant concept intended to satisfy later-phase lunar base power requirements. This system capitalizes on experience gained from operating the initial 100-kWe module and incorporates some technology improvements. For this system, the reactor is emplaced in a lunar regolith excavation to provide man-rated shielding, and the Brayton engines and radiators are mounted on the lunar surface and extend radially from the central reactor. Design emphasis is on performance, safety, long life, and operational flexibility

  18. Analysis of transient coolant void formation during a guillotine-type HX tube rupture event in the Star-LM system employing a supercritical CO2 Brayton cycle

    International Nuclear Information System (INIS)

    One proposed concept for the STAR-LM Lead Fast Reactor (LFR) incorporates a supercritical CO2 gas turbine Brayton cycle to achieve high cycle efficiency and reduced plant footprint. In this design, 100+% of core full power is transferred by natural circulation from the core, located at the bottom of the reactor vessel, to in-vessel heat exchangers (HXs) located at the top of the vessel in the annulus between the core shroud and vessel inner wall. Although this approach extremely simplifies the plant design, the presence of the HXs within the vessel raises concerns regarding the potential rupture of a HX tube that would initiate a high-pressure blowdown of CO2 into the lead coolant. The principal issue is to what extent, if any, is void entrained downwards with the coolant and then upwards through the core where adverse reactivity effects or degraded heat removal could result. To address this question, a scoping analysis of transient void formation during a guillotine-type HX tube rupture event in the STAR-LM employing a supercritical CO2 Brayton cycle has been performed. The void formation process is evaluated by solving a coupled set of ordinary differential equations describing: i) the supercritical CO2 blowdown, ii) bubble center-of-mass trajectory, iii) bubble growth rate, iv) bubble gas internal energy, and v) discrete bubble formation rate due to Taylor instability at the bubble/coolant interface. The results indicate that for thermal hydraulic conditions consistent with the current STAR-LM design, the peak blowdown rate from a single tube rupture is ∼ 2.5 kg/sec. The void formation process is dominated by large coherent gas bubbles that penetrate minimally downwards into the coolant due to the large coolant density. Rather, the gas pockets are predicted to periodically rise due to buoyancy and vent to the core cover gas region, as opposed to being swept downwards with the coolant. Moreover, the total CO2 fraction that is rendered in the form of discrete

  19. Educational Service Improvement Cycle

    OpenAIRE

    Rothe, Hannes

    2016-01-01

    Terms like e-, m- or Blended Learning show, currently many educational services are supported by web technologies. Within such services predominant parts of learner’s usage processes are hidden from the educator’s perception. In front of a service-dominant logic understanding usage processes is essential to comprehend the value-co-creation of educators and learners. Learning analytics may hold methods to enable a continual improvement process by collecting and analyzing usage data. A systemat...

  20. Closed Brayton cycle power system with a high temperature pellet bed reactor heat source for NEP applications

    International Nuclear Information System (INIS)

    Capitalizing on past and future development of high temperature gas reactor (HTGR) technology, a low mass 15 MWe closed gas turbine cycle power system using a pellet bed reactor heating helium working fluid is proposed for Nuclear Electric Propulsion (NEP) applications. Although the design of this directly coupled system architecture, comprising the reactor/power system/space radiator subsystems, is presented in conceptual form, sufficient detail is included to permit an assessment of overall system performance and mass. Furthermore, an attempt is made to show how tailoring of the main subsystem design characteristics can be utilized to achieve synergistic system level advantages that can lead to improved reliability and enhanced system life while reducing the number of parasitic load driven peripheral subsystems

  1. Improved cycling cryopump

    Science.gov (United States)

    Batzer, T.H.; Call, W.R.

    1984-12-04

    The present invention is designed to achieve continuous high efficiency cryopumping of a vacuum vessel by improving upon and combining in a novel way the cryopumping in a novel way the cryopumping methods. The invention consists of a continuous operation cryopump, with movable louvres, with a high efficiency pumping apparatus. The pumping apparatus includes three cryogenic tubes. They are constructed of a substance of high thermal conductivity, such as aluminum and their exterior surfaces are cryogenic condensing surfaces. Through their interior liquid or gaseous helium from two reservoirs can be made to flow, alternately promoting extreme cooling or allowing some warming.

  2. Off-design performance prediction of Radial Compressor of Supercritical CO{sub 2} Brayton Cycle for KAIST Micro Modular Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seongkuk; Lee, Jekyoung; Kim, Seong Gu; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-10-15

    KAIST research team suggested a new concept of SMR, which utilizes S-CO{sub 2} as the operating fluid and coolant. It was named as KAIST MMR(Micro Modular Reactor). Compared with existing SMR concepts, this reactor has advantages of achieving smaller volume of power conversion unit (PCU) containing the core and PCU in one vessel for the complete modularization passive air-cooling system more flexible installation in the inland area. In previous study, performance of turbomachinery in PCU was considered only on-design. But, off-design performances of each component can affect not only PCU but also the core because this reactor adopts the direct S-CO{sub 2} loop in GFR. Nuclear system is applied by relatively conservative criteria of safety. Thus, off-design performances of each component should be considered in order to be more realistic reactor. The suggested turbomachinery size of the S-CO{sub 2} cycle is relatively smaller than those of helium Brayton cycle and steam Rankine cycle. Performance analysis of compressor is conducted by KAIST-TMD in case of on-design and off-design. Compressor efficiency in on-design conditions is obtained 84.51 %. But compressor performance in off-design conditions decreases certainly. This means that more heat than existing prediction is rejected by air-cooling system. KAIST-TMD will be verified with more experiment data for providing the results of more accurate analysis. Also, this code will be modified to couple with safety analysis codes and S-CO{sub 2} cycle analysis codes in the future. Furthermore, authors will consider aerodynamic performance analysis and various losses for more realization.

  3. WWER-1000 fuel cycle improvement

    International Nuclear Information System (INIS)

    The problems of organization of fuel cycles with different operation time of stationary load for the reactor WWER-1000 are considered. The outcomes of matching of the characteristics for stationary load constructed on fuel cells of existing and improved designs are presented. Improved designs of a fuel cell are include increase of an altitude of a fuel stake, change of outside and axial diameters of a fuel pellet, change thickness of a cladding of a fuel cell. Effect of the layout solutions on improving of a fuel cycle WWER-1000 also considered (Authors)

  4. Finite time exergy analysis and multi-objective ecological optimization of a regenerative Brayton cycle considering the impact of flow rate variations

    International Nuclear Information System (INIS)

    Highlights: • Defining a dimensionless parameter includes the finite-time and size concepts. • Inserting the concept of exergy of fluid streams into finite-time thermodynamics. • Defining, drawing and modifying of maximum ecological function curve. • Suggesting the appropriate performance zone, according to maximum ecological curve. - Abstract: In this study, the optimal performance of a regenerative Brayton cycle is sought through power and then ecological function maximization using finite-time thermodynamic concept and finite-size components. Multi-objective optimization is used for maximizing the ecological function. Optimizations are performed using genetic algorithm. In order to take into account the finite-time and finite-size concepts in current problem, a dimensionless mass-flow parameter is introduced deploying time variations. The variations of output power, total exergy destruction of the system, and decision variables for the optimum state (maximum ecological function state) are compared to the maximum power state using the dimensionless parameter. The modified ecological function in optimum state is obtained and plotted relating to the dimensionless mass-flow parameter. One can see that the modified ecological function study results in a better performance than that obtained with the maximum power state. Finally, the appropriate performance zone of the heat engine will be obtained

  5. Performance comparison of an irreversible closed variable-temperature heat reservoir Brayton cycle under maximum power density and maximum power conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chen, L.; Zheng, J.; Sun, F. [Naval University of Engineering, Wuhan (China); Wu, C. [US Naval Academy, Annapolis, MD (United States). Dept. of Mechanical Engineering

    2005-11-15

    The power density is taken as an objective for performance analysis of an irreversible closed Brayton cycle coupled to variable-temperature heat reservoirs. The analytical formulas about the relationship between power density and working fluid temperature ratio (pressure ratio) are derived with the heat resistance losses in the hot- and cold-side heat exchangers, the irreversible compression and expansion losses in the compressor and turbine, and the effect of the finite thermal capacity rate of the heat reservoirs. The obtained results are compared with those results obtained by using the maximum power criterion. The influences of some design parameters, including the temperature ratio of the heat reservoirs, the effectivenesses of the heat exchangers between the working fluid and the heat reservoirs, and the efficiencies of the compressor and the turbine, on the maximum power density are provided by numerical examples, and the advantages and disadvantages of maximum power density design are analysed. The power plant design with maximum power density leads to a higher efficiency and smaller size. When the heat transfers between the working fluid and the heat reservoirs are carried out ideally and the thermal capacity rates of the heat reservoirs are infinite, the results of this article become similar to those obtained in the recent literature. (author)

  6. State space model extraction of thermohydraulic systems – Part II: A linear graph approach applied to a Brayton cycle-based power conversion unit

    International Nuclear Information System (INIS)

    This second paper in a two part series presents the application of a developed state space model extraction methodology applied to a Brayton cycle-based PCU (power conversion unit) of a PBMR (pebble bed modular reactor). The goal is to investigate if the state space extraction methodology can cope with larger and more complex thermohydraulic systems. In Part I the state space model extraction methodology for the purpose of control was described in detail and a state space representation was extracted for a U-tube system to illustrate the concept. In this paper a 25th order nonlinear state space representation in terms of the different energy domains is extracted. This state space representation is solved and the responses of a number of important states are compared with results obtained from a PBMR PCU Flownex® model. Flownex® is a validated thermo fluid simulation software package. The results show that the state space model closely resembles the dynamics of the PBMR PCU. This kind of model may be used for nonlinear MIMO (multi-input, multi-output) type of control strategies. However, there is still a need for linear state space models since many control system design and analysis techniques require a linear state space model. This issue is also addressed in this paper by showing how a linear state space model can be derived from the extracted nonlinear state space model. The linearised state space model is also validated by comparing the state space model to an existing linear Simulink® model of the PBMR PCU system. - Highlights: • State space model extraction of a pebble bed modular reactor PCU (power conversion unit). • A 25th order nonlinear time varying state space model is obtained. • Linearisation of a nonlinear state space model for use in power output control. • Non-minimum phase characteristic that is challenging in terms of control. • Models derived are useful for MIMO control strategies

  7. A liquid-metal reactor/air Brayton-cycle option for a multimegawatt terrestrial power (MTP) plant

    International Nuclear Information System (INIS)

    The LMR/ABC concept presented provides a simple and safe approach to secure nuclear power generation to fulfill possible military requirements for 10-MWc terrestrial applications. The system utilizes an inherently safe liquid metal reactor and a simple, closed-cycle gas turbine power conversion system. The concept incorporates many passive safety features, and it exhibits operating characteristics that ensure the maximum protection against postulated nuclear accidents

  8. Development of a plant dynamics computer code for analysis of a supercritical carbon dioxide Brayton cycle energy converter coupled to a natural circulation lead-cooled fast reactor.

    Energy Technology Data Exchange (ETDEWEB)

    Moisseytsev, A.; Sienicki, J. J.

    2007-03-08

    STAR-LM is a lead-cooled pool-type fast reactor concept operating under natural circulation of the coolant. The reactor core power is 400 MWt. The open-lattice core consists of fuel pins attached to the core support plate, (the does not consist of removable fuel assemblies). The coolant flows outside of the fuel pins. The fuel is transuranic nitride, fabricated from reprocessed LWR spent fuel. The cladding material is HT-9 stainless steel; the steady-state peak cladding temperature is 650 C. The coolant is single-phase liquid lead under atmospheric pressure; the core inlet and outlet temperatures are 438 C and 578 C, respectively. (The Pb coolant freezing and boiling temperatures are 327 C and 1749 C, respectively). The coolant is contained inside of a reactor vessel. The vessel material is Type 316 stainless steel. The reactor is autonomous meaning that the reactor power is self-regulated based on inherent reactivity feedbacks and no external power control (through control rods) is utilized. The shutdown (scram) control rods are used for startup and shutdown and to stop the fission reaction in case of an emergency. The heat from the reactor is transferred to the S-CO{sub 2} Brayton cycle in in-reactor heat exchangers (IRHX) located inside the reactor vessel. The IRHXs are shell-and-tube type heat exchangers with lead flowing downwards on the shell side and CO{sub 2} flowing upwards on the tube side. No intermediate circuit is utilized. The guard vessel surrounds the reactor vessel to contain the coolant, in the very unlikely event of reactor vessel failure. The Reactor Vessel Auxiliary Cooling System (RVACS) implementing the natural circulation of air flowing upwards over the guard vessel is used to cool the reactor, in the case of loss of normal heat removal through the IRHXs. The RVACS is always in operation. The gap between the vessels is filled with liquid lead-bismuth eutectic (LBE) to enhance the heat removal by air by significantly reducing the thermal

  9. Dynamic Modeling and Control of Nuclear Reactors Coupled to Closed-Loop Brayton Cycle Systems using SIMULINKTM

    International Nuclear Information System (INIS)

    The operation of space reactors for both in-space and planetary operations will require unprecedented levels of autonomy and control. Development of these autonomous control systems will require dynamic system models, effective control methodologies, and autonomous control logic. This paper briefly describes the results of reactor, power-conversion, and control models that are implemented in SIMULINKTM (Simulink, 2004). SIMULINKTM is a development environment packaged with MatLabTM (MatLab, 2004) that allows the creation of dynamic state flow models. Simulation modules for liquid metal, gas cooled reactors, and electrically heated systems have been developed, as have modules for dynamic power-conversion components such as, ducting, heat exchangers, turbines, compressors, permanent magnet alternators, and load resistors. Various control modules for the reactor and the power-conversion shaft speed have also been developed and simulated. The modules are compiled into libraries and can be easily connected in different ways to explore the operational space of a number of potential reactor, power-conversion system configurations, and control approaches. The modularity and variability of these SIMULINKTM models provides a way to simulate a variety of complete power generation systems. To date, both Liquid Metal Reactors (LMR), Gas Cooled Reactors (GCR), and electric heaters that are coupled to gas-dynamics systems and thermoelectric systems have been simulated and are used to understand the behavior of these systems. Current efforts are focused on improving the fidelity of the existing SIMULINKTM modules, extending them to include isotopic heaters, heat pipes, Stirling engines, and on developing state flow logic to provide intelligent autonomy. The simulation code is called RPC-SIM (Reactor Power and Control-Simulator)

  10. A hybrid Brayton engine concept

    Science.gov (United States)

    Six, L. D.; Elkins, R.

    1980-01-01

    A first generation open cycle Brayton engine concept for use in full scale solar module testing was defined. The concept extended to include solar/fossil hybrid capability. The combustion system defined for hybrid operation consists of a wide range combustor liner, a single airblast atomizer, an ignitor and a high-voltage ignition unit. Wide range combustor operation would be achieved through combining pilot and primary zones. The hybrid control mode and the solar only control mode are both based on the concept of maintaining constant turbine inlet temperature and varying the engine speed for part-power operation. In addition, the hybrid control concept will allow the operator to set a minimum thermal power input to the engine by setting a corresponding minimum engine speed. When the solar thermal power input falls below this minimum, fossil fuel would be utilized to augment the solar thermal power input.

  11. Brayton heat exchange unit development program

    Science.gov (United States)

    Morse, C. J.; Richard, C. E.; Duncan, J. D.

    1971-01-01

    A Brayton Heat Exchanger Unit (BHXU), consisting of a recuperator, a heat sink heat exchanger and a gas ducting system, was designed, fabricated, and tested. The design was formulated to provide a high performance unit suitable for use in a long-life Brayton-cycle powerplant. A parametric analysis and design study was performed to establish the optimum component configurations to achieve low weight and size and high reliability, while meeting the requirements of high effectiveness and low pressure drop. Layout studies and detailed mechanical and structural design were performed to obtain a flight-type packaging arrangement. Evaluation testing was conducted from which it is estimated that near-design performance can be expected with the use of He-Xe as the working fluid.

  12. Preliminary Study of the Supercritical CO2 Hybrid Cycle for the HTGR Application

    International Nuclear Information System (INIS)

    This study was conducted to explore the potential of Supercritical Carbon Dioxide (S-CO2) Brayton cycle for the HTGR application. The S-CO2 cycle is being considered as a PCS due to its high thermal efficiency, simplicity, compactness and so on. Generally, the S-CO2 Brayton cycle is characterized as a highly recuperated cycle which means that to achieve high thermal efficiency, the cycle requires a highly effective recuperator. Argonne National Laboratory (ANL) showed that direct application of the standard S-CO2 recompressing Brayton cycle to the HTGR or the Very High Temperature Reactor (VHTR) is difficult to achieve high thermal efficiency due to the mismatch of the temperature difference between the temperature drop of helium as the primary reactor coolant and the temperature rise of CO2 as the PCS coolant through an Intermediate Heat Exchanger (IHX). Therefore, our research team suggests a novel S-CO2 cycle configuration, the S-CO2 Brayton and Rankine hybrid cycle, to solve this limitation. This S-CO2 hybrid concept is utilizing the waste heat of the S-CO2 Brayton cycle as heat input to the S-CO2 Rankine cycle. Dividing the thermal capacity of the heat source in to the Brayton cycle part and Rankine cycle part of the S-CO2 hybrid cycle appropriately, the temperature difference at the IHX could be reduced, therefore the net system performance and operating range can be improved. In this study, the ANL research is reviewed by the in-house cycle analysis codes developed by the Korea Advanced Institute of Science and Technology (KAIST) research team. And the S-CO2 Brayton and Rankine hybrid cycle is studied as a PCS for the VHTR condition which was utilized by ANL research team; it was assumed that the core outlet temperature to be 850 .deg. C and the core inlet temperature of 400 .deg. C

  13. Development of a 77K Reverse-Brayton Cryocooler with Multiple Coldheads Project

    Data.gov (United States)

    National Aeronautics and Space Administration — RTI will design and optimize an 80 W, 77K cryocooler based on the reverse turbo Brayton cycle (RTBC) with four identical coldheads for distributed cooling. Based on...

  14. Improved Gene Targeting through Cell Cycle Synchronization.

    Directory of Open Access Journals (Sweden)

    Vasiliki Tsakraklides

    Full Text Available Gene targeting is a challenge in organisms where non-homologous end-joining is the predominant form of recombination. We show that cell division cycle synchronization can be applied to significantly increase the rate of homologous recombination during transformation. Using hydroxyurea-mediated cell cycle arrest, we obtained improved gene targeting rates in Yarrowia lipolytica, Arxula adeninivorans, Saccharomyces cerevisiae, Kluyveromyces lactis and Pichia pastoris demonstrating the broad applicability of the method. Hydroxyurea treatment enriches for S-phase cells that are active in homologous recombination and enables previously unattainable genomic modifications.

  15. Productivity improvement through cycle time analysis

    Science.gov (United States)

    Bonal, Javier; Rios, Luis; Ortega, Carlos; Aparicio, Santiago; Fernandez, Manuel; Rosendo, Maria; Sanchez, Alejandro; Malvar, Sergio

    1996-09-01

    A cycle time (CT) reduction methodology has been developed in the Lucent Technology facility (former AT&T) in Madrid, Spain. It is based on a comparison of the contribution of each process step in each technology with a target generated by a cycle time model. These targeted cycle times are obtained using capacity data of the machines processing those steps, queuing theory and theory of constrains (TOC) principles (buffers to protect bottleneck and low cycle time/inventory everywhere else). Overall efficiency equipment (OEE) like analysis is done in the machine groups with major differences between their target cycle time and real values. Comparisons between the current value of the parameters that command their capacity (process times, availability, idles, reworks, etc.) and the engineering standards are done to detect the cause of exceeding their contribution to the cycle time. Several friendly and graphical tools have been developed to track and analyze those capacity parameters. Specially important have showed to be two tools: ASAP (analysis of scheduling, arrivals and performance) and performer which analyzes interrelation problems among machines procedures and direct labor. The performer is designed for a detailed and daily analysis of an isolate machine. The extensive use of this tool by the whole labor force has demonstrated impressive results in the elimination of multiple small inefficiencies with a direct positive implications on OEE. As for ASAP, it shows the lot in process/queue for different machines at the same time. ASAP is a powerful tool to analyze the product flow management and the assigned capacity for interdependent operations like the cleaning and the oxidation/diffusion. Additional tools have been developed to track, analyze and improve the process times and the availability.

  16. Dynamic simulation of a reverse Brayton refrigerator

    Energy Technology Data Exchange (ETDEWEB)

    Peng, N.; Xiong, L. Y.; Dong, B.; Liu, L. Q. [State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, CAS, Beijing, 100190 (China); Lei, L. L.; Tang, J. C. [State Key Laboratory of Technologies in Space Cryogenic Propellants, Technical Institute of Physics and Chemistry, CAS, Beijing, 100190 China and Graduate University of Chinese Academy of Sciences, Beijing, 100190 (China)

    2014-01-29

    A test refrigerator based on the modified Reverse Brayton cycle has been developed in the Chinese Academy of Sciences recently. To study the behaviors of this test refrigerator, a dynamic simulation has been carried out. The numerical model comprises the typical components of the test refrigerator: compressor, valves, heat exchangers, expander and heater. This simulator is based on the oriented-object approach and each component is represented by a set of differential and algebraic equations. The control system of the test refrigerator is also simulated, which can be used to optimize the control strategies. This paper describes all the models and shows the simulation results. Comparisons between simulation results and experimental data are also presented. Experimental validation on the test refrigerator gives satisfactory results.

  17. Dynamic simulation of a reverse Brayton refrigerator

    International Nuclear Information System (INIS)

    A test refrigerator based on the modified Reverse Brayton cycle has been developed in the Chinese Academy of Sciences recently. To study the behaviors of this test refrigerator, a dynamic simulation has been carried out. The numerical model comprises the typical components of the test refrigerator: compressor, valves, heat exchangers, expander and heater. This simulator is based on the oriented-object approach and each component is represented by a set of differential and algebraic equations. The control system of the test refrigerator is also simulated, which can be used to optimize the control strategies. This paper describes all the models and shows the simulation results. Comparisons between simulation results and experimental data are also presented. Experimental validation on the test refrigerator gives satisfactory results

  18. Improvements in the Rapid Cycling Synchrotron

    International Nuclear Information System (INIS)

    The Rapid Cycling Synchrotron1 (RCS), originally designed as an injection energy booster for the Zero Gradient Synchrotron (ZGS), operated under contraints imposed by ZGS operation until December 1979. Once these restraints were removed, the RCS made rapid strides toward its nearterm goals of 8 μA of protons for Argonne National Laboratory's (ANL) Intense Pulsed Neutron Source (IPNS) program. Reliable 30 Hz operation was achieved in the spring of 1980 with beams as high as 2 x 1012 protons per pulse and weekly average intensities of over 6 μA on target. These gains resulted from better injection matching, more efficient RF turn-on and dynamic chromatricity control. A high intensity small diameter synchrotron, such as the RCS, has special problems with loss control which dictate prudence during intensity improvment activities. Additional improvements were made to the machine starting in August of 1980 while the extraction magnets were relocated for operation with the IPNS-I target. These improvements have now been completed. Startup of the accelerator is now underway, and it is clear that these modifications have resulted in a radio-actively cleaner operation. It is too early to evaluate the effects of the improvements on intensity and reliability, but a single pulse extracted intensity of 2.4 x 1012 protons has been achieved, a 20% increase. The studies and equipment leading to the intensity gains are discussed. (orig.)

  19. Improvements in the rapid cycling synchrotron

    International Nuclear Information System (INIS)

    The Rapid Cycling Snychrotron1 (RCS), originally designed as an injection energy booster for the Zero Gradient Synchrotron (ZGS), operated under constraints imposed by ZGS operation until December 1979. Once these restraints were removed, the RCS made rapid strides toward its nearterm goals of 8 μA of protons for Argonne National Laboratory's (ANL) Intense Pulsed Neutron Source (IPNS) program. Reliable 30 Hz operation was achieved in the spring of 1980 with beams as high as 2 x 1012 protons per pulse and weekly average intensities of over 6 μA on target. These gains resulted from better injection matching, more efficient RF turn-on and dynamic chromaticity control. A high intensity small diameter synchrotron, such as the RCS, has special problems with loss control which dictate prudence during intensity improvement activities. Additional improvements were made to the machine starting in August of 1980 while the extraction magnets were relocated for operation with the IPNS-I target. These improvements have now been completed. Startup of the accelerator is now underway, and it is clear that these modifications have resulted in a radioactively cleaner operation. It is too early to evaluate the effects of the improvements on intensity and reliability, but a single pulse extracted intensity of 2.4 x 1012 protons has been achieved, a 20% increase. The studies and equipment leading to the intensity gains are discussed. (orig.)

  20. Rankline-Brayton engine powered solar thermal aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Charles L. (Livermore, CA)

    2012-03-13

    A solar thermal powered aircraft powered by heat energy from the sun. A Rankine-Brayton hybrid cycle heat engine is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller or other mechanism for enabling sustained free flight. The Rankine-Brayton engine has a thermal battery, preferably containing a lithium-hydride and lithium mixture, operably connected to it so that heat is supplied from the thermal battery to a working fluid. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.

  1. Rankine-Brayton engine powered solar thermal aircraft

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Charles L. (Livermore, CA)

    2009-12-29

    A solar thermal powered aircraft powered by heat energy from the sun. A Rankine-Brayton hybrid cycle heat engine is carried by the aircraft body for producing power for a propulsion mechanism, such as a propeller or other mechanism for enabling sustained free flight. The Rankine-Brayton engine has a thermal battery, preferably containing a lithium-hydride and lithium mixture, operably connected to it so that heat is supplied from the thermal battery to a working fluid. A solar concentrator, such as reflective parabolic trough, is movably connected to an optically transparent section of the aircraft body for receiving and concentrating solar energy from within the aircraft. Concentrated solar energy is collected by a heat collection and transport conduit, and heat transported to the thermal battery. A solar tracker includes a heliostat for determining optimal alignment with the sun, and a drive motor actuating the solar concentrator into optimal alignment with the sun based on a determination by the heliostat.

  2. Thermodynamic design of 10 kW Brayton cryocooler for HTS cable

    Science.gov (United States)

    Chang, Ho-Myung; Park, C. W.; Yang, H. S.; Sohn, Song Ho; Lim, Ji Hyun; Oh, S. R.; Hwang, Si Dole

    2012-06-01

    Thermodynamic design of Brayton cryocooler is presented as part of an ongoing governmental project in Korea, aiming at 1 km HTS power cable in the transmission grid. The refrigeration requirement is 10 kW for continuously sub-cooling liquid nitrogen from 72 K to 65 K. An ideal Brayton cycle for this application is first investigated to examine the fundamental features. Then a practical cycle for a Brayton cryocooler is designed, taking into account the performance of compressor, expander, and heat exchangers. Commercial software (Aspen HYSYS) is used for simulating the refrigeration cycle with real fluid properties of refrigerant. Helium is selected as a refrigerant, as it is superior to neon in thermodynamic efficiency. The operating pressure and flow rate of refrigerant are decided with a constraint to avoid the freezing of liquid nitrogen

  3. Preliminary Study of the Supercritical CO{sub 2} Hybrid Cycle for the HTGR Application

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Seong Jun; Ahn, Yoonhan; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2014-05-15

    This study was conducted to explore the potential of Supercritical Carbon Dioxide (S-CO{sub 2}) Brayton cycle for the HTGR application. The S-CO{sub 2} cycle is being considered as a PCS due to its high thermal efficiency, simplicity, compactness and so on. Generally, the S-CO{sub 2} Brayton cycle is characterized as a highly recuperated cycle which means that to achieve high thermal efficiency, the cycle requires a highly effective recuperator. Argonne National Laboratory (ANL) showed that direct application of the standard S-CO{sub 2} recompressing Brayton cycle to the HTGR or the Very High Temperature Reactor (VHTR) is difficult to achieve high thermal efficiency due to the mismatch of the temperature difference between the temperature drop of helium as the primary reactor coolant and the temperature rise of CO{sub 2} as the PCS coolant through an Intermediate Heat Exchanger (IHX). Therefore, our research team suggests a novel S-CO{sub 2} cycle configuration, the S-CO{sub 2} Brayton and Rankine hybrid cycle, to solve this limitation. This S-CO{sub 2} hybrid concept is utilizing the waste heat of the S-CO{sub 2} Brayton cycle as heat input to the S-CO{sub 2} Rankine cycle. Dividing the thermal capacity of the heat source in to the Brayton cycle part and Rankine cycle part of the S-CO{sub 2} hybrid cycle appropriately, the temperature difference at the IHX could be reduced, therefore the net system performance and operating range can be improved. In this study, the ANL research is reviewed by the in-house cycle analysis codes developed by the Korea Advanced Institute of Science and Technology (KAIST) research team. And the S-CO{sub 2} Brayton and Rankine hybrid cycle is studied as a PCS for the VHTR condition which was utilized by ANL research team; it was assumed that the core outlet temperature to be 850 .deg. C and the core inlet temperature of 400 .deg. C.

  4. Overview of CNES-CEA joint program on space nuclear Brayton systems

    International Nuclear Information System (INIS)

    In this paper French studies on 20-kWe space nuclear power systems are presented. The gas-cooled reactor nuclear systems, some investigations on advanced thermal neutron spectrum systems, a support work on materials, parameters optimization and operating transient analysis, and Brayton cycle-thermoelectric and nuclear-non nuclear systems comparisons

  5. Fuel cycle economical improvement by reaching high fuel burnup

    International Nuclear Information System (INIS)

    Improvements of fuel utilization in the light water reactors, burnup increase have led to a necessity to revise strategic approaches of the fuel cycle development. Different trends of the fuel cycle development are necessary to consider in accordance with the type of reactors used, the uranium market and other features that correspond to the nuclear and economic aspects of the fuel cycle. The fuel burnup step-by-step extension Program that successfully are being realized by the leading, firms - fuel manufacturers and the research centres allow to say that there are no serious technical obstacles for licensing in the near future of water cooling reactors fuel rod burnup (average) limit to 65-70 MWd/kgU and fuel assembly (average) limit to (60-65) MWd/kgU. The operating experience of Ukrainian NPPs with WWER-1000 is 130 reactor * years. At the beginning of 1999, a total quantity of the fuel FA discharged during all time of operation of 11 reactors was 5819 (110 fuel cycles). Economical improvement is reached by increase of fuel burn-up by using of some FA of 3 fuel cycles design in 4th fuel loading cycle. Fuel reliability is satisfactory. The further improvement of FA is necessary, that will allow to reduce the front-end fuel cycle cost (specific natural uranium expenditure), to reduce spent fuel amount and, respectively, the fuel cycle back end costs, and to increase burn-up of the fuel. (author)

  6. Experimental and Analytical Performance of a Dual Brayton Power Conversion System

    Science.gov (United States)

    Lavelle, Thomas A.; Hervol, David S.; Briggs, Maxwell; Owen, A. Karl

    2009-01-01

    The interactions between two closed Brayton cycle (CBC) power conversion units (PCU) which share a common gas inventory and heat source have been studied experimentally using the Dual Brayton Power Conversion System (DBPCS) and analytically using the Closed- Cycle System Simulation (CCSS) computer code. Selected operating modes include steady-state operation at equal and unequal shaft speeds and various start-up scenarios. Equal shaft speed steady-state tests were conducted for heater exit temperatures of 840 to 950 K and speeds of 50 to 90 krpm, providing a system performance map. Unequal shaft speed steady-state testing over the same operating conditions shows that the power produced by each Brayton is sensitive to the operating conditions of the other due to redistribution of gas inventory. Startup scenarios show that starting the engines one at a time can dramatically reduce the required motoring energy. Although the DBPCS is not considered a flight-like system, these insights, as well as the operational experience gained from operating and modeling this system provide valuable information for the future development of Brayton systems.

  7. Comparison of Direct and Indirect Gas Reactor Brayton Systems for Nuclear Electric Space Propulsion

    International Nuclear Information System (INIS)

    Gas reactor systems are being considered as candidates for use in generating power for the Prometheus-1 spacecraft, along with other NASA missions as part of the Prometheus program. Gas reactors offer a benign coolant, which increases core and structural materials options. However, the gas coolant has inferior thermal transport properties, relative to other coolant candidates such as liquid metals. This leads to concerns for providing effective heat transfer and for minimizing pressure drop within the reactor core. In direct gas Brayton systems, i.e. those with one or more Brayton turbines in the reactor cooling loop, the ability to provide effective core cooling and low pressure drop is further constrained by the need for a low pressure, high molecular weight gas, typically a mixture of helium and xenon. Use of separate primary and secondary gas loops, one for the reactor and one or more for the Brayton system(s) separated by heat exchanger(s), allows for independent optimization of the pressure and gas composition of each loop. The reactor loop can use higher pressure pure helium, which provides improved heat transfer and heat transport properties, while the Brayton loop can utilize lower pressure He-Xe. However, this approach requires a separate primary gas circulator and also requires gas to gas heat exchangers. This paper focuses on the trade-offs between the direct gas reactor Brayton system and the indirect gas Brayton system. It discusses heat exchanger arrangement and materials options and projects heat exchanger mass based on heat transfer area and structural design needs. Analysis indicates that these heat exchangers add considerable mass, but result in reactor cooling and system resiliency improvements

  8. Technology for Bayton-cycle powerplants using solar and nuclear energy

    Science.gov (United States)

    English, R. E.

    1986-01-01

    Brayton cycle gas turbines have the potential to use either solar heat or nuclear reactors for generating from tens of kilowatts to tens of megawatts of power in space, all this from a single technology for the power generating system. Their development for solar energy dynamic power generation for the space station could be the first step in an evolution of such powerplants for a very wide range of applications. At the low power level of only 10 kWe, a power generating system has already demonstrated overall efficiency of 0.29 and operated 38 000 hr. Tests of improved components show that these components would raise that efficiency to 0.32, a value twice that demonstrated by any alternate concept. Because of this high efficiency, solar Brayton cycle power generators offer the potential to increase power per unit of solar collector area to levels exceeding four times that from photovoltaic powerplants using present technology for silicon solar cells. The technologies for solar mirrors and heat receivers are reviewed and assessed. This Brayton technology for solar powerplants is equally suitable for use with the nuclear reactors. The available long time creep data on the tantalum alloy ASTAR-811C show that such Brayton cycles can evolve to cycle peak temperatures of 1500 K (2240 F). And this same technology can be extended to generate 10 to 100 MW in space by exploiting existing technology for terrestrial gas turbines in the fields of both aircraft propulsion and stationary power generation.

  9. Effects of vibration and shock on the performance of gas-bearing space-power Brayton cycle turbomachinery. Part 4: Suppression of rotor-bearing system vibrations through flexible bearing support damping

    Science.gov (United States)

    Tessarzik, J. M.; Chiang, T.; Badgley, R. H.

    1974-01-01

    A bearing damper, operating on the support flexure of a pivoted pad in a tilting-pad type gas-lubricated journal bearing, has been designed, built, and tested under externally-applied random vibrations. The NASA Brayton Rotating Unit (BRU), a 36,000 rpm, 10-Kwe turbogenerator had previously been subjected in the MTI Vibration Test Laboratory to external random vibrations, and vibration response data had been recorded and analyzed for amplitude distribution and frequency content at a number of locations in the machine. Based on data from that evaluation, a piston-type damper was designed and developed for each of the two flexibly-supported journal bearing pads (one in each of the two three-pad bearings). A modified BRU, with dampers installed, has been re-tested under random vibration conditions. Root-mean-square vibration amplitudes were determined from the test data, and displacement power spectral density analyses have been performed. Results of these data reduction efforts have been compared with vibration tolerance limits. Results of the tests indicate significant reductions in vibration levels in the bearing gas-lubricant films, particularly in the rigidly-mounted pads. The utility of the gas-lubricated damper for limiting rotor-bearing system vibrations in high-speed turbomachinery has thus been demonstrated.

  10. Phase 2 Brayton/Rankine 10-ton gas-fired space-conditioning system

    Science.gov (United States)

    1982-07-01

    The technical accomplishments to date in the design, development, and demonstration program leading to commercialization of a 10 ton heat actuated space conditioning system for light commercialization of a 10 ton heat actuated space conditioning system for light commercial building applications are summarized. The system consists of a natural gas powered Brayton cycle engine and a Rankine cycle heat pump, combined in a single roof top package. The heat actuated space conditioning system provides more efficient use of natural gas and is intended as an all gas alternative to the electric heat pump. The system employs a subatmospheric natural gas fired heat pump. A centrifugal R-12 refrigerant compressor is driven directly from the Brayton engine rotating group through a hermetically sealed coupling. Unique features that offer high life cycle performance include a permanent magnet coupling, foil bearings, an atmospheric in-line combustor, and a high temperature recuperator.

  11. A New, Highly Improved Two-Cycle Engine

    Science.gov (United States)

    Wiesen, Bernard

    2008-01-01

    The figure presents a cross-sectional view of a supercharged, variable-compression, two-cycle, internal-combustion engine that offers significant advantages over prior such engines. The improvements are embodied in a combination of design changes that contribute synergistically to improvements in performance and economy. Although the combination of design changes and the principles underlying them are complex, one of the main effects of the changes on the overall engine design is reduced (relative to prior two-cycle designs) mechanical complexity, which translates directly to reduced manufacturing cost and increased reliability. Other benefits include increases in the efficiency of both scavenging and supercharging. The improvements retain the simplicity and other advantages of two-cycle engines while affording increases in volumetric efficiency and performance across a wide range of operating conditions that, heretofore have been accessible to four-cycle engines but not to conventionally scavenged two-cycle ones, thereby increasing the range of usefulness of the two-cycle engine into all areas now dominated by the four-cycle engine. The design changes and benefits are too numerous to describe here in detail, but it is possible to summarize the major improvements: Reciprocating Shuttle Inlet Valve The entire reciprocating shuttle inlet valve and its operating gear is constructed as a single member. The shuttle valve is actuated in a lost-motion arrangement in which, at the ends of its stroke, projections on the shuttle valve come to rest against abutments at the ends of grooves in a piston skirt. This shuttle-valve design obviates the customary complex valve mechanism, actuated from an engine crankshaft or camshaft, yet it is effective with every type of two-cycle engine, from small high-speed single cylinder model engines, to large low-speed multiple cylinder engines.

  12. On Brayton and Moser's missing stability theorem

    NARCIS (Netherlands)

    Jeltsema, D.; Scherpen, J. M. A.

    2005-01-01

    In the early 1960s, Brayton and Moser proved three theorems concerning the stability of nonlinear electrical circuits. The applicability of each theorem depends on three different conditions on the type of admissible nonlinearities in circuit. Roughly speaking, this means that the theorems apply to

  13. Brayton Isotope Power System (BIPS) facility specification

    Energy Technology Data Exchange (ETDEWEB)

    1976-05-31

    General requirements for the Brayton Isotope Power System (BIPS)/Ground Demonstration System (GDS) assembly and test facility are defined. The facility will include provisions for a complete test laboratory for GDS checkout, performance, and endurance testing, and a contamination-controlled area for assembly, fabrication, storage, and storage preparation of GDS components. Specifications, schedules, and drawings are included.

  14. Brayton Isotope Power System (BIPS) facility specification

    International Nuclear Information System (INIS)

    General requirements for the Brayton Isotope Power System (BIPS)/Ground Demonstration System (GDS) assembly and test facility are defined. The facility will include provisions for a complete test laboratory for GDS checkout, performance, and endurance testing, and a contamination-controlled area for assembly, fabrication, storage, and storage preparation of GDS components. Specifications, schedules, and drawings are included

  15. Life Cycle Exergy Analysis of Wind Energy Systems : Assessing and improving life cycle analysis methodology

    OpenAIRE

    Davidsson, Simon

    2011-01-01

    Wind power capacity is currently growing fast around the world. At the same time different forms of life cycle analysis are becoming common for measuring the environmental impact of wind energy systems. This thesis identifies several problems with current methods for assessing the environmental impact of wind energy and suggests improvements that will make these assessments more robust. The use of the exergy concept combined with life cycle analysis has been proposed by several researchers ov...

  16. Advanced fuel developments to improve fuel cycle cost in PWR

    International Nuclear Information System (INIS)

    Increasingly lower fuel cycle costs and higher plant availability factors have been two crucial components in keeping the overall cost of electricity produced by nuclear low and competitive with respect to other energy sources. The continuous quest to reduce fuel cycle cost has resulted in some consolidated trends in LWR fuel management schemes: smaller number of feed fuel assemblies with longer residence time; longer cycles, with 18-month cycle as the predominant option, and some plants already operating on, or considering, 24-month refueling intervals; higher power ratings with many plants undergoing power uprates. In order to maintain or improve fuel utilization for the longer cycles and/or higher power ratings, the licensed limits in fuel fissile content (5.0 w/o U235 enrichment) and discharge burnup (62 GWd/tHM for the peak pin) have been approached. In addition, Zr-based fuel cladding materials are also being challenged by the resulting increased duty. For the above reasons further improvements in fuel cycle cost have to overcome one or more of the current limits. This paper discusses an option to break through this 'stalemate', i.e. uranium nitride (UN) fuel with SiC clad. In UN the higher density of the nitride with respect to the oxide fuel leads to higher fissile content and reduction in the number of feed assemblies, improved fuel utilization and potentially higher specific powers. The SiC clad, among other benefits, enables higher clad irradiation, thereby exploiting the full potential of UN fuel. An alternative to employing UN fuel is to maintain UO2 fuel but boost the fissile content increasing the U235 enrichment beyond the 5 w/o limit. The paper describes and compares the potential benefits on fuel cycle cost of either option using realistic full-core calculations and ensuing economic analysis performed using Westinghouse in-house reactor physics tools and methodologies. (author)

  17. Performance analysis and parametric optimal criteria of an irreversible magnetic Brayton-refrigerator

    International Nuclear Information System (INIS)

    An irreversible magnetic Brayton refrigeration-cycle model is established, in which the thermal resistance and irreversibility in the two adiabatic processes are taken into account. Based on the model, the performance characteristics of the magnetic Brayton refrigeration-cycle are investigated and the effects of the irreversibilities and the ratio of the magnetic fields in the two iso-field processes on the performance of the refrigeration cycle are revealed. On the basis of the thermodynamic properties of a paramagnetic material, by using the optimal control-theory, the mathematical expressions for the cooling load and the coefficient of performance are derived and some important performance parameters, e.g., the temperatures of the working substance at several important state-points, are optimized. By means of numerical predictions, the optimal performance characteristic curves of the magnetic Brayton refrigeration-cycle are obtained and analyzed. Furthermore, some optimal operating-regions including those for the cooling load, coefficient of performance and the temperatures of the cyclic working substance at the two important state-points are determined and evaluated. Finally, several special cases are discussed in detail

  18. Exergy performance analysis for irreversible closed Brayton cycle combined cooling, heating and power generation plant driven by residual energy and heat of blast furnace%高炉余能余热驱动的不可逆闭式布雷顿热电冷联产装置(炯)性能分析

    Institute of Scientific and Technical Information of China (English)

    冯辉君; 陈林根; 孙丰瑞

    2013-01-01

    A combined cooling,heating and power (CCHP) generation plant model composing by one irreversible closed Brayton cycle driven by residual energy and heat of blast furnace and one endoreversible four-heat-reservoir absorption refrigeration cycle was established by using finite time thermodynamics.The expressions of the exergy output rate and exergy efficiency were derived.The effects of the cycle parameters on the characteristics of exergy output rate and exergy efficiency versus pressure ratio were analyzed by using numerical calculations.The performances of the maximum exergy output rate was compared with that of the maximum exergy efficiency and some suggestions on the designs and operations of actual CCHP plants were proposed.%用有限时间热力学理论建立了由一个高炉余能余热驱动的不可逆闭式布雷顿循环和一个内可逆四热源吸收式制冷循环组成的热电冷联产循环模型,导出了其(娴)输出率和(炯)效率的表达式.利用数值计算方法,分析了循环各参数对(炯)输出率和(炯)效率与压比关系的影响,比较了最大(炯)输出率和最大(炯)效率性能,给出了实际热电冷联产装置设计和运行的建议.

  19. Teresa Brayton: In an Irish Twilight

    OpenAIRE

    Morrin, Ms. Olive

    2002-01-01

    Teresa Brayton, poet, literary nationalist, author of "The Old Bog Road" was born in Kilbrook, Kilcock in 1868. She emigrated to America in 1895 and became well known in Irish-American circles. She published extensively in many American newspapers and magazines and was closely associated with the 1916 Rising. In 1913 she published her first book of poetry called "Songs of the Dawn, The Flame of Ireland" appeared in 1926 and "Christmas Verses" in 1934. Her main themes were the exile's nost...

  20. Improvements in steam cycle electric power generating plants

    International Nuclear Information System (INIS)

    The invention relates to a steam cycle electric energy generating plants of the type comprising a fossil or nuclear fuel boiler for generating steam and a turbo alternator group, the turbine of which is fed by the boiler steam. The improvement is characterized in that use is made of a second energy generating group in which a fluid (e.g. ammoniac) undergoes a condensation cycle the heat source of said cycle being obtained through a direct or indirect heat exchange with a portion of the boiler generated steam whereby it is possible without overloading the turbo-alternator group, to accomodate any increase of the boiler power resulting from the use of another fuel while maintaining a maximum energy output. This can be applied to electric power stations

  1. Improvements to Emergy evaluations by using Life Cycle Assessment.

    Science.gov (United States)

    Rugani, Benedetto; Benetto, Enrico

    2012-05-01

    Life Cycle Assessment (LCA) is a widely recognized, multicriteria and standardized tool for environmental assessment of products and processes. As an independent evaluation method, emergy assessment has shown to be a promising and relatively novel tool. The technique has gained wide recognition in the past decade but still faces methodological difficulties which prevent it from being accepted by a broader stakeholder community. This review aims to elucidate the fundamental requirements to possibly improve the Emergy evaluation by using LCA. Despite its capability to compare the amount of resources embodied in production systems, Emergy suffers from its vague accounting procedures and lacks accuracy, reproducibility, and completeness. An improvement of Emergy evaluations can be achieved via (1) technical implementation of Emergy algebra in the Life Cycle Inventory (LCI); (2) selection of consistent Unit Emergy Values (UEVs) as characterization factors for Life Cycle Impact Assessment (LCIA); and (3) expansion of the LCI system boundaries to include supporting systems usually considered by Emergy but excluded in LCA (e.g., ecosystem services and human labor). Whereas Emergy rules must be adapted to life-cycle structures, LCA should enlarge its inventory to give Emergy a broader computational framework. The matrix inversion principle used for LCAs is also proposed as an alternative to consistently account for a large number of resource UEVs. PMID:22489863

  2. WWER-440 fuel cycles possibilities using improved fuel assemblies design

    International Nuclear Information System (INIS)

    Practically five years cycle has been achieved in the last years at NPP Dukovany. There are two principal means how it could be achieved. First, it is necessary to use fuel assemblies with higher fuel enrichment and second, to use fuel loading with very low leakage. Both these conditions are fulfilled at NPP Dukovany at this time. It is known, that the fuel cycle economy can be improved by increasing the fuel residence time in the core up to six years. There are at least two ways how this goal could be achieved. The simplest way is to increase enrichment in fuel. There exists a limit, which is 5.0 w % of 235U. Taking into account some uncertainty, the calculation maximum is 4.95 w % of 235U. The second way is to change fuel assembly design. There are several possibilities, which seem to be suitable from the neutron - physical point of view. The first one is higher mass content of uranium in a fuel assembly. The next possibility is to enlarge pin pitch. The last possibility is to 'omit' FA shroud. This is practically unrealistic; anyway, some other structural parts must be introduced. The basic neutron physical characteristics of these cycles for up-rated power are presented showing that the possibilities of fuel assemblies with this improved design in enlargement of fuel cycles are very promising. In the end, on the basis of neutron physical characteristics and necessary economical input parameters, a preliminary evaluation of economic contribution of proposals of advanced fuel assemblies on fuel cycle economy is presented (Authors)

  3. Compressor and Turbine Models of Brayton Units for Space Nuclear Power Systems

    Science.gov (United States)

    Gallo, Bruno M.; El-Genk, Mohamed S.; Tournier, Jean-Michel

    2007-01-01

    Closed Brayton Cycles with centrifugal flow, single-shaft turbo-machines are being considered, with gas cooled nuclear reactors, to provide 10's to 100's of electrical power to support future space exploration missions and Lunar and Mars outposts. Such power system analysis is typically based on the cycle thermodynamics, for given operating pressures and temperatures and assumed polytropic efficiencies of the compressor and turbine of the Brayton energy conversion units. Thus the analysis results not suitable for modeling operation transients such as startup and changes in the electric load. To simulate these transients, accurate models of the turbine and compressor in the Brayton rotating unit, which calculate the changes in the compressor and turbine efficiencies with system operation are needed. This paper presents flow models that account for the design and dimensions of the compressor impeller and diffuser, and the turbine stator and rotor blades. These models calculate the various enthalpy losses and the polytropic efficiencies along with the pressure ratios of the turbine and compressor. The predictions of these models compare well with reported performance data of actual hardware. In addition, the results of a parametric analysis to map the operations of the compressor and turbine, as functions of the rotating shaft speed and inlet Mach number of the gas working fluid, are presented and discussed. The analysis used a binary mixture of He-Xe with a molecular weight of 40 g/mole as the working fluid.

