Control system options and strategies for supercritical CO2 cycles

International Nuclear Information System (INIS)

Moisseytsev, A.; Kulesza, K.P.; Sienicki, J.J.

2009-01-01

The Supercritical Carbon Dioxide (S-CO 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 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 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 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 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 2 Brayton Cycle energy converter incorporating an axial flow turbine and compressors, investigations of the S-CO 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 2 Brayton Cycle. Steady state calculations demonstrate the wider operating range of centrifugal compressors versus axial compressors installed in a S-CO 2 Brayton Cycle as well as the benefits in expanding the range

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

International Nuclear Information System (INIS)

Seo, Seok Bin; Seo, Han; Bang, In Cheol

2014-01-01

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 CO 2 (S-CO 2 ). However, S-CO 2 still has potential for reaction with sodium. CO 2 -sodium reaction produces solid product, which has possibility to have an auto ignition reaction around 600 .deg. C. Thus, instead of S-CO 2 , 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

Corrosion of Structural Materials for Advanced Supercritical Carbon- Dioxide Brayton Cycle

Energy Technology Data Exchange (ETDEWEB)

Sridharan, Kumar [Univ. of Wisconsin, Madison, WI (United States)

2017-05-13

The supercritical carbon-dioxide (referred to as SC-CO₂ hereon) Brayton cycle is being considered for power conversion systems for a number of nuclear reactor concepts, including the sodium fast reactor (SFR), fluoride saltcooled high temperature reactor (FHR), and high temperature gas reactor (HTGR), and several types of small modular reactors (SMR). The SC-CO₂ direct cycle gas fast reactor has also been recently proposed. The SC-CO₂ Brayton cycle (discussed in Chapter 1) provides higher efficiencies compared to the Rankine steam cycle due to less compression work stemming from higher SC-CO₂ densities, and allows for smaller components size, fewer components, and simpler cycle layout. For example, in the case of a SFR using a SC-CO₂ Brayton cycle instead of a steam cycle would also eliminate the possibility of sodium-water interactions. The SC-CO₂ cycle has a higher efficiency than the helium Brayton cycle, with the additional advantage of being able to operate at lower temperatures and higher pressures. In general, the SC-CO₂ Brayton cycle is well-suited for any type of nuclear reactor (including SMR) with core outlet temperature above ~ 500°C in either direct or indirect versions. In all the above applications, materials corrosion in high temperature SC-CO₂ is an important consideration, given their expected lifetimes of 20 years or longer. Our discussions with National Laboratories and private industry early on in this project indicated materials corrosion to be one of the significant gaps in the implementation of SC-CO₂ Brayton cycle. Corrosion can lead to a loss of effective load-bearing wall thickness of a component and can potentially lead to the generation of oxide particulate debris which can lead to three-body wear in turbomachinery components. Another environmental degradation effect that is rather unique to CO₂ environment is the possibility

Dry Air Cooler Modeling for Supercritical Carbon Dioxide Brayton Cycle Analysis

Energy Technology Data Exchange (ETDEWEB)

Moisseytsev, A. [Argonne National Lab. (ANL), Argonne, IL (United States); Sienicki, J. J. [Argonne National Lab. (ANL), Argonne, IL (United States); Lv, Q. [Argonne National Lab. (ANL), Argonne, IL (United States)

2016-07-28

Modeling for commercially available and cost effective dry air coolers such as those manufactured by Harsco Industries has been implemented in the Argonne National Laboratory Plant Dynamics Code for system level dynamic analysis of supercritical carbon dioxide (sCO₂) Brayton cycles. The modeling can now be utilized to optimize and simulate sCO₂ Brayton cycles with dry air cooling whereby heat is rejected directly to the atmospheric heat sink without the need for cooling towers that require makeup water for evaporative losses. It has sometimes been stated that a benefit of the sCO₂ Brayton cycle is that it enables dry air cooling implying that the Rankine steam cycle does not. A preliminary and simple examination of a Rankine superheated steam cycle and an air-cooled condenser indicates that dry air cooling can be utilized with both cycles provided that the cycle conditions are selected appropriately

A Conceptual Study of Using an Isothermal Compressor on a Supercritical CO{sub 2} Brayton Cycle for SMART Application

Energy Technology Data Exchange (ETDEWEB)

Heo, Jin Young; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Ahn, Yoonhan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

To maximize the benefits of modularization, the supercritical CO{sub 2} (S-CO{sub 2}) power cycle can replace the conventional steam Rankine cycle to increase the cycle efficiency and reduce its system size. Previous works have been conducted to evaluate potential advantages of applying the S-CO{sub 2} cycle to SMRs, specifically to SMART (System-integrated Modular Advanced Reactor) which is an integral SMR developed by KAERI (Korea Atomic Energy Institute). One of the optimized S-CO{sub 2} cycle layouts is the recompressing Brayton cycle. This paper attempts to improve the cycle layout by replacing the conventional compressor with an isothermal compressor, of which its potential in the S-CO{sub 2} power cycle is conceptually being evaluated. The SMR applications, for which SMART reactor has been represented, can take advantage of the currently developing S-CO{sub 2} cycle greatly by the reduction of size. By introducing the isothermal compressor, the cycle layout considered in has been further improved by increasing the cycle net efficiency by around 0.5%.

Supercritical CO2 Brayton cycle compression and control near the critical point

International Nuclear Information System (INIS)

Wright, S. A.; Fuller, R.; Noall, J.; Radel, R.; Vernon, M. E.; Pickard, P. S.

2008-01-01

This report describes the supercritical compression and control issues, the analysis, and the measured test results of a small-scale supercritical CO 2 (S-CO 2 ) compression test-loop. The test loop was developed by Sandia and is described in a companion paper in this conference. The results of these experiments will for the first time evaluate and experimentally demonstrate supercritical compression and the required compressor inlet control approaches on an appropriate scale in a series of test loops at Sandia National Laboratories. The Sandia effort is focused on the main compressor of a supercritical Brayton loop while a separate DOE Gen lV program focus is on studying similar behavior in re-compression Brayton cycles that have dual compressors. One of the main goals of this program is to develop and demonstrate the ability to design, operate, and control the supercritical compression process near the critical point due to highly non-linear behavior near this point. This Sandia supercritical test-loop uses a 50 kW radial compressor to pump supercritical CO 2 (S-CO 2 ) through an orifice and through a water-cooled gas-chiller. At the design point the compressor flow rate is 3.5 kg/s, the inlet pressure is 7, 690 kPa, the pressure ratio is 1.8, the inlet temperature is 305 K, and the shaft speed is 75, 000 rpm. The purpose of the loop is to study the compression and control issues near the critical point. To study compression we intend to compare the design code predictions for efficiency and change in enthalpy (or pressure ratio / head) of the radial compressor with the measured results from actual tests. In the tests the inlet flow, temperature, and pressure, will be varied around the critical point of CO 2 (Tc=304.2 K, and Pc=7.377 MPa). To study control, the test loop will use a variety of methods including inventory control, shaft speed control, and cooling water flow rate, and cooling water temperature control methods to set the compressor inlet temperature

Task Order 20: Supercritical Carbon Dioxide Brayton Cycle Energy Conversion Study

Energy Technology Data Exchange (ETDEWEB)

Murray, Paul [AREVA Federal Services, LLC, Charlotte, NC (United States); Lindsay, Edward [AREVA Federal Services, LLC, Charlotte, NC (United States); McDowell, Michael [AREVA Federal Services, LLC, Charlotte, NC (United States); Huang, Megan [AREVA Federal Services, LLC, Charlotte, NC (United States)

2015-04-23

AREVA Inc. developed this study for the US Department of Energy (DOE) office of Nuclear Energy (NE) in accordance with Task Order 20 Statement of Work (SOW) covering research and development activities for the Supercritical Carbon Dioxide (sCO2) Brayton Cycle energy conversion. The study addresses the conversion of sCO2 heat energy to electrical output by use of a Brayton Cycle system and focuses on the potential of a net efficiency increase via cycle recuperation and recompression stages. The study also addresses issues and study needed to advance development and implementation of a 10 MWe sCO2 demonstration project.

Transient Model of a 10 MW Supercritical CO{sub 2} Brayton Cycle for Light Water Reactors by using MARS Code

Energy Technology Data Exchange (ETDEWEB)

Park, Joo-Hyun; Park, Hyun Sun; Kim, Moo Hwan [POSTECH, Pohang (Korea, Republic of); Bae, Sung Won; Cha, Jae-Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

In this study, recuperation cycle was chosen as a reference loop design and the MARS code was chosen as the transient cycle analysis code. Cycle design condition is focus on operation point of the light-water reactor. Development of a transient model was performed for 10MW-electron SCO{sub 2} coupled with light water reactors. In order to perform transient analysis, cycle transient model was developed and steady-state run was performed and presented in the paper. In this study, the transient model of SCO{sub 2} recuperation Brayton cycle was developed and implemented in MARS to study the steady-state simulation. We performed nodalization of the transient model using MARS code and obtained steady-state results. This study is shown that the supercritical CO{sub 2} Brayton cycle can be used as a power conversion system for light water reactors. Future work will include transient analysis such as partial road operation, power swing, start-up, and shutdown. Cycle control strategy will be considered for various control method.

Research on the Development of the Supercritical CO{sub 2} Dual Brayton Cycle

Energy Technology Data Exchange (ETDEWEB)

Baik, Young-Jin; Na, Sun Ik; Cho, Junhyun; Shin, Hyung-Ki; Lee, Gilbong [Korea Institute of Energy Research (KIER), Daejeon (Korea, Republic of)

2016-10-15

Because of the growing interest in supercritical carbon dioxide power cycle technology owing to its potential enhancement in compactness and efficiency, supercritical carbon dioxide cycles have been studied in the fields of nuclear power, concentrated solar power (CSP), and fossil fuel power generation. This study introduces the current status of the research project on the supercritical carbon dioxide power cycle by Korea Institute of Energy Research (KIER). During the first phase of the project, the un-recuperated supercritical Brayton cycle test loop was built and tested. In phase two, researchers are designing and building a supercritical carbon dioxide dual Brayton cycle, which utilizes two turbines and two recuperators. Under the simulation condition considered in this study, it was confirmed that the design parameter has an optimal value for maximizing the net power in the supercritical carbon dioxide dual cycle.

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

International Nuclear Information System (INIS)

Linares, José Ignacio; Herranz, Luis Enrique; Fernández, Iván; Cantizano, Alexis; Moratilla, Beatriz Yolanda

2015-01-01

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 CO 2 Brayton power cycles (S-CO 2 ) 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-CO 2 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 CO 2 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

Optimizing an advanced hybrid of solar-assisted supercritical CO2 Brayton cycle: A vital transition for low-carbon power generation industry

International Nuclear Information System (INIS)

Milani, Dia; Luu, Minh Tri; McNaughton, Robbie; Abbas, Ali

2017-01-01

Highlights: • The layout of 14 demonstrative supercritical CO 2 closed Brayton cycles are analysed. • The key parameters of the “combined” cycle are sensitized and optimized. • The effect of thermal efficiency vs HX area on techno-economic nexus is highlighted. • The design of a matching solar heliostat field in direct configuration is revealed. • The water demand for hybrid vs water-only cooling scenarios are assessed. - Abstract: Current worldwide infrastructure of electrical power generation would mostly continue to rely on fossil-fuel but require a modest transition for the ultimate goal of decarbonizing power generation industry. By relying on those already established and carefully managed centrepiece power plants (PPs), we aim at filling the deficits of the current electrical networks with smaller, cleaner, and also more efficient PPs. In this context, we present a unique model for a small-scale decentralized solar-assisted supercritical CO 2 closed Brayton cycle (sCO 2 -CBC). Our model is based on the optimized values of three key performance indicators (KPIs); thermal efficiency, concentrated solar power (CSP) compatibility, and water demand for cooling. For a case-study of 10 MW e CSP-assisted sCO 2 -CBC power plant, our dynamic model shows a 52.7% thermal efficiency and 25.9% solar penetration and up to 80% of water saving in heat-rejection units. These KPIs show significant promise of the solar-assisted supercritical CO 2 power cycle for an imperative transformation in the power industry towards future sustainable electricity generation.

Parametric Investigation of Brayton Cycle for High Temperature Gas-Cooled Reactor

International Nuclear Information System (INIS)

Chang Oh

2004-01-01

The Idaho National Engineering and Environmental Laboratory (INEEL) is investigating a Brayton cycle efficiency improvement on a high temperature gas-cooled reactor (HTGR) as part of Generation-IV nuclear engineering research initiative. In this project, we are investigating helium Brayton cycles for the secondary side of an indirect energy conversion system. Ultimately we will investigate the improvement of the Brayton cycle using other fluids, such as supercritical carbon dioxide. Prior to the cycle improvement study, we established a number of baseline cases for the helium indirect Brayton cycle. These cases look at both single-shaft and multiple-shaft turbomachinery. The baseline cases are based on a 250 MW thermal pebble bed HTGR. The results from this study are applicable to other reactor concepts such as a very high temperature gas-cooled reactor (VHTR), fast gas-cooled reactor (FGR), supercritical water reactor (SWR), and others. In this study, we are using the HYSYS computer code for optimization of the helium Brayton cycle. Besides the HYSYS process optimization, we performed parametric study to see the effect of important parameters on the cycle efficiency. For these parametric calculations, we use a cycle efficiency model that was developed based on the Visual Basic computer language. As a part of this study we are currently investigated single-shaft vs. multiple shaft arrangement for cycle efficiency and comparison, which will be published in the next paper. The ultimate goal of this study is to use supercritical carbon dioxide for the HTGR power conversion loop in order to improve the cycle efficiency to values great than that of the helium Brayton cycle. This paper includes preliminary calculations of the steady state overall Brayton cycle efficiency based on the pebble bed reactor reference design (helium used as the working fluid) and compares those results with an initial calculation of a CO2 Brayton cycle

Modeling and sizing of the heat exchangers of a new supercritical CO2 Brayton power cycle for energy conversion for fusion reactors

International Nuclear Information System (INIS)

Serrano, I.P.; Cantizano, A.; Linares, J.I.; Moratilla, B.Y.

2014-01-01

Highlights: •We propose a procedure to model the heat exchangers of a S-CO2 Brayton power cycle. •Discretization in sub-heat exchangers is performed due to complex behavior of CO 2 . •Different correlations have been tested, verifying them with CFD when necessary. •Obtained sizes are agree with usual values of printed circuit heat exchangers. -- Abstract: TECNO F US is a research program financed by the Spanish Government to develop technologies related to a dual-coolant (He/Pb–Li) breeding blanket design concept including the auxiliary systems for a future power reactor (DEMO). One of the main issues of this program is the optimization of heat recovery from the reactor and its conversion into electrical power. This paper is focused on the methodology employed for the design and sizing of all the heat exchangers of the supercritical CO 2 Brayton power cycle (S-CO2) proposed by the authors. Due to the large pressure difference between the fluids, and also to their compactness, Printed Circuit Heat Exchangers (PCHE) are suggested in literature for these type of cycles. Because of the complex behavior of CO 2 , their design is performed by a numerical discretization into sub-heat exchangers, thus a higher precision is reached when the thermal properties of the fluids vary along the heat exchanger. Different empirical correlations for the pressure drop and the Nusselt number have been coupled and assessed. The design of the precooler (PC) and the low temperature recuperator (LTR) is also verified by simulations using CFD because of the near-critical behavior of CO 2 . The size of all of the heat exchangers of the cycle have been assessed

CFD aided approach to design printed circuit heat exchangers for supercritical CO2 Brayton cycle application

International Nuclear Information System (INIS)

Kim, Seong Gu; Lee, Youho; Ahn, Yoonhan; Lee, Jeong Ik

2016-01-01

Highlights: • CFD analyses were performed to find performance of PCHE for supercritical CO 2 power cycle. • CFD results were obtained beyond the limits of existing correlations. • Designs of different PCHEs with different correlations were compared. • A new CFD-aided correlation covering a wider Reynolds number range was proposed. - Abstract: While most conventional PCHE designs for working fluid of supercritical CO 2 require an extension of valid Reynolds number limits of experimentally obtained correlations, Computational Fluid Dynamics (CFD) code ANSYS CFX was used to explore validity of existing correlations beyond their tested Reynolds number ranges. For heat transfer coefficient correlations, an appropriate piece-wising with Ishizuka’s and Hesselgreaves’s correlation is found to enable an extension of Reynolds numbers. For friction factors, no single existing correlation is found to capture different temperature and angular dependencies for a wide Reynolds number range. Based on the comparison of CFD results with the experimentally obtained correlations, a new CFD-aided correlation covering an extended range of Reynolds number 2000–58,000 for Nusselt number and friction factor is proposed to facilitate PCHE designs for the supercritical CO 2 Brayton cycle application.

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

Development of a Performance Analysis Code for the Off-design conditions of a S-CO2 Brayton Cycle Energy Conversion System

International Nuclear Information System (INIS)

Yoo, Yong-Hwan; Cha, Jae-Eun; Lee, Tae-Ho; Eoh, Jae-Hyuk; Kim, Seong-O

2008-01-01

For the development of a supercritical carbon dioxide (S-CO2) Brayton cycle energy conversion system coupled to KALIMER-600, a thermal balance has been established on 100% power operating conditions including all the reactor system models such as a primary heat transport system (PHTS), an intermediate heat transport system (IHTS), and an energy conversion system. The S-CO2 Brayton cycle energy conversion system consists of a sodium-CO2 heat exchanger (Hx), turbine, high temperature recuperate (HTR), low temperature recuperate (LTR), precooler, compressor no.1, and compressor no.2. Two compressors were employed to avoid a sharp change of the physical properties near their critical point with a corresponding pressure. The component locations and their operating conditions are illustrated. Energy balance of the power conversion system in KALIMER-600 was designed with the full power condition of each component. Therefore, to predict the off-design conditions and to evaluate each component, an off-design performance analysis code should be accomplished. An off-design performance analysis could be classified into overall system control logic and local system control logic. The former means that mass flow rate and power are controlled by valves, and the latter implies that a bypass or inventory control is an admitted system balance. The ultimate goal of this study is development of the overall system control logic

Extension of the supercritical carbon dioxide Brayton cycle for application to the Very High Temperature Reactor

International Nuclear Information System (INIS)

Moisseytsev, A.; Sienicki, J. J.

2010-01-01

An investigation has been carried out of the feasibility of applying the supercritical carbon dioxide (S-CO 2 ) Brayton cycle to the Very High Temperature Reactor (VHTR). Direct application of the standard S-CO 2 recompression cycle to the VHTR was found to be challenging because of the mismatch in the inherent temperature drops across the He and CO 2 sides of the reactor heat exchanger resulting in a relatively low cycle efficiency of 45 % compared to 48 % for a direct helium cycle. Two approaches consisting of either a cascaded cycle arrangement with three separate cascaded S-CO 2 cycles or, alternately, operation of a single S-CO 2 cycle with the minimum pressure below the critical pressure and the minimum temperature above the critical temperature have been identified and shown to successfully enable the S-CO 2 Brayton cycle to be adapted to the VHTR such that the benefits of the higher S-CO 2 cycle efficiency can be realized. For both approaches, S-CO 2 cycle efficiencies in excess of 49 % are calculated. (authors)

Entropy, exergy, and cost analyses of solar driven cogeneration systems using supercritical CO_2 Brayton cycles and MEE-TVC desalination system

International Nuclear Information System (INIS)

Kouta, Amine; Al-Sulaiman, Fahad; Atif, Maimoon; Marshad, Saud Bin

2016-01-01

Highlights: • The entropy, exergy, and cost analyses for two solar cogeneration configurations are conducted. • The recompression cogeneration cycle achieves lower LCOE as compared to the regeneration cogeneration cycle. • The solar tower is the largest contributor to entropy generation in both configurations reaching almost 80%. • The specific entropy generation in the MEE-TVC decreases with decreasing the fraction. - Abstract: In this study, performance and cost analyses are conducted for a solar power tower integrated with supercritical CO_2 (sCO_2) Brayton cycles for power production and a multiple effect evaporation with a thermal vapor compression (MEE-TVC) desalination system for water production. The study is performed for two configurations based on two different supercritical cycles: the regeneration and recompression sCO_2 Brayton cycles. A two-tank molten salt storage is utilized to ensure a uniform operation throughout the day. From the entropy analysis, it was shown that the solar tower is the largest contributor to entropy generation in both configurations, reaching almost 80% from the total entropy generation, followed by the MEE-TVC desalination system, and the sCO_2 power cycle. The entropy generation in the two-tank thermal storage is negligible, around 0.3% from the total generation. In the MEE-TVC system the highest contributing component is the steam jet ejector, which is varying between 50% and 60% for different number of effects. The specific entropy generation in the MEE-TVC decreases as the fraction of the input heat to the desalination system decreases; while the specific entropy generation of the sCO_2 cycle remains constant. The cost analysis performed for different regions in Saudi Arabia and the findings reveal that the regions characterized by the highest average solar irradiation throughout the year have the lowest LCOE and LCOW values. The region achieving the lowest cost is Yanbu, followed by Khabt Al-Ghusn in the second

Modeling and sizing of the heat exchangers of a new supercritical CO{sub 2} Brayton power cycle for energy conversion for fusion reactors

Energy Technology Data Exchange (ETDEWEB)

Serrano, I.P.; Cantizano, A.; Linares, J.I., E-mail: linares@upcomillas.es; Moratilla, B.Y.

2014-10-15

Highlights: •We propose a procedure to model the heat exchangers of a S-CO2 Brayton power cycle. •Discretization in sub-heat exchangers is performed due to complex behavior of CO{sub 2}. •Different correlations have been tested, verifying them with CFD when necessary. •Obtained sizes are agree with usual values of printed circuit heat exchangers. -- Abstract: TECNO{sub F}US is a research program financed by the Spanish Government to develop technologies related to a dual-coolant (He/Pb–Li) breeding blanket design concept including the auxiliary systems for a future power reactor (DEMO). One of the main issues of this program is the optimization of heat recovery from the reactor and its conversion into electrical power. This paper is focused on the methodology employed for the design and sizing of all the heat exchangers of the supercritical CO{sub 2} Brayton power cycle (S-CO2) proposed by the authors. Due to the large pressure difference between the fluids, and also to their compactness, Printed Circuit Heat Exchangers (PCHE) are suggested in literature for these type of cycles. Because of the complex behavior of CO{sub 2}, their design is performed by a numerical discretization into sub-heat exchangers, thus a higher precision is reached when the thermal properties of the fluids vary along the heat exchanger. Different empirical correlations for the pressure drop and the Nusselt number have been coupled and assessed. The design of the precooler (PC) and the low temperature recuperator (LTR) is also verified by simulations using CFD because of the near-critical behavior of CO{sub 2}. The size of all of the heat exchangers of the cycle have been assessed.

Comparative energy analysis on a new regenerative Brayton cycle

International Nuclear Information System (INIS)

Goodarzi, M.

2016-01-01

Highlights: • New regenerative Brayton cycle has been introduced. • New cycle has higher thermal efficiency and lower exhausted heat per output power. • Regenerator may remain useful in the new cycle even at high pressure ratio. • New regenerative Brayton cycle is suggested for low pressure ratio operations. - Abstract: Gas turbines are frequently used for power generation. Brayton cycle is the basis for gas turbine operation and developing the alternative cycles. Regenerative Brayton cycle is a developed cycle for basic Brayton cycle with higher thermal efficiency at low to moderate pressure ratios. A new regenerative Brayton cycle has been introduced in the present study. Energy analysis has been conducted on ideal cycles to compare them from the first law of thermodynamics viewpoint. Comparative analyses showed that the new regenerative Brayton cycle has higher thermal efficiency than the original one at the same pressure ratio, and also lower heat absorption and exhausted heat per unite output power. Computed results show that new cycle improves thermal efficiency from 12% to 26% relative to the original regenerative Brayton cycle in the range of studied pressure ratios. Contrary to the original regenerative Brayton cycle, regenerator remains useful in the new regenerative Brayton cycle even at higher pressure ratio.

Potential application of Rankine and He-Brayton cycles to sodium fast reactors

International Nuclear Information System (INIS)

Perez-Pichel, G.D.; Linares, J.I.; Herranz, L.E.; Moratilla, B.Y.