  4. Carbon dioxide power cycles using liquid natural gas as heat sink

    International Nuclear Information System (INIS)

    Liquefied natural gas (LNG) is recognized as a source of usable cryogenic exergy for power cycles. The performance of conventional cycles are calculated. A binary steam-Organic Rankine Cycle (ORC) at 550 deg. C has an efficiency of about 52%, somewhat higher than that of a nitrogen Brayton cycle (50.7% at 700 deg. C). Carbon dioxide is recognized as an almost ideal medium for implementing single fluid condensation cycles. Its proven practical use both at low temperature (by the refrigeration industry) and at high temperature (by the nuclear reactor industry) makes it suitable for direct utilization without any extended preliminary research. A carbon dioxide cycle in its basic configuration featuring a pump, a regenerator, a heater and a condenser is much simpler than the binary steam-ORC cycle but has a lower efficiency (around 47%). All condensing cycles (ORC,CO2,...) exhibit a limited capability of exploiting the whole cryogenic exergy of LNG in that they cannot heat the natural gas at temperatures above the condensation temperature. This drawback is fully overcome in nitrogen Brayton cycles which can heat LNG up to ambient temperature. Slightly modifying the basic CO2 cycle so that it can partially use free thermal energy from sea water increases efficiency to 51%. Multiple condensation cycles allow a better overall performance at the cost of a more complex layout. Compound CO2 cycles, featuring also a gas compressor, exhibit an improved thermodynamics by reducing the temperature difference within the regenerator, with the result of increasing the overall efficiency at values better than those of both binary and Brayton cycles. At 600 deg. C top temperature, for example, a compound cycle at 100 bar maximum pressure has an efficiency of 55.3% (52.3% for a binary steam-ORC cycle at 550 deg. C, 150 bar steam parameters; 46.5% for the nitrogen cycle at 600 deg. C top temperature).

  5. HTR-Based Power Plants’ Performance Analysis Applied on Conventional Combined Cycles

    Directory of Open Access Journals (Sweden)

    José Carbia Carril

    2015-01-01

    Full Text Available In high temperature reactors including gas cooled fast reactors and gas turbine modular helium reactors (GT-MHR specifically designed to operate as power plant heat sources, efficiency enhancement at effective cost under safe conditions can be achieved. Mentioned improvements concern the implementation of two cycle structures: (a, a stand alone Brayton operating with helium and a stand alone Rankine cycle (RC with regeneration, operating with carbon dioxide at ultrasupercritical pressure as working fluid (WF, where condensation is carried out at quasicritical conditions, and (b, a combined cycle (CC, in which the topping closed Brayton cycle (CBC operates with helium as WF, while the bottoming RC is operated with one of the following WFs: carbon dioxide, xenon, ethane, ammonia, or water. In both cases, an intermediate heat exchanger (IHE is proposed to provide thermal energy to the closed Brayton or to the Rankine cycles. The results of the case study show that the thermal efficiency, through the use of a CC, is slightly improved (from 45.79% for BC and from 50.17% for RC to 53.63 for the proposed CC with He-H2O operating under safety standards.

  6. Advanced Organic Vapor Cycles for Improving Thermal Conversion Efficiency in Renewable Energy Systems

    OpenAIRE

    Ho, Tony

    2012-01-01

    The Organic Flash Cycle (OFC) is proposed as a vapor power cycle that could potentially increase power generation and improve the utilization efficiency of renewable energy and waste heat recovery systems. A brief review of current advanced vapor power cycles including the Organic Rankine Cycle (ORC), the zeotropic Rankine cycle, the Kalina cycle, the transcritical cycle, and the trilateral flash cycle is presented. The premise and motivation for the OFC concept is that essentially by impro...

  7. Comparison of Analytical Predictions and Experimental Results for a Dual Brayton Power System (Discussion on Test Hardware and Computer Model for a Dual Brayton System)

    Science.gov (United States)

    Johnson, Paul K.

    2007-01-01

    NASA Glenn Research Center (GRC) contracted Barber-Nichols, Arvada, CO to construct a dual Brayton power conversion system for use as a hardware proof of concept and to validate results from a computational code known as the Closed Cycle System Simulation (CCSS). Initial checkout tests were performed at Barber- Nichols to ready the system for delivery to GRC. This presentation describes the system hardware components and lists the types of checkout tests performed along with a couple issues encountered while conducting the tests. A description of the CCSS model is also presented. The checkout tests did not focus on generating data, therefore, no test data or model analyses are presented.

  8. Combined glucose ingestion and mouth rinsing improves sprint cycling performance.

    Science.gov (United States)

    Chong, Edwin; Guelfi, Kym J; Fournier, Paul A

    2014-12-01

    This study investigated whether combined ingestion and mouth rinsing with a carbohydrate solution could improve maximal sprint cycling performance. Twelve competitive male cyclists ingested 100 ml of one of the following solutions 20 min before exercise in a randomized double-blinded counterbalanced order (a) 10% glucose solution, (b) 0.05% aspartame solution, (c) 9.0% maltodextrin solution, or (d) water as a control. Fifteen min after ingestion, repeated mouth rinsing was carried out with 11 × 15 ml bolus doses of the same solution at 30-s intervals. Each participant then performed a 45-s maximal sprint effort on a cycle ergometer. Peak power output was significantly higher in response to the glucose trial (1188 ± 166 W) compared with the water (1036 ± 177 W), aspartame (1088 ± 128 W) and maltodextrin (1024 ± 202 W) trials by 14.7 ± 10.6, 9.2 ± 4.6 and 16.0 ± 6.0% respectively (p glucose trial compared with maltodextrin (p Glucose and maltodextrin resulted in a similar increase in blood glucose, and the responses of blood lactate and pH to sprinting did not differ significantly between treatments (p > .05). These findings suggest that combining the ingestion of glucose with glucose mouth rinsing improves maximal sprint performance. This ergogenic effect is unlikely to be related to changes in blood glucose, sweetness, or energy sensing mechanisms in the gastrointestinal tract. PMID:24668608

  9. Improved once-through fuel cycles for light water reactors

    International Nuclear Information System (INIS)

    This paper is being presented at this time to provide preliminary technical and economic data to INFCE for use in comparisons of alternate nuclear systems. Programs to develop improved once-through fuel cycles for the light water reactor are under way in the United States; therefore, the information presented in this report is preliminary and will be updated in the future as it becomes available. In the meantime, the following limitations should be recognized when using the information in this report: 1. The paper quantifies fuel utilization improvements which should be technically feasible in reactors now operating or under construction and indicates the approximate time frame when the necessary development and demonstration could be completed. It does not attempt to estimate the rate at which these improvements would attain acceptance and use by the industry. 2. One particular set of PWR and one particular set of BWR nuclear reactor and fuel design characteristics are used as base cases, from which many of the improvements are estimated. Many plants operating and being built throughout the world of course differ in design features, fuel management schemes, and fuel utilization efficiencies from the base cases used in this paper. The degree of improvement obtainable in these other designs, for each type of change considered, will vary with each design. 3. The changes emphasized here could all be backfitted in existing plants. Other possible improvements are limited by the need to avoid reducing the power output or capacity factor of the plants. New plants could be designed to accommodate such changes without reducing the power output or capacity factor. This could yield greater improvement in fuel utilization than can be obtained in existing plants. This longer range potential has not been examined here

  10. A parametric study of motor starting for a 2- to 10-kilowatt Brayton power system

    Science.gov (United States)

    Cantoni, D. A.

    1971-01-01

    A study of the motor starting of a Brayton cycle power system was conducted to provide estimates of system sensitivity to several controllable parameters. These sensitivity estimates were used as a basis for selection of an optimum motor-start scheme to be implemented on the 2- to 10-kilowatt Brayton power system designed and presently under test. The studies were conducted with an analog simulation of the Brayton power system and covered a range of frequencies from 400 Hz (33 percent design) to 1200 Hz (design), voltage-to-frequency ratios of 0.050 (50 percent design) to 0.100 (design), turbine-inlet temperatures of 800 K (1440 R, 70 percent design) to 1140 K (2060 deg R, design), and prestart pressure levels of 14.5 psia to 29.0 psia. These studies have shown the effect of selected system variables on motor starting. The final selection of motor-start variables can therefore be made on the basis of motor-start inverter complexity, battery size and weight, desired steady-state pressure level after startup, and other operational limitations. In general, the study showed the time required for motor starting to be inversely proportional to motor frequency, voltage, turbine-inlet temperature, and pressure level. An increase in any of these parameters decreases startup time.

  11. Performance analysis of a large-scale helium Brayton cryo-refrigerator with static gas bearing turboexpander

    International Nuclear Information System (INIS)

    Highlights: • A 2 kW at 20.0 K helium Brayton cryo-refrigerator is built in China. • A series of tests have been systematically conducted to investigate the performance of the cryo-refrigerator. • Maximum heat conductance proportion (90.7%) appears in the heat exchangers of cold box rather than those of heat reservoirs. • A model of helium Brayton cryo-refrigerator/cycle is presented according to finite-time thermodynamics. - Abstract: Large-scale helium cryo-refrigerator is widely used in superconducting systems, nuclear fusion engineering, and scientific researches, etc., however, its energy efficiency is quite low. First, a 2 kW at 20.0 K helium Brayton cryo-refrigerator is built, and a series of tests have been systematically conducted to investigate the performance of the cryo-refrigerator. It is found that maximum heat conductance proportion (90.7%) appears in the heat exchangers of cold box rather than those of heat reservoirs, which is the main characteristic of the helium Brayton cryo-refrigerator/cycle different from the air Brayton refrigerator/cycle. Other three characteristics also lie in the configuration of refrigerant helium bypass, internal purifier and non-linearity of specific heat of helium. Second, a model of helium Brayton cryo-refrigerator/cycle is presented according to finite-time thermodynamics. The assumption named internal purification temperature depth (PTD) is introduced, and the heat capacity rate of whole cycle is divided into three different regions in accordance with the PTD: room temperature region, upper internal purification temperature region and lower one. Analytical expressions of cooling capacity and COP are obtained, and we found that the expressions are piecewise functions. Further, comparison between the model and the experimental results for cooling capacity of the helium cryo-refrigerator shows that error is less than 7.6%. The PTD not only helps to achieve the analytical formulae and indicates the working

  12. Optimum performance analysis of a two-stage irreversible magnetization Brayton refrigeration system

    International Nuclear Information System (INIS)

    A two-stage magnetization Brayton refrigeration cycle model using a paramagnetic material as the working substance is established, in which the regeneration and the irreversibility in the adiabatic processes are taken into account. On the basis of the thermodynamic properties of a paramagnetic material, the expressions of some important parameters such as the coefficient of performance, refrigeration load and work input are derived and used to analyse the performance characteristics of the refrigeration cycle. The influence of the inter-magnetization process, irreversibility in the adiabatic processes and regeneration on the performance of the cycle is discussed in detail. The advantage of adding the inter-magnetization process is expounded and the magnetic field ratio related to the inter-magnetization process is optimized. Moreover, the optimal values of the temperatures of the working substance at different state points and the optimally operating region of the cycle are determined. The results obtained here are compared with those derived from some relevant magnetic Brayton refrigeration cycles, and consequently, some significant conclusions are obtained

  13. Process Cycle Efficiency Improvement Through Lean: A Case Study

    Directory of Open Access Journals (Sweden)

    P.V. Mohanram

    2011-06-01

    Full Text Available Lean manufacturing is an applied methodology of scientific, objective techniques that cause work tasks in a process to be performed with a minimum of non-value adding activities resulting in greatly reduced wait time, queue time, move time, administrative time, and other delays. This work addresses the implementation of lean principles in a construction equipment company. The prime objective is to evolve and test several strategies to eliminate waste on the shop floor. This paper describes an application of value stream mapping (VSM. Consequently, the present and future states of value stream maps are constructed to improve the production process by identifying waste and its sources. A noticeable reduction in cycle time and increase in cycle efficiency is confirmed. The production flow was optimized thus minimizing several non-value added activities/times such as bottlenecking time, waiting time, material handling time, etc. This case study can be useful in developing a more generic approach to design lean environment.

  14. Improved fluoride volatility reprocessing for MOX fuel cycle

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, M.; Fukasawa, T.; Sawa, T.; Yamashita, J.; Kamoshida, M.; Sasahira, A.; Kawamura, F. [Nuclear Systems Div., Hitachi, Ibaraki (Japan)

    2000-07-01

    Several countries had stopped developing fluoride volatility reprocessing method in the 1970's due to difficulties in recovering pure Pu. Although, nuclear societies recently favor dirty Pu (MOX). which has high proliferation resistance and needs remote fuel fabrication technologies. This situation reminded the authors to re-evaluate the fluoride volatility process. Preliminary investigation clarified that conventional fluoride volatility process could be simplified to recover dirty MOX and pure U from spent LWR fuels. Pure U is suitable to transfer it to re-enrichment (LWR cycle again), to storage certain period for future FBRs, and to dispose with relatively simple barrier. The improved process also enables to prepare directly the dirty MOX particles which are suitable for remote fuel fabrication (vibration packing). This paper describes the system of improved fluoride volatility reprocessing, and compatibility of each elemental process such as thermal decladding, two stage fluorination of U and U+Pu, U purification, direct conversion. of mixed fluoride into oxide particles and vibration packing fuel fabrication. (authors)

  15. Comparison of Analytical Predictions and Experimental Results for a Dual Brayton Power System

    Science.gov (United States)

    Johnson, Paul

    2007-01-01

    NASA Glenn Research Center (GRC) contracted Barber- Nichols, Arvada, CO to construct a dual Brayton power conversion system for use as a hardware proof of concept and to validate results from a computational code known as the Closed Cycle System Simulation (CCSS). Initial checkout tests were performed at Barber- Nichols to ready the system for delivery to GRC. This presentation describes the system hardware components and lists the types of checkout tests performed along with a couple issues encountered while conducting the tests. A description of the CCSS model is also presented. The checkout tests did not focus on generating data, therefore, no test data or model analyses are presented.

  16. Quantum-mechanical Brayton engine working with a particle in a one-dimensional harmonic trap

    Science.gov (United States)

    Wang, H.

    2013-05-01

    Based on the quantum version of thermodynamic processes, a quantum-mechanical Brayton engine model has been established. Expressions for the power output and efficiency of the engine are derived. Some fundamental optimal relations and general performance characteristic curves of the cycle are obtained. Furthermore, we note that it is possible to resist the reduction in efficiency, caused by compression of the adiabatic process, by decreasing the amount of energy levels of the quantum system. The results obtained here will provide theoretical guidance for the design of some new quantum-mechanical engines.

  17. Improving geothermal power plants with a binary cycle

    Science.gov (United States)

    Tomarov, G. V.; Shipkov, A. A.; Sorokina, E. V.

    2015-12-01

    The recent development of binary geothermal technology is analyzed. General trends in the introduction of low-temperature geothermal sources are summarized. The use of single-phase low-temperature geothermal fluids in binary power plants proves possible and expedient. The benefits of power plants with a binary cycle in comparison with traditional systems are shown. The selection of the working fluid is considered, and the influence of the fluid's physicochemical properties on the design of the binary power plant is discussed. The design of binary power plants is based on the chemical composition and energy potential of the geothermal fluids and on the landscape and climatic conditions at the intended location. Experience in developing a prototype 2.5 MW Russian binary power unit at Pauzhetka geothermal power plant (Kamchatka) is outlined. Most binary systems are designed individually for a specific location. Means of improving the technology and equipment at binary geothermal power plants are identified. One option is the development of modular systems based on several binary systems that employ the heat from the working fluid at different temperatures.

  18. Design and optimization of a novel organic Rankine cycle with improved boiling process

    DEFF Research Database (Denmark)

    Andreasen, Jesper Graa; Larsen, U.; Knudsen, Thomas;

    2015-01-01

    In this paper we present a novel organic Rankine cycle layout, named the organic split-cycle, designed for utilization of low grade heat. The cycle is developed by implementing a simplified version of the split evaporation concept from the Kalina split-cycle in the organic Rankine cycle in order to...... pinch point temperature difference to be reached at two locations in the boiler. Compared to the transcritical organic Rankine cycle, the organic split-cycle improves the boiling process without an entailing increase in the boiler pressure, thus enabling an efficient low grade heat to power conversion...

  19. Improving the cycling stability of silicon nanowire anodes with conducting polymer coatings

    KAUST Repository

    Yao, Yan

    2012-01-01

    For silicon nanowires (Si NWs) to be used as a successful high capacity lithium-ion battery anode material, improvements in cycling stability are required. Here we show that a conductive polymer surface coating on the Si NWs improves cycling stability; coating with PEDOT causes the capacity retention after 100 charge-discharge cycles to increase from 30% to 80% over bare NWs. The improvement in cycling stability is attributed to the conductive coating maintaining the mechanical integrity of the cycled Si material, along with preserving electrical connections between NWs that would otherwise have become electrically isolated during volume changes. © 2012 The Royal Society of Chemistry.

  20. Improving the quality of care for patients with hypertension in Moshupa District, Botswana: Quality improvement cycle

    Directory of Open Access Journals (Sweden)

    Cathy Kande

    2014-01-01

    Full Text Available Background: Although there are no prevalence studies on hypertension in Botswana, this condition is thought to be common and the quality of care to be poor.Aim: The aim of this project was to assess and improve the quality of primary care forhypertension.Setting: Moshupa clinic and catchment area, Botswana.Methods: Quality improvement cycle.Results: Two hundred participants were included in the audit. Sixty-eight per cent were women with a mean age of 55 years. In the baseline audit none of the target standards were met. During the re-audit six months later, six out of nine structural target standards, five out of 11 process target standards and one out of two outcome target standards were achieved. Statistically-significant improvement in performance (p < 0.05 was shown in 10 criteria although the target standard was not always met. In the re-audit, the target of achieving blood pressure control (< 140/90 in 70% of patients was achieved.Conclusion: The quality of care for hypertension was suboptimal in our setting. Simple interventions were designed and implemented to improve the quality of care. These interventions led to significant improvement in structural and process criteria. A corresponding significant improvement in the control of blood pressure was also seen.

  1. Exergy Analysis of a Subcritical Refrigeration Cycle with an Improved Impulse Turbo Expander

    OpenAIRE

    Zhenying Zhang; Lili Tian

    2014-01-01

    The impulse turbo expander (ITE) is employed to replace the throttling valve in the vapor compression refrigeration cycle to improve the system performance. An improved ITE and the corresponding cycle are presented. In the new cycle, the ITE not only acts as an expansion device with work extraction, but also serves as an economizer with vapor injection. An increase of 20% in the isentropic efficiency can be attained for the improved ITE compared with the conventional ITE owing to the reductio...

  2. Variations on the Zilch Cycle

    Science.gov (United States)

    Binder, P.-M.; Tanoue, C. K. S.

    2013-01-01

    Thermo dynamic cycles in introductory physics courses are usually made up from a small number of permutations of isothermal, adiabatic, and constant-pressure and volume quasistatic strokes, with the working fluid usually being an ideal gas. Among them we find the Carnot, Stirling, Otto, Diesel, and Joule-Brayton cycles; in more advanced courses,…

  3. Heat exchanger design for hot air ericsson-brayton piston engine

    Directory of Open Access Journals (Sweden)

    Ďurčanský P.

    2014-03-01

    Full Text Available One of the solutions without negative consequences for the increasing energy consumption in the world may be use of alternative energy sources in micro-cogeneration. Currently it is looking for different solutions and there are many possible ways. Cogeneration is known for long time and is widely used. But the installations are often large and the installed output is more suitable for cities or industry companies. When we will speak about decentralization, the small machines have to be used. The article deals with the principle of hot-air engines, their use in combined heat and electricity production from biomass and with heat exchangers as primary energy transforming element. In the article is hot air engine presented as a heat engine that allows the conversion of heat into mechanical energy while heat supply can be external. In the contribution are compared cycles of hot-air engine. Then are compared suitable heat exchangers for use with hot air Ericsson-Brayton engine. In the final part is proposal of heat exchanger for use in closed Ericsson-Brayton cycle.

  4. Nanosatellite Architectures for Improved Study of the Hydrologic Cycle

    Science.gov (United States)

    Blackwell, W. J.; Osaretin, I.; Cahoy, K.

    2012-12-01

    The need for low-cost, mission-flexible, and rapidly deployable spaceborne sensors that meet stringent performance requirements pervades the NASA Earth Science measurement programs, including especially the recommended NRC Decadal Survey missions. To address these challenges, we present nanosatellite constellation architectures that would profoundly improve both the performance and cost/risk/schedule profiles of NASA Earth and Space Science missions by leveraging recent technology advancements. As a key enabling element, we describe a scalable and mission-flexible 6U CubeSat-based self-organizing constellation architecture (the Distributed Observatory for Monitoring of Earth, henceforth "DOME") that will achieve state-of-the-art performance (and beyond) relative to current systems with respect to spatial, spectral, and radiometric resolution. A focus of this presentation is an assessment of the viability of a cross-linked CubeSat constellation with onboard propulsion systems for high-fidelity Earth and Space Science research. Such architecture could provide game-changing advances by reducing costs by at least an order of magnitude while increasing robustness to launch and sensor failures, allowing fast-track insertion of new technologies, and improving science performance. High-resolution passive microwave atmospheric sounding is an ideal sensing modality for nanosatellite implementation due to rapidly advancing microwave and millimeterwave receiver technology. The DOME constellation would nominally comprise 6U CubeSat Microwave Atmospheric Sounder (CMAS) satellites. Each CMAS satellite would host a complete 6U CubeSat atmospheric sounder, including a radiometer payload module with passive microwave receivers operating near atmospheric absorption lines near 60 and 183.31 GHz, and a spacecraft bus with attitude determination and control, avionics, power, cross-linked communications (spacecraft-to-spacecraft and spacecraft-to-ground), and propulsion systems. A

  5. Comparison Between helium cycle and Supercritical CO2 Cycle for MMR and AMR

    International Nuclear Information System (INIS)

    Korea Atomic Energy Research Institute (KAERI) started the development of Mobile Multi-Purpose Reactor (MMR), which is a 10MWth gas-cooled reactor. MMR is aiming for maximizing mobility, high performance, durability and safety. This is in order to use the MMR for many purposes such as ship propulsion, train engine and so on. MMR generally uses helium Brayton cycle as a power conversion system since it can obtain very simple system arrangement with direct cycle. However, some researchers have proposed that the supercritical carbon dioxide (S-CO2) Brayton cycle can be more efficient energy converting cycle for the high temperature gas cooled reactor (HTGR) and the very high temperature reactor (VHTR) system as well. Thus, this paper is to compare helium Brayton cycle to the S-CO2 Brayton cycle in terms of the efficiency while varying turbine inlet temperature (T. I. T). A cascaded S-CO2 cycle which had been proposed by Argonne National laboratory (ANL) was used as the S-CO2 Brayton cycle configuration. This cycle is to overcome the mismatch of temperature drop between reactor coolant and CO2 through the reactor heat exchanger (RHX). Our research team reviewed the ANL research by using the in-house codes developed by the Korea Advanced institute of Science and Technology (KAIST) research team. The calculation error between the in-house code and previous result was -0.36%

  6. Comparison Between helium cycle and Supercritical CO{sub 2} Cycle for MMR and AMR

    Energy Technology Data Exchange (ETDEWEB)

    Bae, Seong Jun; Lee, Jeong Ik; Ahn, Yoon Han; Lee, Je Kyoung [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of)

    2013-05-15

    Korea Atomic Energy Research Institute (KAERI) started the development of Mobile Multi-Purpose Reactor (MMR), which is a 10MWth gas-cooled reactor. MMR is aiming for maximizing mobility, high performance, durability and safety. This is in order to use the MMR for many purposes such as ship propulsion, train engine and so on. MMR generally uses helium Brayton cycle as a power conversion system since it can obtain very simple system arrangement with direct cycle. However, some researchers have proposed that the supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle can be more efficient energy converting cycle for the high temperature gas cooled reactor (HTGR) and the very high temperature reactor (VHTR) system as well. Thus, this paper is to compare helium Brayton cycle to the S-CO{sub 2} Brayton cycle in terms of the efficiency while varying turbine inlet temperature (T. I. T). A cascaded S-CO{sub 2} cycle which had been proposed by Argonne National laboratory (ANL) was used as the S-CO{sub 2} Brayton cycle configuration. This cycle is to overcome the mismatch of temperature drop between reactor coolant and CO{sub 2} through the reactor heat exchanger (RHX). Our research team reviewed the ANL research by using the in-house codes developed by the Korea Advanced institute of Science and Technology (KAIST) research team. The calculation error between the in-house code and previous result was -0.36%.

  7. Using report cards to sustain revenue cycle improvement.

    Science.gov (United States)

    Haray, David

    2005-07-01

    Five guiding principles can help your organization achieve revenue cycle success: Have appropriate job functions and work flow design in place. Elevate staff performance through quality and productivity goals. Ensure effective technology infrastructure is in place. Deploy at all levels a comprehensive management tool set and report card metric (dashboard). Sustain a culture of accountability. PMID:16060100

  8. Metabolic Engineering of the Tricarboxylic Acid Cycle for Improved Lysine Production by Corynebacterium glutamicum▿

    OpenAIRE

    Becker, Judith; Klopprogge, Corinna; Schröder, Hartwig; Wittmann, Christoph

    2009-01-01

    In the present work, lysine production by Corynebacterium glutamicum was improved by metabolic engineering of the tricarboxylic acid (TCA) cycle. The 70% decreased activity of isocitrate dehydrogenase, achieved by start codon exchange, resulted in a >40% improved lysine production. By flux analysis, this could be correlated to a flux shift from the TCA cycle toward anaplerotic carboxylation.

  9. Variable geometry gas turbines for improving the part-load performance of marine combined cycles - Combined cycle performance

    DEFF Research Database (Denmark)

    Haglind, Fredrik

    2011-01-01

    -derivative configuration and a single-shaft industrial configuration. The results suggest that by the use of variable geometry gas turbines, the combined cycle part-load performance can be improved. In order to minimise the voyage fuel consumption, a combined cycle featuring two-shaft gas turbines with VAN control is a...... promising alternative for container ships, while a cycle with single-shaft gas turbine configurations with VGV control is indicated to be an equally good choice for tankers and carriers.......The part-load performance of combined cycles intended for naval use is of great importance, and it is influenced by the gas turbine configuration and load control strategy. This paper is aimed at quantifying the effects of variable geometry gas turbines on the part-load efficiency for combined...

  10. Effects of backlash and dead band on temperature control of the primary loop of a conceptual nuclear Brayton space powerplant

    Science.gov (United States)

    Petrick, E. J.

    1973-01-01

    An analytical study was made of the stability of a closed-loop liquid-lithium temperature control of the primary loop of a conceptual nuclear Brayton space powerplant. The operating point was varied from 20 to 120 percent of design. A describing-function technique was used to evaluate the effects of temperature dead band and control coupling backlash. From the system investigation, it was predicted that a limit cycle will not exist with a temperature dead band, but a limit cycle will not exist when backlash is present. The results compare favorably with a digital computer simulation.

  11. Strength training improves cycling performance, fractional utilization of VO2max and cycling economy in female cyclists.

    Science.gov (United States)

    Vikmoen, O; Ellefsen, S; Trøen, Ø; Hollan, I; Hanestadhaugen, M; Raastad, T; Rønnestad, B R

    2016-04-01

    The purpose of this study was to investigate the effect of adding heavy strength training to well-trained female cyclists' normal endurance training on cycling performance. Nineteen female cyclists were randomly assigned to 11 weeks of either normal endurance training combined with heavy strength training (E+S, n = 11) or to normal endurance training only (E, n = 8). E+S increased one repetition maximum in one-legged leg press and quadriceps muscle cross-sectional area (CSA) more than E (P < 0.05), and improved mean power output in a 40-min all-out trial, fractional utilization of VO2 max and cycling economy (P < 0.05). The proportion of type IIAX-IIX muscle fibers in m. vastus lateralis was reduced in E+S with a concomitant increase in type IIA fibers (P < 0.05). No changes occurred in E. The individual changes in performance during the 40-min all-out trial was correlated with both change in IIAX-IIX fiber proportion (r = -0.63) and change in muscle CSA (r = 0.73). In conclusion, adding heavy strength training improved cycling performance, increased fractional utilization of VO2 max , and improved cycling economy. The main mechanisms behind these improvements seemed to be increased quadriceps muscle CSA and fiber type shifts from type IIAX-IIX toward type IIA. PMID:25892654

  12. Exergy Analysis of a Subcritical Refrigeration Cycle with an Improved Impulse Turbo Expander

    Directory of Open Access Journals (Sweden)

    Zhenying Zhang

    2014-08-01

    Full Text Available The impulse turbo expander (ITE is employed to replace the throttling valve in the vapor compression refrigeration cycle to improve the system performance. An improved ITE and the corresponding cycle are presented. In the new cycle, the ITE not only acts as an expansion device with work extraction, but also serves as an economizer with vapor injection. An increase of 20% in the isentropic efficiency can be attained for the improved ITE compared with the conventional ITE owing to the reduction of the friction losses of the rotor. The performance of the novel cycle is investigated based on energy and exergy analysis. A correlation of the optimum intermediate pressure in terms of ITE efficiency is developed. The improved ITE cycle increases the exergy efficiency by 1.4%–6.1% over the conventional ITE cycle, 4.6%–8.3% over the economizer cycle and 7.2%–21.6% over the base cycle. Furthermore, the improved ITE cycle is also preferred due to its lower exergy loss.

  13. Creating a Cycle of Continuous Improvement through Instructional Rounds

    Science.gov (United States)

    Meyer-Looze, Catherine L.

    2015-01-01

    Instructional Rounds is a continuous improvement strategy that focuses on the technical core of educational systems as well as educators collaborating side-by-side. Concentrating on collective learning, this process only makes sense within an overall strategy of improvement. This case study examined the Instructional Rounds process in a northern…

  14. Rapid-fire improvement with short-cycle kaizen.

    Science.gov (United States)

    Heard, E

    1999-05-01

    Continuous improvement is an attractive idea, but it is typically more myth than reality. SCK is no myth. It delivers dramatic improvements in traditional measures quickly. SCK accomplishes this via kaizens: rapid, repeated, time-compressed changes for the better in bite-sized chunks of the business. PMID:10387776

  15. Brayton Power Conversion System Study to Advance Technology Readiness for Nuclear Electric Propulsion — Phase I

    Science.gov (United States)

    Frye, Patrick E.; Allen, Robert; Delventhal, Rex

    2005-02-01

    To investigate and mature space based nuclear power conversion technologies NASA awarded several contracts under Prometheus, the Nuclear Systems Program. The studies described in this paper were performed under one of those contracts, which was to investigate the use of a nuclear power conversion system based on the closed Brayton cycle (CBC). The conceptual design effort performed included BPCS (Brayton power conversion system) trade studies to minimize system weight and radiator area and advance the state of the art of BPCS technology. The primary requirements for studies were a power level of 100 kWe (to the PPU), a low overall power system mass (with a target of less than 3000 kg), and a lifetime of 15 years (10 years full power). For the radiation environment, the system was to operate in the generic space environment and withstand the extreme environments within the Jovian system. The studies defined a BPCS design traceable to NBP (Nuclear Electric Propulsion) requirements and suitable for future potential missions with a sound technology plan for TRL (Technical Readiness Level) advancement identified. The studies assumed a turbine inlet temperature ˜ 100C above the current the state of the art capabilities with materials issues identified and an approach for resolution developed. Analyses and evaluations of six HRS (heat rejection subsystem) concepts and PMAD (Power Management and Distribution) architecture trades will be discussed in the paper.

  16. Study on the matching performance of a low temperature reverse Brayton air refrigerator

    International Nuclear Information System (INIS)

    Highlights: • A relation between operation parameters of expander and brake pressure was obtained. • A matching model was got based on the theoretical analysis and simulation. • Brake pressure feedback control was proposed and applied in the experiment. • The minimum free-load refrigerating temperature of 99.6 K was reached. - Abstract: A small reverse Brayton cycle air refrigerator was designed and fabricated. Bump-type air journal foil bearing, pressurized thrust gas bearing and centrifugal blower as brake were employed in the turboexpander. Usually, constant brake inlet pressure is set in a reverse Brayton refrigerator. However, the unchanged brake inlet pressure cannot adapt to the changing temperature and expansion ratio during the cooling down process, which could go against the system performance. In this article, the relationship between the turboexpander operation parameters and brake pressure was disclosed through theoretical analysis. The performance curve was analyzed through numerical simulation using CFX. A matching model was established based on the theoretical analysis and numerical simulation. Brake pressure feedback control was then proposed and applied in the experimental study. Thermal performance of the refrigerator was tested under varied operating conditions (different expansion ratios, temperatures and brake pressures). The results indicated that the appropriate brake pressure facilitated system good thermal performance under both design and off-design conditions, and the theoretical results agreed well with the experimental data

  17. Offshore Rankine Cycles

    OpenAIRE

    Brandsar, Jo

    2012-01-01

    The title of the thesis - "Offshore Rankine Cycles" - is very general and cover a large range of engineering fields, e.g. thermodynamic cycles (Rankine, ORC, Brayton, Kalina, etc.), mechanical equipment (gas/steam turbine, heat exchangers and additional equipment) and safety concerns (flammable and/or toxic fluids, high temperature and pressures), to name the most important.The thesis try to give a brief overview of all critical points and alternatives, concerning employment of a wa...

  18. Performance Improvement of Combined Cycle Power Plant Based on the Optimization of the Bottom Cycle and Heat Recuperation

    Institute of Scientific and Technical Information of China (English)

    Wenguo XIANG; Yingying CHEN

    2007-01-01

    Many F class gas turbine combined cycle (GTCC) power plants are built in China at present because of less emission and high efficiency. It is of great interest to investigate the efficiency improvement of GTCC plant. A combined cycle with three-pressure reheat heat recovery steam generator (HRSG) is selected for study in this paper.In order to maximize the GTCC efficiency, the optimization of the HRSG operating parameters is performed. The operating parameters are determined by means of a thermodynamic analysis, i.e. the minimization of exergy losses. The influence of HRSG inlet gas temperature on the steam bottoming cycle efficiency is discussed. The result shows that increasing the HRSG inlet temperature has less improvement to steam cycle efficiency when it is over 590℃. Partial gas to gas recuperation in the topping cycle is studied. Joining HRSG optimization with the use of gas to gas heat recuperation, the combined plant efficiency can rise up to 59.05% at base load. In addition,the part load performance of the GTCC power plant gets much better. The efficiency is increased by 2.11% at 75% load and by 4.17% at 50% load.

  19. Pre-exercise glycerol hydration improves cycling endurance time

    Science.gov (United States)

    Montner, P.; Stark, D. M.; Riedesel, M. L.; Murata, G.; Robergs, R.; Timms, M.; Chick, T. W.

    1996-01-01

    The effects of glycerol ingestion (GEH) on hydration and subsequent cycle ergometer submaximal load exercise were examined in well conditioned subjects. We hypothesized that GEH would reduce physiologic strain and increase endurance. The purpose of Study I (n = 11) was to determine if pre-exercise GEH (1.2 gm/kg glycerol in 26 ml/kg solution) compared to pre-exercise placebo hydration (PH) (26 ml/kg of aspartame flavored water) lowered heart rate (HR), lowered rectal temperature (Tc), and prolonged endurance time (ET) during submaximal load cycle ergometry. The purpose of Study II (n = 7) was to determine if the same pre-exercise regimen followed by carbohydrate oral replacement solution (ORS) during exercise also lowered HR, Tc, and prolonged ET. Both studies were double-blind, randomized, crossover trials, performed at an ambient temperature of 23.5-24.5 degrees C, and humidity of 25-27%. Mean HR was lower by 2.8 +/- 0.4 beats/min (p = 0.05) after GEH in Study I and by 4.4 +/- 1.1 beats/min (p = 0.01) in Study II. Endurance time was prolonged after GEH in Study I (93.8 +/- 14 min vs. 77.4 +/- 9 min, p = 0.049) and in Study II (123.4 +/- 17 min vs. 99.0 +/- 11 min, p = 0.03). Rectal temperature did not differ between hydration regimens in both Study I and Study II. Thus, pre-exercise glycerol-enhanced hyperhydration lowers HR and prolongs ET even when combined with ORS during exercise. The regimens tested in this study could potentially be adapted for endurance activities.

  20. Feasibility of Ericsson type isothermal expansion/compression gas turbine cycle for nuclear energy use

    International Nuclear Information System (INIS)

    A gas turbine with potential demand for the next generation nuclear energy use such as HTGR power plants, a gas cooled FBR, a gas cooled nuclear fusion reactor uses helium as working gas and with a closed cycle. Materials constituting a cycle must be set lower than allowable temperature in terms of mechanical strength and radioactivity containment performance and so expansion inlet temperature is remarkably limited. For thermal efficiency improvement, isothermal expansion/isothermal compression Ericsson type gas turbine cycle should be developed using wet surface of an expansion/compressor casing and a duct between stators without depending on an outside heat exchanger performing multistage re-heat/multistage intermediate cooling. Feasibility of an Ericsson cycle in comparison with a Brayton cycle and multi-stage compression/expansion cycle was studied and technologies to be developed were clarified. (author)

  1. Improvements in steam-cycle thermal power-stations

    International Nuclear Information System (INIS)

    The invention concerns means for improving the thermodynamic output of thermal power stations and in particular nuclear power stations. A heat pump is used for compressing steam taken from a generator and the thus pressurized steam is used for re-superheating the operating fluid, once partially expanded or even prior to the expansion thereof. Within a given temperature and pressure range, the additional power thus provided by the turbine is greater than the power spent by the pump. This can be applied to power stations comprising means for re-superheating the operating fluid through quick steam and/or steam drawn from the turbine

  2. Improving Cycling Performance: Transcranial Direct Current Stimulation Increases Time to Exhaustion in Cycling.

    Directory of Open Access Journals (Sweden)

    Marcelo Vitor-Costa

    Full Text Available The central nervous system seems to have an important role in fatigue and exercise tolerance. Novel noninvasive techniques of neuromodulation can provide insights on the relationship between brain function and exercise performance. The purpose of this study was to determine the effects of transcranial direct current stimulation (tDCS on physical performance and physiological and perceptual variables with regard to fatigue and exercise tolerance. Eleven physically active subjects participated in an incremental test on a cycle simulator to define peak power output. During 3 visits, the subjects experienced 3 stimulation conditions (anodal, cathodal, or sham tDCS-with an interval of at least 48 h between conditions in a randomized, counterbalanced order to measure the effects of tDCS on time to exhaustion at 80% of peak power. Stimulation was administered before each test over 13 min at a current intensity of 2.0 mA. In each session, the Brunel Mood State questionnaire was given twice: after stimulation and after the time-to-exhaustion test. Further, during the tests, the electromyographic activity of the vastus lateralis and rectus femoris muscles, perceived exertion, and heart rate were recorded. RM-ANOVA showed that the subjects performed better during anodal primary motor cortex stimulation (491 ± 100 s compared with cathodal stimulation (443 ± 11 s and sham (407 ± 69 s. No significant difference was observed between the cathodal and sham conditions. The effect sizes confirmed the greater effect of anodal M1 tDCS (anodal x cathodal = 0.47; anodal x sham = 0.77; and cathodal x sham = 0.29. Magnitude-based inference suggested the anodal condition to be positive versus the cathodal and sham conditions. There were no differences among the three stimulation conditions in RPE (p = 0.07 or heart rate (p = 0.73. However, as hypothesized, RM- ANOVA revealed a main effect of time for the two variables (RPE and HR: p < 0.001. EMG activity also did not

  3. Brayton Isotope Power System. Phase I. (Ground demonstration system) Configuration Control Document (CCD)

    International Nuclear Information System (INIS)

    The configuration control document (CCD) defines the BIPS-GDS configuration. The GDS configuration is similar to a conceptual flight system design, referred to as the BIPS-FS, which is discussed in App. I. The BIPS is being developed by ERDA as a 500 to 2000 W(e), 7-y life, space power system utilizing a closed Brayton cycle gas turbine engine to convert thermal energy (from an isotope heat source) to electrical energy at a net efficiency exceeding 25 percent. The CCD relates to Phase I of an ERDA Program to qualify a dynamic system for launch in the early 1980's. Phase I is a 35-month effort to provide an FS conceptual design and GDS design, fabrication, and test. The baseline is a 7-year life, 450-pound, 4800 W(t), 1300 W(e) system which will use two multihundred watt (MHW) isotope heat sources being developed

  4. Brayton Isotope Power System. Phase I. (Ground demonstration system) Configuration Control Document (CCD)

    Energy Technology Data Exchange (ETDEWEB)

    1976-03-15

    The configuration control document (CCD) defines the BIPS-GDS configuration. The GDS configuration is similar to a conceptual flight system design, referred to as the BIPS-FS, which is discussed in App. I. The BIPS is being developed by ERDA as a 500 to 2000 W(e), 7-y life, space power system utilizing a closed Brayton cycle gas turbine engine to convert thermal energy (from an isotope heat source) to electrical energy at a net efficiency exceeding 25 percent. The CCD relates to Phase I of an ERDA Program to qualify a dynamic system for launch in the early 1980's. Phase I is a 35-month effort to provide an FS conceptual design and GDS design, fabrication, and test. The baseline is a 7-year life, 450-pound, 4800 W(t), 1300 W(e) system which will use two multihundred watt (MHW) isotope heat sources being developed.

  5. Isotope Brayton ground demonstration testing and flight qualification. Volume 1. Technical program

    Energy Technology Data Exchange (ETDEWEB)

    1974-12-09

    A program is proposed for the ground demonstration, development, and flight qualification of a radioisotope nuclear heated dynamic power system for use on space missions beginning in the 1980's. This type of electrical power system is based upon and combines two aerospace technologies currently under intense development; namely, the MHW isotope heat source and the closed Brayton cycle gas turbine. This power system represents the next generation of reliable, efficient economic electrical power equipment for space, and will be capable of providing 0.5 to 2.0 kW of electric power to a wide variety of spacecraft for earth orbital and interplanetary missions. The immediate design will be based upon the requirements for the Air Force SURVSATCOM mission. The proposal is presented in three volumes plus an Executive Summary. This volume describes the tasks in the technical program.

  6. Control system options and strategies for supercritical CO2 cycles.

    Energy Technology Data Exchange (ETDEWEB)

    Moisseytsev, A.; Kulesza, K. P.; Sienicki, J. J.; Nuclear Engineering Division; Oregon State Univ.

    2009-06-18

    The Supercritical Carbon Dioxide (S-CO{sub 2}) Brayton Cycle is a promising alternative to Rankine steam cycle and recuperated gas Brayton cycle energy converters for use with Sodium-Cooled Fast Reactors (SFRs), Lead-Cooled Fast Reactors (LFRs), as well as other advanced reactor concepts. The S-CO{sub 2} Brayton Cycle offers higher plant efficiencies than Rankine or recuperated gas Brayton cycles operating at the same liquid metal reactor core outlet temperatures as well as reduced costs or size of key components especially the turbomachinery. A new Plant Dynamics Computer Code has been developed at Argonne National Laboratory for simulation of a S-CO{sub 2} Brayton Cycle energy converter coupled to an autonomous load following liquid metal-cooled fast reactor. The Plant Dynamics code has been applied to investigate the effectiveness of a control strategy for the S-CO{sub 2} Brayton Cycle for the STAR-LM 181 MWe (400 MWt) Lead-Cooled Fast Reactor. The strategy, which involves a combination of control mechanisms, is found to be effective for controlling the S-CO{sub 2} Brayton Cycle over the complete operating range from 0 to 100 % load for a representative set of transient load changes. While the system dynamic analysis of control strategy performance for STARLM is carried out for a S-CO{sub 2} Brayton Cycle energy converter incorporating an axial flow turbine and compressors, investigations of the S-CO{sub 2} Brayton Cycle have identified benefits from the use of centrifugal compressors which offer a wider operating range, greater stability near the critical point, and potentially further cost reductions due to fewer stages than axial flow compressors. Models have been developed at Argonne for the conceptual design and performance analysis of centrifugal compressors for use in the SCO{sub 2} Brayton Cycle. Steady state calculations demonstrate the wider operating range of centrifugal compressors versus axial compressors installed in a S-CO{sub 2} Brayton Cycle as

  7. State space model extraction of thermohydraulic systems Part II: a linear graph approach applied to a Brayton cycle–based power conversion unit

    OpenAIRE

    Uren, Kenneth Richard; Schoor, George van

    2013-01-01

    This second paper in a two part series presents the application of a developed state space model extraction methodology applied to a Brayton cycle-based PCU (power conversion unit) of a PBMR (pebble bed modular reactor). The goal is to investigate if the state space extraction methodology can cope with larger and more complex thermohydraulic systems. In Part I the state space model extraction methodology for the purpose of control was described in detail and a state space represen...

  8. A STRATEGIC APPROACH TO IMPROVE ENVIRONMENTAL POLICY-MAKING FOR END-OF-CYCLE PRODUCT MANAGEMENT

    OpenAIRE

    Sharon A. Jones; KEVIN ROSE; KRISTEN TULL

    2011-01-01

    As they make decisions about collective goods, policy makers strive to apply objective standards to complex environmental issues. This challenge requires the use of analytic methods that can include the multiple dimensions of such complex problems. Life-cycle analysis is a physical model that is widely recognised for its utility in investigating and improving the environmental impacts across the supply chain. However, models such as environmental life-cycle analysis are insufficient by themse...

  9. Modeling of the Martian Water Cycle with an Improved Representation of Water Ice Clouds

    OpenAIRE

    Navarro, T.; Madeleine, J.-B.; Forget, François; Spiga, Aymeric; Millour, E.; Montmessin, Franck; Määttänen, Anni

    2014-01-01

    The Martian water cycle has been studied for a long time thanks to remote observations and the use of GCMs (Global Climate Model). Thanks to GCMs, the comprehension of the water cycle has been improved, revealing for instance the impor- tance of clouds in the global water transport [5] with implications for atmospheric dynamics, paleo- climates. From that perspective, the modeling of the Martian water cycle by the LMD (Laboratoire de Météorologie Dynamique) Mars GCM has been im- proved by imp...

  10. Improving Energy Efficiency of a Refrigeration System with a Rankine Cycle and an Expander

    OpenAIRE

    Subiantoro, Alison

    2015-01-01

    A method to increase energy efficiency of a vapor compression refrigeration system by using a Rankine cycle and an expander is studied. The systems studied include the R134a and the transcritical CO2 cycles with a 5 kW capacity. The working fluids of the Rankine cycle are R134a, propane and R123. The available heat input power is 1-5 kW. The results show that in the R134a and CO2 systems, 18-40% and 30-67% improvements of Coefficient of Performance (COP), respectively, can be achieved. The me...

  11. Bridging porous Si-C composites with conducting agents for improving battery cycle life

    Science.gov (United States)

    Li, Zhenzhen; Wang, Wei; Li, Zhihu; Qin, Zhihong; Wang, Jun; Liu, Zhaoping

    2015-07-01

    Porous silicon-carbon (Si-C) composites have been considered to be one of the most effective architectures to improve the cycle life of Si based anode because of its native ability to accommodate the large volume change during discharge/charge process. It is found that lots of reported porous Si-C electrodes employed large amount of binder materials to enhance the structural stability which significantly decreased gravimetric capacity of the whole electrode with limited active materials. In this work, without loss of active materials, various conducting agents were used to build electrical bridges between porous Si-C composites, which significantly improved the structural stability and hence the cycle life. Due to the increase of connection possibilities, cycle life of zero-dimensional MCMB bridged electrode reaches 80 cycles with a capacity retention of 80%, and it can be further promoted to 200 cycles for the VGCF bridged electrode and 220 cycles for the rGO bridged electrode. This work paves an effective route to construct stable Si electrode with porous structures as building blocks without the decrease of active materials.

  12. Bottoming cycles for electric energy generation: Parametric investigation of available and innovative solutions for the exploitation of low and medium temperature heat sources

    International Nuclear Information System (INIS)

    Many industrial processes and conventional fossil fuel energy production systems used in small-medium industries, such as internal combustion engines and gas turbines, provide low or medium temperature (i.e., 200-500 oC) heat fluxes as a by-product, which are typically wasted in the environment. The possibility of exploiting this wasted heat, converting it into electric energy by means of different energy systems, is investigated in this article, by extending the usual range of operation of existing technologies or introducing novel concepts. In particular, among the small size bottoming cycle technologies, the identified solutions which could allow to improve the energy saving performance of an existing plant by generating a certain amount of electric energy are: the Organic Rankine Cycle, the Stirling engine and the Inverted Brayton Cycle; this last is an original thermodynamic concept included in the performed comparative analysis. Moreover, this paper provides a parametric investigation of the thermodynamic performance of the different systems; in particular, for the Inverted Brayton Cycle, the effects of the heat source characteristics and of the cycle design parameters on the achievable efficiency and specific power are shown. Furthermore, a comparison with other existing energy recovery solutions is performed, in order to assess the market potential. The analysis shows that the highest electric efficiency values, more than 20% with reference to the input heat content, are obtained with the Organic Rankine Cycle, while not negligible values of efficiency (up to 10%) are achievable with the Inverted Brayton Cycle, if the available temperature is higher than 400 oC.

  13. New fire diurnal cycle characterizations to improve fire radiative energy assessments made from MODIS observations

    Science.gov (United States)

    Andela, N.; Kaiser, J. W.; van der Werf, G. R.; Wooster, M. J.

    2015-08-01

    cycle generally resulted in an overestimation of FRE, while including information on the climatology of the fire diurnal cycle improved FRE estimates. The approach based on knowledge of the climatology of the fire diurnal cycle also improved distribution of FRE over the day, although only when aggregating model results to coarser spatial and/or temporal scale good correlation was found with the full SEVIRI hourly reference data set. We recommend the use of regionally varying fire diurnal cycle information within the Global Fire Assimilation System (GFAS) used in the Copernicus Atmosphere Monitoring Services, which will improve FRE estimates and may allow for further reconciliation of biomass burning emission estimates from different inventories.

  14. NASA Contributions to Improve Understanding of Extreme Events in the Global Energy and Water Cycle

    Science.gov (United States)

    Lapenta, William M.

    2008-01-01

    The U.S. Climate Change Science Program (CCSP) has established the water cycle goals of the Nation's climate change program. Accomplishing these goals will require, in part, an accurate accounting of the key reservoirs and fluxes associated with the global water and energy cycle, including their spatial and temporal variability. through integration of all necessary observations and research tools, To this end, in conjunction with NASA's Earth science research strategy, the overarching long-term NASA Energy and Water Cycle Study (NEWS) grand challenge can he summarized as documenting and enabling improved, observationally based, predictions of water and energy cycle consequences of Earth system variability and change. This challenge requires documenting and predicting trends in the rate of the Earth's water and energy cycling that corresponds to climate change and changes in the frequency and intensity of naturally occurring related meteorological and hydrologic events, which may vary as climate may vary in the future. The cycling of water and energy has obvious and significant implications for the health and prosperity of our society. The importance of documenting and predicting water and energy cycle variations and extremes is necessary to accomplish this benefit to society.