2011-01-01

Highlights: → This paper has been focused on thermal efficiency of several Rankine and Brayton cycles for SFR. → A sub-critical Rankine configuration could reach a thermal efficiency higher than 43%. → It could be increased to almost 45% using super-critical configurations. → Brayton cycles thermal performance can be enhanced by adding a super-critical organic fluid Rankine cycle. → The moderate coolant temperature at the reactor makes Brayton configurations have poorer. - Abstract: Traditionally all the demos and/or prototypes of the sodium fast reactor (SFR) technology with power output, have used a steam sub-critical Rankine cycle. Sustainability requirement of Gen. IV reactors recommends exploring alternate power cycle configurations capable of reaching high thermal efficiency. By adopting the anticipated working parameters of next SFRs, this paper investigates the potential of some Rankine and He-Brayton layouts to reach thermal efficiencies as high as feasible, so that they could become alternates for SFR reactor balance of plant. The assessment has encompassed from sub-critical to super-critical Rankine cycles and combined cycles based on He-Brayton gas cycles of different complexity coupled to Organic Rankine Cycles. The sub-critical Rankine configuration reached at thermal efficiency higher than 43%, which has been shown to be a superior performance than any of the He-Brayton configurations analyzed. By adopting a super-critical Rankine arrangement, thermal efficiency would increase less than 1.5%. In short, according to the present study a sub-critical layout seems to be the most promising configuration for all those upcoming prototypes to be operated in the short term (10-15 years). The potential of super-critical CO 2 -Brayton cycles should be explored for future SFRs to be deployed in a longer run.

Supercritical CO2 Brayton power cycles for DEMO (demonstration power plant) fusion reactor based on dual coolant lithium lead blanket

International Nuclear Information System (INIS)

Linares, José Ignacio; Cantizano, Alexis; Moratilla, Beatriz Yolanda; Martín-Palacios, Víctor; Batet, Lluis

2016-01-01

This paper presents an exploratory analysis of the suitability of supercritical CO 2 Brayton power cycles as alternative energy conversion systems for a future fusion reactor based on a DCLL (dual coolant lithium-lead) blanket, as prescribed by EUROfusion. The main issue dealt is the optimization of the integration of the different thermal sources with the power cycle in order to achieve the highest electricity production. The analysis includes the assessment of the pumping consumption in the heating and cooling loops, taking into account additional considerations as control issues and integration of thermal energy storage systems. An exergy analysis has been performed in order to understand the behavior of each layout. Up to ten scenarios have been analyzed assessing different locations for thermal sources heat exchangers. Neglecting the worst four scenarios, it is observed less than 2% of variation among the other six ones. One of the best six scenarios clearly stands out over the others due to the location of the thermal sources in a unique island, being this scenario compatible with the control criteria. In this proposal 34.6% of electric efficiency (before the self-consumptions of the reactor but including pumping consumptions and generator efficiency) is achieved. - Highlights: • Supercritical CO 2 Brayton cycles have been proposed for BoP of DCLL fusion reactor. • Integration of different available thermal sources has been analyzed considering ten scenarios. • Neglecting the four worst scenarios the electricity production varies less than 2%. • Control and energy storage integration issues have been considered in the analysis. • Discarding the vacuum vessel and joining the other sources in an island is proposed.

Thermodynamic analyses and optimization of a recompression N2O Brayton power cycle

International Nuclear Information System (INIS)

Sarkar, Jahar

2010-01-01

Thermodynamic analyses and simultaneous optimizations of cycle pressure ratio and flow split fraction to get maximum efficiency of N 2 O recompression Brayton cycle have been performed to study the effects of various operating conditions and component performances. The energetic as well as exergetic performance comparison with its counterpart recompression CO 2 cycle is presented as well. Optimization shows that the optimum minimum cycle pressure is close to pseudo-critical pressure for supercritical cycle, whereas saturation pressure corresponding to minimum cycle temperature for condensation cycle. Results show that the maximum thermal efficiency increases with decrease in minimum cycle temperature and increase in both maximum cycle pressure and temperature. Influence of turbine performance on cycle efficiency is more compared to that of compressors, HTR (high temperature recuperator) and LTR (low temperature recuperator). Comparison shows that N 2 O gives better thermal efficiency (maximum deviation of 1.2%) as well as second law efficiency compared to CO 2 for studied operating conditions. Component wise irreversibility distribution shows the similar trends for both working fluids. Present study reveals that N 2 O is a potential option for the recompression power cycle.

Numerical Comparison of NASA's Dual Brayton Power Generation System Performance Using CO2 or N2 as the Working Fluid

Science.gov (United States)

Ownens, Albert K.; Lavelle, Thomas M.; Hervol, David S.

2010-01-01

A Dual Brayton Power Conversion System (DBPCS) has been tested at the NASA Glenn Research Center using Nitrogen (N2) as the working fluid. This system uses two closed Brayton cycle systems that share a common heat source and working fluid but are otherwise independent. This system has been modeled using the Numerical Propulsion System Simulation (NPSS) environment. This paper presents the results of a numerical study that investigated system performance changes resulting when the working fluid is changed from gaseous (N2) to gaseous carbon dioxide (CO2).

Exergy analysis for combined regenerative Brayton and inverse Brayton cycles

OpenAIRE

Zelong Zhang, Lingen Chen, Fengrui Sun

2012-01-01

This paper presents the study of exergy analysis of combined regenerative Brayton and inverse Brayton cycles. The analytical formulae of exergy loss and exergy efficiency are derived. The largest exergy loss location is determined. By taking the maximum exergy efficiency as the objective, the choice of bottom cycle pressure ratio is optimized by detailed numerical examples, and the corresponding optimal exergy efficiency is obtained. The influences of various parameters on the exergy efficien...

Effect of Uncertainties in CO2 Property Databases on the S-CO2 Compressor Performance

International Nuclear Information System (INIS)

Lee, Je Kyoung; Lee, Jeong Ik; Ahn, Yoonhan; Kim, Seong Gu; Cha, Je Eun

2013-01-01

Various S-CO 2 Brayton cycle experiment facilities are on the state of construction or operation for demonstration of the technology. However, during the data analysis, S-CO 2 property databases are widely used to predict the performance and characteristics of S-CO 2 Brayton cycle. Thus, a reliable property database is very important before any experiment data analyses or calculation. In this paper, deviation of two different property databases which are widely used for the data analysis will be identified by using three selected properties for comparison, C p , density and enthalpy. Furthermore, effect of above mentioned deviation on the analysis of test data will be briefly discussed. From this deviation, results of the test data analysis can have critical error. As the S-CO 2 Brayton cycle researcher knows, CO 2 near the critical point has dramatic change on thermodynamic properties. Thus, it is true that a potential error source of property prediction exists in CO 2 properties near the critical point. During an experiment data analysis with the S-CO 2 Brayton cycle experiment facility, thermodynamic properties are always involved to predict the component performance and characteristics. Thus, construction or defining of precise CO 2 property database should be carried out to develop Korean S-CO 2 Brayton cycle technology

The Application of Supercritical CO{sub 2} Power Cycle to Various Nuclear Systems

Energy Technology Data Exchange (ETDEWEB)

Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2015-10-15

The main reason why the S-CO{sub 2} Brayton cycle has these advantages is that the compressor operates near the critical point of CO{sub 2} (30.98 .deg. C, 7.38MPa) to reduce the compression work significantly compared to the other Brayton cycles. In this paper, various applications of supercritical CO{sub 2} power cycle to nuclear systems will be presented and summarized. The S-CO{sub 2} cycle can achieve relatively high efficiency within the mild turbine inlet temperature range (450 - 850 .deg. C) compared with other power conversion systems. The main benefit of the S-CO{sub 2} cycle is the small size of the overall system and its application includes not only the next generation nuclear reactors but also conventional water-cooled reactors too. Various layouts were compared and the recompression cycle shows the best efficiency. The layout is suitable for application to advanced nuclear reactor systems. To evaluate the S-CO{sub 2} cycle performance, various countries constructed and demonstrated S-CO{sub 2} integral system test loops and similar research works are ongoing in Korea as well. However, to evaluate the commercial S-CO{sub 2} power systems, development of a large scale (> 10 MW) prototype S-CO{sub 2} system is necessary.

Exergy analysis for combined regenerative Brayton and inverse Brayton cycles

Energy Technology Data Exchange (ETDEWEB)

Zhang, Zelong; Chen, Lingen; Sun, Fengrui [College of Naval Architecture and Power, Naval University of Engineering, Wuhan 430033 (China)

2012-07-01

This paper presents the study of exergy analysis of combined regenerative Brayton and inverse Brayton cycles. The analytical formulae of exergy loss and exergy efficiency are derived. The largest exergy loss location is determined. By taking the maximum exergy efficiency as the objective, the choice of bottom cycle pressure ratio is optimized by detailed numerical examples, and the corresponding optimal exergy efficiency is obtained. The influences of various parameters on the exergy efficiency and other performances are analyzed by numerical calculations.

Multi-objective thermodynamic optimization of combined Brayton and inverse Brayton cycles using genetic algorithms

International Nuclear Information System (INIS)

Besarati, S.M.; Atashkari, K.; Jamali, A.; Hajiloo, A.; Nariman-zadeh, N.

2010-01-01

This paper presents a simultaneous optimization study of two outputs performance of a previously proposed combined Brayton and inverse Brayton cycles. It has been carried out by varying the upper cycle pressure ratio, the expansion pressure of the bottom cycle and using variable, above atmospheric, bottom cycle inlet pressure. Multi-objective genetic algorithms are used for Pareto approach optimization of the cycle outputs. The two important conflicting thermodynamic objectives that have been considered in this work are net specific work (w s ) and thermal efficiency (η th ). It is shown that some interesting features among optimal objective functions and decision variables involved in the Baryton and inverse Brayton cycles can be discovered consequently.

Cycle layout studies of S-CO2 cycle for the next generation nuclear system application

International Nuclear Information System (INIS)

Ahn, Yoonhan; Bae, Seong Jun; Kim, Minseok; Cho, Seong Kuk; Baik, Seungjoon; Lee, Jeong Ik; Cha, Jae Eun

2014-01-01

According to the second law of thermodynamics, the next generation nuclear reactor system efficiency can potentially be increased with higher operating temperature. Fig.1 shows several power conversion system efficiencies and heat sources with respect to the system top operating temperature. As shown in Fig.1, the steam Rankine and gas Brayton cycles have been considered as the major power conversion systems more than several decades. In the next generation reactor operating temperature region (450 - 900 .deg. C), the steam Rankine and gas Brayton cycles have limits due to material problems and low efficiency, respectively. Among the future power conversion systems, S-CO 2 cycle is receiving interests due to several benefits including high efficiency under the mild turbine inlet temperature range (450-650 .deg. C), compact turbomachinery and simple layout compared to the steam Rankine cycle. S-CO 2 cycle can show relatively high efficiency under the mild turbine inlet temperature range (450-600 .deg. C) compared to other power conversion systems. The recompression cycle shows the best efficiency among other layouts and it is suitable for the application to advanced nuclear reactor systems. As S-CO 2 cycle performance can vary depending on the layout configuration, further studies on the layouts are required to design a better performing cycle

Design and analysis of helium Brayton power cycles for HiPER reactor

Energy Technology Data Exchange (ETDEWEB)

Sánchez, Consuelo, E-mail: csanchez@ind.uned.es [Dpto. Ingeniería Energética UNED, Madrid (Spain); Juárez, Rafael; Sanz, Javier [Dpto. Ingeniería Energética UNED, Madrid (Spain); Instituto de Fusión Nuclear/UPM, Madrid (Spain); Perlado, Manuel [Instituto de Fusión Nuclear/UPM, Madrid (Spain)

2013-10-15

Highlights: ► A helium Brayton cycle has been designed integrating the two energy sources of HiPER. ► The Brayton cycle has intercooling stages and a recovery process. ► The low temperature of HiPER heat sources results in low cycle efficiency (35.2%). ► Two inter-cooling stages and a reheating process increases efficiency to over 37%. ► Helium Brayton cycles are to be considered as candidates for HiPER power cycles. -- Abstract: Helium Brayton cycles have been studied as power cycles for both fission and fusion reactors obtaining high thermal efficiency. This paper studies several technological schemes of helium Brayton cycles applied for the HiPER reactor proposal. Since HiPER integrates technologies available at short term, its working conditions results in a very low maximum temperature of the energy sources, something that limits the thermal performance of the cycle. The aim of this work is to analyze the potential of the helium Brayton cycles as power cycles for HiPER. Several helium Brayton cycle configurations have been investigated with the purpose of raising the cycle thermal efficiency under the working conditions of HiPER. The effects of inter-cooling and reheating have specifically been studied. Sensitivity analyses of the key cycle parameters and component performances on the maximum thermal efficiency have also been carried out. The addition of several inter-cooling stages in a helium Brayton cycle has allowed obtaining a maximum thermal efficiency of over 36%, and the inclusion of a reheating process may also yield an added increase of nearly 1 percentage point to reach 37%. These results confirm that helium Brayton cycles are to be considered among the power cycle candidates for HiPER.

Design and analysis of helium Brayton power cycles for HiPER reactor

International Nuclear Information System (INIS)

Sánchez, Consuelo; Juárez, Rafael; Sanz, Javier; Perlado, Manuel

2013-01-01

Highlights: ► A helium Brayton cycle has been designed integrating the two energy sources of HiPER. ► The Brayton cycle has intercooling stages and a recovery process. ► The low temperature of HiPER heat sources results in low cycle efficiency (35.2%). ► Two inter-cooling stages and a reheating process increases efficiency to over 37%. ► Helium Brayton cycles are to be considered as candidates for HiPER power cycles. -- Abstract: Helium Brayton cycles have been studied as power cycles for both fission and fusion reactors obtaining high thermal efficiency. This paper studies several technological schemes of helium Brayton cycles applied for the HiPER reactor proposal. Since HiPER integrates technologies available at short term, its working conditions results in a very low maximum temperature of the energy sources, something that limits the thermal performance of the cycle. The aim of this work is to analyze the potential of the helium Brayton cycles as power cycles for HiPER. Several helium Brayton cycle configurations have been investigated with the purpose of raising the cycle thermal efficiency under the working conditions of HiPER. The effects of inter-cooling and reheating have specifically been studied. Sensitivity analyses of the key cycle parameters and component performances on the maximum thermal efficiency have also been carried out. The addition of several inter-cooling stages in a helium Brayton cycle has allowed obtaining a maximum thermal efficiency of over 36%, and the inclusion of a reheating process may also yield an added increase of nearly 1 percentage point to reach 37%. These results confirm that helium Brayton cycles are to be considered among the power cycle candidates for HiPER

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

-through labyrinth seals was proposed. A stepped labyrinth seal, which mimics the behavior of the labyrinth seal used in the Sandia National Laboratory (SNL) S-CO₂ Brayton cycle, was also tested in the experiment along with simulations performed. The rest of this study demonstrates the difference of valves' behavior under supercritical fluid and normal fluid conditions. A small-scale valve was tested in the experiment facility using S-CO₂. Different percentages of opening valves were tested, and the measured mass flow rate agreed with simulation predictions. Two transients from a real S-CO₂ Brayton cycle design provided the data for valve selection. The selected valve was studied using numerical simulation, as experimental data is not available.

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.

Power and efficiency optimization for combined Brayton and inverse Brayton cycles

International Nuclear Information System (INIS)

Zhang Wanli; Chen Lingen; Sun Fengrui

2009-01-01

A thermodynamic model for open combined Brayton and inverse Brayton cycles is established considering the pressure drops of the working fluid along the flow processes and the size constraints of the real power plant using finite time thermodynamics in this paper. There are 11 flow resistances encountered by the gas stream for the combined Brayton and inverse Brayton cycles. Four of these, the friction through the blades and vanes of the compressors and the turbines, are related to the isentropic efficiencies. The remaining flow resistances are always present because of the changes in flow cross-section at the compressor inlet of the top cycle, combustion 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 control the air flow rate and the net power output. The relative pressure drops associated with the flow through various cross-sectional areas are derived as functions of the compressor inlet relative pressure drop of the top cycle. The analytical formulae about the relations between power output, thermal conversion efficiency, and the compressor pressure ratio of the top cycle are derived with the 11 pressure drop losses in the intake, compression, combustion, expansion, and flow process in the piping, the heat transfer loss to the ambient, the irreversible compression and expansion losses in the compressors and the turbines, and the irreversible combustion loss in the combustion chamber. The performance of the model cycle is optimized by adjusting the compressor inlet pressure of the bottom cycle, the air mass flow rate and the distribution of pressure losses along the flow path. It is shown that the power output has a maximum with respect to the compressor inlet pressure of the bottom cycle, the air mass flow rate or any of the overall pressure drops, and the maximized power output has an additional maximum with respect to the compressor pressure

Preliminary Studies of Two-Phase Reactive Process of Sodium-CO2 in S-CO2 Power Conversion Cycle Coupled to SFR System

International Nuclear Information System (INIS)

Jung, Hwa Young; Ahn, Yoon Han; Lee, You Ho; Lee, Jeong Ik

2013-01-01

As a competing alternative to the steam Rankine cycle, the supercritical CO 2 (S-CO 2 ) Brayton cycle has been highlighted due to its high thermal efficiency, compact turbomachinery and heat exchangers sizes, and the reduced risk of SWRs. While the reduced risk of an SWR is considered as the one of most pronounced benefits of S-CO 2 Brayton cycle, there is still an interaction problem between liquid sodium and CO 2 . Although the chemical interaction between liquid sodium and CO 2 demonstrates less serious potential risks than those of a SWR, the Na/CO 2 interaction should be understood to evaluate safety and reliability of Intermediate Heat eXchanger (IHX). A noticeable characteristic of the reaction environment is that there is a large pressure difference between the liquid sodium and CO 2 side by about 1 and 200 bar, respectively. This would imply that the presence of a micro-crack in a heat exchanger tube will cause a high-pressure leak of CO 2 into liquid sodium side. Although the Na/CO 2 interaction may play an important role in the safety of the SFR reactor system, there has not yet been any research on understanding Na/CO 2 reaction by leakage through IHX. For this problem, the Korea Advanced Institute of Science and Technology (KAIST) research team is studying the mechanism of CO 2 leakage and Na/CO 2 interaction in more details. The KAIST research team developed the MATLAB code, KAIST H XD, which can be used to design and evaluate performance of a heat exchanger of an S-CO 2 cycle. The size of heat exchanger and the amount of CO 2 in the cycle are calculated from the KAIST H XD code to estimate the amount of reaction products in Na/CO 2 interaction as well as liquid sodium

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

Thermoeconomic Analysis and Optimization of a New Combined Supercritical Carbon Dioxide Recompression Brayton/Kalina Cycle

Directory of Open Access Journals (Sweden)

S. Mohammad S. Mahmoudi

2016-10-01

Full Text Available A new combined supercritical CO2 recompression Brayton/Kalina cycle (SCRB/KC is proposed. In the proposed system, waste heat from a supercritical CO2 recompression Brayton cycle (SCRBC is recovered by a Kalina cycle (KC to generate additional electrical power. The performances of the two cycles are simulated and compared using mass, energy and exergy balances of the overall systems and their components. Using the SPECO (Specific Exergy Costing approach and employing selected cost balance equations for the components of each system, the total product unit costs of the cycles are obtained. Parametric studies are performed to investigate the effects on the SCRB/KC and SCRBC thermodynamic and thermoeconomic performances of key decision parameters. In addition, considering the exergy efficiency and total product unit cost as criteria, optimization is performed for the SCRBC and SCRB/KC using Engineering Equation Solver software. The results indicate that the maximum exergy efficiency of the SCRB/KC is higher than that of the SCRBC by up to 10%, and that the minimum total product unit cost of the SCRB/KC is lower than that of the SCRBC by up to 4.9%.

RANS simulation of a radial compressor for supercritical CO{sub 2} Brayton cycle

Energy Technology Data Exchange (ETDEWEB)

Kim, Seong Gu; Cho, Seong Kuk; Lee, Jekyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Cha, Jae Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Lee, Si Woo [Jinsol Turbo, Daejeon (Korea, Republic of)

2016-10-15

S-CO{sub 2} cycle has a small footprint due to the compact turbomachine and heat exchanger. It was found that the S-CO{sub 2} compressor consumes small compression work if the operating conditions approach to the critical point (7.38MPa, 31.1℃). Therefore, this reduced compression work contributes to high cycle efficiency. Due to the above mentioned advantages, the S-CO{sub 2} cycle can be applied to various heat sources such as coal power, bottoming cycle of fuel cells, and the next generation nuclear systems. To demonstrate the S-CO{sub 2} cycle performance, an integral test facility is necessary. Therefore, the joint research team of KAERI, KAIST, POSTECH designed a supercritical CO{sub 2} integral experiment loop (SCIEL). The experimental data from this loop are accumulating in various conditions, rotational speed. The design of a S-CO{sub 2} compressor operating near the critical point is one of the major technical challenges in the development of cycle components. A radial compressor geometry designed for supercritical CO{sub 2} loop was utilized for CFD analysis. The preliminary results were compared to the experimental data. In this study, the authors present a CFD approach with accurate CSV type property table. Compared results showed reasonable difference between CFD and experiment except for efficiency curve at 35,000rpm. In future works, the loss models used for the design of S-CO{sub 2} compressor will be validated, and established with CFD results.

Assessment of gas cooled fast reactor with indirect supercritical CO2 cycle

International Nuclear Information System (INIS)

Hejzlar, P.; Driscoll, M. J.; Dostal, V.; Dumaz, P.; Poullennec, G.; Alpy, N.

2006-01-01

Various indirect power cycle options for a helium cooled Gas cooled Fast Reactor (GFR) with particular focus on a supercritical CO 2 (SCO 2 ) indirect cycle are investigated as an alternative to a helium cooled direct cycle GFR. The Balance Of Plant (BOP) options include helium-nitrogen Brayton cycle, supercritical water Rankine cycle, and SCO 2 recompression Brayton power cycle in three versions: (1) basic design with turbine inlet temperature of 550 .deg. C, (2) advanced design with turbine inlet temperature of 650 .deg. C and (3) advanced design with the same turbine inlet temperature and reduced compressor inlet temperature. The indirect SCO 2 recompression cycle is found attractive since in addition to easier BOP maintenance it allows significant reduction of core outlet temperature, making design of the primary system easier while achieving very attractive efficiencies comparable to or slightly lower than, the efficiency of the reference GFR direct cycle design. In addition, the indirect cycle arrangement allows significant reduction of the GFR 'proximate-containment' and the BOP for the SCO 2 cycle is very compact. Both these factors will lead to reduced capital cost

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.

Description of Supercritical CO{sub 2} Compressor Experiment Loop

Energy Technology Data Exchange (ETDEWEB)

Lee, Je Kyoung; Lee, Jeong Ik; Ahn, Yoonhan; Kim, Seong Gu [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Cha, Je Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2013-10-15

The full scope of SCIEL project is to demonstrate high efficiency with simple recuperated cycle layout or recompressing layout, which the final cycle layout will be determined by the obtained compressor performance data. As a part of SCIEL project, S-CO{sub 2} compressor experiment facility has been constructed in KAERI. In this paper, current status of S-CO{sub 2} compressor experiment loop will be reviewed. With the growing interest in developing an advanced nuclear power plant, power conversion cycle innovation has been the part of this effort to secure high economics and enhanced safety. One of the main activities of power conversion cycle innovation is the development of Supercritical CO{sub 2} Brayton cycle technology. S-CO{sub 2} Brayton cycle concept was suggested in 1960s but the development and realization of the technology has been delayed up to now. In Korea, KAIST, KAERI and POSTECH are conducting research and development of Korean S-CO{sub 2} Brayton cycle technology by erecting the Supercritical CO{sub 2} Integral Experiment Loop (SCIEL)

Research and Technology Activities Supporting Closed-Brayton-Cycle Power Conversion System Development

Science.gov (United States)

Barrett, Michael J.

2004-01-01

The elements of Brayton technology development emphasize power conversion system risk mitigation. Risk mitigation is achieved by demonstrating system integration feasibility, subsystem/component life capability (particularly in the context of material creep) and overall spacecraft mass reduction. Closed-Brayton-cycle (CBC) power conversion technology is viewed as relatively mature. At the 2-kWe power level, a CBC conversion system Technology Readiness Level (TRL) of six (6) was achieved during the Solar Dynamic Ground Test Demonstration (SD-GTD) in 1998. A TRL 5 was demonstrated for 10 kWe-class CBC components during the development of the Brayton Rotating Unit (BRU) from 1968 to 1976. Components currently in terrestrial (open cycle) Brayton machines represent TRL 4 for similar uses in 100 kWe-class CBC space systems. Because of the baseline component and subsystem technology maturity, much of the Brayton technology task is focused on issues related to systems integration. A brief description of ongoing technology activities is given.

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

International Nuclear Information System (INIS)

Kim, T. W.; Kim, N. H.; Suh, K. Y.

2007-01-01

Supercritical carbon dioxide (SCO 2 ) 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 SCO 2 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 SCO 2 Brayton cycle needing less room relative to the Rankine steam cycle because of its smaller components. The SCO 2 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 SCO 2 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 SCO 2 going out from the low temperature recuperator. Development of Modular Optimized Brayton Integral System (MOBIS) is being devised as the SCO 2 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 SCO 2 turbine. Liquid-metal Energy Exchanger Integral System (LEXIS) serves to couple BORIS and MOBIS. LEXIS comprises Physical Aspect Thermal Operation System (PATOS) for SCO 2 thermal hydraulic characteristics, Shell-and-tube Overall Layout Optimization Study (SOLOS) for shell-and-tube heat exchanger, Printed

Review of supercritical CO{sub 2} power cycle technology and current status of research and development

Energy Technology Data Exchange (ETDEWEB)

Ahn, Yoon Han; Bae, Seong Jun; Kim, Min Seok; Cho, Seong Kuk; Baik, Seung Joon; Lee, Jeong Ik [Dept. of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Cha, Jae Eun [Fast Reactor Technology Development Division, Korean Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

The supercritical CO{sub 2} (S-CO{sub 2}) Brayton cycle has recently been gaining a lot of attention for application to next generation nuclear reactors. The advantages of the S-CO-2 cycle are high efficiency in the mild turbine inlet temperature region and a small physical footprint with a simple layout, compact turbomachinery, and heat exchangers. Several heat sources including nuclear, fossil fuel, waste heat, and renewable heat sources such as solar thermal or fuel cells are potential application areas of the S-CO-2 cycle. In this paper, the current development progress of the S-CO-2 cycle is introduced. Moreover, a quick comparison of various S-CO{sub 2} layouts is presented in terms of cycle performance.

Counter flow induced draft cooling tower option for supercritical carbon dioxide Brayton cycle

Energy Technology Data Exchange (ETDEWEB)

Pidaparti, Sandeep R., E-mail: sandeep.pidaparti@gmail.com [Georgia Institute of Technology, George W. Woodruff School of Mechanical Engineering, Atlanta, GA 30332 (United States); Moisseytsev, Anton; Sienicki, James J. [Argonne National Laboratory, 9700 South Cass Avenue, Argonne, IL 60439 (United States); Ranjan, Devesh, E-mail: devesh.ranjan@me.gatech.edu [Georgia Institute of Technology, George W. Woodruff School of Mechanical Engineering, Atlanta, GA 30332 (United States)

2015-12-15

Highlights: • A code was developed to investigate the various aspects of using cooling tower for S-CO{sub 2} Brayton cycles. • Cooling tower option to reject heat is quantitatively compared to the direct water cooling and dry air cooling options. • Optimum water conditions resulting in minimal plant capital cost per unit power consumption are calculated. - Abstract: A simplified qualitative analysis was performed to investigate the possibility of using counter flow induced draft cooling tower option to reject heat from the supercritical carbon dioxide Brayton cycle for advanced fast reactor (AFR)-100 and advanced burner reactor (ABR)-1000 plants. A code was developed to estimate the tower dimensions, power and water consumption, and to perform economic analysis. The code developed was verified against a vendor provided quotation and is used to understand the effect of ambient air and water conditions on the design of cooling tower. The calculations indicated that there exists optimum water conditions for given ambient air conditions which will result in minimum power consumption, thereby increasing the cycle efficiency. A cost-based optimization technique is used to estimate the optimum water conditions which will improve the overall plant economics. A comparison of different cooling options for the S-CO{sub 2} cycle indicated that the cooling tower option is a much more practical and economical option compared to the dry air cooling or direct water cooling options.

Combined Brayton-JT cycles with refrigerants for natural gas liquefaction

Science.gov (United States)

Chang, Ho-Myung; Park, Jae Hoon; Lee, Sanggyu; Choe, Kun Hyung

2012-06-01

Thermodynamic cycles for natural gas liquefaction with single-component refrigerants are investigated under a governmental project in Korea, aiming at new processes to meet the requirements on high efficiency, large capacity, and simple equipment. Based upon the optimization theory recently published by the present authors, it is proposed to replace the methane-JT cycle in conventional cascade process with a nitrogen-Brayton cycle. A variety of systems to combine nitrogen-Brayton, ethane-JT and propane-JT cycles are simulated with Aspen HYSYS and quantitatively compared in terms of thermodynamic efficiency, flow rate of refrigerants, and estimated size of heat exchangers. A specific Brayton-JT cycle is suggested with detailed thermodynamic data for further process development. The suggested cycle is expected to be more efficient and simpler than the existing cascade process, while still taking advantage of easy and robust operation with single-component refrigerants.

On the reversed Brayton cycle with high speed machinery

Energy Technology Data Exchange (ETDEWEB)

Backman, J.

1996-12-31

This work was carried out in the laboratory of Fluid Dynamics, at Lappeenranta University of Technology during the years 1991-1996. The research was a part of larger high speed technology development research. First, there was the idea of making high speed machinery applications with the Brayton cycle. There was a clear need to deepen the knowledge of the cycle itself and to make a new approach in the field of the research. Also, the removal of water from the humid air seemed very interesting. The goal of this work was to study methods of designing high speed machinery for the reversed Brayton cycle, from theoretical principles to practical applications. 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. A new calculation method for the Brayton cycle is developed. 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. Also, the influence of calculating the process with actual, achievable process equipment efficiencies is essential for the development of future machinery. The above theoretical calculations are confirmed with two different laboratory prototypes. (53 refs.)

On the reversed Brayton cycle with high speed machinery

Energy Technology Data Exchange (ETDEWEB)

Backman, J

1997-12-31

This work was carried out in the laboratory of Fluid Dynamics, at Lappeenranta University of Technology during the years 1991-1996. The research was a part of larger high speed technology development research. First, there was the idea of making high speed machinery applications with the Brayton cycle. There was a clear need to deepen the knowledge of the cycle itself and to make a new approach in the field of the research. Also, the removal of water from the humid air seemed very interesting. The goal of this work was to study methods of designing high speed machinery for the reversed Brayton cycle, from theoretical principles to practical applications. 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. A new calculation method for the Brayton cycle is developed. 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. Also, the influence of calculating the process with actual, achievable process equipment efficiencies is essential for the development of future machinery. The above theoretical calculations are confirmed with two different laboratory prototypes. (53 refs.)

Experimental Investigation of Gaseous Reaction Products from Na-CO{sub 2} Reaction in Na/CO{sub 2} Heat Exchanger leakage scenario

Energy Technology Data Exchange (ETDEWEB)

Go, A-Reum; Jung, Hwa-Young; Kim, Min Seok; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Min, Jaehong; Wi, Myung-Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

The SFRs have operated with the steam Rankine cycle as a power conversion system. However, the potential sodium-water reaction (SWR) whose chemical reactivity is vigorous and instantaneous has been one of the major issues concerning the safety and integrity of the SFRs. In order to avoid SWR, supercritical CO{sub 2}(S-CO{sub 2}) Brayton cycles have been investigated recently. Compared to conventional steam Rankine cycles, S-CO{sub 2} Brayton cycle features higher thermal efficiency and potential compactness of its required equipment. In spite of the superiority of S-CO{sub 2} Brayton cycle, there is a potential reactive process between sodium and CO{sub 2} if the pressure boundary fails in the sodium-CO{sub 2} heat exchanger. The leakage scenario which could lead to mechanical and thermal problems should be evaluated. Previous studies have reported the following major reaction formulas. Each reaction occurs competitively. In this paper, the experimental setup to observe the pressure variation and CO concentration in Na-CO{sub 2} heat exchanger during the CO{sub 2} leak is explained. Before the experiment is carried out, water-CO{sub 2} mock-up test will be performed. In order to evaluate the leakage scenario in Na-CO{sub 2} heat exchanger more accurately, this study will be important for guaranteeing the system of SFR coupled with S-CO{sub 2} cycle.

Performance estimates for the Space Station power system Brayton Cycle compressor and turbine

Science.gov (United States)

Cummings, Robert L.

1989-01-01

The methods which have been used by the NASA Lewis Research Center for predicting Brayton Cycle compressor and turbine performance for different gases and flow rates are described. These methods were developed by NASA Lewis during the early days of Brayton cycle component development and they can now be applied to the task of predicting the performance of the Closed Brayton Cycle (CBC) Space Station Freedom power system. Computer programs are given for performing these calculations and data from previous NASA Lewis Brayton Compressor and Turbine tests is used to make accurate estimates of the compressor and turbine performance for the CBC power system. Results of these calculations are also given. In general, calculations confirm that the CBC Brayton Cycle contractor has made realistic compressor and turbine performance estimates.

Exergoeconomic analysis of utilizing the transcritical CO_2 cycle and the ORC for a recompression supercritical CO_2 cycle waste heat recovery: A comparative study

International Nuclear Information System (INIS)

Wang, Xurong; Dai, Yiping

2016-01-01

Highlights: • An exergoeconomic analysis is performed for sCO_2/tCO_2 cycle. • Performance of the sCO_2/tCO_2 cycle and sCO_2/ORC cycle are presented and compared. • The sCO_2/tCO_2 cycle performs better than the sCO_2/ORC cycle at lower PRc. • The sCO_2/tCO_2 cycle has comparable total product unit cost with the sCO_2/ORC cycle. - Abstract: Two combined cogeneration cycles are examined in which the waste heat from a recompression supercritical CO_2 Brayton cycle (sCO_2) is recovered by either a transcritical CO_2 cycle (tCO_2) or an Organic Rankine Cycle (ORC) for generating electricity. An exergoeconomic analysis is performed for sCO_2/tCO_2 cycle performance and its comparison to the sCO_2/ORC cycle. The following organic fluids are considered as the working fluids in the ORC: R123, R245fa, toluene, isobutane, isopentane and cyclohexane. Thermodynamic and exergoeconomic models are developed for the cycles on the basis of mass and energy conservations, exergy balance and exergy cost equations. Parametric investigations are conducted to evaluate the influence of decision variables on the performance of sCO_2/tCO_2 and sCO_2/ORC cycles. The performance of these cycles is optimized and then compared. The results show that the sCO_2/tCO_2 cycle is preferable and performs better than the sCO_2/ORC cycle at lower PRc. When the sCO_2 cycle operates at a cycle maximum pressure of around 20 MPa (∼2.8 of PRc), the tCO_2 cycle is preferable to be integrated with the recompression sCO_2 cycle considering the off-design conditions. Moreover, contrary to the sCO_2/ORC system, a higher tCO_2 turbine inlet temperature improves exergoeconomic performance of the sCO_2/tCO_2 cycle. The thermodynamic optimization study reveals that the sCO_2/tCO_2 cycle has comparable second law efficiency with the sCO_2/ORC cycle. When the optimization is conducted based on the exergoeconomics, the total product unit cost of the sCO_2/ORC is slightly lower than that of the sCO_2/tCO_2

A treatment of thermal efficiency improvement in the Brayton cycle

International Nuclear Information System (INIS)

Fujii, Terushige; Akagawa, Koji; Nakanishi, Shigeyasu; Inoue, Kiyoshi; Ishigai, Seikan.

1982-01-01

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, NH 3 , SO 2 , CO 2 and H 2 O were examined as perfect gas and real gas. The advantage of CO 2 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.)

Enhancing power cycle efficiency for a supercritical Brayton cycle power system using tunable supercritical gas mixtures

Science.gov (United States)

Wright, Steven A.; Pickard, Paul S.; Vernon, Milton E.; Radel, Ross F.

2017-08-29

Various technologies pertaining to tuning composition of a fluid mixture in a supercritical Brayton cycle power generation system are described herein. Compounds, such as Alkanes, are selectively added or removed from an operating fluid of the supercritical Brayton cycle power generation system to cause the critical temperature of the fluid to move up or down, depending upon environmental conditions. As efficiency of the supercritical Brayton cycle power generation system is substantially optimized when heat is rejected near the critical temperature of the fluid, dynamically modifying the critical temperature of the fluid based upon sensed environmental conditions improves efficiency of such a system.

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.

Effects of hysteresis and Brayton cycle constraints on magnetocaloric refrigerant performance

Science.gov (United States)

Brown, T. D.; Buffington, T.; Shamberger, P. J.

2018-05-01

Despite promising proofs of concept, system-level implementation of magnetic refrigeration has been critically limited by history-dependent refrigerant losses that interact with governing thermodynamic cycles to adversely impact refrigeration performance. Future development demands a more detailed understanding of how hysteresis limits performance, and of how different types of cycles can mitigate these limitations, but without the extreme cost of experimental realization. Here, the utility of Brayton cycles for magnetic refrigeration is investigated via direct simulation, using a combined thermodynamic-hysteresis modeling framework to compute the path-dependent magnetization and entropy of a model alloy for a variety of feasible Brayton cycles between 0-1.5 T and 0-5 T. By simultaneously varying the model alloy's hysteresis properties and applying extensions of the thermodynamic laws to non-equilibrium systems, heat transfers and efficiencies are quantified throughout the space of hystereses and Brayton cycles and then compared with a previous investigation using Ericsson cycles. It is found that (1) hysteresis losses remain a critical obstacle to magnetic refrigeration implementation, with efficiencies >80% in the model system requiring hysteresis refrigerant transformation temperatures at the relevant fields; (3) for a given hysteresis and field constraint, Brayton and Ericsson-type cycles generate similar efficiencies; for a given temperature span, Ericsson cycles lift more heat per cycle, with the difference decreasing with the refrigerant heat capacity outside the phase transformation region.

Thermodynamic modelling of a recompression CO_2 power cycle for low temperature waste heat recovery

International Nuclear Information System (INIS)

Banik, Shubham; Ray, Satyaki; De, Sudipta

2016-01-01

Highlights: • Thermodynamic model for recompression T-CO_2 is developed. • Energetic and exergetic analysis compared with S-CO_2 and Reg. Brayton cycle. • Maximum efficiency of 13.6% is obtained for T-CO_2 cycle. • Optimum recompression ratio of 0.48 is obtained for minimum irreversibility. • Reg. Brayton has better efficiency, T-CO_2 offers minimum irreversibility. - Abstract: Due to the rising prices of conventional fossil fuels, increasing the overall thermal efficiency of a power plant is essential. One way of doing this is waste heat recovery. This recovery is most difficult for low temperature waste heat, below 240 °C, which also covers majority of the waste heat source. Carbon dioxide, with its low critical temperature and pressure, offers an advantage over ozone-depleting refrigerants used in Organic Rankine Cycles (ORCs) and hence is most suitable for the purpose. This paper introduces parametric optimization of a transcritical carbon dioxide (T-CO_2) power cycle which recompresses part of the total mass flow of working fluid before entering the precooler, thereby showing potential for higher cycle efficiency. Thermodynamic model for a recompression T-CO_2 power cycle has been developed with waste heat source of 2000 kW and at a temperature of 200 °C. Results obtained from this model are analysed to estimate effects on energetic and exergetic performances of the power cycle with varying pressure and mass recompression ratio. Higher pressure ratio always improves thermodynamic performance of the cycle – both energetic and exergetic. Higher recompression ratio also increases exergetic efficiency of the cycle. However, it increases energy efficiency, only if precooler inlet temperature remains constant. Maximum thermal efficiency of the T-CO_2 cycle with a recompression ratio of 0.26 has been found to be 13.6%. To minimize total irreversibility of the cycle, an optimum ratio of 0.48 was found to be suitable.

Supercritical CO2 test loop operation and first test results

International Nuclear Information System (INIS)

Wright, Steven A.; Pickard, Paul S.

2009-01-01

The DOE Office of Nuclear Energy is investigating advanced Brayton cycles for use with next generation nuclear power plants. The focus of this work is on the supercritical CO 2 Brayton cycle which has the potential for high efficiency, and for reduced capital costs due to very compact turbomachinery. Sandia has fabricated and is operating a supercritical CO 2 (S-CO 2 ) test loop to investigate the key technology issues associated with this cycle. This loop is part of a multi-year phased development program to develop a megawatt (MW) class closed S-CO 2 Brayton cycle to demonstrate the applicability of this cycle for DOE Gen-IV program. The current loop has been configured as both a compression loop and as simple heated but unrecuperated Brayton cycle. A second split-flow or re-compression Brayton cycle is currently under development that will use approximately 1 MW of heat to run the Brayton cycle. Early configurations of this split-flow Brayton cycle will be operational later this fiscal year. The key issues for this cycle include the fundamental issues of compressor fluid performance and system control near the critical point, but also the supporting technology issues of bearings, sealing technologies, and rotor windage losses which are also essential to achieving efficiency and cost objectives. These tests are providing the first measurements and information on these key supercritical CO 2 power conversion systems questions. Important data for all these issues has been obtained. This report presents the major results of the testing by showing and comparing the measured compressor performance map with the predicted performance. The compression loop uses a ∼50 kWe motor driven compressor to spin a 37 mm OD compressor at design speeds up to 75,000 rpm with a pressure ratio of 1.8 and a flow rate of 3.53 kg/s for a compressor inlet condition of 305.3 K and 7690 kPa. The most recent configuration of this loop has added a small turbine and 260 kW of heater power is

Thermodynamic Analysis of an Irreversible Maisotsenko Reciprocating Brayton Cycle

Directory of Open Access Journals (Sweden)

Fuli Zhu

2018-03-01

Full Text Available An irreversible Maisotsenko reciprocating Brayton cycle (MRBC model is established using the finite time thermodynamic (FTT theory and taking the heat transfer loss (HTL, piston friction loss (PFL, and internal irreversible losses (IILs into consideration in this paper. A calculation flowchart of the power output (P and efficiency (η of the cycle is provided, and the effects of the mass flow rate (MFR of the injection of water to the cycle and some other design parameters on the performance of cycle are analyzed by detailed numerical examples. Furthermore, the superiority of irreversible MRBC is verified as the cycle and is compared with the traditional irreversible reciprocating Brayton cycle (RBC. The results can provide certain theoretical guiding significance for the optimal design of practical Maisotsenko reciprocating gas turbine plants.

Potential impacts of Brayton and Stirling cycle engines

Science.gov (United States)

Heft, R. C.

1980-01-01

Two engine technologies (Brayton cycle and Stirling cycle) are examined for their potential economic impact and fuel utilization. An economic analysis of the expected response of buyers to the attributes of the alternative engines was performed. Hedonic coefficients for vehicle fuel efficiency, performance and size were estimated for domestic cars based upon historical data. The marketplace value of the fuel efficiency enhancement provided by Brayton or Stirling engines was estimated. Under the assumptions of 10 years for plant conversions and 1990 and 1995 as the introduction data for turbine and Stirling engines respectively, the comparative fuel savings and present value of the future savings in fuel costs were estimated.

A Conceptual Study of Using an Isothermal Compressor on a Supercritical CO2 Cycle for Various Nuclear Applications

International Nuclear Information System (INIS)

Heo, Jin Young; Lee, Jeong Ik

2017-01-01

In order to accelerate the deployment of cleaner and safer energy sources, further development of such advanced nuclear power systems is necessary. By aiming to have higher efficiency, lower costs, and reduced system size, next-generation nuclear reactors can have greater advantages which will justify their adoption. Many research efforts focus on these objectives to also propose new concepts and technologies to improve the present state of the art. To maximize the benefits of advanced reactor designs, the supercritical CO 2 (S-CO 2 ) power cycle can be adopted to enhance the performance of the power conversion systems. The potential of replacing the conventional power block with the S-CO 2 power cycle can increase the cycle efficiency and also reduce its overall system size. The potential of using the S-CO 2 power cycles in advanced nuclear reactors can be further improved by adopting an isothermal compressor to the cycle layout. This paper attempts to improve the cycle layout by replacing the conventional compressor with an isothermal compressor, of which its potential in the S-CO 2 power cycle is conceptually being evaluated. An isothermal compressor minimizes compression work and further reduces the system size by having smaller heat exchanger requirements. The study includes cycle optimization maximizing cycle efficiency with respect to different cycle design parameters. The S-CO 2 iso-Brayton cycle layouts have been effective in improving the cycle efficiencies of the next-generation nuclear reactors. By using the isothermal compressor, the net efficiency can be improved by 8% points for the simple recuperated cycle layout, and 5% points for the recompression cycle layout. It is also noted that the estimated UA values required for the iso-Brayton cycle layouts are almost the same or less compared to those of the reference cycle layouts.

Preliminary S-CO_2 Compressor Design for Micro Modular Reactor

International Nuclear Information System (INIS)

Lee, Jekyoung; Cho, Seong Kuk; Kim, Seong Gu; Lee, Jeong Ik

2016-01-01

Due to economic benefit of S-CO_2 Brayton cycle which is came from high efficiency and compactness, active research is currently conducted by various research groups and various approaches are suggested to take benefits of S-CO_2 Brayton cycle. KAIST research team also has been working on advanced concept for application of S-CO_2 Brayton cycle to nuclear system and Micro Modular Reactor (MMR) concept was suggested. The preliminary compressor design of S-CO_2 compressor for MMR system was carried out to observe feasibility of compressor design. Preliminary S-CO_2 compressor design for MMR system was successfully conducted and some issues are discovered from the design study. From the previous work done by Cho, conceptual design for MMR system was provided. Thus, further preliminary design should be carried out to obtain feasible S-CO_2 compressor design for MMR system. KAIST_TMD which is turbomachinery in-house code for real gases including S-CO_2 is continuously updated and currently it has 3D geometry construction and design optimization capability

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

International Nuclear Information System (INIS)

Bernardos, Eva; López, Ignacio; Rodríguez, Javier; Abánades, Alberto

2013-01-01

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

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

International Nuclear Information System (INIS)

Wang Hao; Liu Sanqiu

2008-01-01

An irreversible cycle model of magnetic Brayton refrigerators is established, in which the thermal resistance and irreversibility in the two adiabatic processes are taken into account. Expressions for several important performance parameters, such as the coefficient of performance, cooling rate and power input are derived. Moreover, the optimal performance parameters are obtained at the maximum coefficient of performance. The optimization region (or criteria) for an irreversible magnetic Brayton refrigerator is obtained. The results obtained here have general significance and will be helpful to understand deeply the performance of a magnetic Brayton refrigeration cycle

Preliminary study of Friction disk type turbine for S-CO_2 cycle application (2016 Autumn Meeting of the KNS)

International Nuclear Information System (INIS)

Baik, Seungjoon; Heo, Jin Young; Kwon, Jinsu; Lee, Jeong Ik

2016-01-01

Among the next generation reactors, a sodium-cooled fast reactor (SFR) with the supercritical carbon dioxide (S-CO_2) Brayton cycle has been suggested as the advanced energy solution. The S-CO_2 power conversion system can achieve high efficiency with the SFR core thermal condition (450-550℃) and also can reduce the total cycle footprint due to high density of the working fluid. Moreover, the S-CO_2 power cycle can reduce the accident consequence compared to the steam Rankine cycle due to the mild sodium-CO_2 interaction. The S-CO_2 power cycle has different characteristic compare to the conventional steam Rankine cycle or gas Brayton cycle. For the turbine section, the expansion ratio is much smaller than the other cycles. Thus, different type of turbine should be evaluated for the advanced S-CO_2 technology and the KAIST research team considered a friction disk type turbine (Tesla turbine) concept for the S-CO_2 cycle applications. In this paper, the test result and analysis of a lab-scale Tesla turbine in the KAIST S-CO_2 experimental facility (S-CO_2PE) are briefly discussed. The KAIST research team investigated a friction disk type turbine, named as Tesla turbine, for the S-CO_2 power cycle applications. The preliminary test of a lab-scale Tesla turbine was conducted with compressed air. The generator, nozzle angle and bearing performances are tested. With the best performing nozzle angle and bearing, the Tesla turbine was tested under various S-CO_2 conditions. As a result, the S-CO_2PE facility generated electricity (0.5-5W). The isentropic efficiency was relatively low (0.8-1.3%). It seemed that, the authors need further study to understand the main mechanism and maximize the efficiency. After developing the design methodology, the design optimization will be conducted to show the applicability of the friction disk type turbine for the S-CO_2 power cycle

Fundamental study of key issues related to advanced sCO₂ Brayton cycle: Prototypic HX development and cavitation

Energy Technology Data Exchange (ETDEWEB)

Ranjan, Devesh [Georgia Inst. of Technology, Atlanta, GA (United States)

2018-01-08

Diffusion bonded heat exchangers are the leading candidates for the sCO₂ Brayton cycles in next generation nuclear power plants. Commercially available diffusion bonded heat exchangers utilize set of continuous semi-circular zigzag micro channels to increase the heat transfer area and enhance heat transfer through increased turbulence production. Such heat exchangers can lead to excessive pressure drop as well as flow maldistribution in the case of poorly designed flow distribution headers. The goal of the current project is to fabricate and test potential discontinuous fin patterns for diffusion bonded heat exchangers; which can achieve desired thermal performance at lower pressure drops. Prototypic discontinuous offset rectangular and Airfoil fin surface geometries were chemically etched on to 316 stainless steel plate and sealed against an un-etched flat pate using O-ring seal emulating diffusion bonded heat exchangers. Thermal-hydraulic performance of these prototypic discontinuous fin geometries was experimentally evaluated and compared to the existing data for the continuous zigzag channels. The data generated from this project will serve as the database for future testing and validation of numerical models.