  15. Technical Meeting on Fast Reactors and Related Fuel Cycle Facilities with Improved Economic Characteristics. Working Material

    International Nuclear Information System (INIS)

    The objectives of the meeting were: - To identify the main issues and technical features that affect capital and energy production costs of fast reactors and related fuel cycle facilities; - To present fast reactor concepts and designs with enhanced economic characteristics, as well as innovative technical solutions (components, subsystems, etc.) that have the potential to reduce the capital costs of fast reactors and related fuel cycle facilities; - To present energy models and advanced tools for the cost assessment of innovative fast reactors and associated nuclear fuel cycles; - To discuss the results of studies and on-going R&D activities that address cost reduction and the future economic competitiveness of fast reactors; and - To identify research and technology development needs in the field, also in view of new IAEA initiatives to help and support Member States in improving the economic competitiveness of fast reactors and associated nuclear fuel cycles

  16. Aspects Regarding the Improving of Fitness and Health Issues by Cycling

    Directory of Open Access Journals (Sweden)

    Cătălin Octavian MĂNESCU

    2014-12-01

    Full Text Available This article is trying to explain all the benefits cycling has over fitness and specific health issues, the importance of a training plan, of a balanced diet and a good hydration during a training period of time and, also, presents the results of some studies regarding the importance of ride biking, generally, and exercising, particularly. Riding a bike is a healthy activity. Regular exercise in the form of cycling will make people fitter, stronger, will help them reduce fat levels and look in better shape, boost their energy and generally improve their mood. For many people, cycling is the first step to independence and exploration. Good planning and preparation are essential to ensure that cycling is a positive experience to everybody.

  17. Technical Meeting on Fast Reactors and Related Fuel Cycle Facilities with Improved Economic Characteristics. Presentations

    International Nuclear Information System (INIS)

    The objectives of the meeting were: • To identify the main issues and technical features that affect capital and energy production costs of fast reactors and related fuel cycle facilities; • To present fast reactor concepts and designs with enhanced economic characteristics, as well as innovative technical solutions (components, subsystems, etc.) that have the potential to reduce the capital costs of fast reactors and related fuel cycle facilities; • To present energy models and advanced tools for the cost assessment of innovative fast reactors and associated nuclear fuel cycles; • To discuss the results of studies and ongoing R&D activities that address cost reduction and the future economic competitiveness of fast reactors; • To identify research and technology development needs in the field, also in view of new IAEA initiatives to help and support Member States in improving the economic competitiveness of fast reactors and associated nuclear fuel cycles

  18. Improved 3D limit-cycle navigation method for path planning quad rotor

    International Nuclear Information System (INIS)

    Quad rotors as a type of rotary wing aerial vehicle must planned their flight path effectively and avoid any disturbance to complete their mission. The extension of 2D limit-cycle navigation into 3D, made it possible to apply for aerial vehicle. The extended limit-cycle has been introduced, but it generate unsuitable path in certain condition. In this research, rendering the obstacle into a cylinder will generate the efficient path and provide the best way in avoiding stationary obstacle. By defining obstacle position, a simulation and performance study is done using limit-cycle characteristic method. The simulations results illustrated the path generation using improved 3D limit cycle with different obstacle condition

  19. Characterization of niobium and vanadium oxide nanocomposites with improved rate performance and cycling stability

    International Nuclear Information System (INIS)

    Highlights: • Niobium and vanadium oxides nanocomposites were synthesized using a facile sol–gel process. • Such nanocomposites exhibit both significantly improved rate and cycling stability. • Possible synergistic mechanism between the constituent components of the nanocomposites was proposed. -- Abstract: Niobium and vanadium oxides nanocomposites are synthesized using a facile sol–gel process, and characterized by scanning and transmission electron microscopy. X-ray diffraction results show that the nanocomposites are composed of Nb2O5 and its solid solutions. Such nanocomposites exhibit both significantly improved rate and cycling stability. At a current density of 1 A g−1, the nanocomposites deliver more than three times of capacity than pure Nb2O5, and remain ∼95% of its initial capacity after 50 cycles. Possible synergistic mechanism between the constituent components of the nanocomposites is also proposed

  20. Analysis of thermal cycles and working fluids for power generation in space

    International Nuclear Information System (INIS)

    Production of power in space for terrestrial use is of great interest in view of the rapidly rising power demand and its environmental impacts. Space also offers a very low temperature, making it a perfect heat sink for power plants, thus offering much higher efficiencies. This paper focuses on the evaluation and analysis of thermal Brayton, Ericsson and Rankine power cycles operating at space conditions on several appropriate working fluids. Under the examined conditions, the thermal efficiency of Brayton cycles reaches 63%, Ericsson 74%, and Rankine 85%. These efficiencies are significantly higher than those for the computed or real terrestrial cycles: by up to 45% for the Brayton, and 17% for the Ericsson; remarkably 44% for the Rankine cycle even when compared with the best terrestrial combined cycles. From the considered working fluids, the diatomic gases (N2 and H2) produce somewhat better efficiencies than the monatomic ones in the Brayton and Rankine cycles. The Rankine cycles require radiator areas that are larger by up to two orders of magnitude than those required for the Brayton and Ericsson cycles. The results of the analysis of the sensitivity of the cycle performance parameters to major parameters such as turbine inlet temperature and pressure ratio are presented, equations or examining the effects of fluid properties on the radiator area and pressure drop were developed, and the effects of the working fluid properties on cycle efficiency and on the power production per unit radiator area were explored to allow decisions on the optimal choice of working fluids

  1. Direct positive selection for improved nitroreductase variants using SOS triggering of bacteriophage lambda lytic cycle.

    Science.gov (United States)

    Guise, C P; Grove, J I; Hyde, E I; Searle, P F

    2007-04-01

    Expression of prodrug-activating enzymes that convert non-toxic substrates to cytotoxic derivatives is a promising strategy for cancer gene therapy. However, their catalytic activity with unnatural, prodrug substrates is often suboptimal. Efforts to improve these enzymes have been limited by the inability to select directly for increased prodrug activation. We have focussed on developing variants of Escherichia coli (E. coli) nitroreductase (NTR) with improved ability to activate the prodrug 5-(aziridin-1-yl)-2,4-dinitrobenzamide (CB1954), and describe here a novel, direct, positive selection for improved enzymes that exploits the alternative life cycles of bacteriophage lambda. In lambda lysogens of E. coli, the activation of the prodrug CB1954 by NTR triggers the SOS response to DNA damage, switching integrated lambda prophages into lytic cycle. This provides a direct, positive selection for phages encoding improved NTR variants, as, upon limiting exposure of lysogenized E. coli to CB1954, only those encoding the most active enzyme variants are triggered into lytic cycle, allowing their selective recovery. We exemplify the selection by isolating highly improved 'turbo-NTR' variants from a library of 6.8 x 10(5) clones, conferring up to 50-fold greater sensitivity to CB1954 than the wild type. Carcinoma cells infected with adenovirus expressing T41Q/N71S/F124T-NTR were sensitized to CB1954 concentrations 40- to 80-fold lower than required with WT-NTR. PMID:17301844

  2. Improvements in Cycling but Not Handcycling 10 km Time Trial Performance in Habitual Caffeine Users.

    Science.gov (United States)

    Graham-Paulson, Terri; Perret, Claudio; Goosey-Tolfrey, Victoria

    2016-01-01

    Caffeine supplementation during whole-/lower-body exercise is well-researched, yet evidence of its effect during upper-body exercise is equivocal. The current study explored the effects of caffeine on cycling/handcycling 10 km time trial (TT) performance in habitual caffeine users. Eleven recreationally trained males (mean (SD) age 24 (4) years, body mass 85.1 (14.6) kg, cycling/handcycling peak oxygen uptake ( V · peak) 42.9 (7.3)/27.6 (5.1) mL∙kg∙min(-1), 160 (168) mg/day caffeine consumption) completed two maximal incremental tests and two familiarization sessions. During four subsequent visits, participants cycled/handcycled for 30 min at 65% mode-specific V · peak (preload) followed by a 10 km TT following the ingestion of 4 mg∙kg(-1) caffeine (CAF) or placebo (PLA). Caffeine significantly improved cycling (2.0 (2.0)%; 16:35 vs. 16:56 min; p = 0.033) but not handcycling (1.8 (3.0)%; 24:10 vs. 24:36 min; p = 0.153) TT performance compared to PLA. The improvement during cycling can be attributed to the increased power output during the first and last 2 km during CAF. Higher blood lactate concentration (Bla) was reported during CAF compared to PLA (p cycling (11.2 ± 2.6 and 8.8 ± 3.2 mmol/L; p = 0.001) and handcycling (10.6 ± 2.5 and 9.2 ± 2.9 mmol/L; p = 0.006). Lower overall ratings of perceived exertion (RPE) were seen following CAF during the preload (p cycling and at 30 min during handcycling, and lower central RPE was seen at 30 min during cycling (p cycling but not handcycling TT performance. The lack of improvement during handcycling may be due to the smaller active muscle mass, elevated (Bla) and/or participants' training status. PMID:27348000

  3. The model for the strategic management of technology. The improvement cycle and matrixes deployment QFD

    International Nuclear Information System (INIS)

    In spite of the importance of innovative firms, few contributions study in depth the strategic management of their technological resources. After describing the process of strategic management of technology, we propose a model that enables the application of that process and guarantees organizational flexibility in technological companies. For it, such a process has been adapted to She wart cycle (Deeming wheel) and combined with the quality function deployment (QFD). As a result, we propose the improvement cycle of technology. It contains two matrixes that allow identifying and prioritizing with greater clarity the activities related to the management of technological resources. (Authors)

  4. Technical Meeting on Fast Reactors and Related Fuel Cycle Facilities with Improved Economic Characteristics. Working Material

    International Nuclear Information System (INIS)

    In recent years, engineering oriented work, rather than basic research and development (R&D), has led to significant progress in improving the economics of innovative fast reactors and associated fuel cycle facilities, while maintaining and even enhancing the safety features of these systems. Optimization of plant size and layout, more compact designs, reduction of the amount of plant materials and the building volumes, higher operating temperatures to attain higher generating efficiencies, improvement of load factor, extended core lifetimes, high fuel burnup, etc. are good examples of achievements to date that have improved the economics of fast neutron systems. The IAEA, through its Technical Working Group on Fast Reactors (TWG-FR) and Technical Working Group on Nuclear Fuel Cycle Options and Spent Fuel Management (TWG-NFCO), devotes many of its initiatives to encouraging technical cooperation and promoting common research and technology development projects among Member States with fast reactor and advanced fuel cycle development programmes, with the general aim of catalysing and accelerating technology advances in these fields. In particular the theme of fast reactor deployment, scenarios and economics has been largely debated during the recent IAEA International Conference on Fast Reactors and Related Fuel Cycles: Safe Technologies and Sustainable Scenarios, held in Paris in March 2013. Several papers presented at this conference discussed the economics of fast reactors from different national and regional perspectives, including business cases, investment scenarios, funding mechanisms and design options that offer significant capital and energy production cost reductions. This Technical Meeting on Fast Reactors and Related Fuel Cycle Facilities with Improved Economic Characteristics addresses Member States’ expressed need for information exchange in the field, with the aim of identifying the main open issues and launching possible initiatives to help and

  5. Improvement of InP-GaAs-Si quality by thermal-cycle growth

    International Nuclear Information System (INIS)

    This paper reports on single-crystal films of InP that have been deposited on GaAs, GaAs-coated Si, and InP substrates by metalorganic chemical vapor deposition (MOCVD). Defect-reduction schemes involving various thermal annealing recipes have been developed and characterized. Material quality ha been assessed by a variety of methods including transmission electron microscopy, X-ray rocking curve analysis, low-temperature photoluminescence, lifetime measurements, Hall-effect measurements, electrochemical profiling, and Nomarski microscopy. The use of either a thermal-cycle-growth or a thermal-cycle-annealing process leads to heteroepitaxial InP film quality which is significantly improved over that of its as-grown state, with the thermal-cycle growth appearing to be the more effective technique

  6. Power conversion cycles study for He-cooled reactor concepts for DEMO

    International Nuclear Information System (INIS)

    The study of different power conversion cycles have been performed in the framework of the DEMO scoping studies. The latter studies have the aim of providing technical information focused on the selection of DEMO parameters. The purpose of the study of conversion cycles has been the investigation of '' advanced cycles '' in order to get an improvement on the thermodynamic efficiency. Starting from the '' near term '' He-cooled blanket concepts (named, HCLL and HCPB), developed within the Power Plant Conceptual Studies (PPCS)and currently considered for DEMO, conversion cycles based on a standard Rankine cycle were shown to yield net efficiencies (net power/fusion power) of approximately 35 %. Two main features limit the efficiency of these cycles. Firstly, the heat sources in the reactor: the blanket provides the main source, over 80 % of the total thermal power. However, the blanket only produces moderate coolant temperatures with a range of 300-500 oC. The remaining thermal power, less than 20%, is deposited in the divertor as high-grade heat with a more respectable coolant temperature range of 540-717 oC. Secondly, the low inlet temperature of blanket coolant limits the possibilities to achieve efficient heat exchange with the power conversion cycle. The parameters of HCLL model AB (He-cooled divertor) have been used for the analysis of the following cycles: · Supercritical steam Rankine cycle: different configurations such as superheat cycle, reheat cycle, etc. have been studied. · Supercritical CO2 indirect Brayton cycle: the recompression cycle yields the best thermal efficiency for the Brayton cycle options. A discussion on the results considering different parameters of the cycle will be presented in the paper. · Separate cycles ('' dual cycle ''): in order to make an optimum use of the divertor high-grade heat source, independent cycles for the blanket and divertor have been considered. A comparison of the gross and net efficiencies obtained from these

  7. Optimization of a Brayton cryocooler for ZBO liquid hydrogen storage in space

    Science.gov (United States)

    Deserranno, D.; Zagarola, M.; Li, X.; Mustafi, S.

    2014-11-01

    NASA is evaluating and developing technology for long-term storage of cryogenic propellant in space. A key technology is a cryogenic refrigerator which intercepts heat loads to the storage tank, resulting in a reduced- or zero-boil-off condition. Turbo-Brayton cryocoolers are particularly well suited for cryogen storage applications because the technology scales well to high capacities and low temperatures. In addition, the continuous-flow nature of the cycle allows direct cooling of the cryogen storage tank without mass and power penalties associated with a cryogenic heat transport system. To quantify the benefits and mature the cryocooler technology, Creare Inc. performed a design study and technology demonstration effort for NASA on a 20 W, 20 K cryocooler for liquid hydrogen storage. During the design study, we optimized these key components: three centrifugal compressors, a modular high-capacity plate-fin recuperator, and a single-stage turboalternator. The optimization of the compressors and turboalternator were supported by component testing. The optimized cryocooler has an overall flight mass of 88 kg and a specific power of 61 W/W. The coefficient of performance of the cryocooler is 23% of the Carnot cycle. This is significantly better performance than any 20 K space cryocooler existing or under development.

  8. Use of isotopically modified erbium to improve fuel cycle economics in IRIS

    International Nuclear Information System (INIS)

    IRIS is a 335 MWe PWR with integral primary circuit. Its design is compatible with long cycles, up to 4 years. Advanced fuel management techniques are employed to support this objective; among others, novel use of burnable absorbers is considered. Erbium is one absorber that is currently utilized in PWRs. It has several desirable properties, notably, it is a resonant absorber, thus making the reactivity feedback coefficients more negative. However, it also has a non-trivial residual reactivity penalty, due primarily to its isotope 166Er. This paper examines the improvement in core neutronics and cycle economics that could be achieved if isotopically modified erbium (with reduced 166Er fraction and increased 167Er fraction) is employed as burnable absorber, instead of natural erbium, thus eliminating or reducing the reactivity penalty. The core performance with modified erbium absorber remains otherwise similar to that employing natural erbium burnable absorber. The gain in reactivity may be used to extend the cycle, or, the 235U enrichment may be reduced (for the same cycle length) with a corresponding saving in the uranium enrichment cost. This gain has been employed to estimate the breakeven cost of producing the modified erbium through Laser Isotope Separation (LIS). A model to evaluate LIS economics is being developed and will serve as a basis for further studies. Preliminary analysis indicates that this approach may result in an overall reduction of the fuel cycle cost.(author)

  9. Metal hydrides reactors with improved dynamic characteristics for a fast cycling hydrogen compressor

    International Nuclear Information System (INIS)

    This paper presents an investigation of coupled heat and mass transfer process in metal hydrides hydrogen storage reactors. Hydrogen storage and compression performance of our designed and developed reactors are studied by varying the operating parameters and analyzing the effects of metal hydride bed parameters. The metal alloy selected to characterize the cycling behaviour of reactors is LaNi5, material synthesized and characterized by us in the range 20-800C. Four types of metal hydride reactors were tested with the aim to provide a fast hydrogen absorption-desorption cycle, able to be thermally cycled at rapid rates. Some new technical solutions have been studied to make a step forward in reducing the duration of the reactors cycle, which combines the effective increase of the thermal conductivity and good permeability to hydrogen gas. Dynamic characteristic of developed fast metal hydride reactors is improved using our novel mixture metal hydride-CA conductive additive due to the increased effective thermal conductivity of the alloy bed. The advanced hydride bed design with high heat transfer capabilities can be thermally cycled at a rapid rate, under 120 seconds, in order to process high hydrogen flow rates.

  10. A Virtual Reality-Cycling Training System for Lower Limb Balance Improvement.

    Science.gov (United States)

    Yin, Chieh; Hsueh, Ya-Hsin; Yeh, Chun-Yu; Lo, Hsin-Chang; Lan, Yi-Ting

    2016-01-01

    Stroke survivors might lose their walking and balancing abilities, but many studies pointed out that cycling is an effective means for lower limb rehabilitation. However, during cycle training, the unaffected limb tends to compensate for the affected one, which resulted in suboptimal rehabilitation. To address this issue, we present a Virtual Reality-Cycling Training System (VRCTS), which senses the cycling force and speed in real-time, analyzes the acquired data to produce feedback to patients with a controllable VR car in a VR rehabilitation program, and thus specifically trains the affected side. The aim of the study was to verify the functionality of the VRCTS and to verify the results from the ten stroke patients participants and to compare the result of Asymmetry Ratio Index (ARI) between the experimental group and the control group, after their training, by using the bilateral pedal force and force plate to determine any training effect. The results showed that after the VRCTS training in bilateral pedal force it had improved by 0.22 (p = 0.046) and in force plate the stand balance has also improved by 0.29 (p = 0.031); thus both methods show the significant difference. PMID:27034953

  11. Cycling with video feedback improves performance in untrained, but not in trained women.

    Science.gov (United States)

    Macrae, Holden

    2003-12-01

    The objectives of this study were to assess whether exercise performance responses could be altered when subjects were exposed to interactive video feedback and music (VFM), compared to music only feedback (M). Ten women, 5 well-trained (46.4 ± 4.7 ml × kg(-1) × min(-1)) and 5 untrained (34.5 ± 5.7 ml × kg(-1) × min(-1)) participated in the study. Neither the trained nor the untrained group exhibited significant differences in HR and VO2 between the VFM and M conditions. The trained subjects cycled at similar speeds and for similar distances during the VFM and M conditions, and also cycled at a higher average speed (23.5 ± 2.1 vs. 15.6 ± 3.2 km × h(-1)) and further (11.9 ± 1.1 vs. 7.8 ± 1.6 km) than the untrained subjects (p improved in the VFM versus M condition (p improve cycling performance in trained women, but untrained women cycle faster and further during a 30-min exercise session when exposed to a combination of interactive video and music feedback. PMID:21851318

  12. Uranium resource utilization improvements in the once-through PWR fuel cycle

    International Nuclear Information System (INIS)

    In support of the Nonproliferation Alternative Systems Assessment Program (NASAP), Combustion Engineering, Inc. performed a comprehensive analytical study of potential uranium utilization improvement options that can be backfit into existing PWRs operating on the once-through uranium fuel cycle. A large number of potential improvement options were examined as part of a preliminary survey of candidate options. The most attractive of these, from the standpoint of uranium utilization improvement, economic viability, and ease of implementation, were then selected for detailed analysis and were included in a single composite improvement case. This composite case represents an estimate of the total savings in U3O8 consumption that can be achieved in current-design PWRs by implementing improvements which can be developed and demonstrated in the near term. The improvement options which were evaluated in detail and included in the composite case were a new five-batch, extended-burnup fuel management scheme, low-leakage fuel management, modified lattice designs, axial blankets, reinsertion of initial core batches, and end-of-cycle stretchout

  13. A Closed Brayton Power Conversion Unit Concept for Nuclear Electric Propulsion for Deep Space Missions

    Science.gov (United States)

    Joyner, Claude Russell; Fowler, Bruce; Matthews, John

    2003-01-01

    In space, whether in a stable satellite orbit around a planetary body or traveling as a deep space exploration craft, power is just as important as the propulsion. The need for power is especially important for in-space vehicles that use Electric Propulsion. Using nuclear power with electric propulsion has the potential to provide increased payload fractions and reduced mission times to the outer planets. One of the critical engineering and design aspects of nuclear electric propulsion at required mission optimized power levels is the mechanism that is used to convert the thermal energy of the reactor to electrical power. The use of closed Brayton cycles has been studied over the past 30 or years and shown to be the optimum approach for power requirements that range from ten to hundreds of kilowatts of power. It also has been found to be scalable to higher power levels. The Closed Brayton Cycle (CBC) engine power conversion unit (PCU) is the most flexible for a wide range of power conversion needs and uses state-of-the-art, demonstrated engineering approaches. It also is in use with many commercial power plants today. The long life requirements and need for uninterrupted operation for nuclear electric propulsion demands high reliability from a CBC engine. A CBC engine design for use with a Nuclear Electric Propulsion (NEP) system has been defined based on Pratt & Whitney's data from designing long-life turbo-machines such as the Space Shuttle turbopumps and military gas turbines and the use of proven integrated control/health management systems (EHMS). An integrated CBC and EHMS design that is focused on using low-risk and proven technologies will over come many of the life-related design issues. This paper will discuss the use of a CBC engine as the power conversion unit coupled to a gas-cooled nuclear reactor and the design trends relative to its use for powering electric thrusters in the 25 kWe to 100kWe power level.

  14. A closed Brayton power conversion unit concept for nuclear electric propulsion for deep space missions

    International Nuclear Information System (INIS)

    In space, whether in a stable satellite orbit around a planetary body or traveling as a deep space exploration craft, power is just as important as the propulsion. The need for power is especially important for in-space vehicles that use Electric Propulsion. Using nuclear power with electric propulsion has the potential to provide increased payload fractions and reduced mission times to the outer planets. One of the critical engineering and design aspects of nuclear electric propulsion at required mission optimized power levels is the mechanism that is used to convert the thermal energy of the reactor to electrical power. The use of closed Brayton cycles has been studied over the past 30 or years and shown to be the optimum approach for power requirements that range from ten to hundreds of kilowatts of power. It also has been found to be scalable to higher power levels. The Closed Brayton Cycle (CBC) engine power conversion unit (PCU) is the most flexible for a wide range of power conversion needs and uses state-of-the-art, demonstrated engineering approaches. It also is in use with many commercial power plants today. The long life requirements and need for uninterrupted operation for nuclear electric propulsion demands high reliability from a CBC engine. A CBC engine design for use with a Nuclear Electric Propulsion (NEP) system has been defined based on Pratt and Whitney's data from designing long-life turbo-machines such as the Space Shuttle turbopumps and military gas turbines and the use of proven integrated control/health management systems (EHMS). An integrated CBC and EHMS design that is focused on using low-risk and proven technologies will over come many of the life-related design issues. This paper will discuss the use of a CBC engine as the power conversion unit coupled to a gas-cooled nuclear reactor and the design trends relative to its use for powering electric thrusters in the 25 kWe to 100kWe power level

  15. Improvements in manual dexterity relate to improvements in cognitive planning after assisted cycling therapy (ACT) in adolescents with down syndrome.

    Science.gov (United States)

    Holzapfel, Simon D; Ringenbach, Shannon D R; Mulvey, Genna M; Sandoval-Menendez, Amber M; Cook, Megan R; Ganger, Rachel O; Bennett, Kristen

    2015-01-01

    We have previously reported beneficial effects of acute (i.e., single session) Assisted Cycling Therapy (ACT) on manual dexterity and cognitive planning ability in adolescents with Down syndrome (DS). In the present study, we report the chronic effects of eight weeks of ACT, voluntary cycling (VC), and no cycling (NC), on the same measures in adolescents with DS. Participants completed 8 weeks of ACT, VC, or NC. Those in the ACT and VC groups completed 30min sessions three times per week on a stationary bicycle. During ACT, the mechanical motor of the bicycle augmented the cadence to a rate which was on average 79% faster than the voluntary cadence. During VC, the participants pedaled at a self-selected rate. Unimanual dexterity scores as measured with the Purdue Pegboard test (PPT) improved significantly more for the ACT and VC groups compared to the NC group. ACT lead to greater improvements than VC and NC in the assembly sub-test, which is a task that requires more advanced temporal and spatial processing. The ACT group improved significantly more than the VC group and non-significantly more than the NC group in cognitive planning ability as measured by the Tower of London test (ToL). There were also significant correlations between the assembly subtest of the PPT and all measures of the ToL. These correlations were stronger during post-testing than pre-testing. Pre-post changes in the combined PPT score and ToL number of correct moves correlated positively in the ACT group. These results support the efficacy of the salutary effects of ACT on global fine motor function and executive function in DS. Additionally, the performance on complex bimanual dexterity tasks appears to be related to the capacity of cognitive planning ability. This research has important implications for persons with movement deficits that affect activities of daily living. PMID:26280691

  16. Biologically enhanced cathode design for improved capacity and cycle life for lithium-oxygen batteries

    OpenAIRE

    Oh, Dahyun; QI, JIFA; Lu, Yi-Chun; Zhang, Yong; Shao-Horn, Yang; Belcher, Angela M.

    2013-01-01

    Lithium-oxygen batteries have a great potential to enhance the gravimetric energy density of fully packaged batteries by 2–3 times that of lithium-ion cells. Recent studies have focused on finding stable electrolytes to address poor cycling capability and improve practical limitations of current lithium-oxygen batteries. In this study, the catalyst electrode, where discharge products are deposited and decomposed, was investigated since it plays a critical role in the operation of rechargeable...

  17. Methodologies to improve product life cycle decision making in the telecommunications industry

    OpenAIRE

    Mead, Carl Dennis

    2003-01-01

    This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University. As pressure from regulation and customers increases on telecommunications equipment manufacturers and service providers to reduce the hazardous material content of telecommunications products and generally improve environmental performance, new methods for Product Life Cycle Management are required. Supplier and component environmental evaluation are vital and fundamental elements of any Prod...

  18. Fuel performance and operation experience of WWER-440 fuel in improved fuel cycle

    International Nuclear Information System (INIS)

    The paper summarizes WWER-440 second-generation fuel operation experience in improved fuel cycles using the example of Kola NPP units 3 and 4. Basic parameters of fuel assemblies, fuel rods and uranium-gadolinium fuel rods, as well as the principal neutronic parameters and burn-up achieved in fuel assemblies are presented. The paper also contains some data concerning the activity of coolant during operation (Authors)

  19. Key Factors Influencing the Decision on the Number of Brayton Units for the Prometheus Space Reactor

    Science.gov (United States)

    Ashcroft, John; Belanger, Sean; Burdge, Wayne; Clementoni, Eric; Jensen, Krista; Proctor, N. Beth; Zemo-Fulkerson, Annie

    2007-01-01

    The Naval Reactors (NR) Program and its DOE Laboratories, KAPL and Bettis, were assigned responsibility to develop space reactor systems for the Prometheus Program. After investigating all of the potential reactor and energy conversion options, KAPL and Bettis selected a direct gas Brayton system as the reference approach for the nuclear electric propulsion missions, including the Jupiter Icy Moons Orbiter (JIMO). In order to determine the optimal plant architecture for the direct gas system, KAPL and Bettis investigated systems with one or two active Brayton units and up to two spare units. No final decision was made on the optimal system configuration for the NEP gas-Brayton system prior to closeout of the project. The two most promising options appear to be a single system without spares and a three Brayton system with two operating units, each producing half of the required load, with a single spare unit. The studies show that a single Brayton system, without spares, offers the lowest mass system, with potential for lower operating temperature, and a minimum of system and operational complexity. The lower required mass and increased system efficiency inherent in the single Brayton system may be exploited to satisfy other design objectives such as reduced reactor and radiator operating temperatures. While Brayton system lifetimes applicable to a JIMO or other nuclear electric propulsion (NEP) mission have not been demonstrated, there is no fundamental limit on the lifetime of the Brayton hardware. Use of additional Brayton units with installed spares will allow for continued operation in the event of a failure of an individual Brayton unit. However, preliminary system reliability evaluations do not point to any substantial reliability benefit provided by carrying spare Brayton units. If a spare unit is used, operating two of the units at full power with an unpowered spare proved more efficient than operating all three units at a reduced power and temperature

  20. Cell cycle is disturbed in mucopolysaccharidosis type II fibroblasts, and can be improved by genistein.

    Science.gov (United States)

    Moskot, Marta; Gabig-Cimińska, Magdalena; Jakóbkiewicz-Banecka, Joanna; Węsierska, Magdalena; Bocheńska, Katarzyna; Węgrzyn, Grzegorz

    2016-07-01

    Mucopolysaccharidoses (MPSs) are inherited metabolic diseases caused by mutations resulting in deficiency of one of enzymes involved in degradation of glycosaminoglycans (GAGs). These compounds accumulate in cells causing their dysfunctions. Genistein is a molecule previously found to both modify GAG metabolism and modulate cell cycle. Therefore, we investigated whether the cell cycle is affected in MPS cells and if genistein can influence this process. Fibroblasts derived from patients suffering from MPS types I, II, IIIA and IIIB, as well as normal human fibroblasts (the HDFa cell line) were investigated. MTT assay was used for determination of cell proliferation, and the cell cycle was analyzed by using the MUSE® Cell Analyzer. While effects of genistein on cell proliferation were similar in both normal and MPS fibroblasts, fractions of cells in the G0/G1 phase were higher, and number of cells entering the S and G2/M phases was considerably lower in MPS II fibroblasts relative to control cells. Somewhat similar tendency, though significantly less pronounced, could be noted in MPS I, but only at longer times of incubation. However, this was not observed in MPS IIIA and MPS IIIB fibroblasts. Genistein (5, 7-dihydroxy-3-(4-hydroxyphenyl)-4H-1-benzopyran-4-one) was found to be able to partially correct the disturbances in the MPS II cell cycle, and to some extent in MPS I, at higher concentrations of this compound. The tendency to increase the fractions of cells entering the S and G2/M phases was also observed in MPS IIIA and IIIB fibroblasts treated with genistein. In conclusion, this is the first report indicating that the cell cycle can be impaired in MPS cells. The finding that genistein can improve the MPS II (and to some extent also MPS I) cell cycle provides an input to our knowledge on the molecular mechanisms of action of this compound. PMID:27016302

  1. Improved thermal cycling durability and PCR compatibility of polymer coated quantum dot

    International Nuclear Information System (INIS)

    Quantum dots have experienced rapid development in imaging, labeling and sensing in medicine and life science. To be suitable for polymerase chain reaction (PCR) assay, we have tested QD thermal cycling durability and compatibility, which have not been addressed in previous reports. In this study, we synthesized CdSe/ZnS QDs with a surface modification with high-MW amphiphilic copolymers and observed that Mg2+ ions in the PCR reaction could induce the QDs to precipitate and reduce their fluorescence signal significantly after thermal cycling. To overcome this problem, we used mPEG2000 to conjugate the QD surface for further protection, and found that this modification enables QDs to endure 40 thermal cycles in the presence of other components essential for PCR reactions. We have also identified that QDs have different effects on rTaq and Ex Taq polymerization systems. A high QD concentration could apparently reduce the PCR efficiency, but this inhibition was relieved significantly in the Ex PCR system as the concentration of Ex Taq polymerase was increased. Real-time PCR amplification results showed that QDs could provide a sufficiently measurable fluorescence signal without excessively inhibiting the DNA amplification. Based on this improved thermal cycling durability and compatibility with the PCR system, QDs have the potential to be developed as stable fluorescent sensors in PCR and real-time PCR amplification. (paper)

  2. Improved thermal cycling durability and PCR compatibility of polymer coated quantum dot

    Science.gov (United States)

    Xun, Zhe; Zhao, Xiaoyun; Guan, Yifu

    2013-09-01

    Quantum dots have experienced rapid development in imaging, labeling and sensing in medicine and life science. To be suitable for polymerase chain reaction (PCR) assay, we have tested QD thermal cycling durability and compatibility, which have not been addressed in previous reports. In this study, we synthesized CdSe/ZnS QDs with a surface modification with high-MW amphiphilic copolymers and observed that Mg2+ ions in the PCR reaction could induce the QDs to precipitate and reduce their fluorescence signal significantly after thermal cycling. To overcome this problem, we used mPEG2000 to conjugate the QD surface for further protection, and found that this modification enables QDs to endure 40 thermal cycles in the presence of other components essential for PCR reactions. We have also identified that QDs have different effects on rTaq and Ex Taq polymerization systems. A high QD concentration could apparently reduce the PCR efficiency, but this inhibition was relieved significantly in the Ex PCR system as the concentration of Ex Taq polymerase was increased. Real-time PCR amplification results showed that QDs could provide a sufficiently measurable fluorescence signal without excessively inhibiting the DNA amplification. Based on this improved thermal cycling durability and compatibility with the PCR system, QDs have the potential to be developed as stable fluorescent sensors in PCR and real-time PCR amplification.

  3. Evaluation of Silicon Nitride for Brayton Turbine Wheel Application

    Science.gov (United States)

    Freedman, Marc R.

    2008-01-01

    Silicon nitride (Si3N4) is being evaluated as a risk-reduction alternative for a Jupiter Icy Moons Orbiter Brayton turbine wheel in the event that the Prometheus program design requirements exceed the creep strength of the baseline metallic superalloys. Five Si3N4 ceramics, each processed by a different method, were screened based on the Weibull distribution of bend strength at 1700 F (927 C). Three of the Si3N4 ceramics, Honeywell AS800, Kyocera SN282, and Saint-Gobain NT154, had bend strengths in excess of 87 ksi (600 MPa) at 1700 F (927 C). These were chosen for further assessment and consideration for future subcomponent and component fabrication and testing.

  4. Improved cycling performance of P2-type layered sodium cobalt oxide by calcium substitution

    Science.gov (United States)

    Matsui, Masaki; Mizukoshi, Fumikazu; Imanishi, Nobuyuki

    2015-04-01

    P2-type Na2/3-xCaxCoO2 is synthesized via a conventional solid-state reaction. The substituted calcium ions occupy the sodium ion layer and eliminate the lattice mismatches of the two phases in Na2/3-xCaxCoO2. Several voltage steps typically observed in the voltage profiles of NaxCoO2 are mostly disappeared associated with the expansion of single-phase regions, because the substituted calcium ions hinder the ordering of sodium ions and vacancies. Furthermore the Na2/3-xCaxCoO2 shows improved cycling performance especially at high charging-discharging rate. During the cycling test, the calcium-free Na0.74CoO2 shows phase separation to form an inactive sodium poor phase, while the Na5/8Ca1/24CoO2 maintained the single phase, suggesting that the calcium substitution suppress the structural change of the P2-type NaxCoO2 to prevent the phase separation, resulting in the improved cycling performance.

  5. Brayton isotope power system. Volume II. System evaluation attributes

    Energy Technology Data Exchange (ETDEWEB)

    1978-03-15

    This volume of the Brayton Isotope Power System, Phase II Plan, contains the self-evaluation by AiResearch, GE, and TECO, addressing Section 3 of The Dynamic Systems Evaluation Criteria and Procedures established by the Department of Energy. These evaluation criteria addresses: Component Feasibility; Flight System Design Performance; GDS Test Results; Reliability and Practicality; Safety; Spacecraft Integration; and Cost and Risk. Included in each of these general categories are several attributes, each of which addresses a separate component, feature, or area of interest related to the power system, its development status, degree of preparedness for proceeding into a flight program, and/or the contractors' performance during Phase I. The key elements which indicate the readiness of a radioisotope power system to progress into a flight qualification program are: an advanced state of development of the power conversion system; demonstrated or exhibited potential for space systems standards of reliability; evident capability of meeting system safety requirements; favorable cost/benefit tradeoff considering projected missions and technology advancement potential; and proven feasibility of fabricating and qualifying a flight system and integrating it with a candidate spacecraft and launch vehicle. As a result of considerable government investment in Brayton system component development, the MHW isotope heat source and the BIPS Phase I Ground Demonstration System, the BIPS is a more advanced state of development than any previous radioisotope power system technology. Evidence of this is presented along with a complete review of the attributes, the contractor recommended ratings, and the rationale for the self-evaluation.

  6. Phase I: controls preliminary design report for Brayton Isotope Power System (BIPS)

    International Nuclear Information System (INIS)

    Background analyses of three control systems capable of controlling the speed, output voltage, and start rate of Brayton Isotope Power Systems (BIPS) are presented. Conclusions of all functions considered are summarized

  7. System design specification Brayton Isotope Power System (BIPS) Flight System (FS), and Ground Demonstration System (GDS)

    Energy Technology Data Exchange (ETDEWEB)

    1976-06-14

    The system design specification for ground demonstration, development, and flight qualification of a Brayton Isotope Power System (BIPS) is presented. The requirements for both a BIPS conceptual Flight System (FS) and a Ground Demonstration System (GDS) are defined.

  8. System design specification Brayton Isotope Power System (BIPS) Flight System (FS), and Ground Demonstration System (GDS)

    International Nuclear Information System (INIS)

    The system design specification for ground demonstration, development, and flight qualification of a Brayton Isotope Power System (BIPS) is presented. The requirements for both a BIPS conceptual Flight System (FS) and a Ground Demonstration System (GDS) are defined

  9. Phase I: controls preliminary design report for Brayton Isotope Power System (BIPS)

    Energy Technology Data Exchange (ETDEWEB)

    1976-08-20

    Background analyses of three control systems capable of controlling the speed, output voltage, and start rate of Brayton Isotope Power Systems (BIPS) are presented. Conclusions of all functions considered are summarized. (TFD)

  10. Improvement of cycle performance for silicon/carbon composite used as anode for lithium ion batteries

    International Nuclear Information System (INIS)

    The silicon/carbon composite was prepared by mixing the silicon, graphite and pitch in the tetra-hydrofuran solution followed by pyrolyzing the blends after the evaporation of solvent. The electrochemical performance of the silicon/carbon anode for lithium ion batteries was improved by the treatment of composite powders with KCl aqueous solutions. Scanning electron microscope (SEM) observation and electrochemical impedance spectroscopy (EIS) results showed that the morphology stability of the composite electrodes can be kept during the electrochemical charge/discharge process. The composite electrode of silicon/carbon composite showed an initial reversible capacity of 575 mAh g-1 and still maintained a high reversible capacity of 506 mAh g-1 after 40 cycles with the capacity loss of ∼0.3% per cycle.

  11. Analyze and Improve Lifetime in 3L-NPC Inverter from Power Cycle and Thermal Balance

    DEFF Research Database (Denmark)

    Chen, Quan; Chen, Zhe; Wang, Qunjing;

    2014-01-01

    load voltage is applied to reduce power cycle and switching losses. And then, three-level active neutral point-clamped topology is taken into account to wake the most thermo stressed device. In order to validate the improve lifetime method in this paper, a 2MW 3L-NPC converter used in wind energy has......Three-level Neutral-point-clamped (3L-NPC) topology is becoming a realistic alternative to the conventional one in high-voltage and high-power application. Studies show that the power cycling mean time to failure (MTTF) of the semiconductor bond wire in 3L-NPC inverter system may be very short...

  12. Variable geometry gas turbines for improving the part-load performance of marine combined cycles ? Combined cycle performance

    OpenAIRE

    Haglind, F.

    2010-01-01

    Abstract The part-load performance of combined cycles intended for naval use is of great importance, and it is influenced by the gas turbine configuration and load control strategy. This paper is aimed at quantifying the effects of variable geometry gas turbines on the part-load efficiency for combined cycles used for ship propulsion. Moreover, the paper is aimed at developing methodologies and deriving models for part-load simulations suitable for energy system analysis of various...

  13. Advanced thermal-energy-storage concept-definition study for solar Brayton power plants. Final technical report, Volume I

    Energy Technology Data Exchange (ETDEWEB)

    1976-01-01

    The detailed results are presented of a technical and economic assessment of phase change and thermochemical energy storage systems in a solar power plant employing a high temperature Brayton cycle thermal engine with helium as the heat transport fluid. The assessment included an examination of the storage system operation, efficiency, power plant interaction, design, materials, safety, maintenance, environmental impact, system life, and economics. These considerations are implemented in the conceptual design of three baseline storage systems and their components for use in a solar power plant module of 50 megawatt electrical power output. Rationale is provided to support the configuration, operation and material choices. A preliminary assessment of the technology development and experimental test program requirements are also included. The report is contained in four separate volumes. This volume is the technical report.

  14. Improvement to the gas cycle energy generating installations with heat recuperation

    International Nuclear Information System (INIS)

    Improvement to the gas cycle energy generating installations with heat recuperation, comprising a heat source, supplying a fluid at high temperature and pressure, an expansion turbine, at least one recuperator fitted to the turbine outlet, a cooler and compressor in series, the compressor returning the high pressure fluid to the source after heat exchange in the recuperator with the low pressure fluid from the turbine. It is characterised in that at least one steam generator is connected to the low pressure end of the recuperator

  15. Low cycle fatigue improvement of powder metallurgy titanium alloy through thermomechanical treatment

    Institute of Scientific and Technical Information of China (English)

    LIU Bin; LIU Yong; HE Xiao-yu; TANG Hui-ping; CHEN Li-fang

    2008-01-01

    A low-cost β type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd (mass fraction, %)(T12LCC) alloy was produced by blended elemental powder metallurgy(P/M) method and subsequent thermomechanical treatment. Low cycle fatigue(LCF) behavior of P/M T12LCC alloy before and after thermomechanical treatment was studied. The results show that the LCF resistance of P/M titanium alloy is significantly enhanced through the thermomechanical treatment. The mechanisms for the improvement of LCF behavior are attributed to the elimination of residual pores, the microstructure refining and homogenization.

  16. An optimization approach to cycle quality network chain based on improved SCOR model

    Institute of Scientific and Technical Information of China (English)

    Renbin Xiao; Zhengying Cai; Xinhui Zhang

    2009-01-01

    Based on the improved supply chain operations reference (SCOR) model, a network-topology structure of cycle quality chain oper-ations reference (CQCOR) model is built up, which realizes the cycle operation by an added quality process of reverse manufacturing. The concept of cycle quality chain management is defined, and its cost structure is analyzed according to positive and reverse quality processes. If the quality level is controlled by the positive quality cost, then the reverse quality cost is a nonlinear function of quality level. All the quality processes are connected by acceptable probability, so the optimized objective function is described as a fuzzy multi-objective function comprising maximum of the total profit of quality chain, maximum of the recycling efficiency and maximum of environment protection and source saving. The effects of different quality policies on fuzzy rules are compared by a simplified example. When the policy of recycling efficiency dominates, the total quality profit will be less than that of maximum profit policy.

  17. Back-end fuel cycle efficiencies with respect to improved uranium utilization

    International Nuclear Information System (INIS)

    The world-wide nuclear power plant (NPP) capacity is at present 160 GW(e). If one adds the power stations under construction and ordered, a plant capacity of approximately 480 GW(e) is obtained for 1990, with the share of LWRs making up more than 80%. A modern LWR consumes in the open fuel cycle about 4400 metric tonnes of natural uranium per GW(e), assuming a lifetime of 30 years and a load factor of 70%. Considering the natural uranium reserves known at present and exploitable under economic conditions, it can be conveniently estimated that, with the present NPP capacity extension perspective, the natural uranium resources may be exhausted in a few decades. This trend can be counteracted in a flexible manner by various approaches in fuel cycle technology and strategy: (i) by steady further development of the established LWR technology the uranium consumption can be reduced by about 15%; (ii) closing the nuclear fuel cycle on the basis of LWRs (i.e. thermal uranium and plutonium recycling) implies up to 40% savings in natural uranium consumption; (iii) more recent considerations include the advanced pressurized water reactor (APWR). The APWR combines the proven PWR technology with a newly developed tight lattice core with greatly improved conversion characteristics (conversion ratio = 0.90 to 0.95). In terms of uranium utilization, the APWR has an efficiency three to five times higher than a PWR; (iv) Commercial introduction of FBR systems results in an optimal utilization of uranium which, at the same time, guarantees the supply of nuclear fuel well beyond the present century. For a corresponding transition period an energy supply system can be conceived which relies essentially on extended back-end fuel cycle capacities. These would facilitate a symbiosis of PWR, APWR and FBR, characterized by high flexibility with respect to long-term developments on the energy market. (author)

  18. Non-circular chainring improves aerobic cycling performance in non-cyclists.

    Science.gov (United States)

    Hintzy, Frédérique; Horvais, Nicolas

    2016-06-01

    Non-circular chainrings alter the crank velocity profile over a pedalling cycle. The aim of this study was to investigate the effect of this altered crank velocity profile on the aerobic performance compared to a circular chainring (CC). Ten male non-cyclists performed two incremental maximal tests at 80 rpm on a cycle ergometer: one with a circular (Shimano) and the other with a non-circular chainring Osymetric(®) (Somovedi), at least 50 h apart. Each test started with a workload of 100 W lasting 3 min. During the first 12 min, the workload was increased by 30 W every 3 min. Thereafter, the workload was increased by 30 W every 2 min until exhaustion. The power output, the intra-cycle crank angular velocity and the physiological parameters were monitored continuously, averaged over the last 30 s of each increment and at exhaustion, and compared for the two chainrings. Results showed a higher maximal aerobic power attained with the non-circular chainring (362.6 ± 37.9 vs. 338.8 ± 32.6 W, p < .001; moderate effect), which could be explained by a significantly lower energy expenditure during the first increment at 100 W. It could be hypothesised that the use of the non-circular chainring allowed saving a small part of energy expenditure throughout the test, allowing the exhaustion of the subject at a higher increment for a similar maximal energy expenditure, in comparison with a CC. Although this improvement is obtained only for non-cyclists, it allowed highlighting the link between cycling equipment modifying the pedalling motion and physiological responses. PMID:26406359

  19. Toward improving the representation of the water cycle at High Northern Latitudes

    Science.gov (United States)

    Lahoz, William; Svendby, Tove; Hamer, Paul; Blyverket, Jostein; Kristiansen, Jørn; Luijting, Hanneke

    2016-04-01

    The rapid warming at northern latitude regions in recent decades has resulted in a lengthening of the growing season, greater photosynthetic activity and enhanced carbon sequestration by the ecosystem. These changes are likely to intensify summer droughts, tree mortality and wildfires. A potential major climate change feedback is the release of carbon-bearing compounds from soil thawing. These changes make it important to have information on the land surface (soil moisture and temperature) at high northern latitude regions. The availability of soil moisture measurements from several satellite platforms provides an opportunity to address issues associated with the effects of climate change, e.g., assessing multi-decadal links between increasing temperatures, snow cover, soil moisture variability and vegetation dynamics. The relatively poor information on water cycle parameters for biomes at northern high latitudes make it important that efforts are expended on improving the representation of the water cycle at these latitudes. In a collaboration between NILU and Met Norway, we evaluate the soil moisture observations over Norway from the ESA satellite SMOS (Soil Moisture and Ocean Salinity) using in situ ground based soil moisture measurements, with reference to drought and flood episodes. We will use data assimilation of the quality-controlled SMOS soil moisture observations into a land surface model and a numerical weather prediction model to assess the added value from satellite observations of soil moisture for improving the representation of the water cycle at high northern latitudes. This presentation provides first results from this work. We discuss the evaluation of SMOS soil moisture data (and from other satellites) against ground-based in situ data over Norway; the performance of the SMOS soil moisture data for selected drought and flood conditions over Norway; and the first results from data assimilation experiments with land surface models and numerical

  20. Anticipated Improvements in Precipitation Physics and Understanding of Water Cycle from GPM Mission

    Science.gov (United States)

    Smith, Eric A.