Energy and exergy analysis of a closed Brayton cycle-based combined cycle for solar power tower plants

International Nuclear Information System (INIS)

Zare, V.; Hasanzadeh, M.

2016-01-01

Highlights: • A novel combined cycle is proposed for solar power tower plants. • The effects of solar subsystem and power cycle parameters are examined. • The proposed combined cycle yields exergy efficiencies of higher than 70%. • For the overall power plant exergy efficiencies of higher than 30% is achievable. - Abstract: Concentrating Solar Power (CSP) technology offers an interesting potential for future power generation and research on CSP systems of all types, particularly those with central receiver system (CRS) has been attracting a lot of attention recently. Today, these power plants cannot compete with the conventional power generation systems in terms of Levelized Cost of Electricity (LCOE) and if a competitive LCOE is to be reached, employing an efficient thermodynamic power cycle is deemed essential. In the present work, a novel combined cycle is proposed for power generation from solar power towers. The proposed system consists of a closed Brayton cycle, which uses helium as the working fluid, and two organic Rankine cycles which are employed to recover the waste heat of the Brayton cycle. The system is thermodynamically assessed from both the first and second law viewpoints. A parametric study is conducted to examine the effects of key operating parameters (including solar subsystem and power cycle parameters) on the overall power plant performance. The results indicate that exergy efficiencies of higher than 30% are achieved for the overall power plant. Also, according to the results, the power cycle proposed in this work has a better performance than the other investigated Rankine and supercritical CO_2 systems operating under similar conditions, for these types of solar power plants.

Preliminary study of Friction disk type turbine for S-CO{sub 2} cycle application (2016 Autumn Meeting of the KNS)

Energy Technology Data Exchange (ETDEWEB)

Baik, Seungjoon; Heo, Jin Young; Kwon, Jinsu; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-10-15

Among the next generation reactors, a sodium-cooled fast reactor (SFR) with the supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle has been suggested as the advanced energy solution. The S-CO{sub 2} power conversion system can achieve high efficiency with the SFR core thermal condition (450-550℃) and also can reduce the total cycle footprint due to high density of the working fluid. Moreover, the S-CO{sub 2} power cycle can reduce the accident consequence compared to the steam Rankine cycle due to the mild sodium-CO{sub 2} interaction. The S-CO{sub 2} power cycle has different characteristic compare to the conventional steam Rankine cycle or gas Brayton cycle. For the turbine section, the expansion ratio is much smaller than the other cycles. Thus, different type of turbine should be evaluated for the advanced S-CO{sub 2} technology and the KAIST research team considered a friction disk type turbine (Tesla turbine) concept for the S-CO{sub 2} cycle applications. In this paper, the test result and analysis of a lab-scale Tesla turbine in the KAIST S-CO{sub 2} experimental facility (S-CO{sub 2}PE) are briefly discussed. The KAIST research team investigated a friction disk type turbine, named as Tesla turbine, for the S-CO{sub 2} power cycle applications. The preliminary test of a lab-scale Tesla turbine was conducted with compressed air. The generator, nozzle angle and bearing performances are tested. With the best performing nozzle angle and bearing, the Tesla turbine was tested under various S-CO{sub 2} conditions. As a result, the S-CO{sub 2}PE facility generated electricity (0.5-5W). The isentropic efficiency was relatively low (0.8-1.3%). It seemed that, the authors need further study to understand the main mechanism and maximize the efficiency. After developing the design methodology, the design optimization will be conducted to show the applicability of the friction disk type turbine for the S-CO{sub 2} power cycle.

Application of S-CO_2 Cycle for Small Modular Reactor coupled with Desalination System

International Nuclear Information System (INIS)

Lee, Won Woong; Bae, Seong Jun; Lee, Jeong Ik

2016-01-01

The Korean small modular reactor, SMART (System-integrated Modular Advanced ReacTor, 100MWe), is designed to achieve enhanced safety and improved economics through reliable passive safety systems, a system simplification and component modularization. SMART can generate electricity and provide water by seawater desalination. However, due to the desalination aspect of SMART, the total amount of net electricity generation is decreased from 100MWe to 90MWe. The authors suggest in this presentation that the reduction of electricity generation can be replenished by applying S-CO_2 power cycle technology. The S-CO_2 Brayton cycle, which is recently receiving significant attention as the next generation power conversion system, has some benefits such as high cycle efficiency, simple configuration, compactness and so on. In this study, the cycle performance analysis of the S-CO_2 cycles for SMART with desalination system is conducted. The simple recuperated S-CO_2 cycle is revised for coupling with desalination system. The three revised layout are proposed for the cycle performance comparison. In this results of the 3rd revised layout, the cycle efficiency reached 37.8%, which is higher than the efficiency of current SMART with the conventional power conversion system 30%

High exergetic modified Brayton cycle with thermoelectric energy conversion

International Nuclear Information System (INIS)

Yazawa, Kazuaki; Fisher, Timothy S.; Groll, Eckhard A.; Shakouri, Ali

2017-01-01

Highlights: • Modified Brayton cycle with thermoelectric generators. • 1 kW power output scale hybrid gas turbine for residential applications. • Low profile TEGs are embedded in combustor/recuperator/heat-exchangers. • Analytical primary energy efficiency achieves more than 40%. - Abstract: A novel concept using thermoelectric direct power generators (TEGs) integrated into a 1 kW scale miniature Brayton cycle is investigated based on an analytical study. The work considers a residential scale application aiming to achieve 40% primary energy efficiency in contrast to the state-of-the-art miniature gas turbine alone, which can only achieve <16%. A topping cycle TEG for a hot gas temperature at 1600–1700 °C is embedded in the combustor scale of a kitchen stove. This TEG converts a fraction of the heat into electricity, while all the remaining thermal energy proceeds to the Brayton cycle. Turbine-inlet gas temperature regulates to 800–1100 °C by optimizing the air mixture. A second TEG is built in the recuperator; hence, the associated temperature is similar to that of a vehicle exhaust. A third TEG is used for waste heat recovery from flue gas, and then the downstream heat flow is used by a combined-heat-power system. By taking advantage of low-profile modules, the TEG embedded heat exchanges can be compact and low-cost at 0.2–0.3 $/W. The figure-of-merit of the thermoelectric materials considers ZT 1.0–1.8. Assuming that all advanced components are utilized, the primary energy efficiency predicts 42% with power output 720 W from the alternator and 325 W from the TEGs out of 0.456 g/s of a pipeline natural gas input.

Exergy and exergoeconomic analyses of a supercritical CO_2 cycle for a cogeneration application

International Nuclear Information System (INIS)

Wang, Xurong; Yang, Yi; Zheng, Ya; Dai, Yiping

2017-01-01

Detailed exergy and exergoeconomic analyses are performed for a combined cogeneration cycle in which the waste heat from a recompression supercritical CO_2 Brayton cycle (sCO_2) is recovered by a transcritical CO_2 cycle (tCO_2) for generating electricity. Thermodynamic and exergoeconomic models are developed on the basis of mass and energy conservations, exergy balance and exergy cost equations. Parametric investigations are then conducted to evaluate the influence of key decision variables on the sCO_2/tCO_2 performance. Finally, the combined cycle is optimized from the viewpoint of exergoeconomics. It is found that, combining the sCO_2 with a tCO_2 cycle not only enhances the energy and exergy efficiencies of the sCO_2, but also improves the cycle exergoeconomic performance. The results show that the most exergy destruction rate takes place in the reactor, and the components of the tCO_2 bottoming cycle have less exergy destruction. When the optimization is conducted based on the exergoeconomics, the overall exergoeconomic factor, the total cost rate and the exergy destruction cost rate are 53.52%, 11243.15 $/h and 5225.17 $/h, respectively. The optimization study reveals that an increase in reactor outlet temperature leads to a decrease in total cost rate and total exergy destruction cost rate of the system. - Highlights: • Exergy and exergoeconomic analyses of a combined sCO_2/tCO_2 cycle were performed. • Exergoeconomic optimization of the sCO_2/tCO_2 cycle was presented. • The reactor had the highest exergy loss among sCO_2/tCO_2 cycle components. • The overall exergoeconomic factor was up to 53.5% for the optimum case.

Brayton Cycle Numerical Modeling using the RELAP5-3D code, version 4.3.4

Energy Technology Data Exchange (ETDEWEB)

Longhini, Eduardo P.; Lobo, Paulo D.C.; Guimarães, Lamartine N.F.; Filho, Francisco A.B.; Ribeiro, Guilherme B., E-mail: edu_longhini@yahoo.com.br [Instituto de Estudos Avançados (IEAv), São José dos Campos, SP (Brazil). Divisão de Energia Nuclear

2017-07-01

This work contributes to enable and develop technologies to mount fast micro reactors, to generate heat and electric energy, for the purpose to warm and to supply electrically spacecraft equipment and, also, the production of nuclear space propulsion effect. So, for this purpose, the Brayton Cycle demonstrates to be an optimum approach for space nuclear power. The Brayton thermal cycle gas has as characteristic to be a closed cycle, with two adiabatic processes and two isobaric processes. The components performing the cycle's processes are compressor, turbine, heat source, cold source and recuperator. Therefore, the working fluid's mass flow runs the thermal cycle that converts thermal energy into electrical energy, able to use in spaces and land devices. The objective is numerically to model the Brayton thermal cycle gas on nominal operation with one turbomachine composed for a radial-inflow compressor and turbine of a 40.8 kWe Brayton Rotating Unit (BRU). The Brayton cycle numerical modeling is being performed with the program RELAP5-3D, version 4.3.4. The nominal operation uses as working fluid a mixture 40 g/mole He-Xe with a flow rate of 1.85 kg/s, shaft rotational speed of 45 krpm, compressor and turbine inlet temperature of 400 K and 1149 K, respectively, and compressor exit pressure 0.931 MPa. Then, the aim is to get physical corresponding data to operate each cycle component and the general cycle on this nominal operation. (author)

Brayton Cycle Numerical Modeling using the RELAP5-3D code, version 4.3.4

International Nuclear Information System (INIS)

Longhini, Eduardo P.; Lobo, Paulo D.C.; Guimarães, Lamartine N.F.; Filho, Francisco A.B.; Ribeiro, Guilherme B.

2017-01-01

This work contributes to enable and develop technologies to mount fast micro reactors, to generate heat and electric energy, for the purpose to warm and to supply electrically spacecraft equipment and, also, the production of nuclear space propulsion effect. So, for this purpose, the Brayton Cycle demonstrates to be an optimum approach for space nuclear power. The Brayton thermal cycle gas has as characteristic to be a closed cycle, with two adiabatic processes and two isobaric processes. The components performing the cycle's processes are compressor, turbine, heat source, cold source and recuperator. Therefore, the working fluid's mass flow runs the thermal cycle that converts thermal energy into electrical energy, able to use in spaces and land devices. The objective is numerically to model the Brayton thermal cycle gas on nominal operation with one turbomachine composed for a radial-inflow compressor and turbine of a 40.8 kWe Brayton Rotating Unit (BRU). The Brayton cycle numerical modeling is being performed with the program RELAP5-3D, version 4.3.4. The nominal operation uses as working fluid a mixture 40 g/mole He-Xe with a flow rate of 1.85 kg/s, shaft rotational speed of 45 krpm, compressor and turbine inlet temperature of 400 K and 1149 K, respectively, and compressor exit pressure 0.931 MPa. Then, the aim is to get physical corresponding data to operate each cycle component and the general cycle on this nominal operation. (author)

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.

Preliminary Test of Friction disk type turbine for S-CO{sub 2} cycle application

Energy Technology Data Exchange (ETDEWEB)

Baik, Seungjoon; Kim, Hyeon Tae; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

Due to the relatively mild sodium-CO{sub 2} interaction, the S-CO{sub 2} Brayton cycle can reduce the accident consequence compared to the steam Rankine cycle. Also the S-CO{sub 2} power conversion cycle can achieve high efficiency for SFR core thermal condition. Moreover, the S-CO{sub 2} power cycle can reduce the total cycle footprint due to high density of the working fluid. However, the high pressure operating condition and low viscosity of the fluid cause difficulties in designing appropriate seals and multi-stage turbo machineries. To solve the problem for designing turbo machineries in a creative way, KAIST research team tested a friction disk type turbine concept for the S-CO{sub 2} cycle application. In this paper, the investigation of the Tesla turbine and preliminary test results with compressed air are covered. The KAIST research team investigated a friction disk type turbine, named as Tesla turbine, for the S-CO{sub 2} power cycle applications. Due to the robust design of the fiction disk type, the Tesla turbine technology can be utilized not only for S-CO{sub 2} turbo machinery but also for the multi-phase or sludge flow turbo machinery. The preliminary test of lab-scale Tesla turbine with compressed air was conducted. The high pressure vessel was manufactured for the S-CO{sub 2} operating condition. The test will be concentrated on the turbine efficiency measurement under various conditions and development of the design methodology.

Closed Brayton cycle power conversion systems for nuclear reactors :

Energy Technology Data Exchange (ETDEWEB)

Wright, Steven A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Lipinski, Ronald J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vernon, Milton E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Sanchez, Travis [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

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

Brayton-Cycle Baseload Power Tower CSP System

Energy Technology Data Exchange (ETDEWEB)

Anderson, Bruce [Wilson Solarpower Corporation, Boston, MA (United States)

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.

Investigation of CO{sub 2} Recovery System Design in Supercritical Carbon Dioxide Power Cycle for Sodium-cooled Fast Reactor

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Seok; Jung, Hwa-Young; Ahn, Yoonhan; Cho, Seong Kuk; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2015-10-15

These are mainly possible because the S-CO{sub 2} Brayton cycle has lower compressing work than other Brayton cycles due to its high density and low compressibility near the critical point. These attributes make easier to achieve higher turbine inlet temperature. Furthermore, the coolant chemistry control and component cooling systems are relatively simple for the S-CO{sub 2} cycle unlike the steam Rankine cycle, and therefore the total plant footprint can be greatly reduced further. However, certain amount of leakage flow is inevitable in the rotating turbo-machinery since the S-CO{sub 2} power cycle is a highly pressurized system. A computational model of critical flow in turbo-machinery seal is essential to predict the leakage flow and calculate the required total mass of working fluid in S-CO{sub 2} power system. Before designing a computational model of critical flow in turbo-machinery seal, this paper will identify what the issues are in predicting leakage flow and how these issues can be successfully addressed. Also, suitability of this solution in a large scale S-CO{sub 2} power cycle will be discussed, because this solution is for the small scale. S-CO{sub 2} power cycle has gained interest especially for the SFR application as an alternative to the conventional steam Rankine cycle, since S-CO{sub 2} power cycle can provide better performance and enhance safety. This paper discussed what the problem in leakage flow is and how to deal with this problem at present. High cavity pressure causing instability of gas foil bearing and large windage losses can be reduced by booster pump used to scavenge the gas in the rotor cavity. Also, labyrinth seals can be another good solution to decrease the rotor cavity pressure. Additionally, difference between large and small scale S-CO{sub 2} power cycle in turbo-machinery leakage is addressed. It is shown that optimization of CO{sub 2} recovery system design is more important to large scale S-CO{sub 2} power cycle. For

Identified corrosion and erosion mechanisms in SCO2 Brayton Cycles.

Energy Technology Data Exchange (ETDEWEB)

Fleming, Darryn D.; Kruizenga, Alan Michael

2014-06-01

Supercritical Carbon Dioxide (S-CO2) is an efficient and flexible working fluid for power production. Research to interface S-CO2 systems with nuclear, thermal solar, and fossil energy sources is currently underway. To proceed, we must address concerns regarding compatibility of materials, at high temperature, and compatibility between significantly different heat transfer fluids. Dry, pure S-CO2 is thought to be relatively inert [1], while the addition of ppm levels of water and oxygen result in formation of a protective chromia layer and iron oxide [2]. Thin oxides are favorable as diffusion barriers, and for their minimal impact on heat transfer. While S-CO2 is typically understood to be the secondary fluid, many varieties of primary fluids exist for nuclear applications. Molten salts, for use in the Molten Salt Reactor concept, are given as an example to contrast the materials requirements of primary and secondary fluids. Thin chromia layers are soluble in molten salt systems (nitrate, chloride, and fluoride based salts) [3-8], making materials selection for heat exchangers a precarious balancing act between high temperature oxidation (S-CO2) and metal dissolution (salt side of heat exchanger). Because concerns have been raised regarding component lifetimes, S-CO2 work has begun to characterize starting materials and to establish a baseline by analysis of 1) as-received stainless steel piping, and 2) piping exposed to S-CO2 under typical operating conditions with Sandia National Laboratories Brayton systems. A second issue discovered by SNL involves substantial erosion in the turbine blade and inlet nozzle. It is believed that this is caused by small particulates that originate from different materials around the loop that are entrained by the S-CO2 to the nozzle, where they impact the inlet nozzle vanes, causing erosion. We believe that, in some way, this is linked to the purity of the S-CO2, the corrosion contaminants, and the metal particulates that

Validation of the CATHARE2 code against experimental data from Brayton-cycle plants

International Nuclear Information System (INIS)

Bentivoglio, Fabrice; Tauveron, Nicolas; Geffraye, Genevieve; Gentner, Herve

2008-01-01

In recent years the Commissariat a l'Energie Atomique (CEA) has commissioned a wide range of feasibility studies of future-advanced nuclear reactors, in particular gas-cooled reactors (GCR). The thermohydraulic behaviour of these systems is a key issue for, among other things, the design of the core, the assessment of thermal stresses, and the design of decay heat removal systems. These studies therefore require efficient and reliable simulation tools capable of modelling the whole reactor, including the core, the core vessel, piping, heat exchangers and turbo-machinery. CATHARE2 is a thermal-hydraulic 1D reference safety code developed and extensively validated for the French pressurized water reactors. It has been recently adapted to deal also with gas-cooled reactor applications. In order to validate CATHARE2 for these new applications, CEA has initiated an ambitious long-term experimental program. The foreseen experimental facilities range from small-scale loops for physical correlations, to component technology and system demonstration loops. In the short-term perspective, CATHARE2 is being validated against existing experimental data. And in particular from the German power plants Oberhausen I and II. These facilities have both been operated by the German utility Energie Versorgung Oberhausen (E.V.O.) and their power conversion systems resemble to the high-temperature reactor concepts: Oberhausen I is a 13.75-MWe Brayton-cycle air turbine plant, and Oberhausen II is a 50-MWe Brayton-cycle helium turbine plant. The paper presents these two plants, the adopted CATHARE2 modelling and a comparison between experimental data and code results for both steady state and transient cases

Performance analysis of different working gases for concentrated solar gas engines: Stirling & Brayton

International Nuclear Information System (INIS)

Sharaf Eldean, Mohamed A.; Rafi, Khwaja M.; Soliman, A.M.

2017-01-01

Highlights: • Different working gases are used to power on Concentrated Solar Gas Engines. • Gases are used to increase the system efficiency. • Specific heat capacity is considered a vital role for the comparison. • Brayton engine resulted higher design limits. • CO 2 is favorable as a working gas more than C 2 H 2 . - Abstract: This article presents a performance study of using different working fluids (gases) to power on Concentrated Solar Gas Engine (CSGE-Stirling and/or Brayton). Different working gases such as Monatomic (five types), Diatomic (three types) and Polyatomic (four types) are used in this investigation. The survey purported to increase the solar gas engine efficiency hence; decreasing the price of the output power. The effect of using different working gases is noticed on the engine volume, dish area, total plant area, efficiency, compression and pressure ratios thence; the Total Plant Cost (TPC, $). The results reveal that the top cycle temperature effect is reflected on the cycle by increasing the total plant efficiency (2–10%) for Brayton operational case and 5–25% for Stirling operational case. Moreover; Brayton engine resulted higher design limits against the Stirling related to total plant area, m 2 and TPC, $ while generating 1–100 MW e as an economic case study plant. C 2 H 2 achieved remarkable results however, CO 2 is considered for both cycles operation putting in consideration the gas flammability and safety issues.

Application of S-CO{sub 2} Cycle for Small Modular Reactor coupled with Desalination System

Energy Technology Data Exchange (ETDEWEB)

Lee, Won Woong; Bae, Seong Jun; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-10-15

The Korean small modular reactor, SMART (System-integrated Modular Advanced ReacTor, 100MWe), is designed to achieve enhanced safety and improved economics through reliable passive safety systems, a system simplification and component modularization. SMART can generate electricity and provide water by seawater desalination. However, due to the desalination aspect of SMART, the total amount of net electricity generation is decreased from 100MWe to 90MWe. The authors suggest in this presentation that the reduction of electricity generation can be replenished by applying S-CO{sub 2} power cycle technology. The S-CO{sub 2} Brayton cycle, which is recently receiving significant attention as the next generation power conversion system, has some benefits such as high cycle efficiency, simple configuration, compactness and so on. In this study, the cycle performance analysis of the S-CO{sub 2} cycles for SMART with desalination system is conducted. The simple recuperated S-CO{sub 2} cycle is revised for coupling with desalination system. The three revised layout are proposed for the cycle performance comparison. In this results of the 3rd revised layout, the cycle efficiency reached 37.8%, which is higher than the efficiency of current SMART with the conventional power conversion system 30%.

Optimization of advanced high-temperature Brayton cycles with multiple reheat stages

International Nuclear Information System (INIS)

Haihua Zhao; Per F Peterson

2005-01-01

Full text of publication follows: This paper presents an overview and a few point designs for multiple-reheat Brayton cycle power conversion systems using high temperature molten salts (or liquid metals). All designs are derived from the General Atomics GT-MHR power conversion unit (PCU). The GT-MHR PCU is currently the only closed helium cycle system that has undergone detailed engineering design analysis, and that has turbomachinery which is sufficiently large to extrapolate to a >1000 MW(e) multiple reheat gas cycle power conversion system. Analysis shows that, with relatively small engineering modifications, multiple GT-MHR PCU's can be connected together to create a power conversion system in the >1000 MW(e) class. The resulting power conversion system is quite compact, and results in what is likely the minimum gas duct volume possible for a multiple-reheat system. To realize this, compact offset fin plate type liquid-to-gas heat exchangers (power densities from 10 to 120 MW/m 3 ) are needed. Both metal and non-metal heat exchangers are being investigated for high-temperature, gas-cooled reactors for temperatures to 1000 deg. C. Recent high temperature heat exchanger studies for nuclear hydrogen production has suggested that carbon-coated composite materials such as liquid silicon infiltrated chopped fiber carbon-carbon preformed material potentially could be used to fabricate plate fin heat exchangers with reasonable price. Different fluids such as helium, nitrogen and helium mixture, and supercritical CO 2 are compared for these multiple reheat Brayton cycles. Nitrogen and helium mixture cycle need about 40% more total PCU volume than helium cycle while keeping the same net cycle efficiency. Supercritical CO 2 needs very high pressure to optimize. Due to relatively detailed design for components such as heat exchangers, turbomachinery, and duct system, relatively accurate total pressure loss can be obtained, which results in more credible net efficiency

Study on CO{sub 2} Recovery System Design in Supercritical CO{sub 2} Cycle for SFR Application

Energy Technology Data Exchange (ETDEWEB)

Kim, Min Seok; Jung, Hwa-Young; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-10-15

As a part of Sodium-cooled Fast Reactor (SFR) development in Korea, the supercritical CO{sub 2} (S-CO{sub 2}) Brayton cycle is considered as an alternative power conversion system to eliminate sodium-water reaction (SWR) when the current conventional steam Rankine cycle is utilized with SFR. The parasitic loss caused by the leakage flow should be minimized since this greatly influences the cycle efficiency. Thus, a simple model for estimating the critical flow in a turbo-machinery seal was developed to predict the leakage flow rate and calculate the required total mass of working fluid in a S-CO{sub 2} power system to minimize the parasitic loss. In this work, study on CO{sub 2} recovery system design was conducted by finding the suitable recovery point with the developed simple CO{sub 2} critical flow model and sensitivity analysis was performed on the power system performance with respect to multiple CO{sub 2} recovery process options. The study of a CO{sub 2} recovery system design was conducted to minimize the thermal efficiency losses caused by CO{sub 2} inventory recovery system. For the first step, the configuration of a seal was selected. A labyrinth seal has suitable features for the S-CO{sub 2} power cycle application. Then, thermal efficiency losses with different CO{sub 2} leak rate and recovery point were evaluated. To calculate the leak rate in turbo-machinery by using the developed CO{sub 2} critical flow model, the conditions of storage tank is set to be closer to the recovery point. After modifying the critical flow model appropriately, total mass flow rate of leakage flow was calculated. Finally, the CO{sub 2} recovery system design work was performed to minimize the loss of thermal efficiency. The suggested system is not only simple and intuitive but also has relatively very low additional work loss from the compressor than other considered systems. When each leak rate is set to the conventional leakage rate of 1 kg/s per seal, the minimum and

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

International Nuclear Information System (INIS)

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 (sCO 2 ) 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 sCO 2 Brayton cycles, can be assessed as a retrofit measure for present light water reactors. Transient simulations are hereby of great importance. The heat removal system has to be modeled explicitly to account for the interaction between the system and the behavior of the plant during different accident conditions. As a first step, transport and thermodynamic fluid properties of supercritical carbon dioxide have been implemented in ATHLET to allow for the simulation of the new working fluid. Additionally, a heat transfer correlation has been selected to represent the specific heat transfer of supercritical carbon dioxide. For the calculation of pressure losses due to wall friction, an approach for turbulent single phase flow has been adopted that is already implemented in ATHLET. In a second step, a component model for radial compressors has been implemented in the system code. Furthermore, the available model for axial turbines has been adapted to simulate the transient behavior of radial turbines. All extensions have been validated against experimental data. In order to simulate the interaction between the self-propelling heat removal system and a generic boiling water reactor, the components of the sCO 2 Brayton cycle have been dimensioned with first principles. An available input deck of a generic BWR has then been extended by the residual heat removal system. The modeled application has shown that the extended version of ATHLET is suitable to simulate sCO 2 Brayton cycles and to evaluate the introduced heat removal system

Cascaded recompression closed brayton cycle system

Energy Technology Data Exchange (ETDEWEB)

Pasch, James J.

2018-01-02

The present disclosure is directed to a cascaded recompression closed Brayton cycle (CRCBC) system and method of operation thereof, where the CRCBC system includes a compressor for compressing the system fluid, a separator for generating fluid feed streams for each of the system's turbines, and separate segments of a heater that heat the fluid feed streams to different feed temperatures for the system's turbines. Fluid exiting each turbine is used to preheat the fluid to the turbine. In an embodiment, the amount of heat extracted is determined by operational costs.

Cascaded recompression closed brayton cycle system

Science.gov (United States)

Pasch, James J.

2018-01-02

The present disclosure is directed to a cascaded recompression closed Brayton cycle (CRCBC) system and method of operation thereof, where the CRCBC system includes a compressor for compressing the system fluid, a separator for generating fluid feed streams for each of the system's turbines, and separate segments of a heater that heat the fluid feed streams to different feed temperatures for the system's turbines. Fluid exiting each turbine is used to preheat the fluid to the turbine. In an embodiment, the amount of heat extracted is determined by operational costs.

Performance Estimation of Supercritical CO2 Cycle for the PG-SFR application with Heat Sink Temperature Variation

International Nuclear Information System (INIS)

Ahn, Yoonhan; Cho, Seong Kuk; Lee, Jeong Ik

2015-01-01

The heat sink temperature conditions are referred from the annual database of sea water temperature in East sea. When the heat sink temperature increases, the compressor inlet temperature can be influenced and the sudden power decrease can happen due to the large water pumping power. When designing the water pump, the pumping margin should be considered as well. As a part of Prototype Generation IV Sodium-cooled Fast Reactor (PG-SFR) development, the Supercritical CO 2 cycle (S-CO 2 ) is considered as one of the promising candidate that can potentially replace the steam Rankine cycle. S-CO 2 cycle can achieve distinctively high efficiency compared to other Brayton cycles and even competitive performance to the steam Rankine cycle under the mild turbine inlet temperature region. Previous studies explored the optimum size of the S-CO 2 cycle considering component designs including turbomachinery, heat exchangers and pipes. Based on the preliminary design, the thermal efficiency is 31.5% when CO 2 is sufficiently cooled to the design temperature. However, the S-CO 2 compressor performance is highly influenced by the inlet temperature and the compressor inlet temperature can be changed when the heat sink temperature, in this case sea water temperature varies. To estimate the S-CO 2 cycle performance of PG-SFR in the various regions, a Quasi-static system analysis code for S-CO 2 cycle is developed by the KAIST research team. A S-CO 2 cycle for PG-SFR is designed and assessed for off-design performance with the heat sink temperature variation

Performance analysis of Brayton cycle system for space power reactor

International Nuclear Information System (INIS)

Li Zhi; Yang Xiaoyong; Zhao Gang; Wang Jie; Zhang Zuoyi

2017-01-01

The closed Brayton cycle system now is the potential choice as the power conversion system for High Temperature Gas-cooled Reactors because of its high energy conversion efficiency and compact configuration. The helium is the best working fluid for the system for its chemical stability and small neutron absorption cross section. However, the Helium has small mole mass and big specific volume, which would lead to larger pipes and heat exchanger. What's more, the big compressor enthalpy rise of helium would also lead to an unacceptably large number of compressor's stage. For space use, it's more important to satisfy the limit of the system's volume and mass, instead of the requirement of the system's thermal capacity. So Noble-Gas binary mixture of helium and xenon is presented as the working fluid for space Brayton cycle. This paper makes a mathematical model for space Brayton cycle system by Fortran language, then analyzes the binary mixture of helium and xenon's properties and effects on power conversion units of the space power reactor, which would be helpful to understand and design the space power reactor. The results show that xenon would lead to a worse system's thermodynamic property, the cycle's efficiency and specific power decrease as xenon's mole fraction increasing. On the other hand, proper amount of xenon would decrease the enthalpy changes in turbomachines, which would be good for turbomachines' design. Another optimization method – the specific power optimization is also proposed to make a comparison. (author)

Exergoeconomic multi objective optimization and sensitivity analysis of a regenerative Brayton cycle

International Nuclear Information System (INIS)

Naserian, Mohammad Mahdi; Farahat, Said; Sarhaddi, Faramarz

2016-01-01

Highlights: • Finite time exergoeconomic multi objective optimization of a Brayton cycle. • Comparing the exergoeconomic and the ecological function optimization results. • Inserting the cost of fluid streams concept into finite-time thermodynamics. • Exergoeconomic sensitivity analysis of a regenerative Brayton cycle. • Suggesting the cycle performance curve drawing and utilization. - Abstract: In this study, the optimal performance of a regenerative Brayton cycle is sought through power maximization and then exergoeconomic optimization using finite-time thermodynamic concept and finite-size components. 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 used deploying time variations. The decision variables for the optimum state (of multi objective exergoeconomic optimization) are compared to the maximum power state. One can see that the multi objective exergoeconomic optimization results in a better performance than that obtained with the maximum power state. The results demonstrate that system performance at optimum point of multi objective optimization yields 71% of the maximum power, but only with exergy destruction as 24% of the amount that is produced at the maximum power state and 67% lower total cost rate than that of the maximum power state. In order to assess the impact of the variation of the decision variables on the objective functions, sensitivity analysis is conducted. Finally, the cycle performance curve drawing according to exergoeconomic multi objective optimization results and its utilization, are suggested.

New exergy analysis of a regenerative closed Brayton cycle

International Nuclear Information System (INIS)

Naserian, Mohammad Mahdi; Farahat, Said; Sarhaddi, Faramarz

2017-01-01

Highlights: • The maximum power is studied relating to time and size constraints variations. • The influence of time and size constraints on exergy destruction are investigated. • The definitions of heat exergy, and second law efficiency are modified. - Abstract: In this study, the optimal performance of a regenerative closed Brayton cycle is sought through power maximization. Optimization is performed on the output power as the objective function using genetic algorithm. In order to take into account the time and the size constraints in current problem, the dimensionless mass-flow parameter is used. The influence of the unavoidable exergy destruction due to finite-time constraint is taken into account by developing the definition of heat exergy. Finally, the improved definitions are proposed for heat exergy, and the second law efficiency. Moreover, the new definitions will be compared with the conventional ones. For example, at a specified dimensionless mass-flow parameter, exergy overestimation in conventional definition, causes about 31% lower estimation of the second law efficiency. These results could be expected to be utilized in future solar thermal Brayton cycle assessment and optimization.

Brayton-Cycle Power-Conversion Unit Tested With Ion Thruster

Science.gov (United States)

Hervol, David S.

2005-01-01

Nuclear electric propulsion has been identified as an enabling technology for future NASA space science missions, such as the Jupiter Icy Moons Orbiter (JIMO) now under study. An important element of the nuclear electric propulsion spacecraft is the power conversion system, which converts the reactor heat to electrical power for use by the ion propulsion system and other spacecraft loads. The electrical integration of the power converter and ion thruster represents a key technical challenge in making nuclear electric propulsion technology possible. This technical hurdle was addressed extensively on December 1, 2003, when a closed- Brayton-cycle power-conversion unit was tested with a gridded ion thruster at the NASA Glenn Research Center. The test demonstrated end-to-end power throughput and marked the first-ever coupling of a Brayton turbo alternator and a gridded ion thruster, both of which are candidates for use on JIMO-type missions. The testing was conducted at Glenn's Vacuum Facility 6, where the Brayton unit was installed in the 3-m-diameter vacuum test port and the ion thruster was installed in the 7.6-m-diameter main chamber.

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

Small particle bed reactors: Sensitivity to Brayton cycle parameters

Science.gov (United States)

Coiner, John R.; Short, Barry J.

Relatively simple particle bed reactor (PBR) algorithms were developed for optimizing low power closed Brayton cycle (CBC) systems. These algorithms allow the system designer to understand the relationship among key system parameters as well as the sensitivity of the PBR size and mass (a major system component) to variations in these parameters. Thus, system optimization can be achieved.

Supercritical CO2 Compressor with Active Magnetic Bearing

International Nuclear Information System (INIS)

Cha, Jae Eun; Cho, Seong Kuk; Lee, JeKyoung; Lee, Jeong Ik

2016-01-01

For the stable operation of the sCO 2 integral test facility SCIEL, KAERI prepared Active Magnetic Bearing sCO 2 compressor for the 70,000RPM operation. Power generation test with AMB compressor will be finished within first half year of 2016 under supercritical state. The principal advantages of the sCO 2 Cycle are high efficiency at moderate temperature range, compact components size, simple cycle configuration, and compatibility with various heat sources. The Supercritical CO 2 Brayton Cycle Integral Experiment Loop (SCIEL) has been installed in Korea Atomic Energy Research Institute (KAERI) to develop the base technologies for the sCO 2 cycle power generation system. The operation of the SCIEL has mainly focused on sCO 2 compressor development and establishing sCO 2 system control logic

PCU arrangement of a supercritical CO{sub 2} cooled micro modular reactor

Energy Technology Data Exchange (ETDEWEB)

Kim, Seong Gu; Baik, Seungjoon; Cho, Seong Kuk; Oh, Bong Seong; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

As part of the SMR(Small Modular Reactor)s development effort, the authors propose a concept of supercritical CO{sub 2} (S-CO{sub 2}) cooled fast reactor combined with the S-CO{sub 2} Brayton cycle. The reactor concept is named as KAIST Micro Modular Reactor (MMR). The S-CO{sub 2} Brayton cycle has many strong points when it is used for SMR's power conversion unit. It occupies small footprints due to the compact cycle components and simple layout. Thus, a concept of one module containing the S-CO{sub 2} cooled fast reactor and power conversion system is possible. This module can be shipped via ground transportation (by trailer) or marine transportation. In this study, the authors propose a new conceptual layout for the S-CO{sub 2} cooled direct cycle while considering various issues for arranging cycle components. The new design has an improved cycle efficiency (from 31% to 34%) than the earlier version of MMR by reducing pressure drops in the heat exchangers. As a more efficient option, a recompression recuperated cycle was also designed. It improves 5% of thermal efficiency while 18tons of mass can be added in comparison to the simple recuperated cycle. Even if we adopt recompression cycle as a PCU, the weight of module (152tons) is less than the ground transportable limit (260tons)

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

Energy Technology Data Exchange (ETDEWEB)

Venker, Jeanne

2015-03-31

The objective of the current work was to develop a model that is able to describe the transient behavior of supercritical carbon dioxide (sCO{sub 2}) 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 sCO{sub 2} Brayton cycles, can be assessed as a retrofit measure for present light water reactors. Transient simulations are hereby of great importance. The heat removal system has to be modeled explicitly to account for the interaction between the system and the behavior of the plant during different accident conditions. As a first step, transport and thermodynamic fluid properties of supercritical carbon dioxide have been implemented in ATHLET to allow for the simulation of the new working fluid. Additionally, a heat transfer correlation has been selected to represent the specific heat transfer of supercritical carbon dioxide. For the calculation of pressure losses due to wall friction, an approach for turbulent single phase flow has been adopted that is already implemented in ATHLET. In a second step, a component model for radial compressors has been implemented in the system code. Furthermore, the available model for axial turbines has been adapted to simulate the transient behavior of radial turbines. All extensions have been validated against experimental data. In order to simulate the interaction between the self-propelling heat removal system and a generic boiling water reactor, the components of the sCO{sub 2} Brayton cycle have been dimensioned with first principles. An available input deck of a generic BWR has then been extended by the residual heat removal system. The modeled application has shown that the extended version of ATHLET is suitable to simulate sCO{sub 2} Brayton cycles and to evaluate the introduced

Evaluation and Optimization of a Supercritical Carbon Dioxide Power Conversion Cycle for Nuclear Applications

International Nuclear Information System (INIS)

Harvego, Edwin A.; McKellar, Michael G.

2011-01-01

There have been a number of studies involving the use of gases operating in the supercritical mode for power production and process heat applications. Supercritical carbon dioxide (CO2) is particularly attractive because it is capable of achieving relatively high power conversion cycle efficiencies in the temperature range between 550 C and 750 C. Therefore, it has the potential for use with any type of high-temperature nuclear reactor concept, assuming reactor core outlet temperatures of at least 550 C. The particular power cycle investigated in this paper is a supercritical CO2 Recompression Brayton Cycle. The CO2 Recompression Brayton Cycle can be used as either a direct or indirect power conversion cycle, depending on the reactor type and reactor outlet temperature. The advantage of this cycle when compared to the helium Brayton Cycle is the lower required operating temperature; 550 C versus 850 C. However, the supercritical CO2 Recompression Brayton Cycle requires an operating pressure in the range of 20 MPa, which is considerably higher than the required helium Brayton cycle operating pressure of 8 MPa. This paper presents results of analyses performed using the UniSim process analyses software to evaluate the performance of the supercritical CO2 Brayton Recompression Cycle for different reactor outlet temperatures. The UniSim model assumed a 600 MWt reactor power source, which provides heat to the power cycle at a maximum temperature of between 550 C and 750 C. The UniSim model used realistic component parameters and operating conditions to model the complete power conversion system. CO2 properties were evaluated, and the operating range for the cycle was adjusted to take advantage of the rapidly changing conditions near the critical point. The UniSim model was then optimized to maximize the power cycle thermal efficiency at the different maximum power cycle operating temperatures. The results of the analyses showed that power cycle thermal efficiencies in

FY-05 Second Quarter Report On Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving PBR Efficiency and Testing Material Compatibility

International Nuclear Information System (INIS)

Chang Oh

2005-01-01

The objective of this research is to improve a helium Brayton cycle and to develop a supercritical carbon dioxide Brayton cycle for the Pebble Bed Reactor (PBR) that can also be applied to the Fast Gas-Cooled Reactor (FGR) and the Very-High-Temperature Gas-Cooled Reactor (VHTR). The proposed supercritical carbon dioxide Brayton cycle will be used to improve the PBR, FGR, and VHTR net plant efficiency. Another objective of this research is to test materials to be used in the power conversion side at supercritical carbon dioxide conditions. Generally, the optimized Brayton cycle and balance of plant (BOP) to be developed from this study can be applied to Generation-IV reactor concepts. Particularly, we are interested in VHTR because it has a good chance of being built in the near future

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

International Nuclear Information System (INIS)

Ashe, T.L.; Baggenstoss, W.G.; Bons, R.

1990-01-01

Extra-terrestrial exploration and development missions of the next century will require reliable, low-mass power generation modules of 100 kW e 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

High-Efficiency Low-Cost Solar Receiver for Use Ina a Supercritical CO₂ Recompression Cycle

Energy Technology Data Exchange (ETDEWEB)

Sullivan, Shaun D. [Brayton Energy, LLC, Portsmouth, NH (United States); Kesseli, James [Brayton Energy, LLC, Portsmouth, NH (United States); Nash, James [Brayton Energy, LLC, Portsmouth, NH (United States); Farias, Jason [Brayton Energy, LLC, Portsmouth, NH (United States); Kesseli, Devon [Brayton Energy, LLC, Portsmouth, NH (United States); Caruso, William [Brayton Energy, LLC, Portsmouth, NH (United States)

2016-04-06

This project has performed solar receiver designs for two supercritical carbon dioxide (sCO₂) power cycles. The first half of the program focused on a nominally 2 MWe power cycle, with a receiver designed for test at the Sandia Solar Thermal Test Facility. This led to an economical cavity-type receiver. The second half of the program focused on a 10 MWe power cycle, incorporating a surround open receiver. Rigorous component life and performance testing was performed in support of both receiver designs. The receiver performance objectives are set to conform to the US DOE goals of 6¢/kWh by 2020 . Key findings for both cavity-type and direct open receiver are highlighted below: A tube-based absorber design is impractical at specified temperatures, pressures and heat fluxes for the application; a plate-fin architecture however has been shown to meet performance and life targets; the $148/kW_th cost of the design is significantly less than the SunShot cost target with a margin of 30%; the proposed receiver design is scalable, and may be applied to both modular cavity-type installations as well as large utility-scale open receiver installations; the design may be integrated with thermal storage systems, allowing for continuous high-efficiency electrical production during off-sun hours; costs associated with a direct sCO₂ receiver for a sCO₂ Brayton power cycle are comparable to those of a typical molten salt receiver; lifetimes in excess of the 90,000 hour goal are achievable with an optimal cell geometry; the thermal performance of the Brayton receiver is significantly higher than the industry standard, and enables at least a 30% efficiency improvement over the performance of the baseline steam-Rankine boiler/cycle system; brayton’s patent-pending quartz tube window provides a greater than five-percent efficiency benefit to the receiver by reducing both convection and radiation losses.

The feasibility study on supercritical methane Recuperated Brayton Cycle for waste heat recovery

KAUST Repository

Dyuisenakhmetov, Aibolat

2017-05-01

Recuperated Brayton Cycle (RBC) has attracted the attention of research scientists not only as a possible replacement for the steam cycle at nuclear power plants but also as an efficient bottoming cycle for waste heat recovery and for concentrated solar power. RBC’s compactness and the ease at which it can be integrated into existent power plants for waste heat recovery require few modifications. Methane, carbon dioxide and trifluoromethane are analyzed as possible working fluids. This work shows that it is possible to achieve higher efficiencies using methane under some operating conditions. However, as it turns out, the performance of Recuperated Brayton Cycle should be evaluated based on net output work. When the performance is assessed on the net output work criteria carbon dioxide still proves to be superior to other gases. This work also suggests that piston engines as compressors and expanders may be used instead of rotating turbines since reciprocating pistons have higher isentropic efficiencies.

Supercritical CO{sub 2} Compressor with Active Magnetic Bearing

Energy Technology Data Exchange (ETDEWEB)

Cha, Jae Eun [KAERI, Daejeon (Korea, Republic of); Cho, Seong Kuk; Lee, JeKyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

For the stable operation of the sCO{sub 2} integral test facility SCIEL, KAERI prepared Active Magnetic Bearing sCO{sub 2} compressor for the 70,000RPM operation. Power generation test with AMB compressor will be finished within first half year of 2016 under supercritical state. The principal advantages of the sCO{sub 2} Cycle are high efficiency at moderate temperature range, compact components size, simple cycle configuration, and compatibility with various heat sources. The Supercritical CO{sub 2} Brayton Cycle Integral Experiment Loop (SCIEL) has been installed in Korea Atomic Energy Research Institute (KAERI) to develop the base technologies for the sCO{sub 2} cycle power generation system. The operation of the SCIEL has mainly focused on sCO{sub 2} compressor development and establishing sCO{sub 2} system control logic.

Design and analysis of Helium Brayton cycle for energy conversion system of RGTT200K

International Nuclear Information System (INIS)

Ignatius Djoko Irianto

2016-01-01

The helium Brayton cycle for the design of cogeneration energy conversion system for RGTT200K have been analyzed to obtain the higher thermal efficiency and energy utilization factor. The aim of this research is to analyze the potential of the helium Brayton cycle to be implemented in the design of cogeneration energy conversion system of RGTT200K. Three configuration models of cogeneration energy conversion systems have been investigated. In the first configuration model, an intermediate heat exchanger (IHX) is installed in series with the gas turbine, while in the second configuration model, IHX and gas turbines are installed in parallel. The third configuration model is similar to the first configuration, but with two compressors. Performance analysis of Brayton cycle used for cogeneration energy conversion system of RGTT200K has been done by simulating and calculating using CHEMCAD code. The simulation result shows that the three configuration models of cogeneration energy conversion system give the temperature of thermal energy in the secondary side of IHX more than 800 °C at the reactor coolant mass flow rate of 145 kg/s. Nevertheless, the performance parameters, which include thermal efficiency and energy utilization factor (EUF), are different for each configuration model. By comparing the performance parameter in the three configurations of helium Brayton cycle for cogeneration energy conversion systems RGTT200K, it is found that the energy conversion system with a first configuration has the highest thermal efficiency and energy utilization factor (EUF). Thermal efficiency and energy utilization factor for the first configuration of the reactor coolant mass flow rate of 145 kg/s are 35.82 % and 80.63 %. (author)

Numerical Analysis of S-CO{sub 2} Test Loop Transient Conditions near the Critical Point of CO{sub 2}

Energy Technology Data Exchange (ETDEWEB)

Bae, Seong Jun; Oh, Bongseong; Ahn, Yoonhan; Baik, Seongjoon; Lee, Jekyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-05-15

It was identified that controlling CO{sub 2} compressor operation near the critical point is one of the most important issues to operate a S-CO{sub 2} Brayton cycle with a high efficiency. Despite the growing interest in the S-CO{sub 2} Brayton cycle, a few previous research on the transient analysis of the S-CO{sub 2} system has been conducted previously. Moreover, previous studies have some limitation in the modelled test facility, and the experiment was not performed to observe specific scenario. The KAIST research team has conducted S-CO{sub 2} system transient experiments with the CO{sub 2} compressing test facility called SCO{sub 2}PE (Supercritical CO{sub 2} Pressurizing Experiment) at KAIST In this study, authors use the transient analysis code GAMMA (Gas Multidimensional Multicomponent mixture Analysis) code for analyzing the experiment. Two transient scenarios were selected in this study; over cooling and under cooling situations. The selected transient situation is of particular interest since the compressor inlet conditions start to drift away from the critical point of CO{sub 2}. The results represent that the GAMMA code can simulate the S-CO{sub 2} test facility, SCO{sub 2}PE. However, as shown in the cooling water flow rate increasing scenario, the GAMMA code shows calculation error when the phase change occurs. Furthermore, although the results of the cooling water flow rate decrease case shows reasonable agreement with the experimental data, there are still some unexplained differences between the experimental data and the GAMMA code prediction.