    2003-01-01

    The GPM mission is currently planned for start in the late-2007 to early-2008 time frame. Its main scientific goal is to help answer pressing scientific problems arising within the context of global and regional water cycles. These problems cut across a hierarchy of scales and include climate-water cycle interactions, techniques for improving weather and climate predictions, and better methods for combining observed precipitation with hydrometeorological prediction models for applications to hazardous flood-producing storms, seasonal flood/draught conditions, and fresh water resource assessments. The GPM mission will expand the scope of precipitation measurement through the use of a constellation of some 9 satellites, one of which will be an advanced TRMM-like core satellite carrying a dual-frequency Ku-Ka band precipitation radar and an advanced, multifrequency passive microwave radiometer with vertical-horizontal polarization discrimination. The other constellation members will include new dedicated satellites and co-existing operational/research satellites carrying similar (but not identical) passive microwave radiometers. The goal of the constellation is to achieve approximately 3-hour sampling at any spot on the globe -- continuously. The constellation s orbit architecture will consist of a mix of sun-synchronous and non-sun-synchronous satellites with the core satellite providing measurements of cloud-precipitation microphysical processes plus calibration-quality rainrate retrievals to be used with the other retrieval information to ensure bias-free constellation coverage. GPM is organized internationally, involving existing, pending, projected, and under-study partnerships which will link NASA and NOAA in the US, NASDA in Japan, ESA in Europe, ISRO in India, CNES in France, and possibly AS1 in Italy, KARI in South Korea, CSA in Canada, and AEB in Brazil. Additionally, the program is actively pursuing agreements with other international collaborators and

  1. Improving the estimation of fractional-cycle biases for ambiguity resolution in precise point positioning

    Science.gov (United States)

    Geng, Jianghui; Shi, Chuang; Ge, Maorong; Dodson, Alan H.; Lou, Yidong; Zhao, Qile; Liu, Jingnan

    2012-08-01

    Ambiguity resolution dedicated to a single global positioning system (GPS) station can improve the accuracy of precise point positioning. In this process, the estimation accuracy of the narrow-lane fractional-cycle biases (FCBs), which destroy the integer nature of undifferenced ambiguities, is crucial to the ambiguity-fixed positioning accuracy. In this study, we hence propose the improved narrow-lane FCBs derived from an ambiguity-fixed GPS network solution, rather than the original (i.e. previously proposed) FCBs derived from an ambiguity-float network solution. The improved FCBs outperform the original FCBs by ensuring that the resulting ambiguity-fixed daily positions coincide in nature with the state-of-the-art positions generated by the International GNSS Service (IGS). To verify this improvement, 1 year of GPS measurements from about 350 globally distributed stations were processed. We find that the original FCBs differ more from the improved FCBs when fewer stations are involved in the FCB estimation, especially when the number of stations is less than 20. Moreover, when comparing the ambiguity-fixed daily positions with the IGS weekly positions for 248 stations through a Helmert transformation, for the East component, we find that on 359 days of the year the daily RMS of the transformed residuals based on the improved FCBs is smaller by up to 0.8 mm than those based on the original FCBs, and the mean RMS over the year falls evidently from 2.6 to 2.2 mm. Meanwhile, when using the improved rather than the original FCBs, the RMS of the transformed residuals for the East component of 239 stations (i.e. 96.4% of all 248 stations) is clearly reduced by up to 1.6 mm, especially for stations located within a sparse GPS network. Therefore, we suggest that narrow-lane FCBs should be determined with ambiguity-fixed, rather than ambiguity-float, GPS network solutions.

  2. How can LCA approaches contribute to improve geo-cycles management

    Science.gov (United States)

    Carreiras, M.; Ferreira, A. J. D.; Esteves, T. C. J.; Delgado, F.; Andrade, F.; Franco, J.; Pereira, C. D.

    2012-04-01

    Climate change and land use have become a major challenge for mankind and the natural environment. Greenhouse gas (GHG) emissions released into the atmosphere in ever rapidly growing volumes are most likely to be responsible for this change. Carbon dioxide gas (CO2) is suggested to be the main cause of global warming. Carbon reduction is the key to preventing this, for example, by enhancing energy efficiency and mitigating carbon emissions by means of green energy and adjusting the use of natural resources. Different activities produce distinguish impacts, and each product generates specific impacts on nature. The impact of man activities in the geo-cycles is of paramount importance in what concerns long term sustainability. Nevertheless, the environmental and sustainability impacts of different approaches and techniques of ecosystem management is a difficult question that can be assessed using LCA techniques LCA is a technique to assess environmental impacts associated with all the stages of a product's life from-cradle-to-grave. Based on that, LCA can be effective in supporting the assessment of decision making on complex sustainability issues because it can integrate the diversity of impacts categories guise and it can be adapted to a large variety of contexts. By incorporating quantitative data LCA allows decision makers to include a full range of economic, environmental, social and technical criteria. The integrated framework is configured such that the pros and cons of alternative environmental and energy strategies can be measured in terms of their ability to achieve the overall goals and objectives of the sustainable development, while satisfying the pollution control requirements. Because it is holistic, integrate and dynamic, this approach represents a state of the art tool for enhance the sustainable development of a sector, allowing a more transparent and participated management, a basic instrument for improved competitiveness. This approach may serve

  3. An audit cycle of consent form completion: A useful tool to improve junior doctor training

    Directory of Open Access Journals (Sweden)

    Catherine Leng

    2016-01-01

    Full Text Available Background: Consent for surgical procedures is an essential part of the patient's pathway. Junior doctors are often expected to do this, especially in the emergency setting. As a result, the aim of our audit was to assess our practice in consenting and institute changes within our department to maintain best medical practice. Methods: An audit of consent form completion was conducted in March 2013. Standards were taken from Good Surgical Practice (2008 and General Medical Council guidelines. Inclusion of consent teaching at a formal consultant delivered orientation programme was then instituted. A re-audit was completed to reassess compliance. Results: Thirty-seven consent forms were analysed. The re-audit demonstrated an improvement in documentation of benefits (91–100% and additional procedures (0–7.5%. Additional areas for improvement such as offering a copy of the consent form to the patient and confirmation of consent if a delay occurred between consenting and the procedure were identified. Conclusion: The re-audit demonstrated an improvement in the consent process. It also identified new areas of emphasis that were addressed in formal teaching sessions. The audit cycle can be a useful tool in monitoring, assessing and improving clinical practice to ensure the provision of best patient care.

  4. Does a Non-Circular Chainring Improve Performance in the Bicycle Motocross Cycling Start Sprint?

    Science.gov (United States)

    Mateo-March, Manuel; Fernández-Peña, Eneko; Blasco-Lafarga, Cristina; Morente-Sánchez, Jaime; Zabala, Mikel

    2014-01-01

    Maximising power output during the initial acceleration phase of a bicycle motocross (BMX) race increases the chance to lead the group for the rest of the race. The purpose of this study was to investigate the effect of non-circular chainrings (Q-ring) on performance during the initial acceleration phase of a BMX race. Sixteen male cyclists (Spanish National BMX team) performed two counterbalanced and randomized initial sprints (3.95s), using Q- ring vs. circular chainring, on a BMX track. The sample was divided into two different groups according to their performance (Elite; n = 8 vs. Cadet; n = 8). Elite group covered a greater distance using Q-ring (+0.26 m, p = 0.02; D = 0.23), whilst the improvement for the Cadet (+0.04 m) was not significant (p = 0.87; D = -0.02). Also, there was no significant difference in power output for the Elite group, while the Cadet group revealed larger peak power with the circular chainring. Neither lactate level, nor heart rate showed significant differences due to the different chainring used. The non-circular chainring improved the initial acceleration capacity only in the Elite riders. Key Points This work provides novel results demonstrating very significant improvements in the sprint performance of BMX cycling discipline using a non-circular chainring system. This study seeks a practical application from scientific analysis All data are obtained in a real context of high competition using a sample comprised by the National Spanish Team. Some variables influencing performance as subjects’ physical fitness are discussed. Technical equipment approved by International Cycling Union is studied to check its potentially beneficial influence on performance. PMID:24570612

  5. Increased Mesohippocampal Dopaminergic Activity and Improved Depression-Like Behaviors in Maternally Separated Rats Following Repeated Fasting/Refeeding Cycles

    Directory of Open Access Journals (Sweden)

    Jeong Won Jahng

    2012-01-01

    Full Text Available We have previously reported that rats that experienced 3 h of daily maternal separation during the first 2 weeks of birth (MS showed binge-like eating behaviors with increased activity of the hypothalamic-pituitary-adrenal axis when they were subjected to fasting/refeeding cycles repeatedly. In this study, we have examined the psychoemotional behaviors of MS rats on the fasting/refeeding cycles, together with their brain dopamine levels. Fasting/refeeding cycles normalized the ambulatory activity of MS rats, which was decreased by MS experience. Depression-like behaviors, but not anxiety, by MS experience were improved after fasting/refeeding cycles. Fasting/refeeding cycles did not significantly affect the behavioral scores of nonhandled (NH control rats. Fasting/refeeding cycles increased dopamine levels not only in the hippocampus but also in the midbrain dopaminergic neurons in MS rats, but not in NH controls. Results demonstrate that fasting/refeeding cycles increase the mesohippocampal dopaminergic activity and improve depression-like behaviors in rats that experienced MS. Together with our previous paper, it is suggested that increased dopamine neurotransmission in the hippocampus may be implicated in the underlying mechanisms by which the fasting/refeeding cycles induce binge-like eating and improve depression-like behaviors in MS rats.

  6. Supercritical carbon dioxide cycle control analysis.

    Energy Technology Data Exchange (ETDEWEB)

    Moisseytsev, A.; Sienicki, J. J. (Nuclear Engineering Division)

    2011-04-11

    . In particular, the peak heat removal capacity of the shutdown heat removal loop may be specified to be 1.1 % of the nominal reactor power. An investigation of the oscillating cycle behavior calculated by the ANL Plant Dynamics Code under specific conditions has been carried out. It has been found that the calculation of unstable operation of the cycle during power reduction to 0 % may be attributed to the modeling of main compressor operation. The most probable reason for such instabilities is the limit of applicability of the currently used one-dimensional compressor performance subroutines which are based on empirical loss coefficients. A development of more detailed compressor design and performance models is required and is recommended for future work in order to better investigate and possibly eliminate the calculated instabilities. Also, as part of such model development, more reliable surge criteria should be developed for compressor operation close to the critical point. It is expected that more detailed compressor models will be developed as a part of validation of the Plant Dynamics Code through model comparison with the experiment data generated in the small S-CO{sub 2} loops being constructed at Barber-Nichols Inc. and Sandia National Laboratories (SNL). Although such a comparison activity had been planned to be initiated in FY 2008, data from the SNL compression loop currently in operation at Barber Nichols Inc. has not yet become available by the due date of this report. To enable the transient S-CO{sub 2} cycle investigations to be carried out, the ANL Plant Dynamics Code for the S-CO{sub 2} Brayton cycle was further developed and improved. The improvements include further optimization and tuning of the control mechanisms as well as an adaptation of the code for reactor systems other than the Lead-Cooled Fast Reactor (LFR). Since the focus of the ANL work on S-CO{sub 2} cycle development for the majority of the current year has been on the

  7. Supercritical carbon dioxide cycle control analysis

    International Nuclear Information System (INIS)

    capacity of the shutdown heat removal loop may be specified to be 1.1 % of the nominal reactor power. An investigation of the oscillating cycle behavior calculated by the ANL Plant Dynamics Code under specific conditions has been carried out. It has been found that the calculation of unstable operation of the cycle during power reduction to 0 % may be attributed to the modeling of main compressor operation. The most probable reason for such instabilities is the limit of applicability of the currently used one-dimensional compressor performance subroutines which are based on empirical loss coefficients. A development of more detailed compressor design and performance models is required and is recommended for future work in order to better investigate and possibly eliminate the calculated instabilities. Also, as part of such model development, more reliable surge criteria should be developed for compressor operation close to the critical point. It is expected that more detailed compressor models will be developed as a part of validation of the Plant Dynamics Code through model comparison with the experiment data generated in the small S-CO2 loops being constructed at Barber-Nichols Inc. and Sandia National Laboratories (SNL). Although such a comparison activity had been planned to be initiated in FY 2008, data from the SNL compression loop currently in operation at Barber Nichols Inc. has not yet become available by the due date of this report. To enable the transient S-CO2 cycle investigations to be carried out, the ANL Plant Dynamics Code for the S-CO2 Brayton cycle was further developed and improved. The improvements include further optimization and tuning of the control mechanisms as well as an adaptation of the code for reactor systems other than the Lead-Cooled Fast Reactor (LFR). Since the focus of the ANL work on S-CO2 cycle development for the majority of the current year has been on the applicability of the cycle to SFRs, work has started on modification of the ANL

  8. Preliminary Studies of Na2CO3 Elimination from Na/CO2 Reaction in S-CO2 Power Cycle coupled to SFR System

    International Nuclear Information System (INIS)

    In order to avoid the SWR, the supercritical CO2 (S-CO2) Brayton cycle was proposed as a design alternative to the steam Rankine cycle. The S-CO2 Brayton cycle has good features such as improved thermal efficiency, reduced total plant size by having compact turbomachinery and heat exchangers and relatively simplified cycle layout. However, several technical challenges are still remaining for application of S-CO2 Brayton cycle to SFR. This is because when the pressure boundary in sodium-CO2 heat exchanger (HX) fails then leaked CO2 reacts with sodium, although the SWR is eliminated. The reaction between sodium and CO2 is much milder than SWR but more complex. The reaction is affected by the reaction temperature and there is the possibility of sodium ignition at very high temperature. So far, some research works on Na/CO2 reaction has been done. The experiments for Na/CO2 surface reaction, wastage phenomenon and self-plugging of narrow flow channel of Na/CO2 HXs were successfully conducted in KAERI. CEA proposed the major Na/CO2 reaction formulas and performed the calorimetric studies. JAEA experimentally investigated reaction behavior of CO2 with a liquid sodium pool. However, any research works for treatment and removal of reaction products from Na/CO2 reaction has not been done so far. Generally, when the pressure boundary fails CO2 will be released to sodium side and the amount of leakage will be depending on the rupture size. CO2 will react with sodium in the sodium-CO2 HX. It will lead to an economical problem if the channel is plugged by the solid reaction products of Na/CO2 reaction. Since the whole system operation should be stopped or some sort of bypass system should be applied to replace the plugged channel, which will affect the system economics. Therefore, it needs a material which can clean up the solid reaction products of Na/CO2 reaction and contaminated system while minimizing the impact on economics. If there is a material that can act as a

  9. Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24

    CERN Document Server

    Javaraiah, J

    2009-01-01

    Recently, using Greenwich and Solar Optical Observing Network sunspot group data during the period 1874-2006, (Javaraiah, MNRAS, 377, L34, 2007: Paper I), has found that: (1) the sum of the areas of the sunspot groups in 0-10 deg latitude interval of the Sun's northern hemisphere and in the time-interval of -1.35 year to +2.15 year from the time of the preceding minimum of a solar cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of the smoothed monthly sunspot number) of the next cycle n+1. (2) The sum of the areas of the spot groups in 0-10 deg latitude interval of the southern hemisphere and in the time-interval of 1.0 year to 1.75 year just after the time of the maximum of the cycle n correlates very well (r=0.966) with the amplitude of cycle n+1. Using these relations, (1) and (2), the values 112 + or - 13 and 74 + or -10, respectively, were predicted in Paper I for the amplitude of the upcoming cycle 24. Here we found that in case of (1), the north-south asymmetry in the area su...

  10. Life Cycle Considerations for Improving Sustainability Assessments in Seafood Awareness Campaigns

    Science.gov (United States)

    Pelletier, Nathan; Tyedmers, Peter

    2008-11-01

    It is widely accepted that improving the sustainability of seafood production requires efforts to reverse declines in global fisheries due to overfishing and to reduce the impacts to host ecosystems from fishing and aquaculture production technologies. Reflective of on-going dialogue amongst participants in an international research project applying Life Cycle Assessment to better understand and manage global salmon production systems, we argue here that such efforts must also address the wider range of biophysical, ecological, and socioeconomic impacts stemming from the material and energetic throughput associated with these industries. This is of particular relevance given the interconnectivity of global environmental change, ocean health, and the viability of seafood production in both fisheries and aquaculture. Although the growing popularity of numerous ecolabeling, certification, and consumer education programs may be making headway in influencing Western consumer perceptions of the relative sustainability of alternative seafood products, we also posit that the efficacy of these initiatives in furthering sustainability objectives is compromised by the use of incomplete criteria. An emerging body of Life Cycle Assessment research of fisheries and aquaculture provides valuable insights into the biophysical dimensions of environmental performance in alternative seafood production and consumption systems, and should be used to inform a more holistic approach to labeling, certifying, and educating for sustainability in seafood production. More research, however, must be undertaken to develop novel techniques for incorporating other critical dimensions, in particular, socioeconomic considerations, into our sustainability decision-making.

  11. Cooling tower performance improvements for a cycling PC-fired unit

    International Nuclear Information System (INIS)

    The inevitable deregulation of the electric utility industry has caused many electric utility companies to look closely at their existing assets and predict what role these units will play in the future. Reducing a unit's production cost is the best way to prepare for the deregulated market but this benefit often comes with an associated capital expenditure. Spending capital dollars today can pose a quandary for an investor-owned utility committed to maintaining low consumer rates. The dilemma is: How does a utility improve its competitiveness position today while ensuring that the shareholders are getting a fair return on their investment when any fuel savings are passed through to the consumer? Illinois Power (IP) has been aggressively looking to improve their current competitive position while facing the current regulatory challenges. Studies have been commissioned to identify the most attractive cost reduction opportunities available. One study identified that improving the performance of the Unit 6 cooling tower at the Havana Station would be a very economically attractive option. This paper addresses the economics of refurbishing a cooling tower for a cycling pulverized-coal (PC) unit to provide a competitive advantage leading into the deregulated electricity market

  12. Brayton isotope power system. Phase I (Ground demonstration system) configuration control document (CCD)

    Energy Technology Data Exchange (ETDEWEB)

    1975-09-25

    The Brayton Isotope Power System (BIPS) Ground Demonstration System (GDS) configuration is defined. The GDS is configured to be similar to a conceptual flight system design referred to herein as the BIPS Flight System (FS). The Brayton Isotope Power System is being developed by the ERDA as a 500 to 2000 W/sub e/, 7 year life 3.5 W/sub e/ per pound space power system. The system was a closed Brayton dynamic system to convert energy from an isotope heat source at a net efficiency exceeding 25%. This CCD is for the first phase of the ERDA program to have a qualified system ready for launch by June 30, 1981. Phase I is a 36 month effort to provide a conceptual design of the flight system and design, fabricate and test a ground demonstration system. The baseline system is predicated on using two of the multihundred-watt isotope heat sources being developed for the ERDA by GE. The Ground Demonstration System will simulate, as closely as possible, the Brayton Isotope Power Flight System and will utilize components and technology being developed by NASA for the Mini-Brayton rotating unit (AIRPHX), recuperator (AIRLA) and heat source assembly (GE). The Ground Demonstration System includes a performance test and a 1000-hour endurance test.

  13. Quality Improvement Methodologies – PDCA Cycle, RADAR Matrix, DMAIC and DFSS

    Directory of Open Access Journals (Sweden)

    M. Sokovic

    2010-11-01

    Full Text Available Purpose: of this paper is to introduce the reader to the characteristics of PDCA tool and Six Sigma (DMAIC, DFSS techniques and EFQM Excellence Model (RADAR matrix, which are possible to use for the continuous quality improvement of products, processes and services in organizations.Design/methodology/approach: We compared the main characteristics of the presented methodologies aiming to show the main prerequisites, differences, strengths and limits in their application.Findings: Depending on the purpose every organization will have to find a proper way and a combination of methodologies in its implementation process. The PDCA cycle is a well known fundamental concept of continuous-improvement processes, RADAR matrix provides a structured approach assessing the organizational performance, DMAIC is a systematic, and fact based approach providing framework of results-oriented project management, DFSS is a systematic approach to new products or processes design focusing on prevent activities.Research limitations/implications: This paper provides general information and observations on four presented methodologies. Further research could be done towards more detailed study of characteristics and positive effects of these methodologies.Practical implications: The paper presents condensed presentation of main characteristics, strengths and limitations of presented methodologies. Our findings could be used as solid information for management decisions about the introduction of various quality programmes.Originality/value: We compared four methodologies and showed their main characteristics and differences. We showed that some methodologies are more simple and therefore easily to understand and introduce (e.g. PDCA cycle. On the contrary Six Sigma and EFQM Excellence model are more complex and demanding methodologies and therefore need more time and resources for their proper implementation.

  14. Improving Fuel Cycle Design and Safety Characteristics of a Gas Cooled Fast Reactor

    International Nuclear Information System (INIS)

    gradients within the fuel assemblies would be too high, and fuel economy is poor. Two improved fuel concepts are proposed: (1) a redesign of the classic TRISO coated particle fuel, and (2) an innovative hollow sphere design. Both fuel elements are used in a core design based on direct cooling of the coated particle fuel. To increase the neutronic margins and obtain adequate self-breeding capabilities, the proposed reactor has 2400 MWth power output and a power density of 50 MW/m3. With both types of fuel, it is possible to obtain a closed fuel cycle. Long irradiation intervals (several years) are possible with a low burnup reactivity swing, which reduces the required over-reactivity of the fresh core and reduces control rod requirements during operation. In the closed fuel cycle it is important to be able to predict whether a certain initial fuel composition will in fact yield a new fuel, after irradiation, cool down and reprocessing, with which the reactor can be restarted. A theoretical framework is presented in this thesis which allows calculation of the ‘Breeding Gain’ (BG) of the reactor. The BG quantifies the performance of the fuel for batch i + 1 as a function of the composition of the initial fuel of batch i. If this BG can be made equal to zero, both fuel compositions give the same nuclear performance. To be able to calculate the fuel performance, the reactivity weight, i.e. the contribution of each isotope to the overall reactivity of the reactor, needs to be estimated. It is proposed in this thesis to calculate these reactivity weights using a first-order eigenvalue perturbation calculation. It is shown that this approach yields an expression which reduces to a well-established formula for reactivity weights. All steps in the fuel cycle, i.e. irradiation, cool down and reprocessing, have to be taken into account to calculate the Breeding Gain for the closed fuel cycle. First order nuclide perturbation theory provides an efficient method to calculate the

  15. ECONOMICS AND FEASIBILITY OF RANKINE CYCLE IMPROVEMENTS FOR COAL FIRED POWER PLANTS

    Energy Technology Data Exchange (ETDEWEB)

    Richard E. Waryasz; Gregory N. Liljedahl

    2004-09-08

    ALSTOM Power Inc.'s Power Plant Laboratories (ALSTOM) has teamed with the U.S. Department of Energy National Energy Technology Laboratory (DOE NETL), American Electric Company (AEP) and Parsons Energy and Chemical Group to conduct a comprehensive study evaluating coal fired steam power plants, known as Rankine Cycles, equipped with three different combustion systems: Pulverized Coal (PC), Circulating Fluidized Bed (CFB), and Circulating Moving Bed (CMB{trademark}). Five steam cycles utilizing a wide range of steam conditions were used with these combustion systems. The motivation for this study was to establish through engineering analysis, the most cost-effective performance potential available through improvement in the Rankine Cycle steam conditions and combustion systems while at the same time ensuring that the most stringent emission performance based on CURC (Coal Utilization Research Council) 2010 targets are met: > 98% sulfur removal; < 0.05 lbm/MM-Btu NO{sub x}; < 0.01 lbm/MM-Btu Particulate Matter; and > 90% Hg removal. The final report discusses the results of a coal fired steam power plant project, which is comprised of two parts. The main part of the study is the analysis of ten (10) Greenfield steam power plants employing three different coal combustion technologies: Pulverized Coal (PC), Circulating Fluidized Bed (CFB), and Circulating Moving Bed (CMB{trademark}) integrated with five different steam cycles. The study explores the technical feasibility, thermal performance, environmental performance, and economic viability of ten power plants that could be deployed currently, in the near, intermediate, and long-term time frame. For the five steam cycles, main steam temperatures vary from 1,000 F to 1,292 F and pressures from 2,400 psi to 5,075 psi. Reheat steam temperatures vary from 1,000 F to 1,328 F. The number of feedwater heaters varies from 7 to 9 and the associated feedwater temperature varies from 500 F to 626 F. The main part of the

  16. Preliminary Failure Modes, Effects and Criticality Analysis (FMECA) of the conceptual Brayton Isotope Power System (BIPS) Flight System

    International Nuclear Information System (INIS)

    A failure modes, effects and criticality analysis (FMECA) was made of the Brayton Isotope Power System Flight System (BIPS-FS) as presently conceived. The components analyzed include: Mini-BRU; Heat Source Assembly (HSA); Mini-Brayton Recuperator (MBR); Space Radiator; Ducts and Bellows, Insulation System; Controls; and Isotope Heat Source (IHS)

  17. Cost and price estimate of Brayton and Stirling engines in selected production volumes

    Science.gov (United States)

    Fortgang, H. R.; Mayers, H. F.

    1980-01-01

    The methods used to determine the production costs and required selling price of Brayton and Stirling engines modified for use in solar power conversion units are presented. Each engine part, component and assembly was examined and evaluated to determine the costs of its material and the method of manufacture based on specific annual production volumes. Cost estimates are presented for both the Stirling and Brayton engines in annual production volumes of 1,000, 25,000, 100,000 and 400,000. At annual production volumes above 50,000 units, the costs of both engines are similar, although the Stirling engine costs are somewhat lower. It is concluded that modifications to both the Brayton and Stirling engine designs could reduce the estimated costs.

  18. Nuclear fuel cycle waste stream immobilization with cermets for improved thermal properties and waste consolidation

    Energy Technology Data Exchange (ETDEWEB)

    Ortega, Luis H., E-mail: bertortega@tamu.edu [Texas A and M University, Department of Nuclear Engineering, 3133 TAMU, College Station, TX (United States); Kaminski, Michael D., E-mail: kaminski@anl.gov [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL (United States); Zeng, Zuotao, E-mail: zeng@anl.gov [Nuclear Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL (United States); Cunnane, James, E-mail: cunnane@anl.gov [Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL (United States)

    2013-07-15

    In the pursuit of methods to improve nuclear waste form thermal properties and combine potential nuclear fuel cycle wastes, a bronze alloy was combined with an alkali, alkaline earth metal bearing ceramic to form a cermet. The alloy was prepared from copper and tin (10 mass%) powders. Pre-sintered ceramic consisting of cesium, strontium, barium and rubidium alumino-silicates was mixed with unalloyed bronze precursor powders and cold pressed to 300 × 10{sup 3} kPa, then sintered at 600 °C and 800 °C under hydrogen. Cermets were also prepared that incorporated molybdenum, which has a limited solubility in glass, under similar conditions. The cermet thermal conductivities were seven times that of the ceramic alone. These improved thermal properties can reduce thermal gradients within the waste forms thus lowering internal temperature gradients and thermal stresses, allowing for larger waste forms and higher waste loadings. These benefits can reduce the total number of waste packages necessary to immobilize a given amount of high level waste and immobilize troublesome elements.

  19. Life cycle assessment (LCA) of an integrated biomass gasification combined cycle (IBGCC) with CO2 removal

    International Nuclear Information System (INIS)

    Based on the results of previous studies, the efficiency of a Brayton/Hirn combined cycle fuelled with a clean syngas produced by means of biomass gasification and equipped with CO2 removal by chemical absorption reached 33.94%, considering also the separate CO2 compression process. The specific CO2 emission of the power plant was 178 kg/MW h. In comparison with values previously found for an integrated coal gasification combined cycle (ICGCC) with upstream CO2 chemical absorption (38-39% efficiency, 130 kg/MW h specific CO2 emissions), this configuration seems to be attractive because of the possibility of operating with a simplified scheme and because of the possibility of using biomass in a more efficient way with respect to conventional systems. In this paper, a life cycle assessment (LCA) was conducted with presenting the results on the basis of the Eco-Indicator 95 impact assessment methodology. Further, a comparison with the results previously obtained for the LCA of the ICGCC was performed in order to highlight the environmental impact of biomass production with fossil fuels utilisation. The LCA shows the important environmental advantages of biomass utilisation in terms of reduction of both greenhouse gas emissions and natural resource depletion, although an improved impact assessment methodology may better highlight the advantages due to the biomass utilisation

  20. A Virtual Reality-Cycling Training System for Lower Limb Balance Improvement

    OpenAIRE

    Yin, Chieh; Hsueh, Ya-Hsin; Yeh, Chun-Yu; Lo, Hsin-Chang; Lan, Yi-Ting

    2016-01-01

    Stroke survivors might lose their walking and balancing abilities, but many studies pointed out that cycling is an effective means for lower limb rehabilitation. However, during cycle training, the unaffected limb tends to compensate for the affected one, which resulted in suboptimal rehabilitation. To address this issue, we present a Virtual Reality-Cycling Training System (VRCTS), which senses the cycling force and speed in real-time, analyzes the acquired data to produce feedback to patien...

  1. The improvement of approaches to marketing testing of ecological innovative products in the stages of innovative cycle

    OpenAIRE

    Ye.I. Nagornyi; T.V. Kasianenko

    2013-01-01

    The aim of the article. The aim of the article is theoretical justification and improvement of approaches to marketing testing of ecological innovative production in the stages of innovative cycle, and the sequence of decision-making procedures on its readiness to entry into the market by results of testing. The results of the analysis. Launch of the ecological innovative products on the market and providing its passage through the stages of the innovative cycle requires continuous and hig...

  2. Design of a three-phase, 15-kilovolt-ampere static inverter for motor-starting a Brayton space power system

    Science.gov (United States)

    Frye, R. J.; Birchenough, A. G.

    1971-01-01

    The design of a three-phase, 400-Hz, 15-kVA static inverter for motor-starting the 2- to 15-kWe Brayton electrical space power system is described. The inverter operates from a nominal 56-V dc source to provide a 28-V, rms, quasi-square-wave output. The inverter is capable of supplying a 200-A peak current. Integrated circuitry is used to generate the three-phase, 400-Hz reference signals. Performance data for a drive stage that improves switching speed and provides efficient operation over a range of output current and drive supply voltage are presented. A transformerless, transistor output stage is used.

  3. Teaching Reitlinger Cycles To Improve Students' Knowledge And Comprehension Of Thermodynamics

    OpenAIRE

    Sparavigna, Amelia Carolina

    2016-01-01

    The second law of thermodynamics puts a limit on the thermal efficiency of heat engines. This limit value is the efficiency of the ideal reversible engine represented by the Carnot cycle. During the lectures on physics, the emphasis on this cycle is generally so strong that students could be induced to consider the Carnot cycle as the only cycle having the best thermal efficiency. In fact, an entire class of cycles exists possessing the same maximum efficiency: this class is that of the regen...

  4. Predicting the Amplitude of a Solar Cycle Using the North-South Asymmetry in the Previous Cycle: II. An Improved Prediction for Solar Cycle~24

    OpenAIRE

    Javaraiah, J.

    2009-01-01

    Recently, using Greenwich and Solar Optical Observing Network sunspot group data during the period 1874-2006, (Javaraiah, MNRAS, 377, L34, 2007: Paper I), has found that: (1) the sum of the areas of the sunspot groups in 0-10 deg latitude interval of the Sun's northern hemisphere and in the time-interval of -1.35 year to +2.15 year from the time of the preceding minimum of a solar cycle n correlates well (corr. coeff. r=0.947) with the amplitude (maximum of the smoothed monthly sunspot number...

  5. Cooling, freezing and heating with the air cycle: air as the ultimate green refrigerant

    NARCIS (Netherlands)

    Verschoor, M.J.E.

    2000-01-01

    Due to the recent concern about the damage that CFCs cause to the environment (ozone layer, global warming) and the absence of commonly acceptable alternative refrigerants, the search for alternative refrigeration concepts is going on. Air as refrigerant in the Joule-Brayton cycle (air cycle) is one

  6. Acute Beetroot Juice Supplementation Does Not Improve Cycling Performance in Normoxia or Moderate Hypoxia.

    Science.gov (United States)

    MacLeod, Kristin E; Nugent, Sean F; Barr, Susan I; Koehle, Michael S; Sporer, Benjamin C; MacInnis, Martin J

    2015-08-01

    Beetroot juice (BR) has been shown to lower the oxygen cost of exercise in normoxia and may have similar effects in hypoxia. We investigated the effect of BR on steady-state exercise economy and 10-km time trial (TT) performance in normoxia and moderate hypoxia (simulated altitude: ~2500 m). Eleven trained male cyclists (VO 2peak ≥ 60 ml · kg(-1) · min(-1)) completed four exercise trials. Two hours before exercise, subjects consumed 70 mL BR (~6 mmol nitrate) or placebo (nitrate-depleted BR) in a randomized, double-blind manner. Subjects then completed a 15-min self-selected cycling warm-up, a 15-min steady-state exercise bout at 50% maximum power output, and a 10-km time trial (TT) in either normoxia or hypoxia. Environmental conditions were randomized and single-blind. BR supplementation increased plasma nitrate concentration and fraction of exhaled nitric oxide relative to PL (p .05), but mean power output was greater in the normoxic TT relative to the hypoxic TT (p hypoxia (p > .05 in all comparisons). In conclusion, BR did not lower the oxygen cost of steady-state exercise or improve exercise performance in normoxia or hypoxia in a small sample of well-trained male cyclists. PMID:25811674

  7. Environmental Life Cycle Assessment of Diets with Improved Omega-3 Fatty Acid Profiles

    Science.gov (United States)

    Coelho, Carla R. V.; Pernollet, Franck; van der Werf, Hayo M. G.

    2016-01-01

    A high incidence of cardiovascular disease is observed worldwide, and dietary habits are one of the risk factors for these diseases. Omega-3 polyunsaturated fatty acids in the diet help to prevent cardiovascular disease. We used life cycle assessment to analyse the potential of two strategies to improve the nutritional and environmental characteristics of French diets: 1) modifying diets by changing the quantities and proportions of foods and 2) increasing the omega-3 contents in diets by replacing mainly animal foods with equivalent animal foods having higher omega-3 contents. We also investigated other possibilities for reducing environmental impacts. Our results showed that a diet compliant with nutritional recommendations for macronutrients had fewer environmental impacts than the current average French diet. Moving from an omnivorous to a vegetarian diet further reduced environmental impacts. Increasing the omega-3 contents in animal rations increased Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) in animal food products. Providing these enriched animal foods in human diets increased their EPA and DHA contents without affecting their environmental impacts. However, in diets that did not contain fish, EPA and DHA contents were well below the levels recommended by health authorities, despite the inclusion of animal products enriched in EPA and DHA. Reducing meat consumption and avoidable waste at home are two main avenues for reducing environmental impacts of diets. PMID:27504959

  8. Environmental Life Cycle Assessment of Diets with Improved Omega-3 Fatty Acid Profiles.

    Science.gov (United States)

    Coelho, Carla R V; Pernollet, Franck; van der Werf, Hayo M G

    2016-01-01

    A high incidence of cardiovascular disease is observed worldwide, and dietary habits are one of the risk factors for these diseases. Omega-3 polyunsaturated fatty acids in the diet help to prevent cardiovascular disease. We used life cycle assessment to analyse the potential of two strategies to improve the nutritional and environmental characteristics of French diets: 1) modifying diets by changing the quantities and proportions of foods and 2) increasing the omega-3 contents in diets by replacing mainly animal foods with equivalent animal foods having higher omega-3 contents. We also investigated other possibilities for reducing environmental impacts. Our results showed that a diet compliant with nutritional recommendations for macronutrients had fewer environmental impacts than the current average French diet. Moving from an omnivorous to a vegetarian diet further reduced environmental impacts. Increasing the omega-3 contents in animal rations increased Eicosapentaenoic Acid (EPA) and Docosahexaenoic Acid (DHA) in animal food products. Providing these enriched animal foods in human diets increased their EPA and DHA contents without affecting their environmental impacts. However, in diets that did not contain fish, EPA and DHA contents were well below the levels recommended by health authorities, despite the inclusion of animal products enriched in EPA and DHA. Reducing meat consumption and avoidable waste at home are two main avenues for reducing environmental impacts of diets. PMID:27504959

  9. Specification requirements summary for the Brayton Isotope Power System (BIPS) Ground Demonstration System (GDS)

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, E.E.

    1976-02-10

    This document provides a summary of the required program specifications and procedures for the ERDA Phase I Brayton Isotope Power System (BIPS) Program. Also included are document definitions, descriptions, and formats, and a listing of commonly used abbreviations. This document is intended to be used as a guide in document preparation and control.

  10. Isotope Brayton ground demonstration testing and flight qualification program. Volume 1. Technical program

    Energy Technology Data Exchange (ETDEWEB)

    1974-12-09

    A proposal for the demonstration, development and production of the Isotope Brayton Flight System for space vehicles is presented with details on the technical requirements for designing and testing a ground demonstration system and on the program organization and personnel. (LCL)

  11. Improving fuel cycle design and safety characteristics of a gas cooled fast reactor

    NARCIS (Netherlands)

    van Rooijen, W.F.G.

    2006-01-01

    This research concerns the fuel cycle and safety aspects of a Gas Cooled Fast Reactor, one of the so-called "Generation IV" nuclear reactor designs. The Generation IV Gas Cooled Fast Reactor uses helium as coolant at high temperature. The goal of the GCFR is to obtain a "closed nuclear fuel cycle",

  12. Swing-Leg Retraction for Limit Cycle Walkers Improves Disturbance Rejection

    NARCIS (Netherlands)

    Hobbelen, D.G.E.; Wisse, M.

    2008-01-01

    Limit cycle walkers are bipeds that exhibit a stable cyclic gaitwithout requiring local controllability at all times during gait. A well-known example of limit cycle walking is McGeer’s “passive dynamic walking,” but the concept expands to actuated bipeds as involved in this study. One of the stabil

  13. Reciprocating heat-engine cycles

    International Nuclear Information System (INIS)

    The performance of a generalized irreversible reciprocating heat-engine cycle model consisting of two heating branches, two cooling branches and two adiabatic branches with heat-transfer loss and friction-like term loss was analyzed using finite-time thermodynamics. The relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, as well as the optimal relation between the power output and the efficiency of the cycle are derived. Moreover, analysis and optimization of the model were carried out in order to investigate the effect of the cycle process on the performances of the cycles using numerical examples. The results obtained herein include the performance characteristics of irreversible reciprocating Diesel, Otto, Atkinson, Brayton, Dual and Miller cycles

  14. New fire diurnal cycle characterizations to improve fire radiative energy assessments made from low-Earth orbit satellites sampling

    Science.gov (United States)

    Andela, N.; Kaiser, J. W.; van der Werf, G. R.; Wooster, M. J.

    2015-03-01

    errors, while generally overestimating FRE. Including information on the climatology of the fire diurnal cycle provided the most promising avenue to improve FRE estimations. This approach also improved the performance on relatively high spatiotemporal resolutions, although only when aggregating model results to coarser spatial and/or temporal scale good correlation was found with the full SEVIRI hourly reference dataset. In general model performance was best in areas of frequent fire and low errors of omission. We recommend the use of regionally varying fire diurnal cycle information within the Global Fire Assimilation System (GFAS) used in the Copernicus Atmosphere Monitoring Services, which will improve FRE estimates and may allow for further reconciliation of biomass burning emission estimates from different inventories.

  15. Improving Climate Projections Through the Assessment of Model Uncertainty and Bias in the Global Water Cycle

    Science.gov (United States)

    Baker, Noel C.

    The implications of a changing climate have a profound impact on human life, society, and policy making. The need for accurate climate prediction becomes increasingly important as we better understand these implications. Currently, the most widely used climate prediction relies on the synthesis of climate model simulations organized by the Coupled Model Intercomparison Project (CMIP); these simulations are ensemble-averaged to construct projections for the 21st century climate. However, a significant degree of bias and variability in the model simulations for the 20th century climate is well-known at both global and regional scales. Based on that insight, this study provides an alternative approach for constructing climate projections that incorporates knowledge of model bias. This approach is demonstrated to be a viable alternative which can be easily implemented by water resource managers for potentially more accurate projections. Tests of the new approach are provided on a global scale with an emphasis on semiarid regional studies for their particular vulnerability to water resource changes, using both the former CMIP Phase 3 (CMIP3) and current Phase 5 (CMIP5) model archives. This investigation is accompanied by a detailed analysis of the dynamical processes and water budget to understand the behaviors and sources of model biases. Sensitivity studies of selected CMIP5 models are also performed with an atmospheric component model by testing the relationship between climate change forcings and model simulated response. The information derived from each study is used to determine the progressive quality of coupled climate models in simulating the global water cycle by rigorously investigating sources of model bias related to the moisture budget. As such, the conclusions of this project are highly relevant to model development and potentially may be used to further improve climate projections.

  16. MELCOR Extensions for Simulation of Modular Power Cycles and Thermochemical Cycles for the Generation of Hydrogen via Nuclear Reactors

    Energy Technology Data Exchange (ETDEWEB)

    Sal B Rodriguez; Randall O Gauntt; Randy Cole; Marcos Modesto; Katherine McFadden; Len Malczynski; Billy Martin [Sandia National Laboratories, P.O. Box 5800, MS 0748, Albuquerque, NM 87123 (United States); Shripad T Revankar; Karen Vierow [Purdue University, 355 North Lansing Street, West Lafayette, IN 46202 (United States); Dave Louie; Louis Archuleta [Omicron, Inc., 2500 Louisiana Blvd. NE, Suite 410, Albuquerque, NM 87110 (United States)

    2006-07-01

    Sandia National Laboratories (SNL) is currently extending MELCOR so that it can be used to simulate high-temperature nuclear reactors with modular secondary-side power components that are coupled to thermochemical cycles such as sulfur iodine (SI), the Westinghouse hybrid sulfur (HyS), and a generalized thermochemical cycle. To this extent, we will begin by extending MELCOR models for high-temperature gas cooled reactors, Brayton power cycles, an SI thermochemical cycle, and a graphical user interface (GUI). In addition, future versions of MELCOR will include a Monte Carlo module for uncertainty and optimization studies, modular components for major power cycles, a financial module, and a generalized thermochemical cycle. (authors)

  17. A non-endoreversible Otto cycle model: improving power output and efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Angulo-Brown, F. [Instituto Politecnico Nacional, Mexico City (Mexico). Escuela Superior de Fisica y Matematicas; Rocha-Martinez, J.A.; Navarrete-Gonzalez, T.D. [Universidad Autonoma Metropolitana-Azcapotzalco, Mexico City (Mexico). Dept. de Ciencias Basicas

    1996-01-14

    We propose a finite-time thermodynamics model for an Otto thermal cycle. Our model considers global losses in a simplified way lumped into a friction-like term, and takes into account the departure from an endoreversible regime through a parameter (R) arising from the Clausius inequality. Our numerical results suggest that the cycle`s power output and efficiency are very sensitive to that parameter. We find that R is the ratio of the constant-volume heat capacities of the reactants and products in the combustion reaction occurring inside the working fluid. Our results have implications in the search for new fuels for internal combustion engines. (author)

  18. Recent developments in thermally-driven seawater desalination: Energy efficiency improvement by hybridization of the MED and AD cycles

    KAUST Repository

    Ng, K. C.

    2015-01-01

    The energy, water and environment nexus is a crucial factor when considering the future development of desalination plants or industry in the water-stressed economies. New generation of desalination processes or plants has to meet the stringent environment discharge requirements and yet the industry remains highly energy efficient and sustainable when producing good potable water. Water sources, either brackish or seawater, have become more contaminated as feed while the demand for desalination capacities increase around the world. One immediate solution for energy efficiency improvement comes from the hybridization of the proven desalination processes to the newer processes of desalination: For example, the integration of the available thermally-driven to adsorption desalination (AD) cycles where significant thermodynamic synergy can be attained when cycles are combined. For these hybrid cycles, a quantum improvement in energy efficiency as well as in increase in water production can be expected. The advent of MED with AD cycles, or simply called the MEDAD cycles, is one such example where seawater desalination can be pursued and operated in cogeneration with the electricity production plants: The hybrid desalination cycles utilize only the low exergy bled-steam at low temperatures, complemented with waste exhaust or renewable solar thermal heat at temperatures between 60 and 80. °C. In this paper, the authors have reported their pioneered research on aspects of AD and related hybrid MEDAD cycles, both at theoretical models and experimental pilots. Using the cogeneration of electricity and desalination concept, the authors examined the cost apportionment of fuel cost by the quality or exergy of working steam for such cogeneration configurations.

  19. Improvement of Taihu water quality by the technology of immobilized nitrogen cycle bacteria

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Experimental studies were carried out on the purification of eutrophicTaihu Lake water by dynamic experiment using immobilized nitrogen cycle bacteria(INCB). The results showed that the eutrophic water of Taihu Lake can be purifiedeffectively as it passes through the experimental reactor into which some immobilizednitrogen cycle bacteria were put. The removal efficiencies for Total N (TN), NH4+-Nwith immobilized nitrogen cycle bacteria were 72.4% and 85.6%, respectively. It wasfound that the immobilized nitrogen cycle bacteria also have purificatory effect oneutrophic water of Taihu Lake at winter temperature (7°C), and that the removalmefficiencies for Total N (TN), NH4+-N were 55.6%, and 58.9%, respectively. Theremoval efficiencies for TN and NH4+-N depend on the time the water stays in theexperimental reactor.``

  20. Improvement by the Life Cycle Control System of University Production With Use of CALS-Tehnology

    OpenAIRE

    Yuriy I. Dreizis

    2013-01-01

    The mechanism of management by life cycle of production of university with use of CALS technologies is described. Tasks of service of marketing and the quality management department, connected with university product quality control are defined

  1. Improvement of Taihu water quality by the technology of immobilized nitrogen cycle bacteria

    International Nuclear Information System (INIS)

    Experimental studies were carried out on the purification of eutrophic Taihu Lake water by dynamic experiment using immobilized nitrogen cycle bacteria (INCB). The results showed that the eutrophic water of Taihu Lake can be purified effectively as it passes through the experimental reactor into which some immobilized nitrogen cycle bacteria were put. The removal efficiencies for Total N (TN), NH4+-N with immobilized nitrogen cycle bacteria were 72.4% and 85.6%, respectively. It was found that the immobilized nitrogen cycle bacteria also have purificatory effect on eutrophic water of Taihu Lake at winter temperature (7 degree C), and that the removal efficiencies for Total N (TN), NH4+-N were 55.6%, and 58.9%, respectively. The removal efficiencies for TN and NH4+-N depend on the time the water stays in the experimental reactor

  2. Use of polyethylene glycol for the improvement of the cycling stability of bischofite as thermal energy storage material

    International Nuclear Information System (INIS)

    Highlights: • Bischofite as phase change material for TES is studied. • Thermophysical properties of bischofite mixtures with PEG were determined. • The aim was to improve the cycling stability of bischofite. • The heating and cooling during 30 cycles were measured. • The most stable sample was bischofite + 5% PEG 2 000. - Abstract: Bischofite is a by-product of the non-metallic mining industry. It has been evaluated as phase change material in thermal energy storage, but it shows little cycling stability, therefore in this paper the mixture of bischofite with an additive was studied. Since polyethylene glycol (PEG) is a PCM itself, in this paper PEG (with different molecular weights) is used as additive in a PCM (bischofite) to improve its thermal behaviour. Results show that adding 5% PEG 2 000 to bischofite gives a more cycling stable PCM without affecting its melting temperature neither decreasing significantly its heat of fusion. This research shows that mixing an inorganic PCM with an organic additive can be a good option to improve the thermal performance of the PCM

  3. Aspects Regarding the Improving of Fitness and Health Issues by Cycling

    OpenAIRE

    Cătălin Octavian MĂNESCU

    2014-01-01

    This article is trying to explain all the benefits cycling has over fitness and specific health issues, the importance of a training plan, of a balanced diet and a good hydration during a training period of time and, also, presents the results of some studies regarding the importance of ride biking, generally, and exercising, particularly. Riding a bike is a healthy activity. Regular exercise in the form of cycling will make people fitter, stronger, will help them reduce fat levels and loo...

  4. Suggestions to improve oil shale industry water management basing on inventory analysis of life cycle assessment

    International Nuclear Information System (INIS)

    Principles of Life Cycle Assessment (LCA) are implemented for the investigation of the Estonian oil shale energy production system. The energy produced on the smallest of Estonia's thermal power plants is studied as a product. A brief description of the inventory analysis and material balance for this product system is presented. A possible change in water management of investigated life cycle is discussed. Implementing these suggestions will diminish the pressure on local water resources in an economically effective way. (author)

  5. Exergy Analysis of Combined Cycle Power Plant: NTPC Dadri, India

    OpenAIRE

    Tiwari, Arvind Kumar; M. M. Hasan; Islam, Mohd.

    2013-01-01

    The aim of the present paper is to exergy analysis of combined Brayton/Rankine power cycle of NTPC Dadri India. Theoretical exergy analysis is carried out for different components of dadri combined cycle power plant which consists of a gas turbine unit, heat recovery steam generator without extra fuel consumption and steam turbine unit. The results pinpoint that more exergy losses occurred in the gas turbine combustion chamber. Its reached 35% of the total exergy losses while the exergy losse...

  6. Exergy Analysis of Combined Cycle Power Plant: NTPC Dadri, India

    OpenAIRE

    Arvind Kumar Tiwari; M. M. Hasan; Mohd Islam,

    2012-01-01

    The aim of the present paper is to exergy analysis of combined Brayton/Rankine power cycle of NTPC Dadri India. Theoretical exergy analysis is carried out for different components of dadri combined cycle power plant which consists of a gas turbine unit, heat recovery steam generator without extra fuel consumption and steam turbine unit. The results pinpoint that more exergy losses occurred in the gas turbine combustion chamber. Its reached 35% of the total exergy losses while the exergy losse...

  7. Fuel conversion efficiency improvements in a highly boosted spark-ignition engine with ultra-expansion cycle

    International Nuclear Information System (INIS)

    Highlights: • Ultra-expansion cycle SI engine is investigated. • An improvement of 9–26% in BSFC at most frequently operated conditions is obtained. • At high and medium loads, BSFC improvement is attributed to the increased combustion efficiency and reduced exhaust energy. • At low loads, reduction in pumping loss and exhaust energy is the primary contributors to BSFC improvement. • Technical challenge in practical application of this type of engine is discussed. - Abstract: A four-cylinder, intake boosted, port fuel injection (PFI), spark-ignition (SI) engine is modified to a three-cylinder engine with the outer two cylinders working in the conventional four stroke cycle and with the inner cylinder working only with the expansion and exhausting strokes. After calibration and validation of the engine cycle simulation models using the experimental data in the original engine, the performance of the three-cylinder engine with the ultra-expansion cycle is numerically studied. Compared to the original engine, the fuel consumptions under the most-frequently operated conditions are improved by 9–26% and the low fuel consumption area on the operating map are drastically enlarged for the ultra-expansion cycle engine with the proper design. Nonetheless, a higher intake boosting is needed for the ultra-expansion cycle engine to circumvent the significant drop in the wide-open-throttle (WOT) performance, and compression ratio of the combustion cylinder must be reduced to avoid knocking combustion. Despite of the reduced compression ratio, however, the total expansion ratio is increased to 13.8 with the extra expansion of the working gas in the inner cylinder. Compared to the conventional engine, the theoretical thermal efficiency is therefore increased by up to above 4.0% with the ultra-expansion cycle over the most load range. The energy balance analysis shows that the increased combustion efficiency, reduced exhaust energy and the extra expansion work in the

  8. BCO-DMO: Improving Access to Ocean Research Data throughout the Data Life Cycle

    Science.gov (United States)

    Chandler, C. L.; Groman, R. C.; Allison, M. D.; Wiebe, P. H.; Glover, D. M.