Optimization of a regenerative Brayton cycle by maximization of a newly defined second law efficiency

NARCIS (Netherlands)

Haseli, Y.

2013-01-01

The idea is to find out whether 2nd law efficiency optimization may be a suitable trade-off between maximum work output and maximum 1st law efficiency designs for a regenerative gas turbine engine operating on the basis of an open Brayton cycle. The primary emphasis is placed on analyzing the ideal

Optimization of airfoil-type PCHE for the recuperator of small scale brayton cycle by cost-based objective function

International Nuclear Information System (INIS)

Kwon, Jin Gyu; Kim, Tae Ho; Park, Hyun Sun; Cha, Jae Eun; Kim, Moo Hwan

2016-01-01

Highlights: • Suggest the Nusselt number and Fanning friction factor correlation for airfoil-type PCHE. • Show that cost-based optimization is available to airfoil-type PCHE. • Suggest the recuperator design for SCIEL test loop at KAERI by cost-based objective function with correlations from numerical analysis. - Abstract: Supercritical carbon dioxide (SCO_2) Brayton cycle gives high efficiency of power cycle with small size. Printed circuit heat exchangers (PCHE) are proper selection for the Brayton cycle because their operability at high temperature and high pressure with small size. Airfoil fin PCHE was suggested by Kim et al. (2008b), it can provide high heat transfer-like zigzag channel PCHE with low pressure drop-like straight channel PCHE. Optimization of the airfoil fin PCHE was not performed like the zigzag channel PCHE. For optimization of the airfoil fin PCHE, the operating condition of the recuperator of SCO_2 Integral Experiment Loop (SCIEL) Brayton cycle test loop at Korea Atomic Energy Research Institute (KAERI) was used. We performed CFD analysis for various airfoil fin configurations using ANSYS CFX 15.0, and made correlations for predicting the Nusselt number and the Fanning friction factor. The recuperator was designed by the simple energy balance code with our correlations. Using the cost-based objective function with production cost and operation cost from size and pressure drop of the recuperator, we evaluated airfoil fin configuration by using total cost and suggested the optimization configuration of the airfoil fin PCHE.

Optimization of airfoil-type PCHE for the recuperator of small scale brayton cycle by cost-based objective function

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jin Gyu [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Kim, Tae Ho [Department of Mechanical Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Park, Hyun Sun, E-mail: hejsunny@postech.ac.kr [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Cha, Jae Eun [Korea Atomic Energy Research Institute, Daejeon 305-353 (Korea, Republic of); Kim, Moo Hwan [Division of Advanced Nuclear Engineering, POSTECH, Pohang 790-784 (Korea, Republic of); Korea Institute of Nuclear Safety, Daejeon 305-338 (Korea, Republic of)

2016-03-15

Highlights: • Suggest the Nusselt number and Fanning friction factor correlation for airfoil-type PCHE. • Show that cost-based optimization is available to airfoil-type PCHE. • Suggest the recuperator design for SCIEL test loop at KAERI by cost-based objective function with correlations from numerical analysis. - Abstract: Supercritical carbon dioxide (SCO{sub 2}) Brayton cycle gives high efficiency of power cycle with small size. Printed circuit heat exchangers (PCHE) are proper selection for the Brayton cycle because their operability at high temperature and high pressure with small size. Airfoil fin PCHE was suggested by Kim et al. (2008b), it can provide high heat transfer-like zigzag channel PCHE with low pressure drop-like straight channel PCHE. Optimization of the airfoil fin PCHE was not performed like the zigzag channel PCHE. For optimization of the airfoil fin PCHE, the operating condition of the recuperator of SCO{sub 2} Integral Experiment Loop (SCIEL) Brayton cycle test loop at Korea Atomic Energy Research Institute (KAERI) was used. We performed CFD analysis for various airfoil fin configurations using ANSYS CFX 15.0, and made correlations for predicting the Nusselt number and the Fanning friction factor. The recuperator was designed by the simple energy balance code with our correlations. Using the cost-based objective function with production cost and operation cost from size and pressure drop of the recuperator, we evaluated airfoil fin configuration by using total cost and suggested the optimization configuration of the airfoil fin PCHE.

Preliminary closed Brayton cycle study for a space reactor application

International Nuclear Information System (INIS)

Guimaraes, Lamartine Nogueira Frutuoso; Carvalho, Ricardo Pinto de; Camillo, Giannino Ponchio

2007-01-01

The Nuclear Energy Division (ENU) of the Institute for Advanced Studies (IEAv) has started a preliminary design study for a Closed Brayton Cycle Loop (CBCL) aimed at a space reactor application. The main objectives of the study are to establish a starting concept for the CBCL components specifications, and to develop a demonstrative simulator of CBCL in nominal operation conditions. The ENU/IEAv preliminary design study is developing the CBCL around the NOELLE 60290 turbo machine. The actual nuclear reactor study is being conducted independently. Because of that, a conventional heat source is being used for the CBCL, in this preliminary design phase. This paper describes the steady state simulator of the CBCL operating with NOELLE 60290 turbo machine. In principle, several gases are being considered as working fluid, as for instance: air, helium, nitrogen, CO2 and gas mixtures such as helium and xenon. At this moment the simulator is running with Helium as the working fluid. Simplified models of heat and mass transfer are being developed to simulate thermal components. Future efforts will focus on keeping track of the modifications being implemented at the NOELLE 60290 turbo machine in order to build the CBCL. (author)

Preliminary closed Brayton cycle study for a space reactor application

Energy Technology Data Exchange (ETDEWEB)

Guimaraes, Lamartine Nogueira Frutuoso; Carvalho, Ricardo Pinto de [Institute for Advanced Studies, Sao Jose dos Campos, SP (Brazil)]. E-mail: guimarae@ieav.cta.br; Camillo, Giannino Ponchio [Instituto Tecnologico de Aeronautica (ITA), Sao Jose dos Campos, SP (Brazil)]. E-mail: gianninocamillo@gmail.com

2007-07-01

The Nuclear Energy Division (ENU) of the Institute for Advanced Studies (IEAv) has started a preliminary design study for a Closed Brayton Cycle Loop (CBCL) aimed at a space reactor application. The main objectives of the study are to establish a starting concept for the CBCL components specifications, and to develop a demonstrative simulator of CBCL in nominal operation conditions. The ENU/IEAv preliminary design study is developing the CBCL around the NOELLE 60290 turbo machine. The actual nuclear reactor study is being conducted independently. Because of that, a conventional heat source is being used for the CBCL, in this preliminary design phase. This paper describes the steady state simulator of the CBCL operating with NOELLE 60290 turbo machine. In principle, several gases are being considered as working fluid, as for instance: air, helium, nitrogen, CO2 and gas mixtures such as helium and xenon. At this moment the simulator is running with Helium as the working fluid. Simplified models of heat and mass transfer are being developed to simulate thermal components. Future efforts will focus on keeping track of the modifications being implemented at the NOELLE 60290 turbo machine in order to build the CBCL. (author)

NERI Quarterly Progress Report -- April 1 - June 30, 2005 -- Development of a Supercritical Carbon Dioxide Brayton Cycle: Improving PBR Efficiency and Testing Material Compatibility

International Nuclear Information System (INIS)

Chang Oh

2005-01-01

The objective of this research is to improve a helium Brayton cycle and to develop a supercritical carbon dioxide Brayton cycle for the Pebble Bed Reactor (PBR) that can also be applied to the Fast Gas-Cooled Reactor (FGR) and the Very-High-Temperature Gas-Cooled Reactor (VHTR). The proposed supercritical carbon dioxide Brayton cycle will be used to improve the PBR, FGR, and VHTR net plant efficiency. Another objective of this research is to test materials to be used in the power conversion side at supercritical carbon dioxide conditions. Generally, the optimized Brayton cycle and balance of plant (BOP) to be developed from this study can be applied to Generation-IV reactor concepts. Particularly, we are interested in VHTR because it has a good chance of being built in the near future

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.

Evaluation and optimization of a supercritical carbon dioxide power conversion cycle for nuclear applications

International Nuclear Information System (INIS)

Harvego, Edwin A.; McKellar, Michael G.

2011-01-01

There have been a number of studies involving the use of gases operating in the supercritical mode for power production and process heat applications. Supercritical carbon dioxide (CO 2 ) is particularly attractive because it is capable of achieving relatively high power conversion cycle efficiencies in the temperature range between 550degC and 750degC. Therefore, it has the potential for use with any type of high-temperature nuclear reactor concept, assuming reactor core outlet temperatures of at least 550degC. The particular power cycle investigated in this paper is a supercritical CO 2 recompression Brayton Cycle. The CO 2 recompression Brayton Cycle can be used as either a direct or indirect power conversion cycle, depending on the reactor type and reactor outlet temperature. The advantage of this cycle when compared to the helium Brayton Cycle is the lower required operating temperature; 550degC versus 750degC. However, the supercritical CO 2 recompression Brayton Cycle requires a high end operating pressure in the range of 20 MPa, which is considerably higher than the required helium Brayton cycle high end operating pressure of 7 MPa. This paper presents results of analyses performed using the UniSim process analyses software to evaluate the performance of the supercritical CO 2 recompression Brayton cycle for different reactor coolant outlet temperatures and mass flow rates. The UniSim model assumed a 600 MWt reactor power source, which provides heat to the power cycle at a maximum temperature of between 550degC and 850degC. Sensitivity calculations were also performed to determine the affect of reactor coolant mass flow rates for a reference reactor coolant outlet temperature of 750degC. The UniSim model used realistic component parameters and operating conditions to model the complete power conversion system. CO 2 properties were evaluated, and the operating range for the cycle was adjusted to take advantage of the rapidly changing conditions near the

The maximum power condition of the brayton cycle with heat exchange processes

International Nuclear Information System (INIS)

Jung, Pyung Suk; Cha, Jin Girl; Ro, Sung Tack

1985-01-01

The ideal brayton cycle has been analyzed with the heat exchange processes between the working fluid and the heat source and the sink while their heat capacity rates are constant. The power of the cycle can be expressed in terms of a temperature of the cycle and the heat capacity rate of the working fluid. There exists an optimum power condition where the heat capacity rate of the working fluid has a value between those of the heat source and the heat sink, and the cycle efficiency is determined by the inlet temperatures of the heat source and the sink. (Author)

System Design of a Supercritical CO_2 cooled Micro Modular Reactor

International Nuclear Information System (INIS)

Kim, Seong Gu; Cho, Seongkuk; Yu, Hwanyeal; Kim, Yonghee; Jeong, Yong Hoon; Lee, Jeong Ik

2014-01-01

Small modular reactor (SMR) systems that have advantages of little initial capital cost and small restriction on construction site are being developed by many research organizations around the world. Existing SMR concepts have the same objective: to achieve compact size and a long life core. Most of small modular reactors have much smaller size than the large nuclear power plant. However, existing SMR concepts are not fully modularized. This paper suggests a complete modular reactor with an innovative concept for reactor cooling by using a supercritical carbon dioxide. The authors propose the supercritical CO_2 Brayton cycle (S-CO_2 cycle) as a power conversion system to achieve small volume of power conversion unit (PCU) and to contain the reactor core and PCU in one vessel. A conceptual design of the proposed small modular reactor was developed, which is named as KAIST Micro Modular Reactor (MMR). The supercritical CO_2 Brayton cycle for the S-CO_2 cooled reactor core was optimized and the size of turbomachinery and heat exchanger were estimated preliminary. The nuclear fuel composed with UN was proposed and the core lifetime was obtained from a burnup versus reactivity calculation. Furthermore, a system layout with fully passive safety systems for both normal operation and emergency operation was proposed. (author)

An investigation of sodium–CO{sub 2} interaction byproduct cleaning agent for SFR coupled with S-CO{sub 2} Brayton cycle

Energy Technology Data Exchange (ETDEWEB)

Jung, Hwa-Young, E-mail: jhy0523@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Division of SFR NSSS System Design, Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Lee, Jeong Ik, E-mail: jeongiklee@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Wi, Myung-Hwan, E-mail: mhwi@kaeri.re.kr [Division of SFR NSSS System Design, Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 305-353 (Korea, Republic of); Ahn, Hong Joo, E-mail: ahjoo@kaeri.re.kr [Division of Nuclear Chemistry Research, Korea Atomic Energy Research Institute, 111, Daedeok-daero 989beon-gil, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

2016-02-15

Highlights: • Study on cleaning agent was conducted to remove Na–CO{sub 2} interaction byproducts. • Screening criteria to select candidate substances as cleaning agents were suggested. • The mixtures of Na{sub 2}CO{sub 3} with NaBrO{sub 3}, NaClO{sub 3}, or NaBF{sub 4} were thermally analyzed with the TG/DTA studies. • Three candidate substances decomposed before 600 °C and did not react with Na{sub 2}CO{sub 3}. - Abstract: One of the promising future nuclear energy systems, the Sodium-cooled Fast Reactor (SFR) has been actively developed internationally. Recently, to improve safety and economics of a SFR further, coupling supercritical CO{sub 2} power cycle was suggested. However, there can be a chemical reaction between sodium and CO{sub 2} at high temperature (more than 400 °C) when the pressure boundary fails in a sodium–CO{sub 2} heat exchanger. To ensure the performance of such a system, it is important to employ a cleaning agent to recover the system back to normal condition after the reaction. When sodium and CO{sub 2} react, solid and gaseous reaction products such as sodium carbonate (Na{sub 2}CO{sub 3}) and carbon monoxide (CO) appear. Since most of solid reaction products are hard and can deteriorate system performance, quick removal of solid reaction products becomes very important for economic performance of the system. Thus, the authors propose the conceptual method to remove the byproducts with a chemical reaction at high temperature. The chemical reaction will take place between the reaction byproducts and a cleaning agent while the cleaning agent is inert with sodium. Thus, various sodium-based compounds were first investigated and three candidate substances satisfying several criteria were selected; sodium bromate (NaBrO{sub 3}), sodium chlorate (NaClO{sub 3}), and sodium tetrafluoroborate (NaBF{sub 4}). The selected substances were thermally analyzed with the TG/DTA studies. Unfortunately, it was revealed that all candidate

Thermo-economic performance of HTGR Brayton power cycles

International Nuclear Information System (INIS)

Linares, J. L.; Herranz, L. E.; Moratilla, B. Y.; Fernandez-Perez, A.

2008-01-01

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)

CO2 cycle

Science.gov (United States)

Titus, Timothy N.; Byrne, Shane; Colaprete, Anthony; Forget, Francois; Michaels, Timothy I.; Prettyman, Thomas H.

2017-01-01

This chapter discusses the use of models, observations, and laboratory experiments to understand the cycling of CO2 between the atmosphere and seasonal Martian polar caps. This cycle is primarily controlled by the polar heat budget, and thus the emphasis here is on its components, including solar and infrared radiation, the effect of clouds (water- and CO2-ice), atmospheric transport, and subsurface heat conduction. There is a discussion about cap properties including growth and regression rates, albedos and emissivities, grain sizes and dust and/or water-ice contamination, and curious features like cold gas jets and araneiform (spider-shaped) terrain. The nature of the residual south polar cap is discussed as well as its long-term stability and ability to buffer atmospheric pressures. There is also a discussion of the consequences of the CO2 cycle as revealed by the non-condensable gas enrichment observed by Odyssey and modeled by various groups.

Parametrized overview of CO_2 power cycles for different operation conditions and configurations – An absolute and relative performance analysis

International Nuclear Information System (INIS)

Cardemil, José M.; Silva, Alexandre K. da

2016-01-01

Highlights: • Thermodynamic modeling of CO_2-based power cycles. • A multi-parameter analysis for different cycle configurations. • Performance comparison between CO_2 and four other fluids. • Detailed discussion considering optimized operational parameters (i.e., pressure, HX size). • Overview of the technical applicability of the CO_2. - Abstract: This thermodynamically based study focuses on the thermal performance of power cycles using CO_2 as the working fluid. The work considers numerous aspects that can influence the cycle's performance, such as the type of cycle (i.e., Rankine or Brayton), its configuration (i.e., with and without a recuperator), and different operational conditions (i.e., heat source temperature and the upper and lower operating pressures of the CO_2). To account for all possible scenarios, a thermodynamic routine was especially implemented and linked to a library that contained all the thermodynamics properties of CO_2. The results are mostly presented in terms of the absolute and relative 1st and 2nd Law efficiencies of CO_2 as well as the cycle's scale, here represented by the global conductance (UA) of the heat exchangers used within the cycle. For the relative performance assessment, four other working fluids, commonly used in energy conversion cycles, were considered (i.e., ethane, toluene, D4 siloxane and water). As expected, the absolute performance results indicate a strong dependence of the cycle's efficiencies on the operational conditions. As for the relative performance, the results suggest that while the CO_2's 1st Law efficiency might be lower than other fluids, its exergetic efficiency can be significantly higher. Furthermore, the calculations also indicate that the CO_2's needed global conductance is potentially lower than competing fluids (e.g., toluene) for certain operational conditions, which suggests that CO_2-based power plants can be more compact, since they might require smaller heat exchangers to produce

Computer simulation of transitional process to the final stable Brayton cycle in magnetic refrigeration

International Nuclear Information System (INIS)

Numasawa, T.; Hashimoto, T.

1981-01-01

The final working cycle in the magnetic refrigeration largely depends on the heat transfer coefficient β in the system, the parameter γ of the heat inflow from the outer system to this cycle and the period tau of the cycle. Therefore, so as to make clear this dependence, the time variation of the Brayton cycle with β, γ and tau has been investigated. In the present paper the transitional process of this cycle and the dependence of the final cooling temperature of the heat load on β, γ and tau have all been shown. (orig.)

Thermal performance of Brayton power cycles. A study based on high-temperature gas-cooled reactors

International Nuclear Information System (INIS)

Herranz, Luis E.; Linares, Jose I.; Moratilla, Beatriz Y.

2005-01-01

Power cycles optimization has become an essential ingredient to achieve sustainability and improve economic competitiveness of forthcoming Generation IV designs. This paper investigates performance of several configurations of direct helium Brayton cycles. An optimum layout is proposed based on multiple intercooled compression stages and in-between turbines reheating: C(IC) 2 HTRTX. Under the hypotheses and approximations made, a 59% is estimated and it increases even further (67%) when the foreseen technological development is considered. A sensitive analysis identified key components and variables for cycle performance. Particular attention is paid to the effect of the extracted gas mass fraction for reheating. It is shown that the C(IC) 2 HTRTX cycle provides a feasible and simple way to operate the power plant the load-follow mode with a very little loss of efficiency. (author)

Promising designs of compact heat exchangers for modular HTRs using the Brayton cycle

International Nuclear Information System (INIS)

Pra, Franck; Tochon, Patrice; Mauget, Christian; Fokkens, Jan; Willemsen, Sander

2008-01-01

The presented study was carried out within the Work Package 2 'Recuperator' of the High Temperature Reactor-E European program. High Temperature gas cooled Reactor concepts with a direct cycle have become potentially interesting for the future. Theoretically, these concepts provide higher efficiency than a classical steam cycle. Within the Brayton cycle the helium/helium recuperator, required to achieve the high efficiency, has to work under very harsh conditions (temperature, pressure, and pressure difference between circuits). Within the project the most promising technologies for the compact recuperator were investigated. First, the requirements for the recuperator to operate under the direct Brayton cycle have been defined. Based on these requirements the various potential technologies available on the market have been investigated. Two particular technologies (HEATRIC Printed Circuit Heat Exchanger, NORDON plate fin concept) have been selected as most promising. For the former, a precise description has been given and a mock-up has been fabricated and tested in the Claire loop at CEA. In the Claire loop the Printed Circuit Heat Exchanger mock-up has been subjected to thermal shocks, which are considered to be representative for a recuperator. Prior to the experimental testing coupled Computational Fluid Dynamic (CFD) and Finite Element analyses have been performed to give insight into the thermal and mechanical behaviour of the mock-ups during the thermal shock. Based on these results the experimental measuring program has been optimized. Upon completion of the tests the experimental and numerical results have been compared. Based on the results from the investigation performed recommendations are given for the full-size recuperator using the selected technologies

Optimized, Competitive Supercritical-CO2 Cycle GFR for Gen IV Service

International Nuclear Information System (INIS)

M.J. Driscoll; P. Hejzlar; G. Apostolakis

2008-01-01

An overall plant design was developed for a gas-cooled fast reactor employing a direct supercritical Brayton power conversion system. The most important findings were that (1) the concept could be capital-cost competitive, but startup fuel cycle costs are penalized by the low core power density, specified in large part to satisfy the goal of significant post-accident passive natural convection cooling; (2) active decay heat removal is preferable as the first line of defense, with passive performance in a backup role; (3) an innovative tube-in-duct fuel assembly, vented to the primary coolant, appears to be practicable; and (4) use of the S-Co2 GFR to support hydrogen production is a synergistic application, since sufficient energy can be recuperated from the product H2 and 02 to allow the electrolysis cell to run 250 C hotter than the reactor coolant, and the water boilers can be used for reactor decay heat removal. Increasing core power density is identified as the top priority for future work on GFRs of this type

Compressor Modeling for Transient Analysis of Supercritical CO2 Brayton Cycle by using MARS code

Energy Technology Data Exchange (ETDEWEB)

Park, Joo Hyun; Park, Hyun Sun; Kim, Tae Ho; Kwon, Jin Gyu [POSTECH, Pohang (Korea, Republic of); Bae, Sung Won; Cha, Jae Eun [KAERI, Daejeon (Korea, Republic of)

2016-05-15

In this study, SCIEL (Supercritical CO{sub 2} Integral Experimental Loop) was chosen as a reference loop and the MARS code was as the transient cycle analysis code. As a result, the compressor homologous curve was developed from the SCIEL experimental data and MARS analysis was performed and presented in the paper. The advantages attract SCO{sub 2}BC as a promising next generation power cycles. The high thermal efficiency comes from the operation of compressor near the critical point where the properties of SCO{sub 2}. The approaches to those of liquid phase, leading drastically lower the compression work loss. However, the advantage requires precise and smooth operation of the cycle near the critical point. However, it is one of the key technical challenges. The experimental data was steady state at compressor rotating speed of 25,000 rpm. The time, 3133 second, was starting point of steady state. Numerical solutions were well matched with the experimental data. The mass flow rate from the MARS analysis of approximately 0.7 kg/s was close to the experimental result of 0.9 kg/s. It is expected that the difference come from the measurement error in the experiment. In this study, the compressor model was developed and implemented in MARS to study the transient analysis of SCO{sub 2}BC in SCIEL. We obtained the homologous curves for the SCIEL compressor using experimental data and performed nodalization of the compressor model using MARS code. In conclusions, it was found that numerical solutions from the MARS model were well matched with experimental data.

Predicting the ultimate potential of natural gas SOFC power cycles with CO2 capture - Part A: Methodology and reference cases

Science.gov (United States)

Campanari, Stefano; Mastropasqua, Luca; Gazzani, Matteo; Chiesa, Paolo; Romano, Matteo C.

2016-08-01

Driven by the search for the highest theoretical efficiency, in the latest years several studies investigated the integration of high temperature fuel cells in natural gas fired power plants, where fuel cells are integrated with simple or modified Brayton cycles and/or with additional bottoming cycles, and CO2 can be separated via chemical or physical separation, oxy-combustion and cryogenic methods. Focusing on Solid Oxide Fuel Cells (SOFC) and following a comprehensive review and analysis of possible plant configurations, this work investigates their theoretical potential efficiency and proposes two ultra-high efficiency plant configurations based on advanced intermediate-temperature SOFCs integrated with a steam turbine or gas turbine cycle. The SOFC works at atmospheric or pressurized conditions and the resulting power plant exceeds 78% LHV efficiency without CO2 capture (as discussed in part A of the work) and 70% LHV efficiency with substantial CO2 capture (part B). The power plants are simulated at the 100 MW scale with a complete set of realistic assumptions about fuel cell (FC) performance, plant components and auxiliaries, presenting detailed energy and material balances together with a second law analysis.

Performance Optimization of a Solar-Driven Multi-Step Irreversible Brayton Cycle Based on a Multi-Objective Genetic Algorithm

Directory of Open Access Journals (Sweden)

Ahmadi Mohammad Hosein

2016-01-01

Full Text Available An applicable approach for a multi-step regenerative irreversible Brayton cycle on the basis of thermodynamics and optimization of thermal efficiency and normalized output power is presented in this work. In the present study, thermodynamic analysis and a NSGA II algorithm are coupled to determine the optimum values of thermal efficiency and normalized power output for a Brayton cycle system. Moreover, three well-known decision-making methods are employed to indicate definite answers from the outputs gained from the aforementioned approach. Finally, with the aim of error analysis, the values of the average and maximum error of the results are also calculated.

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

International Nuclear Information System (INIS)

Chang H. Oh

2006-01-01

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 state-of-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

Preliminary Design and Model Assessment of a Supercritical CO2 Compressor

Directory of Open Access Journals (Sweden)

Zhiyuan Liu

2018-04-01

Full Text Available The compressor is a key component in the supercritical carbon dioxide (SCO2 Brayton cycle. In this paper, the authors designed a series of supercritical CO2 compressors with different parameters. These compressors are designed for 100 MWe, 10 MWe and 1 MWe scale power systems, respectively. For the 100 MWe SCO2 Brayton cycle, an axial compressor has been designed by the Smith chart to test whether an axial compressor is suitable for the SCO2 Brayton cycle. Using a specific speed and a specific diameter, the remaining two compressors were designed as centrifugal compressors with different pressure ratios to examine whether models used for air in the past are applicable to SCO2. All compressors were generated and analyzed with internal MATLAB programs coupled with the NIST REFPROP database. Finally, the design results are all checked by numerical simulations due to the lack of reliable experimental data. Research has found that in order to meet the de Haller stall criterion, axial compressors require a considerable number of stages, which introduces many additional problems. Thus, a centrifugal compressor is more suitable for the SCO2 Brayton cycle, even for a 100 MWe scale system. For the performance prediction model of a centrifugal compressor, the stall predictions are compared with steady numerical calculation, which indicates that past stall criteria may also be suitable for SCO2 compressors, but more validations are needed. However, the accuracy of original loss models is found to be inadequate, particularly for lower flow and higher pressure ratio cases. Deviations may be attributed to the underestimation of clearance loss according to the result of steady simulation. A modified model is adopted which can improve the precision to a certain extent, but more general and reasonable loss models are needed to improve design accuracy in the future.

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

International Nuclear Information System (INIS)

Rovira, Antonio; Muñoz-Antón, Javier; Montes, María José; Martínez-Val, José María

2013-01-01

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/c p 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/c p factor measured at the ideal gas condition should be as low as possible

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

Brayton cycle for internal combustion engine exhaust gas waste heat recovery

Directory of Open Access Journals (Sweden)

J Galindo

2015-06-01

Full Text Available An average passenger car engine effectively uses about one-third of the fuel combustion energy, while the two-thirds are wasted through exhaust gases and engine cooling. It is of great interest to automotive industry to recover some of this wasted energy, thus increasing the engine efficiency and lowering fuel consumption and contamination. Waste heat recovery for internal combustion engine exhaust gases using Brayton cycle machine was investigated. The principle problems of application of such a system in a passenger car were considered: compressor and expander machine selection, machine size for packaging under the hood, efficiency of the cycle, and improvement of engine efficiency. Important parameters of machines design have been determined and analyzed. An average 2-L turbocharged gasoline engine’s New European Driving Cycle points were taken as inlet points for waste heat recovery system. It is theoretically estimated that the recuperated power of 1515 W can be achieved along with 5.7% improvement in engine efficiency, at the point where engine power is 26550 W.

Adaptability of Brayton cycle conversion systems to fast, epithermal and thermal spectrum space nuclear reactors

International Nuclear Information System (INIS)

Tilliette, Z.P.

1988-01-01

The two French Government Agencies C.N.E.S. (Centre National d'Etudes Spatiales) and C.E.A. (Commissariat a l'Energie Atomique) are carrying out joint preliminary studies on space nuclear power systems for future ARIANE 5 launch vehicle applications. The Brayton cycle is the reference conversion system, whether the heat source is a liquid metal-cooled (NaK, Na or Li) reactor or a gas-cooled direct cycle concept. The search for an adequate utilization of this energy conversion means has prompted additional evaluations featuring the definition of satisfactory cycle conditions for these various kinds of reactor concepts. In addition to firstly studied fast and epithermal spectrum ones, thermal spectrum reactors can offer an opportunity of bringing out some distinctive features of the Brayton cycle, in particular for the temperature conditioning of the efficient metal hydrides (ZrH, Li/sub 7/H) moderators. One of the purposes of the paper is to confirm the potential of long lifetime ZrH moderated reactors associated with a gas cycle and to assess the thermodynamical consequences for both Nak(Na)-cooled or gas-cooled nuclear heat sources. This investigation is complemented by the definition of appropriate reactor arrangements which could be presented on a further occasion

Features of supercritical carbon dioxide Brayton cycle coupled with reactor

International Nuclear Information System (INIS)

Duan Chengjie; Wang Jie; Yang Xiaoyong

2010-01-01

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 CO 2 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 CO 2 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 CO 2 power cycle can achieve quite satisfied efficiency at a lower cycle highest temperature than helium cycle, and CO 2 is a promising working fluid. (authors)

Comparative thermodynamic performance of some Rankine/Brayton cycle configurations for a low-temperature energy application

Science.gov (United States)

Lansing, F. L.

1977-01-01

Various configurations combining solar-Rankine and fuel-Brayton cycles were analyzed in order to find the arrangement which has the highest thermal efficiency and the smallest fuel share. A numerical example is given to evaluate both the thermodynamic performance and the economic feasibility of each configuration. The solar-assisted regenerative Rankine cycle was found to be leading the candidates from both points of energy utilization and fuel conservation.

Method for controlling start-up and steady state performance of a closed split flow recompression brayton cycle

Science.gov (United States)

Pasch, James Jay

2017-02-07

A method of resolving a balanced condition that generates control parameters for start-up and steady state operating points and various component and cycle performances for a closed split flow recompression cycle system. The method provides for improved control of a Brayton cycle thermal to electrical power conversion system. The method may also be used for system design, operational simulation and/or parameter prediction.

A four-year investigation of Brayton cycle systems for future french space power applications

International Nuclear Information System (INIS)

Tilliette, Z.P.; Proust, E.; Carre, F.

1988-01-01

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: the matching of the power system to the available radiator dimensions up to 200 kWe, the direct or indirect waste heat transfer to the radiator, the use of a recuperator, the recent work on moderate (25 kWe) power levels, the simulation studies related to various operating conditions and the 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. As far as a gas-cooled reactor, direct cycle system is concerned, the relevance to the reactor technology and the concept for moderator thermal conditioning, is particularly addressed

Thermodynamic design of hydrogen liquefaction systems with helium or neon Brayton refrigerator

Science.gov (United States)

Chang, Ho-Myung; Ryu, Ki Nam; Baik, Jong Hoon

2018-04-01

A thermodynamic study is carried out for the design of hydrogen liquefaction systems with helium (He) or neon (Ne) Brayton refrigerator. This effort is motivated by our immediate goal to develop a small-capacity (100 L/h) liquefier for domestic use in Korea. Eight different cycles are proposed and their thermodynamic performance is investigated in comparison with the existing liquefaction systems. The proposed cycles include the standard and modified versions of He Brayton refrigerators whose lowest temperature is below 20 K. The Brayton refrigerator is in direct thermal contact with the hydrogen flow at atmospheric pressure from ambient-temperature gas to cryogenic liquid. The Linde-Hampson system pre-cooled by a Ne Brayton refrigerator is also considered. Full cycle analysis is performed with the real properties of fluids to estimate the figure of merit (FOM) under an optimized operation condition. It is concluded that He Brayton refrigerators are feasible for this small-scale liquefaction, because a reasonably high efficiency can be achieved with simple and safe (low-pressure) operation. The complete cycles with He Brayton refrigerator are presented for the development of a prototype, including the ortho-to-para conversion.

Fluidized-Bed Heat Transfer Modeling for the Development of Particle/Supercritical-CO2 Heat Exchanger

Energy Technology Data Exchange (ETDEWEB)

Ma, Zhiwen [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Martinek, Janna G [National Renewable Energy Laboratory (NREL), Golden, CO (United States)

2017-06-03

Concentrating solar power (CSP) technology is moving toward high-temperature and high-performance design. One technology approach is to explore high-temperature heat-transfer fluids and storage, integrated with a high-efficiency power cycle such as the supercritical carbon dioxide (s-CO2) Brayton power cycle. The s-CO2 Brayton power system has great potential to enable the future CSP system to achieve high solar-to-electricity conversion efficiency and to reduce the cost of power generation. Solid particles have been proposed as a possible high-temperature heat-transfer medium that is inexpensive and stable at high temperatures above 1,000 degrees C. The particle/heat exchanger provides a connection between the particles and s-CO2 fluid in the emerging s-CO2 power cycles in order to meet CSP power-cycle performance targets of 50% thermal-to-electric efficiency, and dry cooling at an ambient temperature of 40 degrees C. The development goals for a particle/s-CO2 heat exchanger are to heat s-CO2 to =720 degrees C and to use direct thermal storage with low-cost, stable solid particles. This paper presents heat-transfer modeling to inform the particle/s-CO2 heat-exchanger design and assess design tradeoffs. The heat-transfer process was modeled based on a particle/s-CO2 counterflow configuration. Empirical heat-transfer correlations for the fluidized bed and s-CO2 were used in calculating the heat-transfer area and optimizing the tube layout. A 2-D computational fluid-dynamics simulation was applied for particle distribution and fluidization characterization. The operating conditions were studied from the heat-transfer analysis, and cost was estimated from the sizing of the heat exchanger. The paper shows the path in achieving the cost and performance objectives for a heat-exchanger design.

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

1998-12-31

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.

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.

Concept Design for a High Temperature Helium Brayton Cycle with Interstage Heating and Cooling

Energy Technology Data Exchange (ETDEWEB)

Wright, Steven A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Vernon, Milton E. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Pickard, Paul S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2013-12-01

The primary metric for the viability of these next generation nuclear power plants will be the cost of generated electricity. One important component in achieving these objectives is the development of power conversion technologies that maximize the electrical power output of these advanced reactors for a given thermal power. More efficient power conversion systems can directly reduce the cost of nuclear generated electricity and therefore advanced power conversion cycle research is an important area of investigation for the Generation IV Program. Brayton cycles using inert or other gas working fluids, have the potential to take advantage of the higher outlet temperature range of Generation IV systems and allow substantial increases in nuclear power conversion efficiency, and potentially reductions in power conversion system capital costs compared to the steam Rankine cycle used in current light water reactors. For the Very High Temperature Reactor (VHTR), Helium Brayton cycles which can operate in the 900 to 950 C range have been the focus of power conversion research. Previous Generation IV studies examined several options for He Brayton cycles that could increase efficiency with acceptable capital cost implications. At these high outlet temperatures, Interstage Heating and Cooling (IHC) was shown to provide significant efficiency improvement (a few to 12%) but required increased system complexity and therefore had potential for increased costs. These scoping studies identified the potential for increased efficiency, but a more detailed analysis of the turbomachinery and heat exchanger sizes and costs was needed to determine whether this approach could be cost effective. The purpose of this study is to examine the turbomachinery and heat exchanger implications of interstage heating and cooling configurations. In general, this analysis illustrates that these engineering considerations introduce new constraints to the design of IHC systems that may require

Design and fabrication of gas bearings for Brayton cycle rotating unit

Science.gov (United States)

Frost, A.; Tessarzik, J. M.; Arwas, E. B.; Waldron, W. D. (Editor)

1973-01-01

Analysis, design, and testing of two types of pivoted pad journal bearings and a spiral-grooved thrust bearing suitable for direct installation into the NASA 2 to 15 KW Brayton Cycle Rotating Unit (BRU) have been accomplished. Both types of tilting pad bearing assemblies are of the preloaded type, consisting of three pads with one pad flexibly mounted. One type utilizes a non-conforming pivot, while the other replaces the conventional spherical pivot with a cruciform flexible member. The thrust bearing is flexure mounted to accommodate static machine mislinement. Test results indicate that both types of journal bearings should satisfy the requirements imposed by the BRU. Hydrostatic tests of the spiral-grooved thrust bearing showed it to be free of pneumatic hammer with as many as 24 orifices over the BRU pressure and load range.

Integration between direct steam generation in linear solar collectors and supercritical carbon dioxide Brayton power cycles

OpenAIRE

Coco Enríquez, Luis; Muñoz Antón, Javier; Martínez-Val Peñalosa, José María

2015-01-01

Direct Steam Generation in Parabolic Troughs or Linear Fresnel solar collectors is a technology under development since beginning of nineties (1990's) for replacing thermal oils and molten salts as heat transfer fluids in concentrated solar power plants, avoiding environmental impacts. In parallel to the direct steam generation technology development, supercritical Carbon Dioxide Brayton power cycles are maturing as an alternative to traditional Rankine cycles for increasing net plant efficie...

Preliminary Design of Supercritical CO{sub 2} Radial Turbine for Micro Modular Reactor

Energy Technology Data Exchange (ETDEWEB)

Cho, Seong Kuk; Lee, Jekyoung; Kim, Seong Gu; Lee, Jeong Ik [KAIST (Korea, Republic of); Cha, Jae Eun [KAERI, Daejeon (Korea, Republic of)

2016-05-15

The KAIST research team suggested an innovative concept of SMR called KAIST Micro Modular Reactor (MMR). It is aimed for achieving complete modularization of a nuclear power plant including the Power Conversion Unit (PCU) for simple transportation and installation. In consideration of the maintenance, S-CO{sub 2} has superior characteristic to the light water because it is less corrosive. Table I represents summary of the main design results of KAIST MMR. As such efforts the study on S-CO{sub 2} turbomachinery has been actively conducted because the S-CO{sub 2} Brayton cycle operates under extreme conditions such as high rotational speed, high pressure, and dramatic change of thermodynamic properties near the critical point (30.98 .deg. C, 7377kPa). To achieve higher thermal efficiency, the operation near the critical point is prerequisite in the S-CO{sub 2} Brayton cycle. For these reasons, research works on the S-CO{sub 2} turbomachinery naturally have been focused on the compressor which operates near the critical point. Due to the absence of loss models in S-CO{sub 2} field, loss models with air turbine were first utilized to design and predict the off design performance of a S-CO{sub 2} turbine. To check propriety of the code logic the code results compared with experimental data measured in air condition. The predicted values showed good agreement with the experiment data. Lastly, performance maps for S-CO{sub 2} turbine for the MMR were generated with change of mass flow rate and rotational speed.

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.

Impact of closed Brayton cycle test results on gas cooled reactor operation and safety

International Nuclear Information System (INIS)

Wright, St.A.; Pickard, P.S.

2007-01-01

This report summarizes the measurements and model predictions for a series of tests supported by the U.S. Department of Energy that were performed using the recently constructed Sandia Brayton Loop (SBL-30). From the test results we have developed steady-state power operating curves, controls methodologies, and transient data for normal and off-normal behavior, such as loss of load events, and for decay heat removal conditions after shutdown. These tests and models show that because the turbomachinery operates off of the temperature difference (between the heat source and the heat sink), that the turbomachinery can continue to operate (off of sensible heat) for long periods of time without auxiliary power. For our test hardware, operations up to one hour have been observed. This effect can provide significant operations and safety benefits for nuclear reactors that are coupled to a Brayton cycles because the operating turbomachinery continues to provide cooling to the reactor. These capabilities mean that the decay-heat removal can be accommodated by properly managing the electrical power produced by the generator/alternator. In some conditions, it may even be possible to produce sufficient power to continue operating auxiliary systems including the waste heat circulatory system. In addition, the Brayton plant impacts the consequences of off-normal and accident events including loss of load and loss of on-site power. We have observed that for a loss of load or a loss of on-site power event, with a reactor scram, the transient consists initially of a turbomachinery speed increase to a new stable operating point. Because the turbomachinery is still spinning, the reactor is still being cooled provided the ultimate heat sink remains available. These highly desirable operational characteristics were observed in the Sandia Brayton loop. This type of behavior is also predicted by our models. Ultimately, these results provide the designers the opportunity to design gas

Advanced Rankine and Brayton cycle power systems: Materials needs and opportunities

Science.gov (United States)

Grisaffe, S. J.; Guentert, D. C.

1974-01-01

Conceptual advanced potassium Rankine and closed Brayton power conversion cycles offer the potential for improved efficiency over steam systems through higher operating temperatures. However, for utility service of at least 100,000 hours, materials technology advances will be needed for such high temperature systems. Improved alloys and surface protection must be developed and demonstrated to resist coal combustion gases as well as potassium corrosion or helium surface degradation at high temperatures. Extensions in fabrication technology are necessary to produce large components of high temperature alloys. Long time property data must be obtained under environments of interest to assure high component reliability.

Advanced Rankine and Brayton cycle power systems - Materials needs and opportunities

Science.gov (United States)

Grisaffe, S. J.; Guentert, D. C.

1974-01-01

Conceptual advanced potassium Rankine and closed Brayton power conversion cycles offer the potential for improved efficiency over steam systems through higher operating temperatures. However, for utility service of at least 100,000 hours, materials technology advances will be needed for such high temperature systems. Improved alloys and surface protection must be developed and demonstrated to resist coal combustion gases as well as potassium corrosion or helium surface degradation at high temperatures. Extensions in fabrication technology are necessary to produce large components of high temperature alloys. Long-time property data must be obtained under environments of interest to assure high component reliability.

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.

Brayton cycle space power systems

International Nuclear Information System (INIS)

Pietsch, A.; Trimble, S.W.; Harper, A.D.

1985-01-01

The latest accomplishments in the design and development of the Brayton Isotope Power System (BIPS) for space applications are described, together with a reexamination of the design/cost tradeoffs with respect to current economic parameters and technology status. The results of tests performed on a ground test version of the flight configuration, the workhorse loop, were used to confirm the performance projections made for the flight system. The results of cost-model analysis indicate that the use of the highest attainable power conversion system efficiency will yield the most cost-effective systems. 13 references

Operation Test of the Supercritical CO{sub 2} Compressor Supported with Active Magnetic Bearing

Energy Technology Data Exchange (ETDEWEB)

Cha, Jae Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Cho, Seong Kuk; Lee, Jeong IK [KAIST, Daejeon (Korea, Republic of)

2016-10-15

In this paper, the operation test status of the SCIEL sCO{sub 2} AMB Compressor is briefly described. The Supercritical CO{sub 2} Brayton Cycle Integral Experiment Loop (SCIEL) has been installed in Korea Atomic Energy Research Institute (KAERI) to develop the element technologies for the sCO{sub 2} cycle power generation system. The operation of the SCIEL has mainly focused on sCO{sub 2} compressor development and establishing sCO{sub 2} system control logic. The installation of the SCIEL low compression loop was finished in December 2014 and research team succeeded in generating electric power on the supercritical state of the CO{sub 2} in May 2015. The SCIEL has been built in KAERI to develop the element technologies and the system control logics for the sCO{sub 2} cycle power conversion unit of the next generation reactor. For the stable operation of the sCO{sub 2} compressor under high rotational speed, the AMB sCO{sub 2} compressor was developed and achieved the maximum 40,000 rpm.

Thermodynamic analysis of a novel power plant with LNG (liquefied natural gas) cold exergy exploitation and CO_2 capture

International Nuclear Information System (INIS)

Romero Gómez, Manuel; Romero Gómez, Javier; López-González, Luis M.; López-Ochoa, Luis M.

2016-01-01

The LNG (liquefied natural gas) regasification process is a source of cold exergy that is suitable to be recovered to improve the efficiency of thermal power plants. In this paper, an innovative power plant with LNG (liquefied natural gas) exergy utilisation and the capture of CO_2 proceeding from the flue gases is presented. It is characterised by the recovery of LNG cold exergy in a closed Brayton cycle and through direct expansion in an expander coupled to an electrical generator. Moreover, this novel power plant configuration allows CO_2 capture, through an oxy-fuel combustion system and a Rankine cycle that operates with the flue gases themselves and in quasi-critical conditions. The greatest advantage of this plant is that all the recoverable LNG exergy is used to increase the efficiency of the CBC (closed Brayton cycle) and in direct expansion whereas, in other power cycles found in literature that associate LNG regasification and CO_2 capture, part of the LNG exergy is used for condensing flue gas CO_2 for its subsequent capture. As a result, a high efficiency power plant is achieved, exceeding 65%, with almost zero greenhouse gas emissions. - Highlights: • LNG cold exergy can be recovered to improve the efficiency of power plants. • High efficiency power plant with almost zero greenhouse gas emissions. • CO_2 capture through an oxy-fuel combustion system and a Rankine cycle. • Sensitivity analysis of key parameters to evaluate the effect on the efficiency. • The exergy available in the LNG represents 34.79% of the fuel exergy.

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

International Nuclear Information System (INIS)

Le Roux, W.G.; Bello-Ochende, T.; Meyer, J.P.

2014-01-01

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

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

Science.gov (United States)

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.

Conceptual design study of closed Brayton cycle gas turbines for fusion power generation

International Nuclear Information System (INIS)

Kuo, S.C.

1976-01-01

A conceptual design study is presented of closed Brayton cycle gas turbine power conversion systems suitable for integration with advanced-concept Tokamak fusion reactors (such as UWMAK-III) for efficient power generation without requiring cooling water supply for waste heat rejection. A baseline cycle configuration was selected and parametric performance analyses were made. Based on the results of the parametric analysis and trade-off and interface considerations, the reference design conditions for the baseline cycle were selected. Conceptual designs were made of the major helium gas turbine power system components including a 585-MWe single-shaft turbomachine, (three needed), regenerator, precooler, intercooler, and the piping system connecting them. Structural configuration and significant physical dimensions for major components are illustrated, and a brief discussion on major advantages, power control and crucial technologies for the helium gas turbine power system are presented

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

An evaluation of thermodynamic solar plants with cylindrical parabolic collectors and air turbine engines with open Joule–Brayton cycle

International Nuclear Information System (INIS)

Ferraro, Vittorio; Marinelli, Valerio

2012-01-01

A performance analysis of innovative solar plants operating with cylindrical parabolic collectors and atmospheric air as heat transfer fluid in an open Joule–Brayton cycle, with and without intercooling and regeneration, is presented. The analysis was made for two operating modes of the plants: with variable air flow rate and constant inlet temperature to the turbine and with constant flow rate and variable inlet temperature to the turbine. The obtained results show a good performance of this type of solar plant, in spite of its simplicity; it seems able to compete well with other more complex plants operating with different heat transfer fluids. -- Highlights: ► Innovative CPS solar plants, operating with air in open Joule–Brayton cycle, are proposed. ► They are attractive for their simplicity and present interesting values of global efficiency. ► They seem able to compete well with other more complex solar plants.

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

International Nuclear Information System (INIS)

Zhang, Yu; Li, Qiang; Wu, Jihao; Li, Qing; Lu, Wenhai; Xiong, Lianyou; Liu, Liqiang; Xu, Xiangdong; Sun, Lijia; Sun, Yu; Xie, Xiujuan; Wang, Bingming; Qiu, Yinan; Zhang, Peng

2015-01-01

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

CO/sub 2/ carbon cycle and climate interactions

Energy Technology Data Exchange (ETDEWEB)

Grassl, H; Maier-Reimer, E; Degens, E T; Kempe, S; Spitzy, A

1984-03-01

Past and expected emissions of anthropogenic CO/sub 2/ stimulate carbon cycle and climate research. Prognoses of future CO/sub 2/ levels depend on energy scenarios and on the reaction of the biosphere and hydrosphere to elevated atmospheric CO/sub 2/ concentrations. The reaction of the reservoirs vegetation, freshwater and oceans to disturbances of the carbon cycle is reviewed. For the oceans first results of a simple carbon cycle model implanted in a three-dimensional general circulation model are presented. This model allows experiments not possible with previous box models.

Thermodynamic analysis and optimization of a Closed Regenerative Brayton Cycle for nuclear space power systems

International Nuclear Information System (INIS)

Ribeiro, Guilherme B.; Braz Filho, Francisco A.; Guimarães, Lamartine N.F.