    2012-12-01

    The Biological and Chemical Oceanography Data Management Office (BCO-DMO) was created in late 2006, by combining the formerly independent data management offices for the U.S. GLOBEC and U.S. JGOFS programs. BCO-DMO staff members work with investigators to publish data from research projects funded by the Biological and Chemical Oceanography Sections and the Office of Polar Programs Antarctic Organisms & Ecosystems Program (OPP ANT) at the U.S. National Science Foundation. Since 2006, researchers have been contributing data to the BCO-DMO data system, and it has developed into a rich repository of data from ocean, coastal and Great Lakes research programs. Data management services are provided at no additional cost to investigators funded by those offices. The main goals of BCO-DMO are to ensure preservation of NSF funded project data and to provide open access to those data. BCO-DMO has developed an end-to-end data stewardship process that includes all phases of the data life cycle: (1) working with investigators at the proposal stage to write their two-page NSF data management plan; (2) registering their funded project at BCO-DMO; (3) adding data and supporting documentation to the BCO-DMO data repository; (4) providing geospatial and text-based data access systems that support data discovery, access, display, assessment, integration, and export of data resources; (5) publication of data sets to provide publishers of the peer-reviewed literature with citable references (Digital Object Identifiers) and to encourage proper citation and attribution of data sets in the future and (6) submission of final data sets for preservation in the appropriate long-term data archive. Recent efforts by BCO-DMO staff members have focused on identifying globally unique, persistent identifiers to unambiguously identify resources of interest that are curated by and available from BCO-DMO. The process involves several essential components: (1) identifying a trusted authoritative source

  9. Efficient cycles for carbon capture CLC power plants based on thermally balanced redox reactors

    KAUST Repository

    Iloeje, Chukwunwike

    2015-10-01

    © 2015 Elsevier Ltd. The rotary reactor differs from most alternative chemical looping combustion (CLC) reactor designs because it maintains near-thermal equilibrium between the two stages of the redox process by thermally coupling channels undergoing oxidation and reduction. An earlier study showed that this thermal coupling between the oxidation and reduction reactors increases the efficiency by up to 2% points when implemented in a regenerative Brayton cycle. The present study extends this analysis to alternative CLC cycles with the objective of identifying optimal configurations and design tradeoffs. Results show that the increased efficiency from reactor thermal coupling applies only to cycles that are capable of exploiting the increased availability in the reduction reactor exhaust. Thus, in addition to the regenerative cycle, the combined CLC cycle and the combined-regenerative CLC cycle are suitable for integration with the rotary reactor. Parametric studies are used to compare the sensitivity of the different cycle efficiencies to parameters like pressure ratio, turbine inlet temperature, carrier-gas fraction and purge steam generation. One of the key conclusions from this analysis is that while the optimal efficiency for regenerative CLC cycle was the highest of the three (56% at 3. bars, 1200. °C), the combined-regenerative cycle offers a trade-off that combines a reasonably high efficiency (about 54% at 12. bars, 1200. °C) with much lower gas volumetric flow rate and consequently, smaller reactor size. Unlike the other two cycles, the optimal compressor pressure ratio for the regenerative cycle is weakly dependent on the design turbine inlet temperature. For the regenerative and combined regenerative cycles, steam production in the regenerator below 2× fuel flow rate improves exhaust recovery and consequently, the overall system efficiency. Also, given that the fuel side regenerator flow is unbalanced, it is more efficient to generate steam from the

  10. Global Climate Modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds

    CERN Document Server

    Navarro, Thomas; Forget, François; Spiga, Aymeric; Millour, Ehouarn; Montmessin, Franck

    2013-01-01

    Radiative effects of water ice clouds have noteworthy consequences on the Martian atmosphere, its thermal structure and circulation. Accordingly, the inclusion of such effects in the LMD Mars Global Climate Model (GCM) greatly modifies the simulated Martian water cycle. The intent of this paper is to address the impact of radiatively active clouds on atmospheric water vapor and ice in the GCM and improve its representation. We propose a new enhanced modeling of the water cycle, consisting of detailed cloud microphysics with dynamic condensation nuclei and a better implementation of perennial surface water ice. This physical modeling is based on tunable parameters. This new version of the GCM is compared to the Thermal Emission Spectrometer observations of the water cycle. Satisfying results are reached for both vapor and cloud opacities. However, simulations yield a lack of water vapor in the tropics after Ls=180{\\deg} which is persistent in simulations compared to observations, as a consequence of aphelion c...

  11. Systems Analyses of Advanced Brayton Cycles For High Efficiency Zero Emission Plants

    Energy Technology Data Exchange (ETDEWEB)

    A. D. Rao; J. Francuz; H. Liao; A. Verma; G. S. Samuelsen

    2006-11-01

    Table 1 shows that the systems efficiency, coal (HHV) to power, is 35%. Table 2 summarizes the auxiliary power consumption within the plant. Thermoflex was used to simulate the power block and Aspen Plus the balance of plant. The overall block flow diagram is presented in Figure A1.3-1 and the key unit process flow diagrams are shown in subsequent figures. Stream data are given in Table A1.3-1. Equipment function specifications are provided in Tables A1.3-2 through 17. The overall plant scheme consists of a cryogenic air separation unit supplying 95% purity O{sub 2} to GE type high pressure (HP) total quench gasifiers. The raw gas after scrubbing is treated in a sour shift unit to react the CO with H{sub 2}O to form H{sub 2} and CO{sub 2}. The gas is further treated to remove Hg in a sulfided activated carbon bed. The syngas is desulfurized and decarbonized in a Selexol acid gas removal unit and the decarbonized syngas after humidification and preheat is fired in GE 7H type steam cooled gas turbines. Intermediate pressure (IP) N{sub 2} from the ASU is also supplied to the combustors of the gas turbines as additional diluent for NOx control. A portion of the air required by the ASU is extracted from the gas turbines. The plant consists of the following major process units: (1) Air Separation Unit (ASU); (2) Gasification Unit; (3) CO Shift/Low Temperature Gas Cooling (LTGC) Unit; (4) Acid Gas Removal Unit (AGR) Unit; (5) Fuel Gas Humidification Unit; (6) Carbon Dioxide Compression/Dehydration Unit; (7) Claus Sulfur Recovery/Tail Gas Treating Unit (SRU/TGTU); and (8) Power Block.

  12. Reactor/Brayton power systems for nuclear electric spacecraft

    International Nuclear Information System (INIS)

    Studies are currently underway to assess the technological feasibility of a nuclear-reactor-powered spacecraft propelled by electric thrusters. The purpose of this study was to provide comparative information on a closed cycle gas turbine power conversion system

  13. DIPS power conversion cycle selection

    International Nuclear Information System (INIS)

    This paper presents the results of the dynamic power conversion cycle selection process conducted by the Rocketdyne Division of Rockwell International as part of the Dynamic Isotope Power Subsystem (DIPS) Program, sponsored by the U.S. Department of Energy (DOE). Rocketdyne is under contract with DOE for the DIPS Program. The objective of the DIPS Program is to demonstrate the technology necessary to provide dynamic radioisotope space electrical power systems in the 1 to 10 kWe range to support evolving military and civilian missions in the early 1990s and beyond. Selecting the most appropriate DIPS power conversion cycle that would support this objective was an integral step in this process. The closed Brayton cycle was selected as the preferred power conversion cycle for the DIPS Program based on an evaluation of several key areas concerning spacecraft power systems performance

  14. Exergoeconomic performance optimization of an endoreversible intercooled regenerated Brayton cogeneration plant. Part 1: Thermodynamic model and parameter analyses

    Directory of Open Access Journals (Sweden)

    Lingen Chen, Bo Yang, Fengrui Sun

    2011-03-01

    Full Text Available A thermodynamic model of an endoreversible intercooled regenerative Brayton heat and power cogeneration plant coupled to constant-temperature heat reservoirs is established by using finite time thermodynamics in Part 1 of this paper. The heat resistance losses in the hot-, cold- and consumer-side heat exchangers, the intercooler and the regenerator are taken into account. The finite time exergoeconomic performance of the cogeneration plant is investigated. The analytical formulae about dimensionless profit rate and exergetic efficiency are derived. The numerical examples show that there exists an optimal value of intercooling pressure ratio which leads to an optimal value of dimensionless profit rate for the fixed total pressure ratio. There also exists an optimal total pressure ratio which leads to a maximum profit rate for the variable total pressure ratio. The effects of intercooling, regeneration and the ratio of the hot-side heat reservoir temperature to environment temperature on dimensionless profit rate and the corresponding exergetic efficiency are analyzed. At last, it is found that there exists an optimal consumer-side temperature which leads to a double-maximum dimensionless profit rate. The profit rate of the model cycle is optimized by optimal allocation of the heat conductance of the heat exchangers in Part 2 of this paper.

  15. Improvements on startup physics test program for Daya Bay Nuclear Power Station with 18 months fuel cycle

    International Nuclear Information System (INIS)

    The author issues the improvements on the test technology and program for Daya Nuclear Power Station startup physics tests, and gives the analysis and evaluation for test results. It's proved the success for the execution of 18-month fuel cycle project. It's also valuable as a reference to other nuclear power plants in startup physics test respect, which would change the loading pattern to low leakage reload

  16. Improvement of chemical control in the water-steam cycle of thermal power plants

    International Nuclear Information System (INIS)

    A more effective chemical control in the water-steam cycle (WSC) of thermal power plants (TPP) is proposed in this paper. Minimization of corrosion effects by the production of ultra pure water and its strict control is the basis of all the investigated processes. The research involved the analysis of water samples in the WSC through key water quality parameters and by the most convenient analytical tools. The necessity for the stricter chemical control is demonstrated through a concrete example of the TPP Nikola Tesla, Serbia. After a thorough analysis of the chemical control system of the WSC, diagnostic and control parameters were chosen for continuous systematic measurements. Sodium and chloride ions were recognized as the ions which indicate the corrosion potential of the water and give insight into the proper production and maintenance of water within the WSC. Chemical transformations of crucial corrosion elements, iron and silica, were considered and related to their quantitative values. - Research highlights: → The more effective chemical control in the water-steam cycle of thermal power plant Nikola Tesla, Serbia. → In chemical control the diagnostic and control parameters were optimized and introduced for the systematic measurements in the water-steam cycle. → Sodium and chloride ions were recognized as ions which indicate corrosion potential of water and give insight to proper function of production and maintenance of water within water-team cycle. Chemical transformations of crucial corrosion elements, iron and silica are considered and related with their quantitative values.

  17. Concentrated dual-salt electrolytes for improving the cycling stability of lithium metal anodes

    Science.gov (United States)

    Pin, Liu; Qiang, Ma; Zheng, Fang; Jie, Ma; Yong-Sheng, Hu; Zhi-Bin, Zhou; Hong, Li; Xue-Jie, Huang; Li-Quan, Chen

    2016-07-01

    Lithium (Li) metal is an ideal anode material for rechargeable Li batteries, due to its high theoretical specific capacity (3860 mAh/g), low density (0.534 g/cm3), and low negative electrochemical potential (‑3.040 V vs. standard hydrogen electrode). In this work, the concentrated electrolytes with dual salts, composed of Li[N(SO2F)2] (LiFSI) and Li[N(SO2CF3)2] (LiTFSI) were studied. In this dual-salt system, the capacity retention can even be maintained at 95.7% after 100 cycles in Li|LiFePO4 cells. A Li|Li cell can be cycled at 0.5 mA/cm2 for more than 600 h, and a Li|Cu cell can be cycled at 0.5 mA/cm2 for more than 200 cycles with a high average Coulombi efficiency of 99%. These results show that the concentrated dual-salt electrolytes exhibit superior electrochemical performance and would be a promising candidate for application in rechargeable Li batteries. Project supported by the National Nature Science Foundation of China (Grant Nos. 51222210, 51472268, 51421002, and 11234013) and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA09010300).

  18. Concentrated dual-salt electrolytes for improving the cycling stability of lithium metal anodes

    Institute of Scientific and Technical Information of China (English)

    刘品; 马强; 方铮; 马洁; 胡勇胜; 周志彬; 李泓; 黄学杰; 陈立泉

    2016-01-01

    Lithium (Li) metal is an ideal anode material for rechargeable Li batteries, due to its high theoretical specific ca-pacity (3860 mAh/g), low density (0.534 g/cm3), and low negative electrochemical potential (−3.040 V vs. standard hydrogen electrode). In this work, the concentrated electrolytes with dual salts, composed of Li[N(SO2F)2] (LiFSI) and Li[N(SO2CF3)2] (LiTFSI) were studied. In this dual-salt system, the capacity retention can even be maintained at 95.7%after 100 cycles in Li|LiFePO4 cells. A Li|Li cell can be cycled at 0.5 mA/cm2 for more than 600 h, and a Li|Cu cell can be cycled at 0.5 mA/cm2 for more than 200 cycles with a high average Coulombi efficiency of 99%. These results show that the concentrated dual-salt electrolytes exhibit superior electrochemical performance and would be a promising candidate for application in rechargeable Li batteries.

  19. Evaluation of High-Temperature Tensile Property of Diffusion Bond of Austenitic Alloys for S-CO2 Cycle Heat Exchangers

    International Nuclear Information System (INIS)

    To improve the inherent safety of the sodium-cooled fast reactor (SFR), the supercritical CO2 (S-CO2) Brayton cycle is being considered as an alternative power conversion system to steam the Rankine cycle. In the S-CO2 system, a PCHE (printed circuit heat exchanger) is being considered. In this type of heat exchangers, diffusion bonding is used for joining the thin plates. In this study, the diffusion bonding characteristics of various austenitic alloys were evaluated. The tensile properties were measured at temperatures starting from the room temperature up to 650℃. For the 316H and 347H types of stainless steel, the tensile ductility was well maintained up to 550℃. However, the Incoloy 800HT showed lower strength and ductility at all temperatures. The microstructure near the bond line was examined to understand the reason for the loss of ductility at high temperatures

  20. Research Project BUL-13801 'VVER-1000 Coolant Chemistry Improvement by Extended Fuel Cycles'

    International Nuclear Information System (INIS)

    Unit's power (shut down periods) as an information source for the processes connected with the activity buildup in primary circuits surfaces. Scientific Scope of the Project: (i) The main factors causing AOA will be joined interpreted in order to be explained the critical conditions for the formation of higher local H3BO3 concentration of the core bottom part; (ii) Determination of the most important factors impacting on the corrosion rate of primary circuit's constructive materials, on the solubility, migration and deposition of corrosion products; (iii) Interpretation of the data for hideout and hideout return effects in primary circuits as a possible information source for the activity buildup processes on primary circuit surfaces; (iv) Development of such kind of water chemistry regimes, addressed to the different periods of reactor operation cycle, which will limit the corrosion rate and will provide a limitation of the amount of corrosion product deposits on the fuel assemblies. Expected Outputs: The VVER-1000 coolant chemistry improvement will provide possibilities for: (i) limitation of the occurrence of AOA phenomenon; (ii) limitation of the corrosion of the primary circuit surfaces and mitigation of the corrosion product deposition and activity buildup processes.

  1. Optimum heat power cycles for specified boundary conditions

    International Nuclear Information System (INIS)

    In this paper optimization of the power output of Carnot and closed Brayton cycles is considered for both finite and infinite thermal capacitance rates of the external fluid streams. The method of Lagrange multipliers is used to solve for working fluid temperatures that yield maximum power. Analytical expressions for the maximum power and the cycle efficiency at maximum power are obtained. A comparison of the maximum power from the two cycles for the same boundary conditions, i.e., the same heat source/sink inlet temperatures, thermal capacitance rates, and heat exchanger conductances, shows that the Brayton cycle can produce more power than the Carnot cycle. This comparison illustrates that cycles exist that can produce more power than the Carnot cycle. The optimum heat power cycle, which will provide the upper limit of power obtained from any thermodynamic cycle for specified boundary conditions and heat exchanger conductances is considered. The optimum heat power cycle is identified by optimizing the sum of the power output from a sequence of Carnot cycles. The shape of the optimum heat power cycle, the power output, and corresponding efficiency are presented. The efficiency at maximum power of all cycles investigated in this study is found to be equal to (or well approximated by) η = 1 - sq. root TL.in/φTH.in where φ is a factor relating the entropy changes during heat rejection and heat addition

  2. Technical and economic problems of switching WWER-440 reactors to improved fuel cycles

    International Nuclear Information System (INIS)

    Without the use of new types of fuel assemblies, the mean enrichment of the fuel charged can be increased to a maximum of 3.45%, i.e., 24 assemblies at an enrichment of 3.6% can be left in the reactor in the fourth year. The mean burn-up will increase to 31.3 MWd/kg U and the specific fuel cost will drop 2.9%. The introduction of a complete four-year fuel cycle will allow fuel to be used at an enrichment of up to 4.4%. The mean burnup will increase to 37.8 MWd/kg U and the specific fuel cost will be 11.5% lower than for the three-year cycle using standard fuel. (M.D.). 1 tab

  3. Greenhouse gas emissions of biofuels: improving Life Cycle Assessments by taking into account local production factors

    OpenAIRE

    Bessou, Cécile

    2009-01-01

    Life Cycle Assessments (LCA) make it possible to check for all polluting emissions and potential environmental impacts of biofuels throughout the product chain. However, LCA emission factors only give an estimate of average potential emissions, notably not considering the local kinetics of N2O emissions, the most important agricultural greenhouse gas. Our objective was first to analyse how soil compaction affects N2O emissions by combining field experiments and modelling. With automatic chamb...

  4. A Src inhibitor regulates the cell cycle of human pluripotent stem cells and improves directed differentiation

    OpenAIRE

    Chetty, Sundari; Engquist, Elise N.; Mehanna, Elie; Lui, Kathy O.; Tsankov, Alexander M.; Douglas A Melton

    2015-01-01

    Driving human pluripotent stem cells (hPSCs) into specific lineages is an inefficient and challenging process. We show that a potent Src inhibitor, PP1, regulates expression of genes involved in the G1 to S phase transition of the cell cycle, activates proteins in the retinoblastoma family, and subsequently increases the differentiation propensities of hPSCs into all three germ layers. We further demonstrate that genetic suppression of Src regulates the activity of the retinoblastoma protein ...

  5. Improvements in materials reliability in the back end of the nuclear fuel cycle

    International Nuclear Information System (INIS)

    Many of the problems that occur in the day-to-day operation of nuclear fuel cycle facilities can be traced to the degradation of the physical and chemical properties of the materials involved. In order to provide an international forum for the scientists and engineers working in this field, the IAEA convened a Technical Committee Meeting (TCM) on ''Materials Reliability in the Back End of the Nuclear Fuel Cycle'' in September 1986. The proceedings were subsequently published as IAEA-TECDOC-421. One of the major conclusions of the meeting was to hold a second TCM in 1989 to update progress in the field. This meeting was held in Vienna from 28 November to 1 December 1989, with the participation of 23 scientists and engineers from 13 countries who presented the 14 papers contained in this Technical Document. The papers cover the resistance of materials to corrosion in chemicals and/or under irradiation in three important segments of the back-end of the nuclear fuel cycle: during the interim storage of spent fuel, in reprocessing plants and during the final disposal of high level waste. In addition, a panel discussion was held on each of these three topics. Refs, figs and tabs

  6. Analysis of different image-based biofeedback models for improving cycling performances

    Science.gov (United States)

    Bibbo, D.; Conforto, S.; Bernabucci, I.; Carli, M.; Schmid, M.; D'Alessio, T.

    2012-03-01

    Sport practice can take advantage from the quantitative assessment of task execution, which is strictly connected to the implementation of optimized training procedures. To this aim, it is interesting to explore the effectiveness of biofeedback training techniques. This implies a complete chain for information extraction containing instrumented devices, processing algorithms and graphical user interfaces (GUIs) to extract valuable information (i.e. kinematics, dynamics, and electrophysiology) to be presented in real-time to the athlete. In cycling, performance indexes displayed in a simple and perceivable way can help the cyclist optimize the pedaling. To this purpose, in this study four different GUIs have been designed and used in order to understand if and how a graphical biofeedback can influence the cycling performance. In particular, information related to the mechanical efficiency of pedaling is represented in each of the designed interfaces and then displayed to the user. This index is real-time calculated on the basis of the force signals exerted on the pedals during cycling. Instrumented pedals for bikes, already designed and implemented in our laboratory, have been used to measure those force components. A group of subjects underwent an experimental protocol and pedaled with (the interfaces have been used in a randomized order) and without graphical biofeedback. Preliminary results show how the effective perception of the biofeedback influences the motor performance.

  7. Deceleration of fusion-fission cycles improves mitochondrial quality control during aging.

    Directory of Open Access Journals (Sweden)

    Marc Thilo Figge

    Full Text Available Mitochondrial dynamics and mitophagy play a key role in ensuring mitochondrial quality control. Impairment thereof was proposed to be causative to neurodegenerative diseases, diabetes, and cancer. Accumulation of mitochondrial dysfunction was further linked to aging. Here we applied a probabilistic modeling approach integrating our current knowledge on mitochondrial biology allowing us to simulate mitochondrial function and quality control during aging in silico. We demonstrate that cycles of fusion and fission and mitophagy indeed are essential for ensuring a high average quality of mitochondria, even under conditions in which random molecular damage is present. Prompted by earlier observations that mitochondrial fission itself can cause a partial drop in mitochondrial membrane potential, we tested the consequences of mitochondrial dynamics being harmful on its own. Next to directly impairing mitochondrial function, pre-existing molecular damage may be propagated and enhanced across the mitochondrial population by content mixing. In this situation, such an infection-like phenomenon impairs mitochondrial quality control progressively. However, when imposing an age-dependent deceleration of cycles of fusion and fission, we observe a delay in the loss of average quality of mitochondria. This provides a rational why fusion and fission rates are reduced during aging and why loss of a mitochondrial fission factor can extend life span in fungi. We propose the 'mitochondrial infectious damage adaptation' (MIDA model according to which a deceleration of fusion-fission cycles reflects a systemic adaptation increasing life span.

  8. A Life-cycle Approach to Improve the Sustainability of Rural Water Systems in Resource-Limited Countries

    Directory of Open Access Journals (Sweden)

    Nicholas Stacey

    2012-11-01

    Full Text Available A WHO and UNICEF joint report states that in 2008, 884 million people lacked access to potable drinking water. A life-cycle approach to develop potable water systems may improve the sustainability for such systems, however, a review of the literature shows that such an approach has primarily been used for urban systems located in resourced countries. Although urbanization is increasing globally, over 40 percent of the world’s population is currently rural with many considered poor. In this paper, we present a first step towards using life-cycle assessment to develop sustainable rural water systems in resource-limited countries while pointing out the needs. For example, while there are few differences in costs and environmental impacts for many improved rural water system options, a system that uses groundwater with community standpipes is substantially lower in cost that other alternatives with a somewhat lower environmental inventory. However, a LCA approach shows that from institutional as well as community and managerial perspectives, sustainability includes many other factors besides cost and environment that are a function of the interdependent decision process used across the life cycle of a water system by aid organizations, water user committees, and household users. These factors often present the biggest challenge to designing sustainable rural water systems for resource-limited countries.

  9. Improvement actions in waste management systems at the provincial scale based on a life cycle assessment evaluation

    International Nuclear Information System (INIS)

    Highlights: • LCA was used for evaluating the performance of four provincial waste management systems. • Milano, Bergamo, Pavia and Mantova (Italy) are the provinces selected for the analysis. • Most of the data used to model the systems are primary. • Significant differences were found among the provinces located in the same Region. • LCA was used as a decision-supporting tool by Regione Lombardia. - Abstract: This paper reports some of the findings of the ‘GERLA’ project: GEstione Rifiuti in Lombardia – Analisi del ciclo di vita (Waste management in Lombardia – Life cycle assessment). The project was devoted to support Lombardia Region in the drafting of the new waste management plan by applying a life cycle thinking perspective. The present paper mainly focuses on four Provinces in the Region, which were selected based on their peculiarities. Life cycle assessment (LCA) was adopted as the methodology to assess the current performance of the integrated waste management systems, to discuss strengths and weaknesses of each of them and to design their perspective evolution as of year 2020. Results show that despite a usual business approach that is beneficial to all the provinces, the introduction of technological and management improvements to the system provides in general additional energy and environmental benefits for all four provinces. The same improvements can be easily extended to the whole Region, leading to increased environmental benefits from the waste management sector, in line with the targets set by the European Union for 2020

  10. Thermal efficiency improvement in high output diesel engines a comparison of a Rankine cycle with turbo-compounding

    International Nuclear Information System (INIS)

    Thermal management, in particular, heat recovery and utilisation in internal combustion engines result in improved fuel economy, reduced emissions, fast warm up and optimized cylinder head temperatures. turbo-compounding is a heat recovery technique that has been successfully used in medium and large scale engines. Heat recovery to a secondary fluid and expansion is used in large scale engines, such as in power plants in the form of heat recovery steam generators (HRSG) . The present paper presents a thermodynamic analysis of turbo-compounding and heat recovery and utilisation through a fluid power cycle, a technique that is also applicable to medium and small scale engines. In a fluid power cycle, the working fluid is stored in a reservoir and expanded subsequently. The reservoir acts as an energy buffer that improves the overall efficiency, significantly. This paper highlights the relative advantage of exhaust heat secondary power cycles over turbo-compounding with the aid of MATLAB based QSS Toolbox simulation results. Steam has been selected as the working fluid in this work for its superior heat capacity over organic fluids and gases.

  11. Cooling, freezing and heating with the air cycle: air as the ultimate green refrigerant

    OpenAIRE

    Verschoor, M.J.E.

    2000-01-01

    Due to the recent concern about the damage that CFCs cause to the environment (ozone layer, global warming) and the absence of commonly acceptable alternative refrigerants, the search for alternative refrigeration concepts is going on. Air as refrigerant in the Joule-Brayton cycle (air cycle) is one of the most natural refrigerants, and it meets all criteria for a refrigerant being environmentally benign. For this reason the air cycle is one of the most promising long-term alternatives for re...

  12. Using NASA Products of the Water Cycle for Improved Water Resources Management

    Science.gov (United States)

    Toll, D. L.; Doorn, B.; Engman, E. T.; Lawford, R. G.

    2010-12-01

    NASA Water Resources works within the Earth sciences and GEO community to leverage investments of space-based observation and modeling results including components of the hydrologic cycle into water resources management decision support tools for the goal towards the sustainable use of water. These Earth science hydrologic related observations and modeling products provide a huge volume of valuable data in both near-real-time and extended back nearly 50 years. Observations of this type enable assessment of numerous water resources management issues including water scarcity, extreme events of drought and floods, and water quality. Examples of water cycle estimates make towards the contributions to the water management community include snow cover and snowpack, soil moisture, evapotranspiration, precipitation, streamflow and ground water. The availability of water is also contingent on the quality of water and hence water quality is an important part of NASA Water Resources. Water quality activities include both nonpoint source (agriculture land use, ecosystem disturbances, impervious surfaces, etc.) and direct remote sensing ( i.e., turbidity, algae, aquatic vegetation, temperature, etc.). . The NASA Water Resources Program organizes its projects under five functional themes: 1) stream-flow and flood forecasting; 2) water consumptive use and irrigation (includes evapotranspiration); 3) drought; 4) water quality; and 5) climate impacts on water resources. Currently NASA Water Resources is supporting 21 funded projects with 11 additional projects being concluded. To maximize the use of NASA water cycle measurements end to projects are supported with strong links with decision support systems. The NASA Water Resources Program works closely with other government agencies NOAA, USDA-FAS, USGS, AFWA, USAID, universities, and non-profit, international, and private sector organizations. International water cycle applications include: 1) Famine Early Warning System Network

  13. Strength training improves 5-min all-out performance following 185 min of cycling

    OpenAIRE

    Rønnestad, Bent R.; Hansen, Ernst Albin; Raastad, Truls

    2009-01-01

    To investigate the effects of heavy strength training on the mean power output in a 5-min all-out trial following 185 min of submaximal cycling at 44% of maximal aerobic power output in well-trained cyclists. Twenty well-trained cyclists were assigned to either usual endurance training combined with heavy strength training [E+S; n=11 (♂=11)] or to usual endurance training only [E; n=9 (♂=7, ♀=2)]. The strength training performed by E+S consisted of four lower body exercises [3 × 4–10 repetiti...

  14. A Src inhibitor regulates the cell cycle of human pluripotent stem cells and improves directed differentiation.

    Science.gov (United States)

    Chetty, Sundari; Engquist, Elise N; Mehanna, Elie; Lui, Kathy O; Tsankov, Alexander M; Melton, Douglas A

    2015-09-28

    Driving human pluripotent stem cells (hPSCs) into specific lineages is an inefficient and challenging process. We show that a potent Src inhibitor, PP1, regulates expression of genes involved in the G1 to S phase transition of the cell cycle, activates proteins in the retinoblastoma family, and subsequently increases the differentiation propensities of hPSCs into all three germ layers. We further demonstrate that genetic suppression of Src regulates the activity of the retinoblastoma protein and enhances the differentiation potential of hPSCs across all germ layers. These positive effects extend beyond the initial germ layer specification and enable efficient differentiation at subsequent stages of differentiation. PMID:26416968

  15. Grain boundary precipitation treatment for improving high temperature low cycle fatigue strength of SSS113M for VHTR

    International Nuclear Information System (INIS)

    Grain boundary precipitation treatment was studied for the purpose of improving high temperature low cycle fatigue strength of a Ni-23% Cr-18% W alloy. SSS113M which had been developed as an intermediate heat exchanger material of VHTR and recognized as the best alloy in the national research project concerning nuclear steelmaking in Japan. Conventional single solid solution treatment of 13000C x 1h W.Q. does not cause any massive grain boundary precipitation in SSS113M, but additional heat treatment of 12500C x 1h W.Q. causes discontinuous grain boundary precipitation of α.W phase. This grain boundary precipitation treatment results in two- to fivefold increase of low cycle fatigue strength at 8000C as well as slightly higher creep and stress rupture strength at 10000C

  16. ON IMPROVING AN INTEGRATED INVENTORY MODEL FOR A SINGLE VENDOR AND MULTIPLE BUYERS WITH A RELAXED MATERIAL ORDERING CYCLE POLICY

    Institute of Scientific and Technical Information of China (English)

    Yugang YU; Feng CHU; Haoxun CHEN

    2006-01-01

    In this paper, we propose a new model for improving the lot size obtained with the model of Woo, Hsu, and Wu (2001) proposed in their paper "An integrated inventory model for a single vendor and multiple buyers with ordering cost reduction" (Int. J. Production Economics 73 203-215). The new model can provide a lower or equal joint total cost as compared to Woo, Hsu, and Wu's model due to the relaxation of their integral multiple material ordering cycle policy to a fractional-integral multiple material ordering cycle policy. The proposed model is analyzed and an algorithm for calculating the optimal lot size of the model is developed. A numerical study based on the example used by Woo, Hsu, and Wu is presented.

  17. Application of Data Cubes for Improving Detection of Water Cycle Extreme Events

    Science.gov (United States)

    Albayrak, Arif; Teng, William

    2015-01-01

    As part of an ongoing NASA-funded project to remove a longstanding barrier to accessing NASA data (i.e., accessing archived time-step array data as point-time series), for the hydrology and other point-time series-oriented communities, "data cubes" are created from which time series files (aka "data rods") are generated on-the-fly and made available as Web services from the Goddard Earth Sciences Data and Information Services Center (GES DISC). Data cubes are data as archived rearranged into spatio-temporal matrices, which allow for easy access to the data, both spatially and temporally. A data cube is a specific case of the general optimal strategy of reorganizing data to match the desired means of access. The gain from such reorganization is greater the larger the data set. As a use case of our project, we are leveraging existing software to explore the application of the data cubes concept to machine learning, for the purpose of detecting water cycle extreme events, a specific case of anomaly detection, requiring time series data. We investigate the use of support vector machines (SVM) for anomaly classification. We show an example of detection of water cycle extreme events, using data from the Tropical Rainfall Measuring Mission (TRMM).

  18. Coupling a groundwater model with a land surface model to improve water and energy cycle simulation

    Directory of Open Access Journals (Sweden)

    W. Tian

    2012-12-01

    Full Text Available Water and energy cycles interact, making these two processes closely related. Land surface models (LSMs can describe the water and energy cycles on the land surface, but their description of the subsurface water processes is oversimplified, and lateral groundwater flow is ignored. Groundwater models (GWMs describe the dynamic movement of the subsurface water well, but they cannot depict the physical mechanisms of the evapotranspiration (ET process in detail. In this study, a coupled model of groundwater flow with a simple biosphere (GWSiB is developed based on the full coupling of a typical land surface model (SiB2 and a 3-D variably saturated groundwater model (AquiferFlow. In this coupled model, the infiltration, ET and energy transfer are simulated by SiB2 using the soil moisture results from the groundwater flow model. The infiltration and ET results are applied iteratively to drive the groundwater flow model. After the coupled model is built, a sensitivity test is first performed, and the effect of the groundwater depth and the hydraulic conductivity parameters on the ET are analyzed. The coupled model is then validated using measurements from two stations located in shallow and deep groundwater depth zones. Finally, the coupled model is applied to data from the middle reach of the Heihe River basin in the northwest of China to test the regional simulation capabilities of the model.

  19. Coupling a groundwater model with a land surface model to improve water and energy cycle simulation

    Directory of Open Access Journals (Sweden)

    W. Tian

    2012-09-01

    Full Text Available Water and energy cycles interact, making these two processes closely related. Land surface models (LSMs can describe the water and energy cycles on the land surface, but their description of the subsurface water processes is oversimplified, and lateral groundwater flow is ignored. Groundwater models (GWMs describe the dynamic movement of the subsurface water well, but they cannot depict the physical mechanisms of the evapotranspiration (ET process in detail. In this study, a coupled model of groundwater flow with a simple biosphere (GWSiB is developed based on the full coupling of a typical land surface model (SiB2 and a three-dimensional variably saturated groundwater model (AquiferFlow. In this coupled model, the infiltration, ET and energy transfer are simulated by SiB2 using the soil moisture results from the groundwater flow model. The infiltration and ET results are applied iteratively to drive the groundwater flow model. After the coupled model is built, a sensitivity test is first performed, and the effect of the groundwater depth and the hydraulic conductivity parameters on the ET are analyzed. The coupled model is then validated using measurements from two stations located in shallow and deep groundwater depth zones. Finally, the coupled model is applied to data from the middle reaches of the Heihe River basin in the northwest of China to test the regional simulation capabilities of the model.

  20. WWER-1000 fuel cycle economical improvement by reaching high fuel burnup

    International Nuclear Information System (INIS)

    The use of some Fuel Assemblies (FAs) of conventional design in 4 fuel cycles has allowed to increase unloaded FA average burnup from 38.5-40 MWd/kgU up to 42-43 MWd/kgU. It makes it possible to reduce spent fuel amount and, respectively, the fuel cycle back end costs. The increase of Ukrainian WWER-1000 fuel burnup has not decreased the fuel reliability. The number of leaking, unloaded ahead of schedule FAs, FAs having reached the failure criterion, differ substantially (several times). Correspondingly the share of leaking FAs (FPLR) and the share of failed FAs (FPFR) will be different. Average value of FPFR calculated according to the number of unloaded ahead of schedule FAs for Ukrainian WWER-1000 (except Rovno-3) not more than (0.6-1)x10-5 (6-10 ppm). Average fuel pin leaking rate for Ukrainian WWER-1000 (without taking into account some cases, Rovno-3) corresponds to 2 x10-5 -2.8 x10-5 (20-28) ppm. The experience of fuel operation and principal results of the irradiated FAs examination allow to accept a possibility of further fuel burnup increase. The situation regarding fuel reliability operation on Rovno-3 units requires further analysis and additional measures

  1. Integrated Metrics for Improving the Life Cycle Approach to Assessing Product System Sustainability

    Directory of Open Access Journals (Sweden)

    Wesley Ingwersen

    2014-03-01

    Full Text Available Life cycle approaches are critical for identifying and reducing environmental burdens of products. While these methods can indicate potential environmental impacts of a product, current Life Cycle Assessment (LCA methods fail to integrate the multiple impacts of a system into unified measures of social, economic or environmental performance related to sustainability. Integrated metrics that combine multiple aspects of system performance based on a common scientific or economic principle have proven to be valuable for sustainability evaluation. In this work, we propose methods of adapting four integrated metrics for use with LCAs of product systems: ecological footprint, emergy, green net value added, and Fisher information. These metrics provide information on the full product system in land, energy, monetary equivalents, and as a unitless information index; each bundled with one or more indicators for reporting. When used together and for relative comparison, integrated metrics provide a broader coverage of sustainability aspects from multiple theoretical perspectives that is more likely to illuminate potential issues than individual impact indicators. These integrated metrics are recommended for use in combination with traditional indicators used in LCA. Future work will test and demonstrate the value of using these integrated metrics and combinations to assess product system sustainability.

  2. Supercritical Water Reactor Cycle for Medium Power Applications

    Energy Technology Data Exchange (ETDEWEB)

    BD Middleton; J Buongiorno

    2007-04-25

    Scoping studies for a power conversion system based on a direct-cycle supercritical water reactor have been conducted. The electric power range of interest is 5-30 MWe with a design point of 20 MWe. The overall design objective is to develop a system that has minimized physical size and performs satisfactorily over a broad range of operating conditions. The design constraints are as follows: Net cycle thermal efficiency {ge}20%; Steam turbine outlet quality {ge}90%; and Pumping power {le}2500 kW (at nominal conditions). Three basic cycle configurations were analyzed. Listed in order of increased plant complexity, they are: (1) Simple supercritical Rankine cycle; (2) All-supercritical Brayton cycle; and (3) Supercritical Rankine cycle with feedwater preheating. The sensitivity of these three configurations to various parameters, such as reactor exit temperature, reactor pressure, condenser pressure, etc., was assessed. The Thermoflex software package was used for this task. The results are as follows: (a) The simple supercritical Rankine cycle offers the greatest hardware simplification, but its high reactor temperature rise and reactor outlet temperature may pose serious problems from the viewpoint of thermal stresses, stability and materials in the core. (b) The all-supercritical Brayton cycle is not a contender, due to its poor thermal efficiency. (c) The supercritical Rankine cycle with feedwater preheating affords acceptable thermal efficiency with lower reactor temperature rise and outlet temperature. (d) The use of a moisture separator improves the performance of the supercritical Rankine cycle with feedwater preheating and allows for a further reduction of the reactor outlet temperature, thus it was selected for the next step. Preliminary engineering design of the supercritical Rankine cycle with feedwater preheating and moisture separation was performed. All major components including the turbine, feedwater heater, feedwater pump, condenser, condenser pump

  3. Supercritical Water Reactor Cycle for Medium Power Applications

    International Nuclear Information System (INIS)

    Scoping studies for a power conversion system based on a direct-cycle supercritical water reactor have been conducted. The electric power range of interest is 5-30 MWe with a design point of 20 MWe. The overall design objective is to develop a system that has minimized physical size and performs satisfactorily over a broad range of operating conditions. The design constraints are as follows: Net cycle thermal efficiency (ge)20%; Steam turbine outlet quality (ge)90%; and Pumping power (le)2500 kW (at nominal conditions). Three basic cycle configurations were analyzed. Listed in order of increased plant complexity, they are: (1) Simple supercritical Rankine cycle; (2) All-supercritical Brayton cycle; and (3) Supercritical Rankine cycle with feedwater preheating. The sensitivity of these three configurations to various parameters, such as reactor exit temperature, reactor pressure, condenser pressure, etc., was assessed. The Thermoflex software package was used for this task. The results are as follows: (a) The simple supercritical Rankine cycle offers the greatest hardware simplification, but its high reactor temperature rise and reactor outlet temperature may pose serious problems from the viewpoint of thermal stresses, stability and materials in the core. (b) The all-supercritical Brayton cycle is not a contender, due to its poor thermal efficiency. (c) The supercritical Rankine cycle with feedwater preheating affords acceptable thermal efficiency with lower reactor temperature rise and outlet temperature. (d) The use of a moisture separator improves the performance of the supercritical Rankine cycle with feedwater preheating and allows for a further reduction of the reactor outlet temperature, thus it was selected for the next step. Preliminary engineering design of the supercritical Rankine cycle with feedwater preheating and moisture separation was performed. All major components including the turbine, feedwater heater, feedwater pump, condenser, condenser pump

  4. Improving the exergy efficiency of a cryogenic air separation unit as part of an integrated gasification combined cycle

    International Nuclear Information System (INIS)

    Graphical abstract: Display Omitted Highlights: ► Cryogenic air separation as part of an integrated gasification combined cycle. ► Considerable improvements in the exergy efficiency of a two-column design. ► Heating the separation products using heat of compression. ► Improving heat integration of the columns using heat-integrated distillation stages. - Abstract: The efficiency of a two-column cryogenic ASU (air separation unit) that is part of an IGCC (integrated gasification combined cycle) can be increased significantly by making better use of the heat of compression and by improving the heat integration of the distillation columns. The rational exergy efficiency of the ASU, which is defined as the desired increase in exergy content of the products divided by the amount of work that is added to the process, can be increased from 35% to over 70%. The exergy destruction per amount of feed is reduced with 1.6 kJ/mol air, corresponding to a 0.74% increase in the net electric efficiency of the IGCC. The efficiencies are expected to increase even further because the full potential of using heat-integrated distillation columns is not yet achieved.

  5. Interim Report: Air-Cooled Condensers for Next Generation Geothermal Power Plants Improved Binary Cycle Performance

    Energy Technology Data Exchange (ETDEWEB)

    Daniel S. Wendt; Greg L. Mines

    2010-09-01

    As geothermal resources that are more expensive to develop are utilized for power generation, there will be increased incentive to use more efficient power plants. This is expected to be the case with Enhanced Geothermal System (EGS) resources. These resources will likely require wells drilled to depths greater than encountered with hydrothermal resources, and will have the added costs for stimulation to create the subsurface reservoir. It is postulated that plants generating power from these resources will likely utilize the binary cycle technology where heat is rejected sensibly to the ambient. The consumptive use of a portion of the produced geothermal fluid for evaporative heat rejection in the conventional flash-steam conversion cycle is likely to preclude its use with EGS resources. This will be especially true in those areas where there is a high demand for finite supplies of water. Though they have no consumptive use of water, using air-cooling systems for heat rejection has disadvantages. These systems have higher capital costs, reduced power output (heat is rejected at the higher dry-bulb temperature), increased parasitics (fan power), and greater variability in power generation on both a diurnal and annual basis (larger variation in the dry-bulb temperature). This is an interim report for the task ‘Air-Cooled Condensers in Next- Generation Conversion Systems’. The work performed was specifically aimed at a plant that uses commercially available binary cycle technologies with an EGS resource. Concepts were evaluated that have the potential to increase performance, lower cost, or mitigate the adverse effects of off-design operation. The impact on both cost and performance were determined for the concepts considered, and the scenarios identified where a particular concept is best suited. Most, but not all, of the concepts evaluated are associated with the rejection of heat. This report specifically addresses three of the concepts evaluated: the use of

  6. Life cycle assessment of flexibly fed biogas processes for an improved demand-oriented biogas supply.

    Science.gov (United States)

    Ertem, Funda Cansu; Martínez-Blanco, Julia; Finkbeiner, Matthias; Neubauer, Peter; Junne, Stefan

    2016-11-01

    This paper analyses concepts to facilitate a demand oriented biogas supply at an agricultural biogas plant of a capacity of 500kWhel, operated with the co-digestion of maize, grass, rye silage and chicken manure. In contrast to previous studies, environmental impacts of flexible and the traditional baseload operation are compared. Life Cycle Assessment (LCA) was performed to detect the environmental impacts of: (i) variety of feedstock co-digestion scenarios by substitution of maize and (ii) loading rate scenarios with a focus on flexible feedstock utilization. Demand-driven biogas production is critical for an overall balanced power supply to the electrical grid. It results in lower amounts of emissions; feedstock loading rate scenarios resulted in 48%, 20%, 11% lower global warming (GWP), acidification (AP) and eutrophication potentials, and a 16% higher cumulative energy demand. Substitution of maize with biogenic-waste regarding to feedstock substitution scenarios could create 10% lower GWP and AP. PMID:27522120

  7. The Deming Cycle (PDCA Concept as an Efficient Tool for Continuous Quality Improvement in the Agribusiness

    Directory of Open Access Journals (Sweden)

    Mihail Nikolaevich Dudin

    2014-12-01

    Full Text Available Task statement: This article is an attempt to study the issues of quality management of business processes andproduction with respect to companies operating in the agricultural sector. The global agribusiness is a specialsphere of production, which is aimed at meeting the most important physiological needs of people. Therefore,the quality of the products, and thus the quality of the business processes are crucial for preservation andenhancement of the health of the world's population. The approach of this article is based on thecross-disciplinary concept of quality management with regard to the specifics of the operation and developmentof agro-industrial companies. Results: the study of theoretical, methodological, and empirical aspects shows that,in recent decades, the dynamics of the global agribusiness has changed significantly, and it is caused by multipleobjective factors. At the same time, forecasts say the world food production will fall short of the real need of theworld population in this products, so further stimulation of sustainable development of the world's agribusinesscan be performed through total quality management as well. For agricultural companies, quality managementshould be based on the Deming Cycle concept; this approach orients all business processes to implementation ofthe eight core principles of total quality management. Conclusion / recommendations: materials contained inthis article show the special role of the global agribusiness in social and economic processes. The proposedscheme of quality management is recommended for use in the agricultural companies of the complete productioncycle. For companies of the non-complete cycle, the scheme can be adapted by eliminating unused links.

  8. Mouth Rinsing with Maltodextrin Solutions Fails to Improve Time Trial Endurance Cycling Performance in Recreational Athletes

    Directory of Open Access Journals (Sweden)

    Tuğba Nilay Kulaksız

    2016-05-01

    Full Text Available The carbohydrate (CHO concentration of a mouth rinsing solution might influence the CHO sensing receptors in the mouth, with consequent activation of brain regions involved in reward, motivation and regulation of motor activity. The purpose of the present study was to examine the effects of maltodextrin mouth rinsing with different concentrations (3%, 6% and 12% after an overnight fast on a 20 km cycling time trial performance. Nine recreationally active, healthy males (age: 24 ± 2 years; V ˙ O 2 m a x : 47 ± 5 mL·kg−1·min−1 participated in this study. A double-blind, placebo-controlled randomized study was conducted. Participants mouth-rinsed every 2.5 km for 5 s. Maltodextrin mouth rinse with concentrations of 3%, 6% or 12% did not change time to complete the time trial and power output compared to placebo (p > 0.05. Time trial completion times were 40.2 ± 4.0, 40.1 ± 3.9, 40.1 ± 4.4, and 39.3 ± 4.2 min and power output 205 ± 22, 206 ± 25, 210 ± 24, and 205 ± 23 W for placebo, 3%, 6%, and 12% maltodextrin conditions, respectively. Heart rate, lactate, glucose, and rating of perceived exertion did not differ between trials (p > 0.05. In conclusion, mouth rinsing with different maltodextrin concentrations after an overnight fast did not affect the physiological responses and performance during a 20 km cycling time trial in recreationally active males.

  9. Mouth Rinsing with Maltodextrin Solutions Fails to Improve Time Trial Endurance Cycling Performance in Recreational Athletes.

    Science.gov (United States)

    Kulaksız, Tuğba Nilay; Koşar, Şükran Nazan; Bulut, Suleyman; Güzel, Yasemin; Willems, Marcus Elisabeth Theodorus; Hazir, Tahir; Turnagöl, Hüseyin Hüsrev

    2016-01-01

    The carbohydrate (CHO) concentration of a mouth rinsing solution might influence the CHO sensing receptors in the mouth, with consequent activation of brain regions involved in reward, motivation and regulation of motor activity. The purpose of the present study was to examine the effects of maltodextrin mouth rinsing with different concentrations (3%, 6% and 12%) after an overnight fast on a 20 km cycling time trial performance. Nine recreationally active, healthy males (age: 24 ± 2 years; V ˙ O 2 m a x : 47 ± 5 mL·kg(-1)·min(-1)) participated in this study. A double-blind, placebo-controlled randomized study was conducted. Participants mouth-rinsed every 2.5 km for 5 s. Maltodextrin mouth rinse with concentrations of 3%, 6% or 12% did not change time to complete the time trial and power output compared to placebo (p > 0.05). Time trial completion times were 40.2 ± 4.0, 40.1 ± 3.9, 40.1 ± 4.4, and 39.3 ± 4.2 min and power output 205 ± 22, 206 ± 25, 210 ± 24, and 205 ± 23 W for placebo, 3%, 6%, and 12% maltodextrin conditions, respectively. Heart rate, lactate, glucose, and rating of perceived exertion did not differ between trials (p > 0.05). In conclusion, mouth rinsing with different maltodextrin concentrations after an overnight fast did not affect the physiological responses and performance during a 20 km cycling time trial in recreationally active males. PMID:27171108

  10. Computational efficiency improvement with Wigner rotation technique in studying atoms in intense few-cycle circularly polarized pulses

    International Nuclear Information System (INIS)

    We show that by introducing Wigner rotation technique into the solution of time-dependent Schrödinger equation in length gauge, computational efficiency can be greatly improved in describing atoms in intense few-cycle circularly polarized laser pulses. The methodology with Wigner rotation technique underlying our openMP parallel computational code for circularly polarized laser pulses is described. Results of test calculations to investigate the scaling property of the computational code with the number of the electronic angular basis function l as well as the strong field phenomena are presented and discussed for the hydrogen atom

  11. A Life-cycle Approach to Improve the Sustainability of Rural Water Systems in Resource-Limited Countries

    OpenAIRE

    Nicholas Stacey; Abseen Anya; SHARON A. JONES; Lindsay Weir

    2012-01-01

    A WHO and UNICEF joint report states that in 2008, 884 million people lacked access to potable drinking water. A life-cycle approach to develop potable water systems may improve the sustainability for such systems, however, a review of the literature shows that such an approach has primarily been used for urban systems located in resourced countries. Although urbanization is increasing globally, over 40 percent of the world’s population is currently rural with many considered poor. In this ...

  12. Perioperative dexamethasone administration in tonsillectomy patients: A three-cycle audit showing improvement using printed theatre lists

    OpenAIRE

    Bola, Summy; Bartlett, Annie; Williams, Richard

    2015-01-01

    Dexamethasone administration prior to tonsillectomy has been shown to reduce morbidity and is part of SIGN guideline 117. We conducted a three-cycle audit of 149 patients to ascertain how well guidelines were being met and introduce a sustainable method to improve compliance. A 3-month audit was conducted to ascertain how many tonsillectomy patients didn’t receive pre-operative dexamethasone. ENT secretaries were requested to add ‘Dex Please’ to tonsillectomy theatre lists. A 3-month re-audit...

  13. Improvement of methodological and data background for life cycle assessment of nano-metaloxides

    DEFF Research Database (Denmark)

    Miseljic, Mirko

    technology. The aim of the PhD project was to investigate the status and improvement potential of LCA of ENMs. This was done through three sub-aims: • Review current possibilities and limitations of applying LCA on ENM products. • Improve the limitation in ENM production data inventory by presenting novel....... In conclusion, the project showed that LCA needs overhauling and particularly in relation to the issues broached in this project. By not addressing these, the reliability of one’s LCA of ENMs would be significantly compromised....

  14. A novel nuclear combined power and cooling system integrating high temperature gas-cooled reactor with ammonia–water cycle

    International Nuclear Information System (INIS)

    Highlights: • We propose a novel nuclear ammonia–water power and cooling cogeneration system. • The high temperature reactor is inherently safe, with exhaust heat fully recovered. • The thermal performances are improved compared with nuclear combined cycle. • The base case attains an energy efficiency of 69.9% and exergy efficiency of 72.5%. • Energy conservation and emission reduction are achieved in this cogeneration way. - Abstract: A nuclear ammonia–water power and refrigeration cogeneration system (NAPR) has been proposed and analyzed in this paper. It consists of a closed high temperature gas-cooled reactor (HTGR) topping Brayton cycle and a modified ammonia water power/refrigeration combined bottoming cycle (APR). The HTGR is an inherently safe reactor, and thus could be stable, flexible and suitable for various energy supply situation, and its exhaust heat is fully recovered by the mixture of ammonia and water in the bottoming cycle. To reduce exergy losses and enhance outputs, the ammonia concentrations of the bottoming cycle working fluid are optimized in both power and refrigeration processes. With the HTGR of 200 MW thermal capacity and 900 °C/70 bar reactor-core-outlet helium, the system achieves 88.8 MW net electrical output and 9.27 MW refrigeration capacity, and also attains an energy efficiency of 69.9% and exergy efficiency of 72.5%, which are higher by 5.3%-points and 2.6%-points as compared with the nuclear combined cycle (NCC, like a conventional gas/steam power-only combined cycle while the topping cycle is a closed HTGR Brayton cycle) with the same nuclear energy input. Compared with conventional separate power and refrigeration generation systems, the fossil fuel saving (based on CH4) and CO2 emission reduction of base-case NAPR could reach ∼9.66 × 104 t/y and ∼26.6 × 104 t/y, respectively. The system integration accomplishes the safe and high-efficiency utilization of nuclear energy by power and refrigeration

  15. Taxi Fleet Renewal in Cities with Improved Hybrid Powertrains: Life Cycle and Sensitivity Analysis in Lisbon Case Study

    Directory of Open Access Journals (Sweden)

    António P. Castel-Branco

    2015-09-01

    Full Text Available Stringent emissions regulations in cities and the high amount of daily miles driven by taxi vehicles enforce the need to renew these fleets with more efficient and cleaner technologies. Hybrid vehicles are potential candidates due to their enhanced powertrain, and slower battery depletion and fewer lifetime issues, relative to full electric vehicles. This paper proposes a methodology to analyze the best theoretical hybrid powertrain candidate with maximum in-use efficiency, minimum life cycle greenhouse gas emissions, and minimum additional cost, for a Lisbon taxi fleet case study. A multi-objective genetic algorithm integrated with a vehicle simulator is used to achieve several trade-off optimal solutions for different driving patterns. Potential improvements in taxi carbon footprint are discussed as a function of its lifetime, urban/extra-urban driving and maintenance/fuel life cycle uncertainty. Hybrid powertrains reveal to be advantageous comparatively to the conventional vehicle, especially in urban conditions. Specifically optimized solutions could reduce in-use energy consumption by 43%–47% in urban driving, and 27%–34% in extra-urban driving conditions, and reduce life cycle emissions by 47%–49% and 34%–36% respectively, relative to the conventional taxi. A financial gain of 50 $/km/fleet in extra-urban and 226 $/km/fleet in urban routes could be achieved by replacing the taxi fleet with the optimal solutions.

  16. Improvements of characteristics of open cycle Faraday type MHD power generator

    International Nuclear Information System (INIS)

    MHD power generators are classified into two types: Faraday type and diagonal type (including Hall type). It is considered also in Faraday type generators that the characteristics can be improved further by selecting the aspect ratio appropriately, and employing cap electrodes which approach diagonal conducting side-wall type from parallel plate electrodes. First, the three-dimensional analysis using a new equivalent circuit is introduced, in which finite electrode division and working gas boundary layer are considered using the generalized Ohm's law, Maxwell's electromagnetic equations and others. The above described improvement of characteristics is investigated numerically fully applying this analyzing method. If the wall temperature is low, the increase in the aspect ratio of a generating duct cross-section considerably improves the characteristics because plasma non-uniformity decreases. If the cap electrodes having an optimum side-wall length are used, the output increases considerably because the load current is given and received through the side-wall electrodes. Efficiency is a little lower than the case using parallel plate electrodes. Therefore, if the aspect ratio is taken sufficiently large, and the cap electrodes with optimum side-wall electrode length are used, the generator characteristics are greatly improved since the above mentioned effects are multiplied. (Wakatsuki, Y.)

  17. The development of technologies on new and renewable energies in China to improve the ecological cycle

    International Nuclear Information System (INIS)

    This paper outlines the main objects of the Chinese Academy of Sciences (CAS) research programs on the development of new energy (carried out by 15 research institutes nationwide): replacement of traditional energy by renewable energy technologies and improvement of the ecological environment in rural areas (China is still a developing country), with a special attention on the satisfaction of rural energy demands. (TEC)

  18. Intake of Protein Plus Carbohydrate during the First Two Hours after Exhaustive Cycling Improves Performance the following Day

    Science.gov (United States)

    Rustad, Per I.; Kolnes, Kristoffer J.; Sollie, Ove; Franch, Jesper; Ivy, John L.; Daniel, Hannelore; Jensen, Jørgen

    2016-01-01

    Intake of protein immediately after exercise stimulates protein synthesis but improved recovery of performance is not consistently observed. The primary aim of the present study was to compare performance 18 h after exhaustive cycling in a randomized diet-controlled study (175 kJ·kg-1 during 18 h) when subjects were supplemented with protein plus carbohydrate or carbohydrate only in a 2-h window starting immediately after exhaustive cycling. The second aim was to investigate the effect of no nutrition during the first 2 h and low total energy intake (113 kJ·kg-1 during 18 h) on performance when protein intake was similar. Eight endurance-trained subjects cycled at 237±6 Watt (~72% VO2max) until exhaustion (TTE) on three occasions, and supplemented with 1.2 g carbohydrate·kg-1·h-1 (CHO), 0.8 g carbohydrate + 0.4 g protein·kg-1·h-1 (CHO+PRO) or placebo without energy (PLA). Intake of CHO+PROT increased plasma glucose, insulin, and branch chained amino acids, whereas CHO only increased glucose and insulin. Eighteen hours later, subjects performed another TTE at 237±6 Watt. TTE was increased after intake of CHO+PROT compared to CHO (63.5±4.4 vs 49.8±5.4 min; p<0.05). PLA reduced TTE to 42.8±5.1 min (p<0.05 vs CHO). Nitrogen balance was positive in CHO+PROT, and negative in CHO and PLA. In conclusion, performance was higher 18 h after exhaustive cycling with intake of CHO+PROT compared to an isocaloric amount of carbohydrate during the first 2 h post exercise. Intake of a similar amount of protein but less carbohydrate during the 18 h recovery period reduced performance. PMID:27078151

  19. Radioactive material releases in the nuclear fuel cycle - Recent experience and improvements

    International Nuclear Information System (INIS)

    The nuclear fuel cycle involves a wide range of activities and technologies from the mining of uranium, to the production of electricity and radioisotopes for medical and industrial applications, to the reprocessing and recycling of used fuel, to decommissioning and waste disposal. Worker exposures and releases to the environment are carefully controlled in: (a) all stages of uranium mining, refining and fuel fabrication, where occupational exposures and releases have decreased while production has increased; (b) the operation of nuclear power plants, where occupational exposures and releases have decreased as reactor vendors evolve their products and reactor operators optimize their procedures; (c) fuel reprocessing facilities in the U.K. and France, where occupational exposures and releases have decreased while the amount of fuel processed has increased; and in (d) decommissioning nuclear facilities and waste management activities. The nuclear industry's recent record of achievement in controlling its releases and ensuring the radiological protection of its employees has been excellent. It is clear that releases and occupational exposures from modem nuclear facilities of all types contribute negligibly to the radiation environment to which all biota are exposed. But the general public seems not to appreciate the low environmental impact of nuclear activities. The future of nuclear power and of other applications of nuclear technology applications in medicine, in agriculture and in industry will depend on maintaining a high standard of performance so that the public and decision makers can be assured that the industry is safe. (author)

  20. Rubisco without the Calvin cycle improves the carbon efficiency of developing green seeds.

    Science.gov (United States)

    Schwender, Jörg; Goffman, Fernando; Ohlrogge, John B; Shachar-Hill, Yair

    2004-12-01

    Efficient storage of carbon in seeds is crucial to plant fitness and to agricultural productivity. Oil is a major reserve material in most seeds, and these oils provide the largest source of renewable reduced carbon chains available from nature. However, the conversion of carbohydrate to oil through glycolysis results in the loss of one-third of the carbon as CO2. Here we show that, in developing embryos of Brassica napus L. (oilseed rape), Rubisco (ribulose 1,5-bisphosphate carboxylase/oxygenase) acts without the Calvin cycle and in a previously undescribed metabolic context to increase the efficiency of carbon use during the formation of oil. In comparison with glycolysis, the metabolic conversion we describe provides 20% more acetyl-CoA for fatty-acid synthesis and results in 40% less loss of carbon as CO2. Our conclusions are based on measurements of mass balance, enzyme activity and stable isotope labelling, as well as an analysis of elementary flux modes. PMID:15592419

  1. Water Chemistry Control Technology to Improve the Performance of Nuclear Power Plants for Extended Fuel Cycles

    International Nuclear Information System (INIS)

    Ο To Develop the technology to manage the problems of AOA and radiation, corrosion as long term PWR operation. Ο To Establish the advanced water chemical operating systems. - Development of the proper water chemistry guidelines for long term PWR operation. AOA(Axial Offest Anomaly) has been reported in many PWR plants in the world, including Korea, especially in the plants of higher burn-up and longer cycle operation or power up-rate. A test loop has been designed and made by KAERI, in order to investigate and mitigate AOA problems in Korea. This project included the study of hydrodynamic simulation and the modeling about AOA. The analysis of radioactive crud was performed to investigate of NPPs primary water chemical effect on AOA and to reduce the radioactive dose rate. The high temperature measurement system was developed to on-line monitor of water chemistry in nuclear power plants. The effects of various environmental factors such as temperature, pressure, and flow rate on YSZ-based pH electrode were evaluated for ensuring the accuracy of high-temperature pH measurement. The inhibition technology for fouling and SCC of SG tube was evaluated to establish the water chemistry technology of corrosion control of nuclear system. The high temperature and high pressure crevice chemistry analysis test loop was manufactured to develop the water chemistry technology of crevice chemistry control

  2. Revisiting the Yeast Cell Cycle Problem with the Improved TriGen Algorithm

    OpenAIRE

    Gutiérrez Avilés, David; Rubio Escudero, Cristina; Riquelme Santos, José Cristóbal

    2011-01-01

    Analyzing microarray data represents a computational challenge due to the characteristics of these data. Clustering techniques are widely applied to create groups of genes that exhibit a similar behavior under the conditions tested. Biclustering emerges as an improvement of classical clustering since it relaxes the constraints for grouping allowing genes to be evaluated only under a subset of the conditions and not under all of them. However, this technique is not appr...

  3. Concentrating solar power (CSP) power cycle improvements through application of advanced materials

    Science.gov (United States)

    Siefert, John A.; Libby, Cara; Shingledecker, John

    2016-05-01

    Concentrating solar power (CSP) systems with thermal energy storage (TES) capability offer unique advantages to other renewable energy technologies in that solar radiation can be captured and stored for utilization when the sun is not shining. This makes the technology attractive as a dispatchable resource, and as such the Electric Power Research Institute (EPRI) has been engaged in research and development activities to understand and track the technology, identify key technical challenges, and enable improvements to meet future cost and performance targets to enable greater adoption of this carbon-free energy resource. EPRI is also involved with technically leading a consortium of manufacturers, government labs, and research organizations to enable the next generation of fossil fired power plants with advanced ultrasupercritical (A-USC) steam temperatures up to 760°C (1400°F). Materials are a key enabling technology for both of these seemingly opposed systems. This paper discusses how major strides in structural materials for A-USC fossil fired power plants may be translated into improved CSP systems which meet target requirements.

  4. Does local endometrial injury in the nontransfer cycle improve the IVF-ET outcome in the subsequent cycle in patients with previous unsuccessful IVF? A randomized controlled pilot study

    Directory of Open Access Journals (Sweden)

    Sachin A Narvekar

    2010-01-01

    Full Text Available Background: Management of repeated implantation failure despite transfer of good-quality embryos still remains a dilemma for ART specialists. Scrapping of endometrium in the nontransfer cycle has been shown to improve the pregnancy rate in the subsequent IVF/ET cycle in recent studies. Aim: The objective of this randomized controlled trial (RCT was to determine whether endometrial injury caused by Pipelle sampling in the nontransfer cycle could improve the probability of pregnancy in the subsequent IVF cycle in patients who had previous failed IVF outcome. Setting: Tertiary assisted conception center. Design: Randomized controlled study. Materials and Methods: 100 eligible patients with previous failed IVF despite transfer of good-quality embryos were randomly allocated to the intervention group and control groups. In the intervention group, Pipelle endometrial sampling was done twice: One in the follicular phase and again in the luteal phase in the cycle preceding the embryo transfer cycle. Outcome Measure: The primary outcome measure was live birth rate. The secondary outcome measures were implantation and clinical pregnancy rates. Results: The live birth rate was significantly higher in the intervention group compared to control group (22.4% and 9.8% P = 0.04. The clinical pregnancy rate in the intervention group was 32.7%, while that in the control group was 13.7%, which was also statistically significant ( P = 0.01. The implantation rate was significantly higher in the intervention group as compared to controls (13.07% vs 7.1% P = 0.04. Conclusions: Endometrial injury in nontransfer cycle improves the live birth rate,clinical pregnancy and implantation rates in the subsequent IVF-ET cycle in patients with previous unsuccessful IVF cycles.

  5. Improving life-cycle cost management in the US. Army: analysis of the U.S. Army and Commercial Businesses life-cycle cost management.

    OpenAIRE

    White, Bradley A

    2001-01-01

    The roles and responsibilities of the Army acquisition and logistics communities, as they pertain to the life-cycle management, are undergoing fundamental change. The early identification and total control of life-cycle cost, in particular operations and sustainment costs which comprises as much as 70-80% of a systems total life-cycle cost, is a high priority for the Army. The basis of this change is adoption of commercial best practices to support the Army's goal to organize. tram. equip, an...

  6. Improvement to the pattern of control rods of the equilibrium cycle of 18 months for the CLV using bio-inspired algorithms

    International Nuclear Information System (INIS)

    Nowadays in the National Institute of Nuclear Research are carried out studies with some bio-inspired optimization techniques to improve the performance of the fuel cycles of the boiling water reactors of the Laguna Verde power plant (CLV). In the present work two bio-inspired techniques were applied with the purpose of improving the performance of a balance cycle of 18 months developed for the CLV: genetic algorithms (AG) and systems based on ants colonies (SCH). The design of the reference cycle it represents in several aspects an optimal cycle proposed starting from the experience of several operation decades with the boiling water reactors (BWR initials for Boiling Water Reactor) in the world. To try to improve their performance is beforehand a difficult challenge and it puts on test the feasibility of the optimization methods in the reloads design. The study of the bio-inspired techniques was centered exclusively on the obtaining of the control rod patterns (PBC) trying to overcome the capacity factor reached in the design of the reference cycle. It was fixed the cycle length such that the decrease of the coast down period would represent an increase of the capacity factor of the cycle; so that, it diminishes the annual cost associated with the capital cost of the plant. As consequence of the study, was found that the algorithm based on the ants colonies reaches to diminish the coast down period in five and half days respect to the original balance cycle, what represents an annual saving of $US 74,000. Since the original cycle was optimized, the above-mentioned, shows the ability of the SCH for the optimization of the cycle design. With the AG it was reach to approach to the original balance cycle with a coast down period greater in seven days estimating an annual penalization of $US 130,000. (Author)

  7. Improvement of bottoming cycle efficiency and heat rejection for HD truck applications by utilization of EGR and CAC heat

    International Nuclear Information System (INIS)

    Highlights: ► Heat rejected from EGR cooler and CAC represents ∼50% of the total heat rejected. ► Twenty to thirty percentage increase in radiator capacity is adequate to cover the Rankine demand. ► If heat from EGR cooler and CAC is utilized efficiency improvement is 50% higher. ► Maximum improvement in bsfc in organic Rankine: 11.3%, steam Rankine: ∼9%. ► Recuperation of EGR and CAC heat improves system packaging significantly. - Abstract: Considering continuously rising fuel prices and the global warming problem it is significantly important to reduce fuel consumption of engines used in various applications. Of specific importance is the HD diesel engine used in large haul trucks because these vehicles have an extensive operating schedule, their engines have a high power output in the range of 200–400 kW and their number is significantly high. Considering current achievements, it appears that HDDI diesel engine bsfc cannot be significantly reduced in the future unless new ideas or techniques are employed. Under this framework the utilization of exhaust heat becomes inevitable because approximately 30–40% of fuel energy is rejected to the environment. A promising technique for the recovery of energy from the exhaust gas is the use of a Rankine bottoming cycle. This technical solution has been examined in the past with very positive indications and a strong potential for significant improvement. However various technical challenges have to be solved among which most important are packaging and rejection of excess heat from the engine cooling system. For this reason in the present work a simulation model which has been developed to describe the operation of a Rankine bottoming cycle is utilized to estimate the potential efficiency gain from its application on a heavy duty truck powered by a diesel engine. Using the simulation special attention is given to the utilization of EGR cooler and CA cooler (Charge Air) heat to increase the Rankine

  8. Environmental impacts of innovative dairy farming systems aiming at improved internal nutrient cycling: A multi-scale assessment.

    Science.gov (United States)

    de Vries, W; Kros, J; Dolman, M A; Vellinga, Th V; de Boer, H C; Gerritsen, A L; Sonneveld, M P W; Bouma, J

    2015-12-01

    Several dairy farms in the Netherlands aim at reducing environmental impacts by improving the internal nutrient cycle (INC) on their farm by optimizing the use of available on-farm resources. This study evaluates the environmental performance of selected INC farms in the Northern Friesian Woodlands in comparison to regular benchmark farms using a Life Cycle Assessment. Regular farms were selected on the basis of comparability in terms of milk production per farm and per hectare, soil type and drainage conditions. In addition, the environmental impacts of INC farming at landscape level were evaluated with the integrated modelling system INITIATOR, using spatially explicit input data on animal numbers, land use, agricultural management, meteorology and soil, assuming that all farms practised the principle of INC farming. Impact categories used at both farm and landscape levels were global warming potential, acidification potential and eutrophication potential. Additional farm level indicators were land occupation and non-renewable energy use, and furthermore all farm level indicators were also expressed per kg fat and protein corrected milk. Results showed that both on-farm and off-farm non-renewable energy use was significantly lower at INC farms as compared with regular farms. Although nearly all other environmental impacts were numerically lower, both on-farm and off-farm, differences were not statistically significant. Nitrogen losses to air and water decreased by on average 5 to 10% when INC farming would be implemented for the whole region. The impact of INC farming on the global warming potential and eutrophication potential was, however, almost negligible (phosphorus to water at INC farms, illustrating the focus of these farms on closing the nitrogen cycle. PMID:26231773

  9. Intake of Protein Plus Carbohydrate during the First Two Hours after Exhaustive Cycling Improves Performance the following Day.

    Science.gov (United States)

    Rustad, Per I; Sailer, Manuela; Cumming, Kristoffer T; Jeppesen, Per B; Kolnes, Kristoffer J; Sollie, Ove; Franch, Jesper; Ivy, John L; Daniel, Hannelore; Jensen, Jørgen

    2016-01-01

    Intake of protein immediately after exercise stimulates protein synthesis but improved recovery of performance is not consistently observed. The primary aim of the present study was to compare performance 18 h after exhaustive cycling in a randomized diet-controlled study (175 kJ·kg(-1) during 18 h) when subjects were supplemented with protein plus carbohydrate or carbohydrate only in a 2-h window starting immediately after exhaustive cycling. The second aim was to investigate the effect of no nutrition during the first 2 h and low total energy intake (113 kJ·kg(-1) during 18 h) on performance when protein intake was similar. Eight endurance-trained subjects cycled at 237±6 Watt (~72% VO2max) until exhaustion (TTE) on three occasions, and supplemented with 1.2 g carbohydrate·kg(-1)·h(-1) (CHO), 0.8 g carbohydrate + 0.4 g protein·kg(-1)·h(-1) (CHO+PRO) or placebo without energy (PLA). Intake of CHO+PROT increased plasma glucose, insulin, and branch chained amino acids, whereas CHO only increased glucose and insulin. Eighteen hours later, subjects performed another TTE at 237±6 Watt. TTE was increased after intake of CHO+PROT compared to CHO (63.5±4.4 vs 49.8±5.4 min; pcycling with intake of CHO+PROT compared to an isocaloric amount of carbohydrate during the first 2 h post exercise. Intake of a similar amount of protein but less carbohydrate during the 18 h recovery period reduced performance. PMID:27078151

  10. Oxygen cycling to improve survival of stem cells for myocardial repair: A review.

    Science.gov (United States)

    Dall, Christopher; Khan, Mahmood; Chen, Chun-An; Angelos, Mark G

    2016-05-15

    Heart disease represents the leading cause of death among Americans. There is currently no clinical treatment to regenerate viable myocardium following myocardial infarction, and patients may suffer progressive deterioration and decreased myocardial function from the effects of remodeling of the necrotic myocardium. New therapeutic strategies hold promise for patients who suffer from ischemic heart disease by directly addressing the restoration of functional myocardium following death of cardiomyocytes. Therapeutic stem cell transplantation has shown modest benefit in clinical human trials with decreased fibrosis and increased functional myocardium. Moreover, autologous transplantation holds the potential to implement these therapies while avoiding the immunomodulation concerns of heart transplantation. Despite these benefits, stem cell therapy has been characterized by poor survival and low engraftment of injected stem cells. The hypoxic tissue environment of the ischemic/infracting myocardium impedes stem cell survival and engraftment in myocardial tissue. Hypoxic preconditioning has been suggested as a viable strategy to increase hypoxic tolerance of stem cells. A number of in vivo and in vitro studies have demonstrated improved stem cell viability by altering stem cell secretion of protein signals and up-regulation of numerous paracrine signaling pathways that affect inflammatory, survival, and angiogenic signaling pathways. This review will discuss both the mechanisms of hypoxic preconditioning as well as the effects of hypoxic preconditioning in different cell and animal models, examining the pitfalls in current research and the next steps into potentially implementing this methodology in clinical research trials. PMID:27091653

  11. The efficiency of active cycle of breathing techniques regarding the improvement the quality of life in cystic fibrosis patients

    Directory of Open Access Journals (Sweden)

    Bogdan Almăjan-Guţă

    2008-12-01

    Full Text Available Background: Physiotherapy is well known as one of the most important part of CF patient’s management. The right choice ofappropriate therapy schema will improve the life’s quality of the patients. The purpose of the study was to prove the efficiencyof Active cycle of breathing techniques at children with cystic fibrosis. The study was performed between September 2006-september 2007 and the lot of study consisted of 20 children (11 girls and 9 boys with an age range between 6 and 18 years(average 14,8 years from the records of the Cystic Fibrosis National Centre Timisoara. The results showed an improvement inall measured values: general well-being, coughing, physical signs, X-ray signs and CT, bacteriological exam, nutritional status,functional respiratory tests. The statistical briefing of data shows the fact that there are significant statistical difference (p<0,05, before and after treatment in all ventilator index. The conclusion of this study was that the chosen technique (ACTBproved to be very efficient, in improving of respiratory symptoms and ventilator parameters

  12. Pilot study: rapidly cycling hypobaric pressure improves pain after 5 days in adiposis dolorosa

    Directory of Open Access Journals (Sweden)

    Karen L Herbst

    2010-08-01

    Full Text Available Karen L Herbst1, Thomas Rutledge21Department of Medicine, University of California, San Diego, California, USA; 2Department of Psychiatry, University of California, San Diego, California, USAAbstract: Adiposis dolorosa (AD is a rare disorder of painful nodular subcutaneous fat ­accompanied by fatigue, difficulty with weight loss, inflammation, increased fluid in ­adipose ­tissue (lipedema and lymphedema, and hyperalgesia. Sequential compression relieves ­lymphedema pain; we therefore hypothesized that whole body cyclic pneumatic hypobaric compression may relieve pain in AD. To avoid exacerbating hyperalgesia, we utilized a touch-free method, which is delivered via a high-performance altitude simulator, the Cyclic Variations in Altitude ConditioningTM (CVACTM process. As a pilot study, 10 participants with AD completed pain and quality of life questionnaires before and after 20–40 minutes of CVAC process daily for 5 days. Participants lost weight (195.5 ± 17.6–193.8 ± 17.3 lb; P = 0.03, and bioimpedance significantly decreased (510 ± 36–490 ± 38 ohm; P = 0.01. There was a significant decrease in scores on the Pain Catastrophizing Scale (P = 0.039, in average (P = 0.002, highest (P = 0.029, lowest (P = 0.04, and current pain severity (P = 0.02 on the Visual Analogue Scale, but there was no change in pain quality by the McGill Pain Questionnaire. There were no significant changes in total and physical SF-36 scores, but the mental score improved significantly (P = 0.049. There were no changes in the Pain Disability Index or Pittsburgh Sleep Quality Index. These data present a potential, new, noninvasive means of treating pain in AD by whole body pneumatic compression as part of the CVAC process. Although randomized, controlled trials are needed to confirm these data, the CVAC process could potentially help in treating AD pain and other chronic pain disorders.Keywords: bioimpedance, chronic pain, lipedema

  13. Dynamic simulation of 10 kW Brayton cryocooler for HTS cable

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Ho-Myung; Park, Chan Woo [Hong Ik University, Department of Mechanical Engineering, Seoul, 121-791 (Korea, Republic of); Yang, Hyung Suk; Hwang, Si Dole [KEPCO Research Institute, Daejeon, 305-760 (Korea, Republic of)

    2014-01-29

    Dynamic simulation of a Brayton cryocooler is presented as a partial effort of a Korean governmental project to develop 1∼3 km HTS cable systems at transmission level in Jeju Island. Thermodynamic design of a 10 kW Brayton cryocooler was completed, and a prototype construction is underway with a basis of steady-state operation. This study is the next step to investigate the transient behavior of cryocooler for two purposes. The first is to simulate and design the cool-down process after scheduled or unscheduled stoppage. The second is to predict the transient behavior following the variation of external conditions such as cryogenic load or outdoor temperature. The detailed specifications of key components, including plate-fin heat exchangers and cryogenic turbo-expanders are incorporated into a commercial software (Aspen HYSYS) to estimate the temporal change of temperature and flow rate over the cryocooler. An initial cool-down scenario and some examples on daily variation of cryocooler are presented and discussed, aiming at stable control schemes of a long cable system.

  14. Dynamic simulation of 10 kW Brayton cryocooler for HTS cable

    Science.gov (United States)

    Chang, Ho-Myung; Park, Chan Woo; Yang, Hyung Suk; Hwang, Si Dole

    2014-01-01

    Dynamic simulation of a Brayton cryocooler is presented as a partial effort of a Korean governmental project to develop 1˜3 km HTS cable systems at transmission level in Jeju Island. Thermodynamic design of a 10 kW Brayton cryocooler was completed, and a prototype construction is underway with a basis of steady-state operation. This study is the next step to investigate the transient behavior of cryocooler for two purposes. The first is to simulate and design the cool-down process after scheduled or unscheduled stoppage. The second is to predict the transient behavior following the variation of external conditions such as cryogenic load or outdoor temperature. The detailed specifications of key components, including plate-fin heat exchangers and cryogenic turbo-expanders are incorporated into a commercial software (Aspen HYSYS) to estimate the temporal change of temperature and flow rate over the cryocooler. An initial cool-down scenario and some examples on daily variation of cryocooler are presented and discussed, aiming at stable control schemes of a long cable system.

  15. Development of advanced off-design models for supercritical carbon dioxide power cycles

    International Nuclear Information System (INIS)

    In the search for increased efficiency of utility-scale electricity generation, Brayton cycles operating with supercritical carbon dioxide (S-CO2) have found considerable interest. There are two main advantages of a S-CO2 Brayton cycle compared to a Rankine cycle: 1) equal or greater thermal efficiencies can be realized using significantly smaller turbomachinery, and 2) heat rejection is not limited by the saturation temperature of the working fluid, which has the potential to reduce or completely eliminate the need for cooling water and instead allow dry cooling. While dry cooling is especially advantageous for power generation in arid climates, a reduction of water consumption in any location will be increasingly beneficial as tighter environmental regulations are enacted in the future. Because daily and seasonal weather variations may result in a plant operating away from its design point, models that are capable of predicting the off-design performance of S-CO2 power cycles are necessary for characterizing and evaluating cycle configurations and turbomachinery designs on an annual basis. To this end, an off-design model of a recuperated Brayton cycle was developed based on the radial turbomachinery currently being investigated by Sandia National Laboratory. (authors)

  16. A low pressure thermodynamic cycle for electric power generation without mechanical compressor

    International Nuclear Information System (INIS)

    According to the 2 nd thermodynamic law there is no compulsion to have an expansion from high pressure level to atmospheric pressure, the only reason relying upon the minimization of the plant volumetry which is just one of the overall cost parameters. A thermodynamic cycle without rotating machinery does exist in avionic applications like the RAMJET, in which air flowing at supersonic speed is compressed in a convergent duct before being heated in the combustion chamber and then expanded to a much higher MACH number. The concept discussed here, however, is referred to a physical principle of different nature. In fact the inlet air flow is quasi static, while the propelling kinetic energy is the residual energy following the gas combustion, expansion, cooling in Supersonic Flow and ultimately its fluidic compression in a convergent duct. The concept theoretically relies upon the so called 'Simple T0 change' transformation, according to which, in a Supersonic Flow at constant cross section and without mechanical dissipation, a decrease in the gas stagnation temperature (T0) will turn into an increase of its stagnation pressure. The paper discusses the feasibility of such a process, focusing on a specific conceptual application to a subatmospheric pressure, high temperature Brayton cycle getting to the conclusion that, even with the materials technology limitations, there is the potential for significant improvement of the actual thermodynamic cycle efficiency. (author). 6 figs.,1 tab., 2 refs

  17. Thermodynamic cycles optimised for medium enthalpy units of concentrating solar power

    International Nuclear Information System (INIS)

    Concentrated solar power presents the drawback of decreasing radiation capture efficiency as the temperature of the receiver increases, because thermal losses increase as well. Low temperature at the receiver is an advantage for radiation concentrators, as they present high capture efficiency, but this fact changes into a drawback because of the low efficiency of the thermodynamic cycles working with a low temperature heat source. An analysis is presented on the performance of real fluids working with such a type of heat sources that can be generated in simple solar thermal units. Both Joule–Brayton cycles and dry-turbine Rankine cycles are considered, using regenerative heat exchangers for heat recovering. The driving force of this research is to look for working fluids with actual thermodynamic characteristics which fit well with temperatures of the heat source and sink. Some unconventional substances, as refrigerant R-125 or SF6, show good performance. They may be suitable at certain regimes of Rankine and Brayton cycles and could work in fast-reacting systems. Of course, differences in the performance of Brayton and Rankine cycles convey differences in the complexity and cost of the components, but they offer a wide field for coherently choosing the working fluid and thermal conditions. - Highlights: • Analysis of Brayton and Rankine cycles close to the critical point. • Performance of transcritical and supercritical cycles. • The close to critical point region is a promising region for low-to-moderate temperature applications. • Fluid selection becomes important. SF6 and R-125 present good performance

  18. The universal power and efficiency characteristics for irreversible reciprocating heat engine cycles

    International Nuclear Information System (INIS)

    The performance of irreversible reciprocating heat engine cycles with heat transfer loss and friction-like term loss is analysed using finite-time thermodynamics. The universal relations between the power output and the compression ratio, between the thermal efficiency and the compression ratio, and the optimal relation between power output and the efficiency of the cycles are derived. Moreover, analysis and optimization of the model were carried out in order to investigate the effect of cycle processes on the performance of the cycle using numerical examples. The results obtained herein include the performance characteristics of irreversible reciprocating Diesel, Otto, Atkinson and Brayton cycles

  19. Parametric thermodynamic analysis of closed-cycle gas-laser operation in space

    Science.gov (United States)

    Burns, R. K.

    1974-01-01

    Cycle efficiency and radiator area required were calculated for thermally and electrically pumped lasers operating in closed cycles with a compressor and the required heat exchangers. A thermally pumped laser included within a Brayton cycle was also analyzed. Performance of all components, including the laser, was parametrically varied. For the thermally pumped laser the cycle efficiencies range below 10 percent and are very sensitive to the high-pressure losses associated with the supersonic diffuser required at the laser cavity exit. The efficiencies predicted for the electrically pumped laser cycles range slightly higher, but radiator area also tends to be larger.

  20. The improvement of approaches to marketing testing of ecological innovative products in the stages of innovative cycle

    Directory of Open Access Journals (Sweden)

    Ye.I. Nagornyi

    2013-12-01

    Full Text Available The aim of the article. The aim of the article is theoretical justification and improvement of approaches to marketing testing of ecological innovative production in the stages of innovative cycle, and the sequence of decision-making procedures on its readiness to entry into the market by results of testing. The results of the analysis. Launch of the ecological innovative products on the market and providing its passage through the stages of the innovative cycle requires continuous and high-quality information and analytical support. This support can be reached as a result of marketing testing procedures. The analysis of the existing evolutionary approaches to marketing testing procedure allowed finding out that they are not deprived disadvantages. Separate theoretical and methodological aspects of marketing testing of innovative products are analyzed in the scientific literature. But issues of marketing testing of ecological innovations and introduction of the given procedure at early stages of an innovative cycle are insufficiently investigated. Author's definition of marketing testing concept is reduced to complex process of a choice, an assessment and selection of a subject of the marketing approbation which is carried out at each stage of product development, for stage-by-stage and general definition of progress level of innovative production in the market, and also for the analysis of its readiness degree to entry the market. As a subject of approbation can be used: directions of innovative development of the enterprise, sources of ideas, ideas, concepts, prototypes of new products and their market attributes, and also marketing strategy as a whole. The types of testing taking place at each stage of an innovative cycle of development of goods are allocated in research. Problems (tasks that procedure of marketing testing solves are researched and methodological approaches to its implementation are suggested. Marketing testing is a complex

  1. Valuing Non-market Benefits of Rehabilitation of Hydrologic Cycle Improvements in the Anyangcheon Watershed: Using Mixed Logit Models

    Science.gov (United States)

    Yoo, J.; Kong, K.

    2010-12-01

    This research the findings from a discrete-choice experiment designed to estimate the economic benefits associated with the Anyangcheon watershed improvements in Rep. of Korea. The Anyangcheon watershed has suffered from streamflow depletion and poor stream quality, which often negatively affect instream and near-stream ecologic integrity, as well as water supply. Such distortions in the hydrologic cycle mainly result from rapid increase of impermeable area due to urbanization, decreases of baseflow runoff due to groundwater pumping, and reduced precipitation inputs driven by climate forcing. As well, combined sewer overflows and increase of non-point source pollution from urban regions decrease water quality. The appeal of choice experiments (CE) in economic analysis is that it is based on random utility theory (McFadden, 1974; Ben-Akiva and Lerman, 1985). In contrast to contingent valuation method (CVM), which asks people to choose between a base case and a specific alternative, CE asks people to choice between cases that are described by attributes. The attributes of this study were selected from hydrologic vulnerability components that represent flood damage possibility, instreamflow depletion, water quality deterioration, form of the watershed and tax. Their levels were divided into three grades include status quo. Two grades represented the ideal conditions. These scenarios were constructed from a 35 orthogonal main effect design. This design resulted in twenty-seven choice sets. The design had nine different choice scenarios presented to each respondent. The most popular choice models in use are the conditional logit (CNL). This model provides closed-form choice probability calculation. The shortcoming of CNL comes from irrelevant alternatives (IIA). In this paper, the mixed logit (ML) is applied to allow the coefficient’s variation for random taste heterogeneity in the population. The mixed logit model(with normal distributions for the attributes) fit the

  2. Enhancing Regulatory Inspection Practices and Safety Culture of Regulatory Body Personnel for Improving Safety of Nuclear Fuel Cycle Installations

    International Nuclear Information System (INIS)

    The nuclear fuel cycle installations (NFCIs) are characterized by different physical and chemical processes applied on fissile and radioactive materials in different physical forms, as well as many human interventions required for the control of these operation and maintenance of NFCIs equipments. Therefore, personnel radiation protection requirement is more demanding in these installations. Accordingly, it is necessary to apply a wide range of specific safety measures or actions in addition to inherent design features in the form of administrative safety actions during normal operation of these processes in NFCIs. In this paper, emphasis is focusing on operational administrative safety control measures in NFCIs as a major factor for preventing abnormal conditions and accidents in the NFCIs and hence protection of personnel against release of radiation. The paper presents a systematic and improved Operational Safety Management Approach focusing on administrative safety measures and enhancement of safety culture of NFCIs operators and a Regulatory Inspection Methodology (OSMARIM). This approach can help for enhancing regulatory inspection practices of regulatory body inspectors and ensuring operational safety management in NFCIs. (author)

  3. Carbon-Carbon Composites as Recuperator Materials for Direct Gas Brayton Systems

    International Nuclear Information System (INIS)

    Of the numerous energy conversion options available for a space nuclear power plant (SNPP), one that shows promise in attaining reliable operation and high efficiency is the direct gas Brayton (GB) system. In order to increase efficiency, the GB system incorporates a recuperator that accounts for nearly half the weight of the energy conversion system (ECS). Therefore, development of a recuperator that is lighter and provides better performance than current heat exchangers could prove to be advantageous. The feasibility of a carbon-carbon (C/C) composite recuperator core has been assessed and a mass savings of 60% and volume penalty of 20% were projected. The excellent thermal properties, high-temperature capabilities, and low density of carbon-carbon materials make them attractive in the GB system, but development issues such as material compatibility with other structural materials in the system, such as refractory metals and superalloys, permeability, corrosion, joining, and fabrication must be addressed

  4. Carbon-Carbon Composites as Recuperator Material for Direct Gas Brayton Systems

    Energy Technology Data Exchange (ETDEWEB)

    RA Wolf

    2006-07-19

    Of the numerous energy conversion options available for a space nuclear power plant (SNPP), one that shows promise in attaining reliable operation and high efficiency is the direct gas Brayton (GB) system. In order to increase efficiency, the GB system incorporates a recuperator that accounts for nearly half the weight of the energy conversion system (ECS). Therefore, development of a recuperator that is lighter and provides better performance than current heat exchangers could prove to be advantageous. The feasibility of a carbon-carbon (C/C) composite recuperator core has been assessed and a mass savings of 60% and volume penalty of 20% were projected. The excellent thermal properties, high-temperature capabilities, and low density of carbon-carbon materials make them attractive in the GB system, but development issues such as material compatibility with other structural materials in the system, such as refractory metals and superalloys, permeability, corrosion, joining, and fabrication must be addressed.

  5. Increased Mesohippocampal Dopaminergic Activity and Improved Depression-Like Behaviors in Maternally Separated Rats Following Repeated Fasting/Refeeding Cycles

    OpenAIRE

    Jeong Won Jahng; Sang Bae Yoo; Jin Young Kim; Bom-Taeck Kim; Jong-Ho Lee

    2012-01-01

    We have previously reported that rats that experienced 3 h of daily maternal separation during the first 2 weeks of birth (MS) showed binge-like eating behaviors with increased activity of the hypothalamic-pituitary-adrenal axis when they were subjected to fasting/refeeding cycles repeatedly. In this study, we have examined the psychoemotional behaviors of MS rats on the fasting/refeeding cycles, together with their brain dopamine levels. Fasting/refeeding cycles normalized the ambulatory act...

  6. An improved method for fuel cycle analysis at equilibrium and its application to the study of fast burner reactors with variable conversion ratio

    International Nuclear Information System (INIS)

    Studies related to advanced fuel cycles require a considerable amount of analysis to assess performances both of the reactor cores and of the associated fuel cycles. A physics analysis should provide a sound understanding of major trends and features, in order to provide guidelines for detailed studies. In this paper we present an improved version of a generalization of the Bateman equation that allows performing analysis at equilibrium for a large number of systems. It is shown that the method reproduces very well the results obtained with full depletion calculations. The method is applied to explore the features of the fuel cycles parameters related to fast reactors with different fuel types, different conversion ratios (CR) and different MA/Pu ratios in the fuel feed. It is shown that for cores with CR below ∼0.8, the increase of neutron doses and decay heat can represent a significant drawback to implement the corresponding reactors and associated fuel cycles. (authors)

  7. Dual-shell hollow polyaniline/sulfur-core/polyaniline composites improving the capacity and cycle performance of lithium-sulfur batteries

    Science.gov (United States)

    An, Yanling; Wei, Pan; Fan, Meiqiang; Chen, Da; Chen, Haichao; Ju, QiangJian; Tian, Guanglei; Shu, Kangying

    2016-07-01

    In this study, a dual-shell hollow polyaniline/sulfur-core/polyaniline (hPANI/S/PANI) composite was prepared by successively depositing PANI, S, and PANI on the surface of a template silicon sphere. The electrochemical properties of this composite were evaluated using a lithium plate as an anode in lithium/sulfur cells. The hPANI/S/PANI composite showed a discharge capacity of 572.2 mAh g-1 after 214 cycles at 0.1 C, and the Coulombic efficiency was above 87% in the whole charge/discharge cycle. The improved cycle property of the hPANI/S/PANI composite can be ascribed to the fine sulfur particles homogeneously deposited on the PANI surface and sprawled inside the two PANI layers during the charge/discharge cycle. This behavior stabilized the nanostructure of sulfur and enhanced its conductivity.

  8. Acute Bouts of Assisted Cycling Improves Cognitive and Upper Extremity Movement Functions in Adolescents with Down Syndrome

    Science.gov (United States)

    Ringenbach, Shannon D. R; Albert, Andrew R.; Chen, Chih-Chia; Alberts, Jay L.

    2014-01-01

    The aim of this study was to examine the effectiveness of 2 modes of exercise on cognitive and upper extremity movement functioning in adolescents with Down syndrome (DS). Nine participants randomly completed 3 interventions over 3 consecutive weeks. The interventions were: (a) voluntary cycling (VC), in which participants cycled at their…

  9. Izboljšanje kakovosti - krog PDCA v primerjavi z DMAIC in DFSS: Quality improvement - PDCA cycle vs. DMAIC and DFSS:

    OpenAIRE

    Pavletić, Duško; Soković, Mirko

    2007-01-01

    To achieve continuous quality improvements every organization needs to use an appropriate selection of tools and techniques. The fundamental requirements for success are a clear understanding, both of the tools and techniques as well as the process by which they should be applied. In this paper we provide an overview and the fields of application of the PDCA, Six Sigma and DFSS techniques for the continuous quality improvement of products, processes and services. The PDCA cycle is a simple-to...

  10. Improvement of Capacity and Cycling Performance of Spinel LiMn2O4 Cathode Materials with TiO2-B Nanobelts

    DEFF Research Database (Denmark)

    Zhang, J.Y.; Shen, J.X.; Wang, T.L.;

    2013-01-01

    The spinel LiMn2O4 was modified with TiO2-B nanobelts to improve its specific capacity and cycling performance. TiO2-B/LiMn2O4 composites were fabricated by a facile liquid phase mixing method. The morphology and structure of the samples were characterized by means of X-ray diffraction, scanning...

  11. Potential for improving the energy efficiency of cryogenic air separation unit (ASU) using binary heat recovery cycles

    International Nuclear Information System (INIS)

    In this paper, the potential of improving the energy efficiency of a conventional cryogenic air separation unit (ASU) was investigated through modelling and simulation using Aspen Plus® v 8.1. It is achieved through converting the heat from the compressor effluent to electricity using organic Ranking cycle (ORC). Two different arrangements of combining compressor and waste heat recovery ORC system were compared with the conventional cryogenic ASU which was used as the benchmark. The benchmark is a conventional cryogenic ASU with 3 stages of compression which uses water for intercooling. In the first arrangement the water used as the cooling fluid of the intercooler/after cooler heat exchanger of a conventional cryogenic ASU process was replaced by R134a which also acts as the working fluid for the ORC system (C3WHR) while in the second arrangement, the 3 stages compressor of the conventional process was replaced with a single stage compressor with the same overall pressure ratio as the conventional process and the hot compressor effluent cooled with R134a which also acts as the working fluid of the ORC system (C1WHR). The simulation results based on a cryogenic ASU capable of processing 100 kg/s of atmospheric air at 30 °C as feedstock show that the specific power consumption for the pure products which was 0.32 kWh/kg, 0.37 kWh/kg and 17.35 kWh/kg for oxygen, nitrogen and argon respectively for the conventional cryogenic ASU process was reduced by the addition of the waste heat recovery ORC system. The C1WHR reduced the specific power consumption by an average of 0.2% across the aforementioned pure products while the C3WHR reduced it by an average of 11%. The net power consumption of the conventional cryogenic ASU which was 21826.19 kW was also found to be reduced by the same percentage. - Highlights: • We model two cryogenic air separation unit with compressor waste heat recovery. • We compare the specific energy consumption of the models. • We

  12. A thermodynamic review of cryogenic refrigeration cycles for liquefaction of natural gas

    Science.gov (United States)

    Chang, Ho-Myung

    2015-12-01

    A thermodynamic review is presented on cryogenic refrigeration cycles for the liquefaction process of natural gas. The main purpose of this review is to examine the thermodynamic structure of various cycles and provide a theoretical basis for selecting a cycle in accordance with different needs and design criteria. Based on existing or proposed liquefaction processes, sixteen ideal cycles are selected and the optimal conditions to achieve their best thermodynamic performance are investigated. The selected cycles include standard and modified versions of Joule-Thomson (JT) cycle, Brayton cycle, and their combined cycle with pure refrigerants (PR) or mixed refrigerants (MR). Full details of the cycles are presented and discussed in terms of FOM (figure of merit) and thermodynamic irreversibility. In addition, a new method of nomenclature is proposed to clearly identify the structure of cycles by abbreviation.

  13. Efficiency enhancement of a gas turbine cycle using an optimized tubular recuperative heat exchanger

    International Nuclear Information System (INIS)

    A simple gas turbine cycle namely as the Kraftwerk Union AG unit including a Siemens gas turbine model V93.1 with 60 MW nominal power and 26.0% thermal efficiency utilized in the Fars power plant located is considered for the efficiency enhancement. A typical tubular vertical recuperative heat exchanger is designed in order to integrate into the cycle as an air pre-heater for thermal efficiency improvement. Thermal and geometric specifications of the recuperative heat exchanger are obtained in a multi-objective optimization process. The exergetic efficiency of the gas cycle is maximized while the payback time for the capital investment of the recuperator is minimized. Combination of these objectives and decision variables with suitable engineering and physical constraints makes a set of the MINLP optimization problem. Optimization programming is performed using the NSGA-II algorithm and Pareto optimal frontiers are obtained in three cases including the minimum, average and maximum ambient air temperatures. In each case, the final optimal solution has been selected using three decision-making approaches including the fuzzy Bellman-Zadeh, LINMAP and TOPSIS methods. It has been shown that the TOPSIS and LINMAP decision-makers when applied on the Pareto frontier which is obtained at average ambient air temperature yields best results in comparison to other cases. -- Highlights: ► A simple Brayton gas cycle is considered for the efficiency improvement by integrating of a recuperator. ► Objective functions based on thermodynamic and economic analysis are obtained. ► The payback time for the capital investment is minimized and the exergetic efficiency of the system is maximized. ► Pareto optimal frontiers at various site conditions are obtained. ► A final optimal configuration is found using various decision-making approaches.

  14. Improvement in recuperative gas cycles by means of a heat generator partly by-passing the recuperator. Application to open and closed cycles and to various kinds of energy

    International Nuclear Information System (INIS)

    A particular arrangement applicable to open or closed recuperative gas cycles and consisting of a heat generator partly by-passing the low pressure side of the recuperator is proven to enhance advantages of gas cycles for energy production. The cogeneration of both power with a high efficiency owing to the recuperator and high temperature process heat becomes possible and economically attractive. Furthermore, additional possibilities appear for power generation by combined gas and steam or ammonia cycles. In any case the overall utilization coefficient of the primary energy is increased and the combined production of low or medium temperature heat can also be improved. The great operation flexibility of the system for combined energy generation is worth being emphasized: the by-pass arrangement involves no significant change in the operation conditions of the main turbocompressor as the heat output varies. Applications of this arrangement are made to: - open and closed gas cycle, power plants; - fossil, nuclear and solar energies. The overall heat conversion efficiency is tentatively estimated in order to appreciate the energy conversion capability of the investigated power plants

  15. Combined Turbine and Cycle Optimization for Organic Rankine Cycle Power Systems—Part B

    DEFF Research Database (Denmark)

    La Seta, Angelo; Meroni, Andrea; Andreasen, Jesper Graa; Pierobon, Leonardo; Persico, Giacomo; Haglind, Fredrik

    2016-01-01

    due to the peculiar physical properties of the working fluid and the gas-dynamic phenomena occurring in the machine. Unlike steam Rankine and Brayton engines, organic Rankine cycle expanders combine small enthalpy drops with large expansion ratios. These features yield turbine designs with few highly...... cost of the turbine optimization is tackled by building a model which gives the optimal preliminary design of an axial-flow turbine as a function of the cycle conditions. This allows for estimating the optimal expander performance for each operating condition of interest. The test case is the...... power output of 8.3% compared to the case when the turbine efficiency is assumed to be 80%. This work also demonstrates that this approach can support the plant designer in the selection of the optimal size of the organic Rankine cycle unit when multiple exhaust gas streams are available....

  16. Carbon cost of plant nitrogen acquisition: global carbon cycle impact from an improved plant nitrogen cycle in the Community Land Model.

    Science.gov (United States)

    Shi, Mingjie; Fisher, Joshua B; Brzostek, Edward R; Phillips, Richard P

    2016-03-01

    Plants typically expend a significant portion of their available carbon (C) on nutrient acquisition - C that could otherwise support growth. However, given that most global terrestrial biosphere models (TBMs) do not include the C cost of nutrient acquisition, these models fail to represent current and future constraints to the land C sink. Here, we integrated a plant productivity-optimized nutrient acquisition model - the Fixation and Uptake of Nitrogen Model - into one of the most widely used TBMs, the Community Land Model. Global plant nitrogen (N) uptake is dynamically simulated in the coupled model based on the C costs of N acquisition from mycorrhizal roots, nonmycorrhizal roots, N-fixing microbes, and retranslocation (from senescing leaves). We find that at the global scale, plants spend 2.4 Pg C yr(-1) to acquire 1.0 Pg N yr(-1) , and that the C cost of N acquisition leads to a downregulation of global net primary production (NPP) by 13%. Mycorrhizal uptake represented the dominant pathway by which N is acquired, accounting for ~66% of the N uptake by plants. Notably, roots associating with arbuscular mycorrhizal (AM) fungi - generally considered for their role in phosphorus (P) acquisition - are estimated to be the primary source of global plant N uptake owing to the dominance of AM-associated plants in mid- and low-latitude biomes. Overall, our coupled model improves the representations of NPP downregulation globally and generates spatially explicit patterns of belowground C allocation, soil N uptake, and N retranslocation at the global scale. Such model improvements are critical for predicting how plant responses to altered N availability (owing to N deposition, rising atmospheric CO2 , and warming temperatures) may impact the land C sink. PMID:26473512

  17. Corrigendum to "Sinusoidal potential cycling operation of a direct ethanol fuel cell to improving carbon dioxide yields" [J. Power Sources 268 (5 December 2014) 439-442

    Science.gov (United States)

    Majidi, Pasha; Pickup, Peter G.

    2016-09-01

    The authors regret that Equation (5) is incorrect and has resulted in errors in Fig. 4 and the efficiencies stated on p. 442. The corrected equation, figure and text are presented below. In addition, the title should be 'Sinusoidal potential cycling operation of a direct ethanol fuel cell to improve carbon dioxide yields', and the reversible cell potential quoted on p. 441 should be 1.14 V. The authors would like to apologise for any inconvenience caused.

  18. Automatic adjustment of cycle length and aeration time for improved nitrogen removal in an alternating activated sludge process

    DEFF Research Database (Denmark)

    Isaacs, Steven Howard

    1997-01-01

    The paper examines the nitrogen dynamics in the alternating BIODENITRO and BIODENIPHO processes with a focus on two control handles influencing now scheduling and aeration: the cycle length and the ammonia concentration at which a nitrifying period is terminated. A steady state analysis examining...

  19. Smart Operation of Gas Turbine Combined Cycle Plants: Prediction and Improvement of Thermal Efficiency at Part Load

    NARCIS (Netherlands)

    Boksteen, S.Z.

    2014-01-01

    This thesis investigates various operational aspects of Gas Turbine Combined Cycle Power Plants (GTCC). GTCC power plants are expected to play an increasingly important role in the balancing of supply and demand in the electricity grid. Although originally meant for predominantly base load operatio

  20. Status of the CNES-CEA joint program on space nuclear Brayton systems

    International Nuclear Information System (INIS)

    A cooperative program between the French Centre National d'Etudes Spatiales (CNES) and the Commissariat a l'Energie Atomique (CEA) was initiated in 1983, to investigate the possible development of 20 to 200 kWe space nuclear power systems to be launched by the next version of the European launcher, Ariane V. After completion in 1986 of preliminary conceptual studies of a reference 200 kWe turbo-electric power system, an additional 3 year study phase was decided, with the double objective of assessing the potential advantage of nuclear power systems versus solar photovoltaic or dynamic systems in the 20 kWe power range, and comparing various reactor candidate technologies and system options for 20 kWe space nuclear power systems, likely to meet the projected energy needs of future European space missions. A comprehensive program including conceptual design studies, operating transient analyses and technology base assessment, is currently applied to a few reference concepts of 20 kWe nuclear Brayton and thermoelectric systems, in order to establish sound technical and economical bases for selecting the design options and the development strategy of a first space nuclear power system in Europe

  1. Design and optimization of a single stage centrifugal compressor for a solar dish-Brayton system

    Science.gov (United States)

    Wang, Yongsheng; Wang, Kai; Tong, Zhiting; Lin, Feng; Nie, Chaoqun; Engeda, Abraham

    2013-10-01

    According to the requirements of a solar dish-Brayton system, a centrifugal compressor stage with a minimum total pressure ratio of 5, an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed. A single stage, which consists of impeller, radial vaned diffuser, 90° crossover and two rows of axial stators, was chosen to satisfy this system. To achieve the stage performance, an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program. Radial vaned diffuser was applied downstream of the impeller. Two rows of axial stators after 90° crossover were added to guide the flow into axial direction. Since jet-wake flow, shockwave and boundary layer separation coexisted in the impeller-diffuser region, optimization on the radius ratio of radial diffuser vane inlet to impeller exit, diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point. Finally, an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance. Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6. The surge margin was 15%. The performance map including 80%, 90% and 100% design speed was also presented.

  2. Numerical simulations of LNG vapor dispersion in Brayton Fire Training Field tests with ANSYS CFX

    International Nuclear Information System (INIS)

    Federal safety regulations require the use of validated consequence models to determine the vapor cloud dispersion exclusion zones for accidental liquefied natural gas (LNG) releases. One tool that is being developed in industry for exclusion zone determination and LNG vapor dispersion modeling is computational fluid dynamics (CFD). This paper uses the ANSYS CFX CFD code to model LNG vapor dispersion in the atmosphere. Discussed are important parameters that are essential inputs to the ANSYS CFX simulations, including the atmospheric conditions, LNG evaporation rate and pool area, turbulence in the source term, ground surface temperature and roughness height, and effects of obstacles. A sensitivity analysis was conducted to illustrate uncertainties in the simulation results arising from the mesh size and source term turbulence intensity. In addition, a set of medium-scale LNG spill tests were performed at the Brayton Fire Training Field to collect data for validating the ANSYS CFX prediction results. A comparison of test data with simulation results demonstrated that CFX was able to describe the dense gas behavior of LNG vapor cloud, and its prediction results of downwind gas concentrations close to ground level were in approximate agreement with the test data.

  3. Improvement of the cycling performance of LiCoO2 with assistance of cross-linked PAN for lithium ion batteries

    International Nuclear Information System (INIS)

    Highlights: • Cross-linked PAN coating was prepared without damaging the surface of LiCoO2. • The coating layer owns good electronic conductivity and mechanical strength. • The cross-linked PAN coating layer is more sufficient than Al2O3 coating. • It shows much improved cyclability than that of bare and Al2O3 coated LiCoO2. - Abstract: LiCoO2 has been widely used in lithium ion batteries for digital electronic products. However, the limited cycling performance under high cut-off voltage hinders its commercial application. Many metal oxides and/or phosphorus coating have been reported to improve the cycling performance of LiCoO2. In this paper, we report on cross-linked PAN coated LiCoO2 composite as a cathode material for lithium ion batteries. The coating layer was obtained by intermolecular crosslinking of PAN polymer chain by heat treatment at high temperature in air. The air heating process avoids the possible damage arising from the carbon thermal reduction to the surface structure of LiCoO2. Electrochemical test indicates that the LiCoO2 with the cross-linked PAN coating layer shows much improved cycle performance compared with that of bare and Al2O3 coated LiCoO2. These findings might also open new avenues to explore polymer coating for other cathode materials of lithium ion batteries

  4. Supercritical CO2 Brayton power cycles for DEMO (demonstration power plant) fusion reactor based on dual coolant lithium lead blanket

    OpenAIRE

    Linares, José Ignacio; Cantizano González, Alexis; Moratilla, Beatriz Y.; Martin Palacios, Victor; Batet Miracle, Lluís

    2016-01-01

    The purpose of this website is to provide information about fusion and fusion research, particularly the research activities related to EUROfusion. Neither EUROfusion, the EUROfusion Research Units, the European Commission, nor anyone acting on their behalf, is responsible for any damage resulting from the use of information contained on this website. Unless otherwise explicitly stated, all information, text and electronic images contained on this website are the intellectual property of ...

  5. Fes cycling

    Directory of Open Access Journals (Sweden)

    Berkelmans Rik

    2008-01-01

    Full Text Available Many research with functional electrical stimulation (FES has been done to regain mobility and for health benefits. Better results have been reported for FES-cycling than for FES-walking. The majority of the subjects during such research are people with a spinal cord injury (SCI, cause they often lost skin sensation. Besides using surface stimulation also implanted stimulators can be used. This solves the skin sensation problem, but needs a surgery. Many physiological effects of FES-cycling has been reported, e.g., increase of muscles, better blood flow, reduction of pressure ulcers, improved self-image and some reduction of bone mineral density (BMD loss. Also people with an incomplete SCI benefit by FES-cycling, e.g. cycling time without FES, muscle strength and also the walking abilities increased. Hybrid exercise gives an even better cardiovascular training. Presently 4 companies are involved in FES-cycling. They all have a stationary mobility trainer. Two of them also use an outdoor tricycle. One combined with voluntary arm cranking. By optimizing the stimulation parameters the power output and fatigue resistance will increase, but will still be less compared to voluntary cycling.

  6. Advantages of using a logarithmic scale in pressure-volume diagrams for Carnot and other heat engine cycles

    Science.gov (United States)

    Shieh, Lih-Yir; Kan, Hung-Chih

    2014-04-01

    We demonstrate that plotting the P-V diagram of an ideal gas Carnot cycle on a logarithmic scale results in a more intuitive approach for deriving the final form of the efficiency equation. The same approach also facilitates the derivation of the efficiency of other thermodynamic engines that employ adiabatic ideal gas processes, such as the Brayton cycle, the Otto cycle, and the Diesel engine. We finally demonstrate that logarithmic plots of isothermal and adiabatic processes help with visualization in approximating an arbitrary process in terms of an infinite number of Carnot cycles.

  7. Intake of protein plus carbohydrate during the first two hours after exhaustive cycling improves performance the following day

    DEFF Research Database (Denmark)

    Rustad, Per I.; Sailer, Manuela; Cumming, Kristoffer T.; Jeppesen, Per B.; Kolnes, Kristoffer J.; Sollie, Ove; Franch, Jesper; Ivy, John L.; Daniel, Hannelore; Jensen, Jørgen

    2016-01-01

    ) when subjects were supplemented with protein plus carbohydrate or carbohydrate only in a 2-h window starting immediately after exhaustive cycling. The second aim was to investigate the effect of no nutrition during the first 2 h and low total energy intake (113 kJ·kg-1 during 18 h) on performance when...... protein intake was similar. Eight endurance-trained subjects cycled at 237±6 Watt (~72% VO2max) until exhaustion (TTE) on three occasions, and supplemented with 1.2 g carbohydrate·kg-1·h-1 (CHO), 0.8 g carbohydrate + 0.4 g protein·kg-1·h-1 (CHO+PRO) or placebo without energy (PLA). Intake of CHO...

  8. Smart Operation of Gas Turbine Combined Cycle Plants: Prediction and Improvement of Thermal Efficiency at Part Load

    OpenAIRE

    Boksteen, S.Z.

    2014-01-01

    This thesis investigates various operational aspects of Gas Turbine Combined Cycle Power Plants (GTCC). GTCC power plants are expected to play an increasingly important role in the balancing of supply and demand in the electricity grid. Although originally meant for predominantly base load operation with high efficiencies, market circumstances, namely the increasing supply of unpredictable wind and solar power, force these units to be operated frequently across a wide range of load settings. ...

  9. Air bottoming cycle, an alternative to combined cycles. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kaikko, J. [Royal Inst. of Techn., Stockholm (Sweden). Dept. of Energy Technology

    2001-10-01

    In this work, the idea of Air Bottoming Cycle (ABC) has been studied. The objectives for the work have been to establish an understanding of the concept for power and heat generation as well as to find - if possible - feasible concepts for future use in the Swedish energy system. Combined cycle in power generation is an established technology. In the conventional combined cycle, a gas turbine works as a topping cycle together with the steam (Rankine) bottoming cycle. In the ABC the steam bottoming cycle is replaced with a gas turbine (Brayton) bottoming cycle having air as a working fluid. The two gas turbines are thermally connected over a gas-to-gas heat exchanger. This concept promises savings in weight and cost, as well as operating benefits, compared to the Rankine bottoming technology. The ABC has been modelled using a heat balance program, and a parametric study for the concept optimisation as well as for off-design analysis has been performed. Performance of the ABC has been compared to other, established technologies. A preliminary economic evaluation has been made. As a result of the study, it is clarified that the Rankine bottoming cycle with steam remains superior to the ABC as regards electrical efficiency in the medium and large power scale. For small-scale applications (<10 MW{sub e}) where the thermodynamic advantage of the Rankine cycle is not dominating any longer and its economy is burdened by the heavy investment structure, the ABC becomes the better alternative for energy utilisation. A preliminary economic evaluation shows that (at energy prices autumn 2000) the ABC is at the same level as the comparable small-scale cogeneration installations. Due to high power-to-heat ratio however, higher electricity prices will favour the ABC. One interesting feature of the ABC is that about 50% of the dissipated low-value heat from the cycle is carried by clean (sterile) air at the temperature around 200 deg C. This air can be utilised for space heating or

  10. Air bottoming cycle, an alternative to combined cycles. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Kaikko, J. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Energy Technology

    2002-02-01

    In this work, the idea of Air Bottoming Cycle (ABC) has been studied. The objectives for the work have been to establish an understanding of the concept for power and heat generation as well as to find - if possible - feasible concepts for future use in the Swedish energy system. Combined cycle in power generation is an established technology. In the conventional combined cycle, a gas turbine works as a topping cycle together with the steam (Rankine) bottoming cycle. In the ABC the steam bottoming cycle is replaced with a gas turbine (Brayton) bottoming cycle having air as a working fluid. The two gas turbines are thermally connected over a gas-to-gas heat exchanger. This concept promises savings in weight and cost, as well as operating benefits, compared to the Rankine bottoming technology. The ABC has been modelled using a heat balance program, and a parametric study for the concept optimisation as well as for off-design analysis has been performed. Performance of the ABC has been compared to other, established technologies. A preliminary economic evaluation has been made. As a result of the study, it is clarified that the Rankine bottoming cycle with steam remains superior to the ABC as regards electrical efficiency in the medium and large power scale. For small-scale applications (<10 MW{sub e}) where the thermodynamic advantage of the Rankine cycle is not dominating any longer and its economy is burdened by the heavy investment structure, the ABC becomes the better alternative for energy utilisation. A preliminary economic evaluation shows that (at energy prices autumn 2000) the ABC is at the same level as the comparable small-scale cogeneration installations. Due to high power-to-heat ratio however, higher electricity prices will favour the ABC. One interesting feature of the ABC is that about 50% of the dissipated low-value heat from the cycle is carried by clean (sterile) air at the temperature around 200 deg C. This air can be utilised for space heating or

  11. A unified model of combined energy systems with different cycle modes and its optimum performance characteristics

    International Nuclear Information System (INIS)

    A unified model is presented for a class of combined energy systems, in which the systems mainly consist of a heat engine, a combustor and a counter-flow heat exchanger and the heat engine in the systems may have different thermodynamic cycle modes such as the Brayton cycle, Carnot cycle, Stirling cycle, Ericsson cycle, and so on. Not only the irreversibilities of the heat leak and finite-rate heat transfer but also the different cycle modes of the heat engine are considered in the model. On the basis of Newton's law, expressions for the overall efficiency and power output of the combined energy system with an irreversible Brayton cycle are derived. The maximum overall efficiency and power output and other relevant parameters are calculated. The general characteristic curves of the system are presented for some given parameters. Several interesting cases are discussed in detail. The results obtained here are very general and significant and can be used to discuss the optimal performance characteristics of a class of combined energy systems with different cycle modes. Moreover, it is significant to point out that not only the important conclusions obtained in Bejan's first combustor model and Peterson's general combustion driven model but also the optimal performance of a class of solar-driven heat engine systems can be directly derived from the present paper under some limit conditions

  12. Cycling in Sydney, Australia

    Directory of Open Access Journals (Sweden)

    Alexis Zander

    2013-01-01

    Full Text Available Introduction. Cycling can be an enjoyable way to meet physical activity recommendations and is suitable for older people; however cycling participation by older Australians is low. This qualitative study explored motivators, enablers, and barriers to cycling among older people through an age-targeted cycling promotion program. Methods. Seventeen adults who aged 50–75 years participated in a 12-week cycling promotion program which included a cycling skills course, mentor, and resource pack. Semistructured interviews at the beginning and end of the program explored motivators, enablers, and barriers to cycling. Results. Fitness and recreation were the primary motivators for cycling. The biggest barrier was fear of cars and traffic, and the cycling skills course was the most important enabler for improving participants’ confidence. Reported outcomes from cycling included improved quality of life (better mental health, social benefit, and empowerment and improved physical health. Conclusions. A simple cycling program increased cycling participation among older people. This work confirms the importance of improving confidence in this age group through a skills course, mentors, and maps and highlights additional strategies for promoting cycling, such as ongoing improvement to infrastructure and advertising.

  13. Highly conductive bridges between graphite spheres to improve the cycle performance of a graphite anode in lithium-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Hongyu [IM and T Ltd., Advanced Research Center, Saga University, Yoga-machi 1341, Saga 840-0047 (Japan); Umeno, Tatsuo; Mizuma, Koutarou [Research Center, Mitsui Mining Co. Ltd., Hibiki-machi 1-3, Wakamatsu-ku, Kitakyushu 808-0021 (Japan); Yoshio, Masaki [Advanced Research Center, Saga University, Yoga-machi 1341, Saga 840-0047 (Japan)

    2008-01-10

    Spherical carbon-coated natural graphite (SCCNG) is a promising anode material for lithium-ion batteries, but the smooth surface of graphite spheres is difficult to wet with an aqueous binder solution, and lacks electrical contacts. As a result, the cycle performance of such a graphite anode material is not satisfactory. An effective method has been introduced to tightly connect adjacent SCCNG particles by a highly conductive binder, viz. acetylene black bridges. The effect of the conductive bridges on the cyclability of SCCNG electrode has been investigated. (author)

  14. How physical modelling can improve Life Cycle Inventory accuracy and allow predictive LCA: an application to the steel industry

    International Nuclear Information System (INIS)

    Assessing traditional iron and steelmaking processes from an environmental point of view and developing breakthrough eco-efficient processes for the future are major challenges for the steel industry today. In the framework of the challenging European project ULCOS, which stands for Ultra Low CO2 Steelmaking, Life Cycle Assessment (LCA) was chosen to assess breakthrough processes that could be part of the future iron and steel making landscape and to compare them to the reference classical integrated steel-mill. To carry out such a study we propose a new methodological concept which combines LCA thinking with physicochemical process modelling. Physicochemical models were developed for each processes of the classical integrated steelmaking route in order to generate the data required to draw the Life Cycle Inventory of the route. Such a method bypasses the traditional data collection and brings accuracy to the inventory by introducing rigorous mass and energy balances into the methodology. In addition it was shown that such an approach allows testing and assessing different operational practices of the processes in order to optimise the use of energy and the CO2 emissions, which showed that it can be used as a powerful tool for eco-conception of processes. (authors)

  15. Manganese sequestration and improved high-temperature cycling of Li-ion batteries by polymeric aza-15-crown-5

    Science.gov (United States)

    Li, Zicheng; Pauric, Allen D.; Goward, Gillian R.; Fuller, Timothy J.; Ziegelbauer, Joseph M.; Balogh, Michael P.; Halalay, Ion C.

    2014-12-01

    Mn cation trapping by polymeric aza-15-crown-5 ethers is an effective means for mitigating the consequences of Mn dissolution in Li-ion batteries. Mn cations trapping was investigated in lithium manganese oxide (LMO) spinel-graphite (GR) cells containing 1 M LiPF6 in ethylene carbonate (EC):diethyl carbonate (DEC) 1:2 v/v. A commercial polyolefin separator membrane coated with poly[divinylbenzene-(vinylbenzyl-aza-15-crown-5)-vinylbenzylchloride)] effected a 39% reduction in capacity loss rate during cycling at 50 °C with 100% depth of discharge (DOD) at C/5 rate. Simultaneously, a 50-60% reduction in the Mn deposited at the negative electrode, and a 6× to 10× increase in the Mn on the coated separator were observed for cells with coated separators, over baseline cells with plain separators. X-ray absorption near-edge spectroscopy (XANES) yielded average oxidation states near +3 for Mn cations in graphite electrodes and separators from cycled cells, suggesting that Mn metal or in oxidation state +2 can only be minor fractions of the Mn existing outside the positive electrode. We discuss the implications of these results for choosing an optimal chelating agent. We also show that the cation chelating polymer reported here is compatible with existing manufacturing processes for Li-ion battery separators.

  16. Improvement of the cycling performance of LiCoO{sub 2} with assistance of cross-linked PAN for lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xinhe [School of Chemical Engineering and Environment Science, Beijing Institute of Technology, Beijing 100081 (China); College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China); Shen, Lanyao; Wu, Bin; Zuo, Zicheng [Beijing Engineering Research Center of Power Lithium-ion Battery, Beijing 102200 (China); Mu, Daobin [School of Chemical Engineering and Environment Science, Beijing Institute of Technology, Beijing 100081 (China); Wu, Borong, E-mail: wubr@bit.edu.cn [School of Chemical Engineering and Environment Science, Beijing Institute of Technology, Beijing 100081 (China); Zhou, Henghui, E-mail: hhzhou@pku.edu.cn [College of Chemistry and Molecular Engineering, Peking University, Beijing 100871 (China)

    2015-08-05

    Highlights: • Cross-linked PAN coating was prepared without damaging the surface of LiCoO{sub 2}. • The coating layer owns good electronic conductivity and mechanical strength. • The cross-linked PAN coating layer is more sufficient than Al{sub 2}O{sub 3} coating. • It shows much improved cyclability than that of bare and Al{sub 2}O{sub 3} coated LiCoO{sub 2}. - Abstract: LiCoO{sub 2} has been widely used in lithium ion batteries for digital electronic products. However, the limited cycling performance under high cut-off voltage hinders its commercial application. Many metal oxides and/or phosphorus coating have been reported to improve the cycling performance of LiCoO{sub 2}. In this paper, we report on cross-linked PAN coated LiCoO{sub 2} composite as a cathode material for lithium ion batteries. The coating layer was obtained by intermolecular crosslinking of PAN polymer chain by heat treatment at high temperature in air. The air heating process avoids the possible damage arising from the carbon thermal reduction to the surface structure of LiCoO{sub 2}. Electrochemical test indicates that the LiCoO{sub 2} with the cross-linked PAN coating layer shows much improved cycle performance compared with that of bare and Al{sub 2}O{sub 3} coated LiCoO{sub 2}. These findings might also open new avenues to explore polymer coating for other cathode materials of lithium ion batteries.

  17. Low-temperature behaviour of an ideal Bose gas and some forbidden thermodynamic cycles

    International Nuclear Information System (INIS)

    Based on the equation of state of an ideal Bose gas, the heat capacities at constant volume and constant pressure of the Bose system are derived and used to analyse the low-temperature behaviour of the Bose system. It is expounded that some important thermodynamic processes such as a constant pressure and an adiabatic process cannot be carried out from the region of T > Tc to that of T c, where Tc is the critical temperature of Bose-Einstein condensation of the Bose system. Consequently, some typical thermodynamic cycles such as the Carnot cycle, Brayton cycle, Otto cycle, Ericsson cycle, Diesel cycle and Atkinson cycle cannot be operated across the critical temperature Tc of Bose-Einstein condensation of an ideal Bose gas

  18. Improved analysis on multiple recycling of fuel in prototype fast breeder reactor in a closed fuel cycle

    Indian Academy of Sciences (India)

    G Pandikumar; V Gopalakrishnan; P Mohanakrishnan

    2011-08-01

    An FBR closed fuel cycle involves recycling of the discharge fuel, after reprocessing and refabrication, to utilize the unburnt fuel remains and the freshly bred fissile material. Our previous study in this regard for the PFBR indicated a comfortable feasibility of multiple recycling with selfsufficiency. In the present work, more refined estimations are done using the most recent nuclear data, viz. ENDF/B-VII.0, and with the most recent specification of the fuel composition. Among others, this paper brings out the importance of taking into account the energy self-shielding effects in the cross-section averages used in the study. While self-shielded averages lead to realistic predictions, unshielded averages significantly overpredict breeding in the blankets and underpredict loss in the cores.

  19. Variable geometry gas turbines for improving the part-load performance of marine combined cycles - Gas turbine performance

    DEFF Research Database (Denmark)

    Haglind, Fredrik

    2010-01-01

    The part-load performance of gas and steam turbine combined cycles intended for naval use is of great importance, and it is influenced by the gas turbine configuration and load control strategy. This paper is aimed at quantifying the effects of variable geometry on the gas turbine part...... of various components within gas turbines. Two different gas turbine configurations are studied, a two-shaft aero-derivative configuration and a single-shaft industrial configuration. When both gas turbine configurations are running in part-load using fuel flow control, the results indicate better...... part-load performance for the two-shaft gas turbine. Reducing the load this way is accompanied by a much larger decrease in exhaust gas temperature for the single-shaft gas turbine than for the two-shaft configuration. As used here, the results suggest that variable geometry generally deteriorates the...

  20. Heat acclimatization does not improve VO2max or cycling performance in a cool climate in trained cyclists

    DEFF Research Database (Denmark)

    Karlsen, Anders; Racinais, S; Jensen, M V;

    2015-01-01

    This study investigated if well-trained cyclists improve V ˙ O 2 m a x and performance in cool conditions following heat acclimatization through natural outdoor training in hot conditions. Eighteen trained male cyclists were tested for physiological adaptations, V ˙ O 2 m a x , peak aerobic power...... was associated with marked improvements in TT performance in the heat. However, for the well-trained endurance athletes, this did not transfer to an improved aerobic exercise capacity or outdoor TT performance in cool conditions.......This study investigated if well-trained cyclists improve V ˙ O 2 m a x and performance in cool conditions following heat acclimatization through natural outdoor training in hot conditions. Eighteen trained male cyclists were tested for physiological adaptations, V ˙ O 2 m a x , peak aerobic power...... output, exercise efficiency, and outdoor time trial (TT) performance (43.4 km in cool environment, ∼5-13 °C) before and after 2 weeks of training in a cool (CON, n = 9) or hot (∼35 °C, HA, n = 9) environment. After heat acclimatization, TT performance in the heat was improved by 16%; however...

  1. Final technical report. A sodium-cycle based organism with improved membrane resistance aimed at increasing the efficiency of energy biotransformations

    International Nuclear Information System (INIS)

    The aim of the project was to express in E. coli components that would allow a formation of oxidative phosphorylation based on a sodium cycle. This would improve the resistance of cells to organic solvents, detergents and other toxins. The author cloned and expressed the nqr operon FR-om H. influenzae in E. coli. Experiments with membrane vesicles indicated the presence of the functional recombinant sodium pumping NADH dehydrogenase. A gene for a hybrid E. coli/P.modestum ATPase was constructed which will enable one to co-express a sodium ATPsynthase together with a sodium NADH dehydrogenase

  2. The Miller cycle effects on improvement of fuel economy in a highly boosted, high compression ratio, direct-injection gasoline engine: EIVC vs. LIVC

    International Nuclear Information System (INIS)

    Highlights: • At high load, LIVC is superior over EIVC in improving fuel economy. • The improvement with LIVC is due to advanced combustion phasing and increased pumping work. • At low load, EIVC is better than LIVC in improving fuel economy. • Pumping loss with EIVC is smaller than with LIVC at low load. • But heat release rate with EIVC is slower than with LIVC. - Abstract: A combination of downsizing, highly boosting and direct injection (DI) is an effective way to improve fuel economy of gasoline engines without the penalties of reduced torque or power output. At high loads, however, knock problem becomes severer when increasing the intake boosting. As a compromise, geometric compression ratio (CR) is usually reduced to mitigate knock, and the improvement of fuel economy is discounted. Application of Miller cycle, which can be realized by either early or late intake valve closing (EIVC or LIVC), has the potential to reduce the effective CR and suppress knock. In this paper, the effects of EIVC and LIVC on the fuel economy of a boosted DI gasoline production engine reformed with a geometric CR of 12.0 are experimentally compared at low and high loads. Compared to the original production engine with CR 9.3, at the high load operation, the brake specific fuel consumption (BSFC) is improved by 4.7% with CR12.0 and LIVC, while the effect of EIVC on improving BSFC is negligibly small. At the low load operation, combined with CR12.0, LIVC and EIVC improve the fuel economy by 6.8% and 7.4%, respectively, compared to the production engine. The mechanism behind the effects of LIVC and EIVC on improving the fuel economy is discussed. These results will be a valuable reference for engine designers and researchers

  3. Improvement of the decay heat removal characteristics of the generation IV gas-cooled fast reactor

    International Nuclear Information System (INIS)

    , different injection locations and injection mass flows were considered, and the sensitivity to the number of available DHR loops and LOCA break-sizes was also addressed. It has been found that injecting the heavy gas in the vicinity of the core could lead to overcooling problems. For an injection point sufficiently far from the core, however, both CO2 and N2 are found to be able to cool the core satisfactorily in natural convection. N2 is proposed as the reference, due to possible chemical problems with CO2. The second proposition for DHR improvement is related to the possibility of a simultaneous guard-containment failure, i.e. a loss-of-back-up-pressure (LOBP) combined with a blower failure after a LOCA. In this case the natural convection, even with heavy gas injection, is no longer strong enough to evacuate the decay heat. To address this issue, the possibility of decay heat removal via use of a dedicated autonomous Brayton cycle – as a standalone DHR loop – has been investigated. First, an analytical Brayton cycle model has been set up, so as to identify convenient machine design points and to study the machine’s off-design behavior. Two machine designs have then been drawn up: one for helium in order to provide a reference for understanding the Brayton loop behavior in a generic sense, and the other for nitrogen which is the envisaged gas to be injected after a LOCA. Both, the design of the proposed devices and their validation are discussed. Finally, a detailed transient analysis, involving usage of both heavy-gas injection and the Brayton device (i.e. of the complete, proposed DHR system), is presented. This serves to illustrate the effectiveness of the new strategy for the highly hypothetical worst-case scenario of sequential failures following a LOCA. (author)

  4. Improved cycling stability of lithium-sulfur batteries using a polypropylene-supported nitrogen-doped mesoporous carbon hybrid separator as polysulfide adsorbent

    Science.gov (United States)

    Balach, Juan; Jaumann, Tony; Klose, Markus; Oswald, Steffen; Eckert, Jürgen; Giebeler, Lars

    2016-01-01

    The lithium/sulfur couple is garnering tremendous interest as the next-generation of cost-efficient rechargeable battery systems capable to fulfill emerging energy storage demands. However, the viable commercialization of lithium-sulfur (Li-S) batteries is still an obstacle by fast capacity fading and poor cycling stability mostly caused by the polysulfide shuttle and active sulfur material loss. In this contribution, we show that the surface modification of the commercial polypropylene separator with a nitrogen-doped mesoporous carbon enhances the interfacial interaction between the N-dopants on carbon-coating and the sulfur-related species by coupling interactions. These unique physical and interfacial chemical properties of the N-doped mesoporous carbon-coating promote the chemical adsorption and confinement of lithium (poly)sulfide intermediates in the cathode side, improving the active material utilization and hence the overall electrochemical performance of Li-S batteries: high initial discharge capacity of 1364 mAh g-1 at 0.2C and notable cycling stability with high reversible capacity of 566 mAh g-1 and negligible degradation rate of 0.037% after 1200 cycles at 0.5C. Furthermore, despite the use of a simple-mixed sulfur-carbon black cathode with high-sulfur loading of 3.95 mg cm-2, the cell with a hybrid separator delivers a high areal capacity of ˜3 mAh cm-2.

  5. A single-ion gel polymer electrolyte system for improving cycle performance of LiMn2O4 battery at elevated temperatures

    International Nuclear Information System (INIS)

    Graphical abstract: - Abstract: The LiMn2O4 based lithium batteries using commercially available electrolytes suffer from poor cycling performance at elevated temperatures (above 55 °C). This is mainly caused by the Mn dissolution generated from HF thermally decomposed from the LiPF6 salt at elevated temperatures. In this paper, a single-ion gel polymer electrolyte (polymeric lithium tartaric acid borate @ poly(vinylidene fluoride-co-hexafluoropropylene) was explored for improving the cycling performance of the LiMn2O4 based lithium battery at elevated temperatures owing to superior thermal stability and comparable ionic conductivity. It was manifested that the Li/LiMn2O4 cells using this single-ion gel polymer electrolyte showed stable charge/discharge voltage profiles, preferable rate capability and excellent cycling performance both at room temperature and elevated temperature of 55 °C. The dissolution of metallic Mn in this electrolyte is significantly suppressed than that of LiPF6 electrolyte. These superior performances could endow this single-ion gel polymer electrolyte a promising alternative to the conventional liquid electrolyte system in the LiMn2O4 battery at elevated temperatures

  6. How To Improve Capacity and Cycling Stability for Next Generation Li-O2 Batteries: Approach with a Solid Electrolyte and Elevated Redox Mediator Concentrations.

    Science.gov (United States)

    Bergner, Benjamin J; Busche, Martin R; Pinedo, Ricardo; Berkes, Balázs B; Schröder, Daniel; Janek, Jürgen

    2016-03-30

    Because of their exceptionally high specific energy, aprotic lithium oxygen (Li-O2) batteries are considered as potential future energy stores. Their practical application is, however, still hindered by the high charging overvoltages and detrimental side reactions. Recently, the use of redox mediators dissolved in the electrolyte emerged as a promising tool to enable charging at moderate voltages. The presented work advances this concept and distinctly improves capacity and cycling stability of Li-O2 batteries by combining high redox mediator concentrations with a solid electrolyte (SE). The use of high redox mediator concentrations significantly increases the discharge capacity by including the oxidation and reduction of the redox mediator into charge cycling. Highly efficient cycling is achieved by protecting the lithium anode with a solid electrolyte, which completely inhibits unfavored deactivation of oxidized species at the anode. Surprisingly, the SE also suppresses detrimental side reactions at the carbon electrode to a large extent and enables stable charging completely below 4.0 V over a prolonged period. It is demonstrated that anode and cathode communicate deleteriously via the liquid electrolyte, which induces degradation reactions at the carbon electrode. The separation of cathode and anode with a SE is therefore considered as a key step toward stable Li-O2 batteries, in conjunction with a concentrated redox mediator electrolyte. PMID:26942895

  7. An advanced oxy-fuel power cycle with high efficiency

    Energy Technology Data Exchange (ETDEWEB)

    Gou, C.; Hong, H. [University of Science and Technology, Beijing (China). Mechanical School; Cai, R. [Chinese Academy of Sciences, Beijing (China). Institute of Engineering Thermophysics

    2006-07-01

    In this article, an innovative oxy-fuel power cycle is proposed as a promising CO{sub 2} emission mitigation solution. It includes two cases with different characteristics in the cycle configuration. Case 1 basically consists of a water steam Rankine cycle and a steam-CO{sub 2} recuperative-reheat cycle. Case 2 integrates some characteristics of Case 1 and a top Brayton cycle. The thermodynamic performances for the design conditions of these two cases were analysed using the advanced process simulator Aspen Plus and the results are given in detail. The corresponding exergy loss analyses were carried out to gain an understanding of the loss distribution. The MATIANT cycle, the CES cycle, and the GRAZ cycle were also evaluated as references. The results demonstrate that the proposed cycle has notable advantages in thermal efficiency, specific work, and technical feasibility compared with the reference cycles. For example, the thermal efficiency of Case 2 is 6.58 percentage points higher than that of the MATIANT cycle. (author)

  8. Can we make cycling healthier? An overview of traffic measures to improve the air quality for cyclists

    International Nuclear Information System (INIS)

    Recent measurements have shown that the concentrations of harmful substances next to the road (e.g. bicycle lanes) can be very high. This article provides an overview of the measures that van be taken to improve the air quality for cyclists.

  9. Combination of acid-resistor and -scavenger improves the SEI stability and cycling ability of tin–nickel battery anodes in LiPF6-containing electrolyte

    International Nuclear Information System (INIS)

    Control of electrode–electrolyte interfacial reactivity and the formation of the solid electrolyte interphase (SEI) layer is a key technology for high performance rechargeable lithium batteries. Here we present the first report on a promising interfacial approach for Sn–Ni electrode that the use of acid-resisting and -scavenging fluorine-dopant on Sn combined with acid-scavenging trimethyl phosphite electrolyte additive to LiPF6-contiaing carbonate-based organic electrolyte improves the interfacial stability of Sn to acidic electrolyte species. As a result, a stable SEI layer consisting of a plenty of carbonate decomposition products forms and cycling ability significantly improves, in contrast to less efficient SEI formation and rapid performance fade for the electrodes without fluorine-dopant or trimethyl phosphite additive

  10. Graphite and fiberglass additives for improving high-rate partial-state-of-charge cycle life of valve-regulated lead-acid batteries

    Energy Technology Data Exchange (ETDEWEB)

    Valenciano, J.; Sanchez, A.; Trinidad, F. [Research and Innovation Center, Exide Technologies, Autovia A-2, Km 42, E-19200 Azuqueca de Henares (Spain); Hollenkamp, A.F. [CSIRO Energy Technology, Bayview Avenue, Clayton, Vic. 3168 (Australia)

    2006-08-25

    In order to accommodate regenerative braking energy input in hybrid and mild hybrid vehicles while maintaining boosting power at high rates of discharge, valve-regulated lead-acid (VRLA) batteries must operate permanently at partial-state-of-charge (PSoC) conditions. As a consequence, new failure modes appear, e.g., irreversible sulfation in negative plates, that have to be overcome. In this way, work has been done to apply some solutions like improving charge acceptance in this 'sulfated medium'. Several batches of 6V 20Ah AGM VRLA batteries with spiral cell design have been assembled and tested, each batch containing novel additives in the negative active material (NAM). It has been observed that the addition of a sufficient amount of expanded graphite significantly improves cycle life under PSoC conditions. Moreover, life duration is also extended, although to a lesser extent, by using a novel fiberglass which increases surface area of NAM. (author)

  11. Graphite and fiberglass additives for improving high-rate partial-state-of-charge cycle life of valve-regulated lead-acid batteries

    Science.gov (United States)

    Valenciano, J.; Sánchez, A.; Trinidad, F.; Hollenkamp, A. F.

    In order to accommodate regenerative braking energy input in hybrid and mild hybrid vehicles while maintaining boosting power at high rates of discharge, valve-regulated lead-acid (VRLA) batteries must operate permanently at partial-state-of-charge (PSoC) conditions. As a consequence, new failure modes appear, e.g., irreversible sulfation in negative plates, that have to be overcome. In this way, work has been done to apply some solutions like improving charge acceptance in this "sulfated medium". Several batches of 6 V 20 Ah AGM VRLA batteries with spiral cell design have been assembled and tested, each batch containing novel additives in the negative active material (NAM). It has been observed that the addition of a sufficient amount of expanded graphite significantly improves cycle life under PSoC conditions. Moreover, life duration is also extended, although to a lesser extent, by using a novel fiberglass which increases surface area of NAM.

  12. Application of the combined cycle LWR-gas turbine to PWR for NPP life extension, safety upgrade and improving economy

    International Nuclear Information System (INIS)

    Full text: The unconventional technology to extend the lifetime for the NPPs now in operation and make a construction of new NPPs cheaper - erection of steam-gas toppings to the nuclear power units - is considered in the paper. Application of the steam-gas toppings permits through reducing power of ageing reactors to extend lifetime of nuclear power unit, enhance its safety and at the same time to keep full load operation of NPP turbine and other balance-of-plant equipment. Proposed technology is examined for Russian VVER-440 reactor as an example and, also, as a pilot project, for Russian boiling VK-50 reactor now in operation Application of the steam-gas topping permits: extend the service life of ageing VVER-440 reactor by 10...15 years; use the turbine and other NPP balance-of-plant equipment at full power; increase the efficiency of combined cycle up to 48% and more; enhance the safety of NPP operation; utilize NPP balance-of-plant equipment after reactor decommissioning; perform the cost-effective operation in maneuvering modes; increase capacity factor of the plant. The construction of pilot project on the basis of the VK-50 reactor will allow not only to demonstrate new technology but also to attain appreciable economic effect including that obtained due to using the available reserves of the NPP turbine. (author)

  13. Improving SFR Economics through Innovations from Thermal Design and Analysis Aspects

    Energy Technology Data Exchange (ETDEWEB)

    Haihua Zhao; Hongbin Zhang; Vincent Mousseau; Per F. Peterson

    2008-06-01

    Achieving economic competitiveness as compared to LWRs and other Generation IV (Gen-IV) reactors is one of the major requirements for large-scale investment in commercial sodium cooled fast reactor (SFR) power plants. Advances in R&D for advanced SFR fuel and structural materials provide key long-term opportunities to improve SFR economics. In addition, other new opportunities are emerging to further improve SFR economics. This paper provides an overview on potential ideas from the perspective of thermal hydraulics to improve SFR economics. These include a new hybrid loop-pool reactor design to further optimize economics, safety, and reliability of SFRs with more flexibility, a multiple reheat and intercooling helium Brayton cycle to improve plant thermal efficiency and reduce safety related overnight and operation costs, and modern multi-physics thermal analysis methods to reduce analysis uncertainties and associated requirements for over-conservatism in reactor design. This paper reviews advances in all three of these areas and their potential beneficial impacts on SFR economics.

  14. Pre-hCG 3D and 3D power Doppler assessment of the follicle for improving pregnancy rates in intrauterine insemination cycles

    Directory of Open Access Journals (Sweden)

    Sonal Panchal

    2009-01-01

    Full Text Available Background: The assessment of follicular maturity at the time of human chorionic gonadotropin (hCG is one of the key factors for the success of all assisted reproductive techniques. Aim: To assess follicles by three dimensional (3D and 3D power Doppler (PD before giving hCG to improve pregnancy rates in intrauterine insemination (IUI cycles. Design: Prospective randomized study. Materials and Methods: Ultrasound for pre-hCG follicular assessment was performed over a period of 10 months for all 1000 cycles of IUI. Follicular assessment was performed using a transvaginal multifrequency volume probe. Follicles considered mature by 2D US and color Doppler were assessed by 3D and 3D PD. These values were independently evaluated for the conception and the non-conception groups. Results: Conception rates were 32.3 and 27% respectively and individually when the perifollicular resistance index was 11 cm/s 10-12 h before hCG. Conception rates of 32% were achieved with a follicular volume between 3 and 7 cc. The conception rate was 32.3% in the cumulus group. A perifollicular vascularity index of between six and 20 gave conception rates of 35% and perifollicular flow index of 27-43 gave conception rates of 33%. Conclusions: 3D ultrasound is much more accurate for volume assessment of the follicle. Presence of cumulus increases the surety of the presence of a mature ovum in the follicle. 3D and 3D PD when used with 2D US and color Doppler for pre-hCG follicular assessment would definitely improve pregnancy rates in IUI cycles.

  15. Exogenous calcium alleviates photoinhibition of PSII by improving the xanthophyll cycle in peanut (Arachis hypogaea leaves during heat stress under high irradiance.

    Directory of Open Access Journals (Sweden)

    Sha Yang

    Full Text Available Peanut is one of the calciphilous plants. Calcium (Ca serves as a ubiquitous central hub in a large number of signaling pathways. The effect of exogenous calcium nitrate [Ca(NO32] (6 mM on the dissipation of excess excitation energy in the photosystem II (PSII antenna, especially on the level of D1 protein and the xanthophyll cycle in peanut plants under heat (40°C and high irradiance (HI (1 200 µmol m(-2 s(-1 stress were investigated. Compared with the control plants [cultivated in 0 mM Ca(NO32 medium], the maximal photochemical efficiency of PSII (Fv/Fm in Ca(2+-treated plants showed a slighter decrease after 5 h of stress, accompanied by higher non-photochemical quenching (NPQ, higher expression of antioxidative genes and less reactive oxygen species (ROS accumulation. Meanwhile, higher content of D1 protein and higher ratio of (A+Z/(V+A+Z were also detected in Ca(2+-treated plants under such stress. These results showed that Ca(2+ could help protect the peanut photosynthetic system from severe photoinhibition under heat and HI stress by accelerating the repair of D1 protein and improving the de-epoxidation ratio of the xanthophyll cycle. Furthermore, EGTA (a chelant of Ca ion, LaCl3 (a blocker of Ca(2+ channel in cytoplasmic membrane, and CPZ [a calmodulin (CaM antagonist] were used to analyze the effects of Ca(2+/CaM on the variation of (A+Z/(V+A+Z (% and the expression of violaxanthin de-epoxidase (VDE. The results indicated that CaM, an important component of the Ca(2+ signal transduction pathway, mediated the expression of the VDE gene in the presence of Ca to improve the xanthophyll cycle.

  16. Improving dosing of gentamicin in the obese patient: a 3-cycle drug chart and case note audit

    OpenAIRE

    Manjaly, Joseph G.; Alexander M. Reece-Smith; Sivaloganathan, Sivan S; Thuraisamy, Christina; Smallwood, Katie LM; Jonas, Elizabeth; Longman, Robert J.

    2012-01-01

    Objectives To assess the use of an electronic dose calculator to improve accuracy in the use of a complex Gentamicin prescription policy and assess turnaround time of blood sampling to dose delivery in an NHS hospital. Design Retrospective review of drug chart, case notes and hospital antibiotic database. Setting University Hospitals Bristol, UK Participants Patients receiving once daily intravenous gentamicin using the trust protocol, during the same time window for 3 consecutive years. Main...

  17. High intensity interval and moderate continuous cycle training in a physical education programme improves health-related fitness in young females.

    Science.gov (United States)

    Mazurek, K; Zmijewski, P; Krawczyk, K; Czajkowska, A; Kęska, A; Kapuściński, P; Mazurek, T

    2016-06-01

    The aim of the study was to investigate the effects of eight weeks of regular physical education classes supplemented with high intensity interval cycle exercise (HIIE) or continuous cycle exercises of moderate intensity (CME). Forty-eight collegiate females exercising in two regular physical education classes per week were randomly assigned to two programmes (HIIE; n = 24 or CME; n = 24) of additional (one session of 63 minutes per week) physical activity for 8 weeks. Participants performed HIIE comprising 2 series of 6x10 s sprinting with maximal pedalling cadence and active recovery pedalling with intensity 65%-75% HRmax or performed CME corresponding to 65%-75% HRmax. Before and after the 8-week programmes, anthropometric data and aero- and anaerobic capacity were measured. Two-way ANOVA revealed a significant time main effect for VO2max (p aerobic and anaerobic capacity in collegiate females. Eight weeks of regular physical education classes supplemented with CME sessions are more effective in improving body composition than physical education classes supplemented with HIIE sessions. In contrast to earlier, smaller trials, similar improvements in aerobic capacity were observed following physical activity with additional HIIE or CME sessions. PMID:27274106

  18. Improved High-rate Performance and Cycling Stability of 1D LiFePO4 Nanorods by a Facile Annealing Process

    Institute of Scientific and Technical Information of China (English)

    WANG Xuefei; WANG Yan; CHENG Lin; WU Jing; YU Huogen; HU Zhijian

    2014-01-01

    To alleviate the main limitations of lithium ion diffusion rate and poor electronic conductivity for LiFePO4 cathode material, it is desirable to synthesize nano-size LiFePO4 material due to its enhanced electronic and lithium ion transport rates and thus an improved high-rate performance. However, our previous synthesized LiFePO4 nanorods only exhibited low high-rate and slightly unstable cycle performance. Possible reasons are the poor crystallization and Fe2+oxidation of LiFePO4 nanorods prepared by hydrothermal method. In this paper, LiFePO4 nanorods were simply dealt with at 700℃for 4 h under the protection of Ar and H2 mixture gas. The electrochemical properties of LiFePO4/Li cells were investigated by galvanostatic test and cyclic voltammetry (CV). The experimental results indicated that the annealed LiFePO4 nanorods delivered an excellent cycling stability and obviously improved capacity of 150 mA·h·g-1 at 1C, and even 122 mA·h·g-1 at 5C.

  19. Final Report: Modifications and Optimization of the Organic Rankine Cycle to Improve the Recovery of Waste Heat

    Energy Technology Data Exchange (ETDEWEB)

    Donna Post Guillen; Jalal Zia

    2013-09-01

    This research and development (R&D) project exemplifies a shared public private commitment to advance the development of energy efficient industrial technologies that will reduce the U.S. dependence upon foreign oil, provide energy savings and reduce greenhouse gas emissions. The purpose of this project was to develop and demonstrate a Direct Evaporator for the Organic Rankine Cycle (ORC) for the conversion of waste heat from gas turbine exhaust to electricity. In conventional ORCs, the heat from the exhaust stream is transferred indirectly to a hydrocarbon based working fluid by means of an intermediate thermal oil loop. The Direct Evaporator accomplishes preheating, evaporation and superheating of the working fluid by a heat exchanger placed within the exhaust gas stream. Direct Evaporation is simpler and up to 15% less expensive than conventional ORCs, since the secondary oil loop and associated equipment can be eliminated. However, in the past, Direct Evaporation has been avoided due to technical challenges imposed by decomposition and flammability of the working fluid. The purpose of this project was to retire key risks and overcome the technical barriers to implementing an ORC with Direct Evaporation. R&D was conducted through a partnership between the Idaho National Laboratory (INL) and General Electric (GE) Global Research Center (GRC). The project consisted of four research tasks: (1) Detailed Design & Modeling of the ORC Direct Evaporator, (2) Design and Construction of Partial Prototype Direct Evaporator Test Facility, (3) Working Fluid Decomposition Chemical Analyses, and (4) Prototype Evaluation. Issues pertinent to the selection of an ORC working fluid, along with thermodynamic and design considerations of the direct evaporator, were identified. The FMEA (Failure modes and effects analysis) and HAZOP (Hazards and operability analysis) safety studies performed to mitigate risks are described, followed by a discussion of the flammability analysis of the

  20. Proposal for an advanced heat source assembly for the Isotope Brayton Power System. Volume 1. Technical program and statement of work

    Energy Technology Data Exchange (ETDEWEB)

    1974-12-09

    The technical program plan for evaluating the performance and safety of a radioisotope-fueled Brayton power system for space vehicles is presented with schedules for evaluating heat source design and safety, for specifying power system requirements, and for the development and operation of a ground demonstration system. (LCL)

  1. Improvement of the decay heat removal characteristics of the generation IV gas-cooled fast reactor

    International Nuclear Information System (INIS)

    containment. Furthermore, different injection locations and injection mass flows were considered, and the sensitivity to the number of available DHR loops and LOCA break-sizes was also addressed. It has been found that injecting the heavy gas in the vicinity of the core could lead to overcooling problems. For an injection point sufficiently far from the core, however, both CO2 and N2 are found to be able to cool the core satisfactorily in natural convection. N2 is proposed as the reference, due to possible chemical problems with CO2. The second proposition for DHR improvement is related to the possibility of a simultaneous guard-containment failure, i.e. a loss-of-back-up-pressure (LOBP) combined with a blower failure after a LOCA. In this case the natural convection, even with heavy gas injection, is no longer strong enough to evacuate the decay heat. To address this issue, the possibility of decay heat removal via use of a dedicated autonomous Brayton cycle - as a standalone DHR loop - has been investigated. First, an analytical Brayton cycle model has been set up, so as to identify convenient machine design points and to study the machine - off-design behavior. Two machine designs have then been drawn up: one for helium in order to provide a reference for understanding the Brayton loop behavior in a generic sense, and the other for nitrogen which is the envisaged gas to be injected after a LOCA. Both, the design of the proposed devices and their validation are discussed. Finally, a detailed transient analysis, involving usage of both heavy-gas injection and the Brayton device (i.e. of the complete, proposed DHR system), is presented. This serves to illustrate the effectiveness of the new strategy for the highly hypothetical worst-case scenario of sequential failures following a LOCA. (author)

  2. A study on the role of grain boundary engineering in promoting high-cycle fatigue resistance and improving reliability in nickel base superalloys for propulsion systems

    Science.gov (United States)

    Gao, Yong

    High-cycle fatigue, involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency (vibratory) loading, remains the principal cause of failures in military gas-turbine propulsion systems. The objective of this study is to examine whether the resistance to high-cycle fatigue failures can be enhanced by grain-boundary engineering, i.e., through the modification of the spatial distribution and topology of the grain boundaries in the microstructure. While grain boundary engineering has been used to obtain significant improvements in intergranular corrosion and cracking, creep and cavitation behavior, toughness and plasticity, cold-work embrittlement, and weldability, only very limited, but positive, results exist for fatigue. Accordingly, using a commercial polycrystalline nickel base gamma/gamma' superalloy, ME3, as a typical engine disk material, sequential thermomechanical processing, involving alternate cycles of strain and annealing, is used to (i) modify the proportion of special grain boundaries, and (ii) interrupt the connectivity of the random boundaries in the grain boundary network. The processed microstructures are then subjected to fracture-mechanics based high cycle fatigue testing to evaluate how the crack initiation and small- and large-crack growth properties are affected and to examine how the altered grain boundary population and connectivity can influence growth rates and overall lifetimes. The effect of such grain-boundary engineering on the fatigue-crack-propagation behavior of large (˜8 to 20 mm), through-thickness cracks at 25, 700, and 800°C was examined. Although there was little influence of an increased special boundary fraction at ambient temperatures, the resistance to near-threshold crack growth was definitively improved at elevated temperatures, with fatigue threshold-stress intensities some 10 to 20% higher than at 25°C, concomitant with a lower proportion (˜20%) of intergranular

  3. Thermodynamic Analysis of Supplementary-Fired Gas Turbine Cycles

    Directory of Open Access Journals (Sweden)

    Bjørn Qvale

    2003-06-01

    Full Text Available

    This paper presents an analysis of the possibilities for improving the efficiency of an indi-rectly biomass-fired gas turbine (IBFGT by supplementary direct gas-firing. The supplementary firing may be based on natural gas, biogas or pyrolysis gas. Intuitively, supplementary firing is expected to result in a high marginal efficiency. The paper shows that depending on the application, this is not always the case.

    The interest in this cycle arises from a recent demonstration of the feasibility of a two-stage gasification process through construction of several plants. The gas from this process could be divided into two streams, one for primary and one for supplementary firing. A preliminary analysis of the ideal, recuperated Brayton cycle shows that for this cycle any supplementary firing will have a marginal efficiency of unity per extra unit of fuel. The same result is obtained for the indirectly fired gas turbine (IFGT and for the supplementary-fired IFGT. These results show that the combination of external firing and internal firing have the potential of reducing or solving some problems associated with the use of biomass both in the recuperated and the indirectly fired gas turbine: The former requires a clean, expensive fuel. The latter is limited in efficiency due to limitations in material temperature of the heat exchanger. Thus, in the case of an IBFGT, it would appear be very appropriate to use a cheap biomass or waste fuel for low temperature combustion and external firing and use natural gas at a high marginal efficiency for high temperature heating. However, it is shown that this is not the case for a simple IBFGT supplementary-fired with natural gas. The marginal efficiency of the natural gas is in this case found to be independent of temperature ratio and lower than for the recuperated gas turbine. Instead, other process changes may be considered in order to obtain a high marginal efficiency on natural gas. Two possibilities

  4. Enamel coated steel reinforcement for improved durability and life-cycle performance of concrete structures: microstructure, corrosion, and deterioration

    Science.gov (United States)

    Tang, Fujian

    This study is aimed (a) to statistically characterize the corrosion-induced deterioration process of reinforced concrete structures (concrete cracking, steel mass loss, and rebar-concrete bond degradation), and (b) to develop and apply three types of enamel-coated steel bars for improved corrosion resistance of the structures. Commercially available pure enamel, mixed enamel with 50% calcium silicate, and double enamel with an inner layer of pure enamel and an outer layer of mixed enamel were considered as various steel coatings. Electrochemical tests were respectively conducted on steel plates, smooth bars embedded in concrete, and deformed bars with/without concrete cover in 3.5 wt.% NaCl or saturated Ca(OH)2 solution. The effects of enamel microstructure, coating thickness variation, potential damage, mortar protection, and corrosion environment on corrosion resistance of the steel members were investigated. Extensive test results indicated that corrosion-induced concrete cracking can be divided into four stages that gradually become less correlated with corrosion process over time. The coefficient of variation of crack width increases with the increasing level of corrosion. Corrosion changed the cross section area instead of mechanical properties of steel bars. The bond-slip behavior between the corroded bars and concrete depends on the corrosion level and distribution of corrosion pits. Although it can improve the chemical bond with concrete and steel, the mixed enamel coating is the least corrosion resistant. The double enamel coating provides the most consistent corrosion performance and is thus recommended to coat reinforcing steel bars for concrete structures applied in corrosive environments. Corrosion pits in enamel-coated bars are limited around damage locations.

  5. A prospective study of power cycles based on the expected sodium fast reactor parameters

    International Nuclear Information System (INIS)

    One of the main issues that has not been solved yet in the frame of Sodium Fast Reactors (SFR) is to choose the most appropriate power conversion system. This paper explores the performance of different power cycles, from traditional to innovative layouts trying to find the optimized solution. Based on the expected reactor parameters (i.e., inlet and outlet coolant temperatures, 395 deg.C and 545 deg.C, respectively), a subcritical Rankine similar to those of fossil power plant cycles has been proposed as a reference layout. Then, alternative layouts based on innovative Rankine and Brayton cycles have been investigated. Two Rankine supercritical layouts have been modeled and analyzed: one of them, adopted from the Supercritical Water Reactor of GIV (one reheater, nine pre-heaters and one moisture separator) and the other similar to some fossil plants (two reheaters, nine pre-heaters with no moisture separator). Simple Brayton cycle configurations based on Helium has been also studied. Several layouts have been modeled to study the effects of: inter-cooling between compression stages, absence of an intermediate loop and coupling of an organic Rankine cycle (ORC). (authors)

  6. Improving cycling performance of Li-rich layered cathode materials through combination of Al2O3-based surface modification and stepwise precycling

    Science.gov (United States)

    Kobayashi, Genki; Irii, Yuta; Matsumoto, Futoshi; Ito, Atsushi; Ohsawa, Yasuhiko; Yamamoto, Shinji; Cui, Yitao; Son, Jin-Young; Sato, Yuichi

    2016-01-01

    Controlling a cathode/electrolyte interface by modifying the surface of a cathode material with metal oxides or phosphates is a concept being explored as a possible strategy for improving the electrochemical performance of such materials. This study therefore looks at the crystal structure and chemical bonding state from bulk to surface of Al2O3-coated Li[Li0.2Ni0.18Co0.03Mn0.58]O2 and explores the influence that surface modification has on the electrochemical performance. Investigation by X-ray diffraction, hard X-ray photoelectron spectroscopy (HAXPES) and galvanostatic charge/discharge reaction reveals that the surface-modification layer is composed of Li-Al oxides and Al oxides, with a LiM1-xAlxO2 (M = transition metal) interlayer formed between the modification layer and Li[Li0.2Ni0.18Co0.03Mn0.58]O2 particles. The cycling performance of the Li-rich layered oxide is enhanced by its surface modification with Al2O3, achieving a discharge capacity of more than 310 mA h-1 and excellent cycling stability at 50 °C when combined with a more gradual Li-insertion/de-insertion process (i.e., stepwise precycling treatment).

  7. One-pot synthesis of a metal–organic framework as an anode for Li-ion batteries with improved capacity and cycling stability

    International Nuclear Information System (INIS)

    Metal–organic framework is a kind of novel electrode materials for lithium ion batteries. Here, a 3D metal–organic framework Co2(OH)2BDC (BDC=1,4-benzenedicarboxylate) was synthesized for the first time by the reaction of Co2+ with a bio-inspired renewable organic ligand 1,4-benzenedicarboxylic acid through a solvothermal method. As an anode material for lithium ion batteries, this material exhibited an excellent cyclic stability as well as a large reversible capacity of ca. 650 mA h g−1 at a current density of 50 mA g−1 after 100 cycles within the voltage range of 0.02–3.0 V, higher than that of other BDC based anode. - Graphical abstract: The PXRD pattern and the cycleability curves (inset) of Co2(OH)2BDC. Display Omitted - Highlights: • Co2(OH)2BDC was synthesized through a one pot solvothermal process. • The solvent had a great effect on the purity of this material. • This material was used as anode material for lithium ion batteries for the first time. • Co2(OH)2BDC showed improved capacity and cycling stability

  8. The production of self-assembled Fe2O3–graphene hybrid materials by a hydrothermal process for improved Li-cycling

    International Nuclear Information System (INIS)

    An easy and effective strategy is developed to produce α-Fe2O3 nanoparticles (NPs) anchored on conducting graphene sheets by a hydrothermal reaction, without any reducing agents. Scanning electron microscopy shows that the α-Fe2O3 NPs are 70–85 nm in size and homogeneously anchored on the graphene sheets. As high-performance anodes for lithium-ion batteries, the obtained material exhibits an excellent reversible capacity of ∼1050 mAh g−1 based on the total mass. Its cycling performance and rate capability are drastically improved, exhibiting a high charge capacity of 1000 ± 50 mAh g−1 with no noticeable capacity fading up to 100 cycles in the voltage range 0.1–3.0 V at 50 mA g−1. These results highlight the importance of the anchoring of NPs on graphene sheets for maximum use of electrochemically active Fe2O3 NPs and graphene for energy storage applications.

  9. The capacity fading mechanism and improvement of cycling stability in MoS2-based anode materials for lithium-ion batteries

    Science.gov (United States)

    Shu, Haibo; Li, Feng; Hu, Chenli; Liang, Pei; Cao, Dan; Chen, Xiaoshuang

    2016-01-01

    Two-dimensional (2D) layered MoS2 nanosheets possess great potential as anode materials for lithium ion batteries (LIBs), but they still suffer from poor cycling performance. Improving the cycling stability of electrode materials depends on a deep understanding of their dynamic structural evolution and reaction kinetics in the lithiation process. Herein, thermodynamic phase diagrams and the lithiation dynamics of MoS2-based nanostructures with the intercalation of lithium ions are studied by using first-principles calculations and ab initio molecular dynamics simulations. Our results demonstrate that the continuous intercalation of Li ions induces structural destruction of 2H phase MoS2 nanosheets in the discharge process that follows a layer-by-layer dissociation mechanism. Meanwhile, the intercalation of Li ions leads to a structural transition of MoS2 nanosheets from the 2H to the 1T phase due to the ultralow transition barriers (~0.1 eV). We find that the phase transition can slow down the dissociation of MoS2 nanosheets during lithiation. The result can be applied to explain extensive experimental observation of the fast capacity fading of MoS2-based anode materials between the first and the subsequent discharges. To suppress the dissociation of MoS2 nanosheets in the lithiation process, we propose a strategy by constructing a sandwich-like graphene/MoS2/graphene structure that indicates high chemical stability, superior conductivity, and high Li-ion mobility in the charge/discharge process, implying the possibility to induce an improvement in the anode cycling performance. This work opens a new route to rational design layered transition-metal disulfide (TMD) anode materials for LIBs with superior cycling stability and electrochemical performance.Two-dimensional (2D) layered MoS2 nanosheets possess great potential as anode materials for lithium ion batteries (LIBs), but they still suffer from poor cycling performance. Improving the cycling stability of

  10. ADVANCED MONITORING TO IMPROVE COMBUSTION TURBINE/COMBINED CYCLE CT/(CC) RELIABILITY, AVAILABILITY AND MAINTAINABILITY (RAM)

    Energy Technology Data Exchange (ETDEWEB)

    Leonard Angello

    2004-03-31

    Power generators are concerned with the maintenance costs associated with the advanced turbines that they are purchasing. Since these machines do not have fully established operation and maintenance (O&M) track records, power generators face financial risk due to uncertain future maintenance costs. This risk is of particular concern, as the electricity industry transitions to a competitive business environment in which unexpected O&M costs cannot be passed through to consumers. These concerns have accelerated the need for intelligent software-based diagnostic systems that can monitor the health of a combustion turbine in real time and provide valuable information on the machine's performance to its owner/operators. EPRI, Impact Technologies, Boyce Engineering, and Progress Energy have teamed to develop a suite of intelligent software tools integrated with a diagnostic monitoring platform that will, in real time, interpret data to assess the ''total health'' of combustion turbines. The Combustion Turbine Health Management System (CTHM) will consist of a series of dynamic link library (DLL) programs residing on a diagnostic monitoring platform that accepts turbine health data from existing monitoring instrumentation. The CTHM system will be a significant improvement over currently available techniques for turbine monitoring and diagnostics. CTHM will interpret sensor and instrument outputs, correlate them to a machine's condition, provide interpretative analyses, project servicing intervals, and estimate remaining component life. In addition, it will enable real-time anomaly detection and diagnostics of performance and mechanical faults, enabling power producers to more accurately predict critical component remaining useful life and turbine degradation.

  11. ADVANCED MONITORING TO IMPROVE COMBUSTION TURBINE/COMBINED CYCLE CT/(CC) RELIABILITY, AVAILABILITY AND MAINTAINABILITY (RAM)

    Energy Technology Data Exchange (ETDEWEB)

    Leonard Angello

    2004-09-30

    Power generators are concerned with the maintenance costs associated with the advanced turbines that they are purchasing. Since these machines do not have fully established operation and maintenance (O&M) track records, power generators face financial risk due to uncertain future maintenance costs. This risk is of particular concern, as the electricity industry transitions to a competitive business environment in which unexpected O&M costs cannot be passed through to consumers. These concerns have accelerated the need for intelligent software-based diagnostic systems that can monitor the health of a combustion turbine in real time and provide valuable information on the machine's performance to its owner/operators. EPRI, Impact Technologies, Boyce Engineering, and Progress Energy have teamed to develop a suite of intelligent software tools integrated with a diagnostic monitoring platform that will, in real time, interpret data to assess the ''total health'' of combustion turbines. The Combustion Turbine Health Management System (CTHM) will consist of a series of dynamic link library (DLL) programs residing on a diagnostic monitoring platform that accepts turbine health data from existing monitoring instrumentation. The CTHM system will be a significant improvement over currently available techniques for turbine monitoring and diagnostics. CTHM will interpret sensor and instrument outputs, correlate them to a machine's condition, provide interpretative analyses, project servicing intervals, and estimate remaining component life. In addition, it will enable real-time anomaly detection and diagnostics of performance and mechanical faults, enabling power producers to more accurately predict critical component remaining useful life and turbine degradation.

  12. Preliminary design and study of the indirect coupled cycle: An innovative option for Gas Fast Reactor

    International Nuclear Information System (INIS)

    Highlights: ► The study concerns an alternative design for a Gas Fast Reactor. ► It assumes that the primary compressors are driven by the secondary turbogenerators. ► 1st interest: no requirement for external energy for driving the compression system. ► Safety advantages: no LOFA (motor failure) and improvement of grace delay for LOCA. - Abstract: The gas cooled fast reactor (GFR) is one of the six reactor concepts selected in the framework of the Generation IV forum. The main characteristics of the CEA GFR concept are a 2400MW core based on a ceramic pin type fuel as a reference, with an inlet temperature of 400 °C and an outlet temperature of 780 °C. The power conversion system is based on an indirect cycle with helium on the primary circuit, a Brayton cycle with a mixture of nitrogen and helium on the secondary circuit and a steam cycle on the tertiary circuit. In depressurised situations, the use of the gas coolant circulation as the main way to remove the decay heat has been selected. A specific system (DHR system) has been designed: it consists of three loops (3 × 100% redundancy) in extension of the pressure vessel, equipped with heat exchangers and blowers. In the current preliminary viability studies, GFR primary compression system relies on three axial blowers (operating in parallel) driven by 3 electrical motors. The present study concerns an alternative design of the primary compression systems, assuming that the 3 primary compressors are driven by the 3 turbogenerators of the secondary circuits. This new system requires that the 3 shafts connecting the turbines and the compressors of the secondary circuits are also connected to their corresponding primary blowers, via longer shafts crossing the primary circuit vessel. This new cycle is the only new element of complexity in this alternative design. This fact should be put in regards of the advantage of no requirement for external energy for driving the compression system (excepting for start

  13. Exergy Analysis of Combined Cycle Power Plant: NTPC Dadri, India

    Directory of Open Access Journals (Sweden)

    Arvind Kumar Tiwari

    2012-12-01

    Full Text Available The aim of the present paper is to exergy analysis of combined Brayton/Rankine power cycle of NTPC Dadri India. Theoretical exergy analysis is carried out for different components of dadri combined cycle power plant which consists of a gas turbine unit, heat recovery steam generator without extra fuel consumption and steam turbine unit. The results pinpoint that more exergy losses occurred in the gas turbine combustion chamber. Its reached 35% of the total exergy losses while the exergy losses in other plant components are between 7% -21% of the total exergy losses at 1400o C turbine inlet temperature and pressure ratio 10 .This paper also considered the effect of the pressure ratio, turbine inlet temperature, pressure drop in combustion chamber and heat recovery steam generator on the exergy losses in the plant, there are a clear effects in the exergy losses when changing pressure ratio, turbine inlet temperature.

  14. Evaluation of technical feasibility of closed-cycle non-equilibrium MHD power generation with direct coal firing. Final report, Task I

    Energy Technology Data Exchange (ETDEWEB)

    1981-11-01

    Program accomplishments in a continuing effort to demonstrate the feasibility of direct coal-fired, closed-cycle MHD power generation are reported. This volume contains the following appendices: (A) user's manual for 2-dimensional MHD generator code (2DEM); (B) performance estimates for a nominal 30 MW argon segmented heater; (C) the feedwater cooled Brayton cycle; (D) application of CCMHD in an industrial cogeneration environment; (E) preliminary design for shell and tube primary heat exchanger; and (F) plant efficiency as a function of output power for open and closed cycle MHD power plants. (WHK)

  15. Integration of BpMADS4 on various linkage groups improves the utilization of the rapid cycle breeding system in apple.

    Science.gov (United States)

    Weigl, Kathleen; Wenzel, Stephanie; Flachowsky, Henryk; Peil, Andreas; Hanke, Magda-Viola

    2015-02-01

    Rapid cycle breeding in apple is a new approach for the rapid introgression of agronomically relevant traits (e.g. disease resistances) from wild apple species into domestic apple cultivars (Malus × domestica Borkh.). This technique drastically shortens the long-lasting juvenile phase of apple. The utilization of early-flowering apple lines overexpressing the BpMADS4 gene of the European silver birch (Betula pendula Roth.) in hybridization resulted in one breeding cycle per year. Aiming for the selection of non-transgenic null segregants at the end of the breeding process, the flower-inducing transgene and the gene of interest (e.g. resistance gene) that will be introgressed by hybridization need to be located on different chromosomes. To improve the flexibility of the existing approach in apple, this study was focused on the development and characterization of eleven additional BpMADS4 overexpressing lines of four different apple cultivars. In nine lines, the flowering gene was mapped to different linkage groups. The differences in introgressed T-DNA sequences and plant genome deletions post-transformation highlighted the unique molecular character of each line. However, transgenic lines demonstrated no significant differences in flower organ development and pollen functionality compared with non-transgenic plants. Hybridization studies using pollen from the fire blight-resistant wild species accession Malus fusca MAL0045 and the apple scab-resistant cultivar 'Regia' indicated that BpMADS4 introgression had no significant effect on the breeding value of each transgenic line. PMID:25370729

  16. Characteristics of gas-cooled reactor with water moderator and rankine cycle

    International Nuclear Information System (INIS)

    Full text: Nuclear energy with both thermal and fast neutrons, despite on a number of potential benefits, will economically lose energy on organic fuels, if innovative solutions won't be found. It is presented a gas-cooled channel reactor with water-moderator, working on a piston Brayton cycle engine. Efficiency up to 45 percent is achieved. Thermophysical calculations of fuel assemblies show that the proposed reactor fuel assemblies can be constructed in a simplified scheme without heat shield that reduces the creation costs, the costs of coolant pumping, loss of neutrons and dimensions of the core

  17. Development of cooling system for 66/6.9kV-20MVA REBCO superconducting transformers with Ne turbo-Brayton refrigerator and subcooled liquid nitrogen

    Science.gov (United States)

    Iwakuma, M.; Adachi, K.; Yun, K.; Yoshida, K.; Sato, S.; Suzuki, Y.; Umeno, T.; Konno, M.; Hayashi, H.; Eguchi, T.; Izumi, T.; Shiohara, Y.

    2015-12-01

    We developed a turbo-Brayton refrigerator with Ne gas as a working fluid for a 3 ϕ- 66/6.9kV-2MVA superconducting transformer with coated conductors which was bath-cooled with subcooled LN2. The two-stage compressor and expansion turbine had non-contact magnetic bearings for a long maintenance interval. In the future, we intend to directly install a heat exchanger into the Glass-Fiber-Reinforced-Plastics cryostat of a transformer and make a heat exchange between the working fluid gas and subcooled LN2. In this paper we investigate the behaviour of subcooled LN2 in a test cryostat, in which heater coils were arranged side by side with a flat plate finned-tube heat exchanger. Here a He turbo-Brayton refrigerator was used as a substitute for a Ne turbo-Brayton one. The pressure at the surface of LN2 in the cryostat was one atmosphere. Just under the LN2 surface, a stationary layer of LN2 was created over the depth of 20 cm and temperature dropped from 77 K to 65 K with depth while, in the lower level than that, a natural convection flow of LN2 was formed and temperature was almost uniform over 1 m depth. The boundary plane between the stationary layer and the natural convection region was visible.

  18. Improving the reliability of open-cycle water systems: Application of biofouling surveillance and control techniques to sediment and corrosion fouling at nuclear power plants

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, K.I.; Neitzel, D.A.

    1987-03-01

    Biofouling surveillance and control techniques are evaluated for their applicability to sediment and corrosion fouling and suggestions are given to improve their effectiveness. Alternate techniques to better detect and control sedimentation and corrosion are also evaluated. Environmental conditions that allow biofouling, sedimentation, and corrosion to occur are summarized. A correlation between sediment and corrosion is identified and the causes are described. Environmental regulations, especially those in the Clean Water Act of 1977, are reviewed to identify those that may limit or prevent the use of surveillance and control techniques described in this report. Flow velocity is the major design factor that determines whether or not biofouling, sedimentation, and corrosion will occur. Monitoring flow conditions can provide early warning of conditions that will allow fouling to occur. Visual inspection is the most common and most effective technique for identifying the cause and extent of fouling in the open-cycle water system. Most biofouling control techniques in current use are not effective against sediment and corrosion. Frequent, high-velocity flushing of cooling loops may effectively remove sediment and reduce under-sediment corrosion. Alternate biocide treatments such as targeted chlorination or the use of ozone or 2,2-dibromo-3-nitrilo propionamide (DBNPA) may also be effective in reducing under-sediment corrosion.

  19. Improving the reliability of open-cycle water systems: Application of biofouling surveillance and control techniques to sediment and corrosion fouling at nuclear power plants

    International Nuclear Information System (INIS)

    Biofouling surveillance and control techniques are evaluated for their applicability to sediment and corrosion fouling and suggestions are given to improve their effectiveness. Alternate techniques to better detect and control sedimentation and corrosion are also evaluated. Environmental conditions that allow biofouling, sedimentation, and corrosion to occur are summarized. A correlation between sediment and corrosion is identified and the causes are described. Environmental regulations, especially those in the Clean Water Act of 1977, are reviewed to identify those that may limit or prevent the use of surveillance and control techniques described in this report. Flow velocity is the major design factor that determines whether or not biofouling, sedimentation, and corrosion will occur. Monitoring flow conditions can provide early warning of conditions that will allow fouling to occur. Visual inspection is the most common and most effective technique for identifying the cause and extent of fouling in the open-cycle water system. Most biofouling control techniques in current use are not effective against sediment and corrosion. Frequent, high-velocity flushing of cooling loops may effectively remove sediment and reduce under-sediment corrosion. Alternate biocide treatments such as targeted chlorination or the use of ozone or 2,2-dibromo-3-nitrilo propionamide (DBNPA) may also be effective in reducing under-sediment corrosion

  20. Improvement of Cycling Performance of Lithium-Sulfur Batteries by Using Magnesium Oxide as a Functional Additive for Trapping Lithium Polysulfide.

    Science.gov (United States)

    Ponraj, Rubha; Kannan, Aravindaraj G; Ahn, Jun Hwan; Kim, Dong-Won

    2016-02-17

    Trapping lithium polysulfides formed in the sulfur positive electrode of lithium-sulfur batteries is one of the promising approaches to overcome the issues related to polysulfide dissolution. In this work, we demonstrate that intrinsically hydrophilic magnesium oxide (MgO) nanoparticles having surface hydroxyl groups can be used as effective additives to trap lithium polysulfides in the positive electrode. MgO nanoparticles were uniformly distributed on the surface of the active sulfur, and the addition of MgO into the sulfur electrode resulted in an increase in capacity retention of the lithium-sulfur cell compared to a cell with pristine sulfur electrode. The improvement in cycling stability was attributed to the strong chemical interactions between MgO and lithium polysulfide species, which suppressed the shuttling effect of lithium polysulfides and enhanced the utilization of the sulfur active material. To the best of our knowledge, this report is the first demonstration of MgO as an effective functional additive to trap lithium polysulfides in lithium-sulfur cells. PMID:26808673

  1. Analysis and design of a high-linearity receiver RF front-end with an improved 25%-duty-cycle LO generator for WCDMA/GSM applications

    Institute of Scientific and Technical Information of China (English)

    胡嵩; 李伟男; 黄煜梅; 洪志良

    2012-01-01

    A fully integrated receiver RF front-end that meets WCDMA/GSM system requirements is presented.It supports SAW-less operation for WCDMA.To improve the linearity in terms of both IP3 and IP2,the RF front-end is comprised of multiple-gated LNAs with capacitive desensitization,current-mode passive mixers with the proposed IP2 calibration circuit and reconfigurable Tow-Thomas-like biquad TIAs.A new power-saving multi-mode divider with low phase noise is proposed to provide the 4-phase 25%-duty-cycle LO.In addition,a constant-gm biasing with an on-chip resistor is adopted to make the conversion gain invulnerable to the process and temperature variations of the transimpedance.This RF front-end is integrated in a receiver with an on-chip frequency synthesizer in 0.13 μm CMOS.The measurement results show that owing to this high-linearity RF front-end,the receiver achieves -6 dBm IIP3 and better than +60 dBm IIP2 for all modes and bands.

  2. Analysis and design of a high-linearity receiver RF front-end with an improved 25%-duty-cycle LO generator for WCDMA/GSM applications

    International Nuclear Information System (INIS)

    A fully integrated receiver RF front-end that meets WCDMA/GSM system requirements is presented. It supports SAW-less operation for WCDMA. To improve the linearity in terms of both IP3 and IP2, the RF front-end is comprised of multiple-gated LNAs with capacitive desensitization, current-mode passive mixers with the proposed IP2 calibration circuit and reconfigurable Tow-Thomas-like biquad TIAs. A new power-saving multi-mode divider with low phase noise is proposed to provide the 4-phase 25%-duty-cycle LO. In addition, a constant-gm biasing with a non-chip resistor is adopted to make the conversion gain invulnerable to the process and temperature variations of the transimpedance. This RF front-end is integrated in a receiver with an on-chip frequency synthesizer in 0.13 μm CMOS. The measurement results show that owing to this high-linearity RF front-end, the receiver achieves −6 dBm IIP3 and better than +60 dBm IIP2 for all modes and bands. (semiconductor integrated circuits)

  3. Design of Cycle 3 of the National Water-Quality Assessment Program, 2013-23: Part 2: Science plan for improved water-quality information and management

    Science.gov (United States)

    Rowe, Gary L.; Belitz, Kenneth; Demas, Charlie R.; Essaid, Hedeff I.; Gilliom, Robert J.; Hamilton, Pixie A.; Hoos, Anne B.; Lee, Casey J.; Munn, Mark D.; Wolock, David W.

    2013-01-01

    This report presents a science strategy for the third decade of the National Water-Quality Assessment (NAWQA) Program, which since 1991, has been responsible for providing nationally consistent information on the quality of the Nation's streams and groundwater; how water quality is changing over time; and the major natural and human factors that affect current water quality conditions and trends. The strategy is based on an extensive evaluation of the accomplishments of NAWQA over its first two decades, the current status of water-quality monitoring activities by USGS and its partners, and an updated analysis of stakeholder priorities. The plan is designed to address priority issues and national needs identified by NAWQA stakeholders and the National Research Council (2012) irrespective of budget constraints. This plan describes four major goals for the third decade (Cycle 3), the approaches for monitoring, modeling, and scientific studies, key partnerships required to achieve these goals, and products and outcomes that will result from planned assessment activities. The science plan for 2013–2023 is a comprehensive approach to meet stakeholder priorities for: (1) rebuilding NAWQA monitoring networks for streams, rivers, and groundwater, and (2) upgrading models used to extrapolate and forecast changes in water-quality and stream ecosystem condition in response to changing climate and land use. The Cycle 3 plan continues approaches that have been central to the Program’s long-term success, but adjusts monitoring intensities and study designs to address critical information needs and identified data gaps. Restoration of diminished monitoring networks and new directions in modeling and interpretative studies address growing and evolving public and stakeholder needs for water-quality information and improved management, particularly in the face of increasing challenges related to population growth, increasing demands for water, and changing land use and climate

  4. An important feature of air heat pump cycle: Heating capacity in line with heating load

    International Nuclear Information System (INIS)

    In the conventional vapor-compression heat pumps, the heating capacity and the heating load usually vary in opposite directions, which results in a mismatch of the heating capacity and the heating load at off-design conditions. Air (reversed Brayton) cycle is a potential substitute for the conventional vapor-compression cycles. This paper proved that in theory the air heat pump cycle can make the heating capacity in line with the heating load at a stable level of heating COP (coefficient of performance). A thermodynamic model for the air heat pump cycle with practical compressor and expander was developed. The optimal heating COP and the corresponding pressure ratio were derived from the model. Then the cycle performance was analytically expressed under the optimal COP conditions. The heating capacity under different operating conditions was found in line with the heating load. Comparisons between the air heat pump cycle and two typical vapor-compression heat pump cycles were numerically done for further verification. It also turned out that the energy efficiency of air heat pump is comparable to the transcritical CO2 heat pump, particularly at large temperature difference. - Highlights: • We developed a thermodynamic model for air heat pump cycle. • The optimal COP (coefficient of performance) was derived and the corresponding cycle performance was analyzed. • Comparison of air heat pump cycle and vapor-compression cycles was numerically done. • We proved air heat pump cycle can make heating capacity in line with heating load

  5. Biogeochemical Cycling

    Science.gov (United States)

    Bebout, Brad; Fonda, Mark (Technical Monitor)

    2002-01-01

    This lecture will introduce the concept of biogeochemical cycling. The roles of microbes in the cycling of nutrients, production and consumption of trace gases, and mineralization will be briefly introduced.

  6. Sulfur cycle

    Digital Repository Service at National Institute of Oceanography (India)

    LokaBharathi, P.A.

    Microbes, especially bacteria, play an important role in oxidative and reductive cycle of sulfur. The oxidative part of the cycle is mediated by photosynthetic bacteria in the presence of light energy and chemosynthetic forms in the absence of light...

  7. Carbon dioxide direct cycle modular reactor

    International Nuclear Information System (INIS)

    Recently, as the micro gas-turbine power generation is clean for environment and has high convenience, it is focused as a small size dispersion electric source for super markets, hospitals, factories, and so on. And, a modular high temperature gas reactor (PBMR) adopting the gas turbine is also focused recently, and is progressed on its construction in South Africa and reported on construction plan of the Exelon Inc. in U.S.A. PBMR has specific safety for a small size and pebble-bed reactor and also has some characters on low construction cost similar to that of LWR due to simplification and small size module adoption of its plant. The PBMR uses helium for its coolants, of which exit temperature is set for at 900degC to get higher thermal efficiency. This is because of its adoption of Brayton cycle to fast reduce the efficiency with falling temperature. However, as helium is a costly and easy-emission vapor, it is desired to alternate to cheaper and more difficult-emission vapor. Here were introduced on carbon dioxide (CO2) direct cycle using carbon dioxide with extremely higher thermal efficiency than helium and its applicability to nuclear reactors. (G.K.)

  8. A preliminary assessment of reactor candidate technologies for a 20 kWe space nuclear Brayton system

    International Nuclear Information System (INIS)

    In 1983, a cooperative program between the French Centre National d'Etudes Spaciales (CNES) and the Commissariat a l'Energie Atomique (CEA) was initiated to investigate the possible development of 20 to 200 kWe Brayton nuclear space systems. After the completion of the preliminary design of a reference 200 kWe turboelectric power system known as ERATO in 1986 (Carre et al. 1987), a second 3-year study phase was initiated. The objective of this phase was to assess the various reactor candidate technologies and system design options for 20 kWe power level for meeting the projected electric needs of the first European space missions (Carre et al. 1988). This paper presents the results of the design studies of three reference design concepts of 20 kWe turboelectric power systems covering a wide range of reactor temperatures and relevant material and reactor design technologies. Additionally the critical technology issues of the candidate systems, and other criteria relevant to the space missions are identified. The participation of the French industry in the present design activity is so far restricted to predesign studies of crucial components such as the turbomachinery and the reactor control actuators, and integration studies of the power system into the Ariane V launcher

  9. Exergoeconomic performance optimization of an endoreversible intercooled regenerated Brayton cogeneration plant. Part 2: Heat conductance allocation and pressure ratio optimization

    Directory of Open Access Journals (Sweden)

    Bo Yang, Lingen Chen, Fengrui Sun

    2011-03-01

    Full Text Available Finite time exergoeconomic performance of an endoreversible intercooled regenerative Brayton cogeneration plant is optimized based on the model which is established using finite time thermodynamic in Part 1 of this paper. It is found that the optimal heat conductance allocation of the regenerator is zero. When the total pressure ratio and the heat conductance allocation of the regenerator are fixed, it is shown that there exist an optimal intercooling pressure ratio, and a group of optimal heat conductance allocations among the hot-, cold- and consumer-side heat exchangers and the intercooler, which correspond to a maximum dimensionless profit rate. When the total pressure ratio is variable, there exists an optimal total pressure ratio which corresponds to a double-maximum dimensionless profit rate, and the corresponding exergetic efficiency is obtained. The effects of the total heat exchanger conductance, price ratios and the consumer-side temperature on the double-maximum dimensionless profit rate and the corresponding exergetic efficiency are discussed. It is found that there exists an optimal consumer-side temperature which corresponds to a thrice-maximum dimensionless profit rate.

  10. [Cycling in Zagreb].

    Science.gov (United States)

    Matos, Stipan; Krapac, Ladislav; Krapac, Josip

    2007-01-01

    Cycling in Zagreb, as means of urban transport inside and outside the city, has a bright past, hazy presence but a promising future. Every day, aggressive citizens who lack urban traffic culture mistreat many cyclists but also many pedestrians. Sedentary way of living, unhealthy eating habits and inadequate recreation would surely be reduced if Zagreb had a network of cycling tracks (190 cm) or lanes (80 cm). Main city roads were constructed at the beginning of the 20th century. Today, the lack of cycling tracks is particularly evident in terms of missing connections between northern and southern parts of the city. Transportation of bikes in public vehicles, parking of bikes as well as cycling along the foot of the mountains Medvednica and Zumberacko gorje is not adequately organized. Better organization is necessary not only because of the present young generation but also because of the young who will shortly become citizens of the EU, where cycling is enormously popular. Cycling tourism is not known in Zagreb, partly due to inadequate roads. The surroundings of Zagreb are more suitable for cycling tourism and attractive brochures and tourist guides offer information to tourists on bikes. Professional, acrobatic and sports cycling do not have a tradition in Zagreb and in Croatia. The same holds true for recreational cycling and indoor exercise cycling. The authors discuss the impact of popularization of cycling using print and electronic media. The role of district and local self-government in the construction and improvement of traffic roads in Zagreb is very important. It is also significant for the implementation of legal regulations that must be obeyed by all traffic participants in order to protect cyclists, the most vulnerable group of traffic participants besides passengers. Multidisciplinary action of all benevolent experts would surely increase safety and pleasure of cycling in the city and its surroundings. This would also help reduce daily stress and

  11. Power, efficiency, entropy-generation rate and ecological optimization for a class of generalized irreversible universal heat-engine cycles

    International Nuclear Information System (INIS)

    The optimal performance for a class of generalized irreversible universal steady-flow heat-engine cycle models, consisting of two heating branches, two cooling branches and two adiabatic branches, and with losses due to heat-resistance, heat leaks and internal irreversibility was analyzed using finite-time thermodynamics. The analytical formulae for power, efficiency, entropy-generation rate and an ecological criterion of the irreversible heat-engine cycle are derived. Moreover, analysis and optimization of the model were carried out in order to investigate the effect of the cycle process on the performance of the cycles. The results obtained include the performance characteristics of Diesel, Otto, Brayton, Atkinson, Dual and Miller cycles with the losses of heat-resistance, heat leak and internal irreversibility

  12. A biofeedback cycling training to improve locomotion: a case series study based on gait pattern classification of 153 chronic stroke patients

    Directory of Open Access Journals (Sweden)

    Molteni Franco

    2011-08-01

    Full Text Available Abstract Background The restoration of walking ability is the main goal of post-stroke lower limb rehabilitation and different studies suggest that pedaling may have a positive effect on locomotion. The aim of this study was to explore the feasibility of a biofeedback pedaling treatment and its effects on cycling and walking ability in chronic stroke patients. A case series study was designed and participants were recruited based on a gait pattern classification of a population of 153 chronic stroke patients. Methods In order to optimize participants selection, a k-means cluster analysis was performed to subgroup homogenous gait patterns in terms of gait speed and symmetry. The training consisted of a 2-week treatment of 6 sessions. A visual biofeedback helped the subjects in maintaining a symmetrical contribution of the two legs during pedaling. Participants were assessed before, after training and at follow-up visits (one week after treatment. Outcome measures were the unbalance during a pedaling test, and the temporal, spatial, and symmetry parameters during gait analysis. Results and discussion Three clusters, mainly differing in terms of gait speed, were identified and participants, representative of each cluster, were selected. An intra-subject statistical analysis (ANOVA showed that all patients significantly decreased the pedaling unbalance after treatment and maintained significant improvements with respect to baseline at follow-up. The 2-week treatment induced some modifications in the gait pattern of two patients: one, the most impaired, significantly improved mean velocity and increased gait symmetry; the other one reduced significantly the over-compensation of the healthy limb. No benefits were produced in the gait of the last subject who maintained her slow but almost symmetrical pattern. Thus, this study might suggest that the treatment can be beneficial for patients having a very asymmetrical and inefficient gait and for those

  13. Miniature Turbine for Pulse-Tube/Reverse-Brayton Hybrid Cryocooler Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Many future advances in NASA's ability to perform cutting edge space science will require improvements in cryogenic system technology, including the development of...

  14. Supercritical CO2 direct cycle Gas Fast Reactor (SC-GFR) concept.

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven Alan; Parma, Edward J., Jr.; Suo-Anttila, Ahti Jorma (Computational Engineering Analysis, Albuquerque, NM); Al Rashdan, Ahmad (Texas A& M University, College Station, TX); Tsvetkov, Pavel Valeryevich (Texas A& M University, College Station, TX); Vernon, Milton E.; Fleming, Darryn D.; Rochau, Gary Eugene

    2011-05-01

    This report describes the supercritical carbon dioxide (S-CO{sub 2}) direct cycle gas fast reactor (SC-GFR) concept. The SC-GFR reactor concept was developed to determine the feasibility of a right size reactor (RSR) type concept using S-CO{sub 2} as the working fluid in a direct cycle fast reactor. Scoping analyses were performed for a 200 to 400 MWth reactor and an S-CO{sub 2} Brayton cycle. Although a significant amount of work is still required, this type of reactor concept maintains some potentially significant advantages over ideal gas-cooled systems and liquid metal-cooled systems. The analyses presented in this report show that a relatively small long-life reactor core could be developed that maintains decay heat removal by natural circulation. The concept is based largely on the Advanced Gas Reactor (AGR) commercial power plants operated in the United Kingdom and other GFR concepts.

  15. Design of organic Rankine cycle power systems accounting for expander performance

    DEFF Research Database (Denmark)

    La Seta, Angelo; Andreasen, Jesper Graa; Pierobon, Leonardo;

    2015-01-01

    Organic Rankine cycle power systems have recently emerged as promising solutions for waste heat recovery in low- and medium-size power plants. Their performance and economic feasibility strongly depend on the expander. Its design process and efficiency estimation are particularly challenging due to...... the peculiar physical properties of the working fluid and the gasdynamic phenomena occurring in the machine. Unlike steam Rankine and Brayton engines, organic Rankine cycle expanders have to deal with small enthalpy drops and large expansion ratios. These features yield turbine designs with few highly......-loaded stages in supersonic flow regimes. This paper proposes a design method where the conventional cycle analysis is combined with calculations of the maximum expander performance using a validated mean-line design tool. The high computational cost of the turbine optimization is tackled building a model which...

  16. 90-Day Cycle Handbook

    Science.gov (United States)

    Park, Sandra; Takahashi, Sola

    2013-01-01

    90-Day Cycles are a disciplined and structured form of inquiry designed to produce and test knowledge syntheses, prototyped processes, or products in support of improvement work. With any type of activity, organizations inevitably encounter roadblocks to improving performance and outcomes. These barriers might include intractable problems at…

  17. Improve Supply Chain Sustainability Using Life Cycle Management%供应链可持续发展改进的工具一生命周期管理

    Institute of Scientific and Technical Information of China (English)

    罗卫

    2011-01-01

    Through case studies, this paper introduces the concept of life-cycle management, analyzes life-cycle management protocols under different scenarios, compares the current use of the different life cycle management tools as well as their advantages and disadvantages compared to the traditional environmental management instruments, and stresses that life cycle management is an important alternative approach to improving the sustainability of products and materials within supply chains. Based on the ahove discussion, the paper finds that different supply chain members will have different choices in life-cycle management tools. In spite of the considerable progress made with regard to their application in extensive supply chains, life cycle management tools still need development and improvement for their management protocols.%通过案例研究,引入了生命周期管理的概念,分析了不同情况下的生命周期管理协议,比较了目前使用的不同生命周期管理工具的优势和劣势,对比传统环境管理工具,强调了生命周期管理工具在改进供应链中产品和材料的可持续性方面是一个重要的替代办法.基于上述讨论,发现不同的供应链成员会选择不同生命周期管理工具,尽管其在较长的供应链中已取得很大进展,现在仍需要对各种生命周期管理的管理协议加以完善.

  18. Exfoliation Propensity of Oxide Scale in Heat Exchangers Used for Supercritical CO2 Power Cycles

    Energy Technology Data Exchange (ETDEWEB)

    Sabau, Adrian S [ORNL; Shingledecker, John P. [Electric Power Research Institute (EPRI); Kung, Steve [Electric Power Research Institute (EPRI); Wright, Ian G. [WrightHT, Inc.; Nash, Jim [Brayton Energy, LLC, Hampton, NH

    2016-01-01

    Supercritical CO2 (sCO2) Brayton cycle systems offer the possibility of improved efficiency in future fossil energy power generation plants operating at temperatures of 650 C and above. As there are few data on the oxidation/corrosion behavior of structural alloys in sCO2 at these temperatures, modeling to predict the propensity for oxide exfoliation is not well developed, thus hindering materials selection for these novel cycles. The ultimate goal of this effort is to provide needed data on scale exfoliation behavior in sCO2 for confident alloy selection. To date, a model developed by ORNL and EPRI for the exfoliation of oxide scales formed on boiler tubes in high-temperature, high-pressure steam has proven useful for managing exfoliation in conventional steam plants. A major input provided by the model is the ability to predict the likelihood of scale failure and loss based on understanding of the evolution of the oxide morphologies and the conditions that result in susceptibility to exfoliation. This paper describes initial steps taken to extend the existing model for exfoliation of steam-side oxide scales to sCO2 conditions. The main differences between high-temperature, high-pressure steam and sCO2 that impact the model involve (i) significant geometrical differences in the heat exchangers, ranging from standard pressurized tubes seen typically in steam-producing boilers to designs for sCO2 that employ variously-curved thin walls to create shaped flow paths for extended heat transfer area and small channel cross-sections to promote thermal convection and support pressure loads; (ii) changed operating characteristics with sCO2 due to the differences in physical and thermal properties compared to steam; and (iii) possible modification of the scale morphologies, hence properties that influence exfoliation behavior, due to reaction with carbon species from sCO2. The numerical simulations conducted were based on an assumed sCO2 operating schedule and several

  19. Cycling more for safer cycling

    OpenAIRE

    VAN HOUT, Kurt

    2009-01-01

    Cycling presents a lot of benefits to the individual and to society. Health, environment, accessibility, local businesses, … all gain when more people cycle. Yet many governments are reluctant when it comes to promoting cycling, mainly because of (perceived) safety issues. Since studies have established a clear and consistent relationship between bicycle use and cyclist accident risk, this lack of bicycle promotion will influence the safety outcome of bicyclists. In this paper the relation be...

  20. Cycling injuries.

    OpenAIRE

    Cohen, G. C.

    1993-01-01

    Bicycle-related injuries have increased as cycling has become more popular. Most injuries to recreational riders are associated with overuse or improper fit of the bicycle. Injuries to racers often result from high speeds, which predispose riders to muscle strains, collisions, and falls. Cyclists contact bicycles at the pedals, seat, and handlebars. Each is associated with particular cycling injuries.