2015-01-01

Nuclear power systems turned to space electric propulsion differ strongly from usual ground-based power systems regarding the importance of overall size and mass. For propulsion power systems, size and mass are essential drivers that should be minimized during conception processes. Considering this aspect, this paper aims the development of a design-based model of a Closed Regenerative Brayton Cycle that applies the thermal conductance of the main components in order to predict the energy conversion performance, allowing its use as a preliminary tool for heat exchanger and radiator panel sizing. The centrifugal-flow turbine and compressor characterizations were achieved using algebraic equations from literature data. A binary mixture of Helium–Xenon with molecular weight of 40 g/mole is applied and the impact of the components sizing in the energy efficiency is evaluated in this paper, including the radiator panel area. Moreover, an optimization analysis based on the final mass of heat the exchangers is performed. - Highlights: • A design-based model of a Closed Brayton Cycle is proposed for nuclear space needs. • Turbomachinery efficiency presented a strong influence on the system efficiency. • Radiator area presented the highest potential to increase the system efficiency. • There is maximum system efficiency for each total mass of heat exchangers. • Size or efficiency optimization was performed by changing heat exchanger proportion.

Performance evaluation and parametric choice criteria of a Brayton pumped thermal electricity storage system

International Nuclear Information System (INIS)

Guo, Juncheng; Cai, Ling; Chen, Jincan; Zhou, Yinghui

2016-01-01

A more realistic thermodynamic model of the pumped thermal electricity storage (PTES) system consisting of a Brayton cycle and a reverse Brayton cycle is proposed, where the internal and external irreversible losses are took into account and several important controlling parameters, e.g., the pressure ratio and heat flows of the two isobaric processes in the Brayton cycle, are introduced. Analytic expressions for the round trip efficiency and power output of the PTES system are derived. The general performance characteristics of the PTES system are revealed. The optimal relationship between the round trip efficiency and the power output is obtained. The influences of some important controlling parameters on the performance characteristics of the PTES system are discussed and the optimally operating regions of these parameters are determined. - Highlights: • A cycle model of the Brayton pumped thermal electricity storage system is proposed. • Internal and external irreversible losses are considered. • Maximum power output and efficiency of the system are calculated. • Optimum performance characteristics of the system are revealed. • Rational ranges of key controlling parameters are determined.

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)

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

International Nuclear Information System (INIS)

Ribeiro, Guilherme B.; Guimaraes, Lamartine N.F.; Braz Filho, Francisco A.

2015-01-01

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)

Sodium fast reactors energy conversion systems. Na-CO2 interaction. Comparison with Na-water interaction of conventional water Rankine cycle

International Nuclear Information System (INIS)

Latge, Christian; Simon, Nicole

2006-01-01

The Sodium Fast Reactor is a very promising candidate for the development of Fast Neutron Reactors. It is well known owing to its wide development since the 1950's, throughout all countries involved in the development of nuclear power plants. The development of Sodium-cooled fast neutron reactors is possible due to its very attractive sodium, nuclear, physical and even some of its chemical properties. Nevertheless, the operational feedback has shown that the concept has several drawbacks: difficulties for In-Service Inspection and Repair operations due to the sodium opacity and possible detrimental effects of its reactivity with air and water when the heat conversion is performed with a conventional Rankine cycle. Moreover, the various design projects have shown some difficulties in enhancing its competitiveness with regards to existing NPPs without any new innovative options, i.e. the possibility of suppressing the intermediate circuits and/or the development of an optimized energy conversion system. The Supercritical CO 2 Brayton Cycle option for the energy conversion has been widely suggested because of its high thermodynamic efficiency (over 40%), its potential compactness of the Balance Of Plant equipment due to the small-sized turbo machinery system, and for its applicability to both Direct or Indirect Cycle (Na, PbBi, He) assuming the hypothesis that the Supercritical CO 2 -Na interaction has less serious potential consequences than sodium-water consequences in the conventional Rankine cycle. Within the framework of the SMFR (Small Modular Fast Reactor) project, developed jointly by Argonne National Laboratory (ANL-USA), the 'Commissariat a l'Energie Atomique' (CEA) and Japan Atomic Energy Agency (JAEA, formerly Japan Nuclear Cycle development), this option has been selected and investigated. This paper deals with the study of the interaction between Na and CO 2 , based on a literature review: the result of this study will allow the definition of R and D

Regenerator optimization of a Closed Brayton Cycle via entropy generation minimization

International Nuclear Information System (INIS)

Araújo, Élvis Falcão de; Ribeiro, Guilherme Borges; Guimarães, Lamartine N. F.

2017-01-01

This paper aims the numerical study of the heat transfer and fluid flow of a Closed Brayton Cycle (CBC) regenerator that is part of TERRA microreactor. This regenerator consists in a cross flow heat exchanger, where heat transfer occurs between internal fluid flow in radial tubes and external fluid flow passing perpendicularly to the tubes, which are disposed in a symmetrical cylindrical set where the number of tubes in the axial and radial directions can vary. In the simulations, mass flow inlet is varied for a fixed geometry. The fluid flow solution is provided by a commercial CFD solver and the entropy generation number calculation is later computed for optimization purposes. As a result, the entropy minimization method provides the regenerator configuration that enables the highest energy conversion efficiency. (author)

Regenerator optimization of a Closed Brayton Cycle via entropy generation minimization

Energy Technology Data Exchange (ETDEWEB)

Araújo, Élvis Falcão de; Ribeiro, Guilherme Borges; Guimarães, Lamartine N. F., E-mail: falcao@ieav.cta.br, E-mail: gbribeiro@ieav.cta.br, E-mail: guimarae@ieav.cta.br [Instituto de Estudos Avançacados (IEAv), São José dos Campos, SP (Brazil). Div. de Energia Nuclear

2017-07-01

This paper aims the numerical study of the heat transfer and fluid flow of a Closed Brayton Cycle (CBC) regenerator that is part of TERRA microreactor. This regenerator consists in a cross flow heat exchanger, where heat transfer occurs between internal fluid flow in radial tubes and external fluid flow passing perpendicularly to the tubes, which are disposed in a symmetrical cylindrical set where the number of tubes in the axial and radial directions can vary. In the simulations, mass flow inlet is varied for a fixed geometry. The fluid flow solution is provided by a commercial CFD solver and the entropy generation number calculation is later computed for optimization purposes. As a result, the entropy minimization method provides the regenerator configuration that enables the highest energy conversion efficiency. (author)

Volcanic CO2 Emissions and Glacial Cycles: Coupled Oscillations

Science.gov (United States)

Burley, J. M.; Huybers, P. J.; Katz, R. F.

2016-12-01

Following the mid-Pleistocene transition, the dominant period of glacial cycles changed from 40 ka to 100 ka. It is broadly accepted that the 40 ka glacial cycles were driven by cyclical changes in obliquity. However, this forcing does not explain the 100 ka glacial cycles. Mechanisms proposed for 100 ka cycles include isostatic bed depression and proglacial lakes destabilising the Laurentide ice sheet, non-linear responses to orbital eccentricity, and Antarctic ice sheets influencing deep-ocean stratification. None of these are universally accepted. Here we investigate the hypothesis that variations in volcanic CO2 emissions can cause 100 ka glacial cycles. Any proposed mechanism for 100 ka glacial cycles must give the Earth's climate system a memory of 10^4 - 10^5years. This timescale is difficult to achieve for surface processes, however it is possible for the solid Earth. Recent work suggests volcanic CO2 emissions change in response to glacial cycles [1] and that there could be a 50 ka delay in that response [2]. Such a lagged response could drive glacial cycles from 40 ka cycles to an integer multiple of the forcing period. Under what conditions could the climate system admit such a response? To address this, we use a simplified climate model modified from Huybers and Tziperman [3]. Our version comprises three component models for energy balance, ice sheet growth and atmospheric CO2 concentration. The model is driven by insolation alone with other components varying according to a system of coupled, differential equations. The model is run for 500 ka to produce several glacial cycles and the resulting changes in global ice volume and atmospheric CO2 concentration.We obtain a switch from 40 ka to 100 ka cycles as the volcanic CO2 response to glacial cycles is increased. These 100 ka cycles are phase-locked to obliquity, lasting 80 or 120 ka. Whilst the MOR response required (in this model) is larger than plausible estimates based on [2], it illustrates the

Study on the supercritical CO2 power cycles for landfill gas firing gas turbine bottoming cycle

International Nuclear Information System (INIS)

Kim, Min Seok; Ahn, Yoonhan; Kim, Beomjoo; Lee, Jeong Ik

2016-01-01

In this paper, a comparison of nine supercritical carbon dioxide (S-CO 2 ) bottoming power cycles in conjunction with a topping cycle of landfill gas (LFG) fired 5MWe gas turbine is presented. For the comparison purpose, a sensitivity study of the cycle design parameters for nine different cycles was conducted and each cycle thermodynamic performance is evaluated. In addition, the cycle performance evaluation dependency on the compressor inlet temperature variation is performed to investigate how S-CO 2 cycles sensitive to the heat sink temperature variation. Furthermore, the development of new S-CO 2 cycle layouts is reported and the suggested cycles' performances are compared to the existing cycle layouts. It was found that a recompression cycle is not suitable for the bottoming cycle application, but a partial heating cycle has relatively higher net produced work with a simple layout and small number of components. Although a dual heated and flow split cycle has the highest net produced work, it has disadvantages of having numerous components and complex process which requires more sophisticated operational strategies. This study identified that the recuperation process is much more important than the intercooling process to the S-CO 2 cycle design for increasing the thermal efficiency and the net produced work point of view. - Highlights: • Study of nine S-CO 2 power cycle layouts for a small scale landfill gas power generation application. • Development of new S-CO 2 cycle layouts. • Sensitivity analysis of S-CO 2 cycles to evaluate and compare nine cycles' performances.

Nuclear Bi-Brayton system for aircraft propulsion

International Nuclear Information System (INIS)

Pierce, B.L.

1979-01-01

Recent studies have shown the desirability of new system concept for nuclear aircraft propulsion utilizing the Bi-Brayton system concept, permits coupling of a gas cooled reactor to the power transmission and conversion system in a manner such as to fulfill the safety criteria while eliminating the need for a high temperature intermediate heat exchanger or shaft penetrations of the containment vessel. This system has been shown to minimize the component development required and to allow reduction in total propulsion system weight. This paper presents a description of the system concept and the results of the definition and evaluation studies to date. Parametric and reference system definition studies have been performed. The closed-cycle Bi-Brayton system and component configurations and weight estimates have been derived. Parametric evaluation and cycle variation studies have been performed and interpreted. 7 refs

Potential performance improvement using a reacting gas (nitrogin tetroxide) as the working fluid in a closed Brayton cycle

Science.gov (United States)

Stochl, R. J.

1979-01-01

The results of an analysis to estimate the performance that could be obtained by using a chemically reacting gas (nitrogen tetroxide) as the working fluid in a closed Brayton cycle are presented. Compared with data for helium as the working fluid, these results indicate efficiency improvements from 4 to 90 percent, depending on turbine inlet temperature, pressures, and gas residence time in heat transfer equipment.

Advanced heat pump for the recovery of volatile organic compounds. Phase 1, Conceptual design of an advanced Brayton cycle heat pump for the recovery of volatile organic compounds: Final report

Energy Technology Data Exchange (ETDEWEB)

1992-03-01

Emissions of Volatile Organic Compounds (VOC) from stationary industrial and commercial sources represent a substantial portion of the total US VOC emissions. The ``Toxic-Release Inventory`` of The US Environmental Protection Agency estimates this to be at about 3 billion pounds per year (1987 estimates). The majority of these VOC emissions are from coating processes, cleaning processes, polymer production, fuel production and distribution, foam blowing,refrigerant production, and wood products production. The US Department of Energy`s (DOE) interest in the recovery of VOC stems from the energy embodied in the recovered solvents and the energy required to dispose of them in an environmentally acceptable manner. This Phase I report documents 3M`s work in close working relationship with its subcontractor Nuclear Consulting Services (Nucon) for the preliminary conceptual design of an advanced Brayton cycle heat pump for the recovery of VOC. Nucon designed Brayton cycle heat pump for the recovery of methyl ethyl ketone and toluene from coating operations at 3M Weatherford, OK, was used as a base line for the work under cooperative agreement between 3M and ODE. See appendix A and reference (4) by Kovach of Nucon. This cooperative agreement report evaluates and compares an advanced Brayton cycle heat pump for solvent recovery with other competing technologies for solvent recovery and reuse. This advanced Brayton cycle heat pump is simple (very few components), highly reliable (off the shelf components), energy efficient and economically priced.

COMPARISON OF S-CO2 POWER CYCLES FOR NUCLEAR ENERGY

Directory of Open Access Journals (Sweden)

Ladislav Vesely

2016-12-01

Full Text Available The supercritical carbon dioxide (S-CO2 is a possible cooling system for the new generations of nuclear reactors and fusion reactors. The S-CO2 power cycles have several advantages over other possible coolants such as water and helium. The advantages are the compression work, which is lower than in the case of helium, near the critical point and the S-CO2 is more compact than water and helium. The disadvantage is so called Pinch point which occurs in the regenerative heat exchanger. The pinch point can be eliminated by an arrangement of the cycle or using a mixture of CO2. This paper describes the S-CO2 power cycles for nuclear fission and fusion reactors.

Preliminary Validation and Verification of TURBO{sub D}ESIGN for S-CO{sub 2} Axial Compressor

Energy Technology Data Exchange (ETDEWEB)

Lee, Je Kyoung; Lee, Jeong Ik; Ahn, Yoon Han; Kim, Seong Gu [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Yoon, Ho Joon; Addad, Yacine [Khalifa University of Science, Technology and Research, Abu Dhabi (United Arab Emirates)

2012-05-15

To use the advantages of Supercritical CO{sub 2}(S-CO{sub 2}) Brayton cycle for nuclear power plant, KAIST-Khalifa University joint research team has been focusing on S-CO{sub 2} turbomachinery development. TURBO{sub D}ESIGN code is one of the products of our researches to design a turbomachinery. The major feature of TURBO{sub D}ESIGN is that the formulation is based on the real gas and none of the ideal gas assumption was applied to the code. Thus, TURBO{sub D}ESIGN has high flexibility regarding the type of gases. In this paper, preliminary code validation and verification of TURBO{sub D}ESIGN will be discussed for axial type compressor design

The closed Brayton cycle: An energy conversion system for near-term military space missions

Science.gov (United States)

Davis, Keith A.

The Particle Bed Reactor (PBR)-closed Brayton cycle (CBC) provides a 5 to 30 kWe class nuclear power system for surveillance and communication missions during the 1990s and will scale to 100 kWe and beyond for other space missions. The PBR-CBC is technically feasible and within the existing state of the art. The PBR-CBC system is flexible, scaleable, and offers development economy. The ability to operate over a wide power range promotes commonality between missions with similar but not identical power spectra. The PBR-CBC system mass is very competitive with rival nuclear dynamic and static power conversion and systems. The PBR-CBC provides growth potential for the future with even lower specific masses.

Supercritical Carbon Dioxide turbomachinery design for water-cooled Small Modular Reactor application

International Nuclear Information System (INIS)

Lee, Jekyoung; Lee, Jeong Ik; Yoon, Ho Joon; Cha, Jae Eun

2014-01-01

Highlights: • We described the concept of coupling the S-CO 2 Brayton cycle to the water-cooled SMRs. • We describe a turbomachinery design code called KAISD T MD that can use real gases too. • We suggest changes to the S-CO 2 cycle layout with multiple-independent shafts. • KAIST T MD was used to design the turbomachinery of suggested layout. - Abstract: The Supercritical Carbon Dioxide (S-CO 2 ) Brayton cycle has been gaining attention due to its compactness and high efficiency at moderate turbine inlet temperature. Previous S-CO 2 cycle research works in the field of nuclear engineering were focused on its application to the next generation reactor with higher turbine inlet temperature than the existing conventional water-cooled nuclear power plants. However, it was shown in authors’ previous paper that the advantages of the S-CO 2 Brayton cycle can be also further applied to the water-cooled Small Modular Reactor (SMR) with a success, since SMR requires minimal overall footprint while retaining high performance. One of the major issues in the S-CO 2 Brayton cycle is the selection and design of appropriate turbomachinery for the designed cycle. Because most of the nuclear industry uses incompressible working fluids or ideal gases in the turbomachinery, a more detailed examination of the design of the turbomachinery is required for a power system that uses S-CO 2 as working fluid. This is because the S-CO 2 Brayton cycle high efficiency is the result of the non-ideal variation of properties near the CO 2 critical point. Thus, the major focus of this paper is to suggest the design of the turbomachinery necessary for the S-CO 2 Brayton cycle coupled to water cooled SMRs. For this reason, a S-CO 2 Brayton cycle turbomachinery design methodology was suggested and the suggested design methodology was first tested with the existing experimental data to verify its capability. After then, it was applied to the proposed reference system to demonstrate its

Supercritical Carbon Dioxide turbomachinery design for water-cooled Small Modular Reactor application

Energy Technology Data Exchange (ETDEWEB)

Lee, Jekyoung, E-mail: leejaeky85@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Lee, Jeong Ik, E-mail: jeongiklee@kaist.ac.kr [Department of Nuclear and Quantum Engineering, Korea Advanced Institute of Science and Technology, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of); Yoon, Ho Joon, E-mail: hojoon.yoon@kustar.ac.ae [Khalifa University of Science, Technology and Research (KUSTAR), P.O. Box 127788, Abu Dhabi (United Arab Emirates); Cha, Jae Eun, E-mail: jecha@kaeri.re.kr [Korea Atomic Energy Research Institute, 1045 Daedeok-daero, Yuseong-gu, Daejeon 305-353 (Korea, Republic of)

2014-04-01

Highlights: • We described the concept of coupling the S-CO{sub 2} Brayton cycle to the water-cooled SMRs. • We describe a turbomachinery design code called KAISD{sub T}MD that can use real gases too. • We suggest changes to the S-CO{sub 2} cycle layout with multiple-independent shafts. • KAIST{sub T}MD was used to design the turbomachinery of suggested layout. - Abstract: The Supercritical Carbon Dioxide (S-CO{sub 2}) Brayton cycle has been gaining attention due to its compactness and high efficiency at moderate turbine inlet temperature. Previous S-CO{sub 2} cycle research works in the field of nuclear engineering were focused on its application to the next generation reactor with higher turbine inlet temperature than the existing conventional water-cooled nuclear power plants. However, it was shown in authors’ previous paper that the advantages of the S-CO{sub 2} Brayton cycle can be also further applied to the water-cooled Small Modular Reactor (SMR) with a success, since SMR requires minimal overall footprint while retaining high performance. One of the major issues in the S-CO{sub 2} Brayton cycle is the selection and design of appropriate turbomachinery for the designed cycle. Because most of the nuclear industry uses incompressible working fluids or ideal gases in the turbomachinery, a more detailed examination of the design of the turbomachinery is required for a power system that uses S-CO{sub 2} as working fluid. This is because the S-CO{sub 2} Brayton cycle high efficiency is the result of the non-ideal variation of properties near the CO{sub 2} critical point. Thus, the major focus of this paper is to suggest the design of the turbomachinery necessary for the S-CO{sub 2} Brayton cycle coupled to water cooled SMRs. For this reason, a S-CO{sub 2} Brayton cycle turbomachinery design methodology was suggested and the suggested design methodology was first tested with the existing experimental data to verify its capability. After then, it was

Thermodynamic analysis and preliminary design of closed Brayton cycle using nitrogen as working fluid and coupled to small modular Sodium-cooled fast reactor (SM-SFR)

International Nuclear Information System (INIS)

Olumayegun, Olumide; Wang, Meihong; Kelsall, Greg

2017-01-01

Highlights: • Nitrogen closed Brayton cycle for small modular sodium-cooled fast reactor studied. • Thermodynamic modelling and analysis of closed Brayton cycle performed. • Two-shaft configuration proposed and performance compared to single shaft. • Preliminary design of heat exchangers and turbomachinery carried out. - Abstract: Sodium-cooled fast reactor (SFR) is considered the most promising of the Generation IV reactors for their near-term demonstration of power generation. Small modular SFRs (SM-SFRs) have less investment risk, can be deployed more quickly, are easier to operate and are more flexible in comparison to large nuclear reactor. Currently, SFRs use the proven Rankine steam cycle as the power conversion system. However, a key challenge is to prevent dangerous sodium-water reaction that could happen in SFR coupled to steam cycle. Nitrogen gas is inert and does not react with sodium. Hence, intercooled closed Brayton cycle (CBC) using nitrogen as working fluid and with a single shaft configuration has been one common power conversion system option for possible near-term demonstration of SFR. In this work, a new two shaft nitrogen CBC with parallel turbines was proposed to further simplify the design of the turbomachinery and reduce turbomachinery size without compromising the cycle efficiency. Furthermore, thermodynamic performance analysis and preliminary design of components were carried out in comparison with a reference single shaft nitrogen cycle. Mathematical models in Matlab were developed for steady state thermodynamic analysis of the cycles and for preliminary design of the heat exchangers, turbines and compressors. Studies were performed to investigate the impact of the recuperator minimum terminal temperature difference (TTD) on the overall cycle efficiency and recuperator size. The effect of turbomachinery efficiencies on the overall cycle efficiency was examined. The results showed that the cycle efficiency of the proposed

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

International Nuclear Information System (INIS)

Le Roux, W.G.; Bello-Ochende, T.; Meyer, J.P.

2011-01-01

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.

Design and fabrication of the Mini-Brayton Recuperator (MBR)

Science.gov (United States)

Killackey, J. J.; Graves, R.; Mosinskis, G.

1978-01-01

Development of a recuperator for a 2.0 kW closed Brayton space power system is described. The plate-fin heat exchanger is fabricated entirely from Hastelloy X and is designed for 10 years continuous operation at 1000 K (1300 F) with a Xenon-helium working fluid. Special design provisions assure uniform flow distribution, crucial for meeting 0.975 temperature effectiveness. Low-cycle fatigue, resulting from repeated startup and shutdown cycles, was identified as the most critical structural design problem. It is predicted that the unit has a minimum fatigue life of 220 cycles. This is in excess of the BIPS requirement of 100 cycles. Heat transfer performance and thermal cycle testing with air, using a prototype unit, verified that all design objectives can be met.

Buffer thermal energy storage for a solar Brayton engine

Science.gov (United States)

Strumpf, H. J.; Barr, K. P.

1981-01-01

A study has been completed on the application of latent-heat buffer thermal energy storage to a point-focusing solar receiver equipped with an air Brayton engine. To aid in the study, a computer program was written for complete transient/stead-state Brayton cycle performance. The results indicated that thermal storage can afford a significant decrease in the number of engine shutdowns as compared to operating without thermal storage. However, the number of shutdowns does not continuously decrease as the storage material weight increases. In fact, there appears to be an optimum weight for minimizing the number of shutdowns.

Preliminary Studies of Na{sub 2}CO{sub 3} Cleaning from Na-CO{sub 2} Interaction in S-CO{sub 2} Power Cycle coupled to SFR System

Energy Technology Data Exchange (ETDEWEB)

Jung, Hwa-Young; Lee, Jeong Ik [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Wi, Myung-Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Ahn, Hong Joo [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2014-10-15

Once the flow channel is plugged, to replace the plugged channel, the whole system operation should be stopped or a bypass system is necessary.. Therefore, finding a material which can clean up the solid reaction products from Na-CO{sub 2} interaction and the contaminated system with little or no impact on economics can be a valuable research. Hence, a screening process of selecting candidate materials was adopted to find a potential substance which can act as a cleaning agent in the previous study. It is essential to ensure the system economics as well as safety of SFR coupled with S-CO{sub 2} Brayton power conversion system. For this reason, the experiment was conducted to see the possibility of reaction between each selected potential substance and Na{sub 2}CO{sub 3}, which is the major product of the reaction. Na{sub 2}CO{sub 3} does not melt before 856 .deg. C This study was performed with the collaboration of Korea Atomic Energy Research Institute (KAERI) and Korea Advanced Institute of Science and Technology (KAIST). Liquid sodium and CO{sub 2} gas would react then produce the solid reaction products when the pressure boundary of sodium-CO{sub 2} heat exchanger fails. The solid reaction products are possible to plug the narrow flow channel of PCHE and this concerns the system economics. Thus, it is necessary to search a method for cleaning the solid reaction products which is mainly Na{sub 2}CO{sub 3}. From the preliminary study, some sodium-based compounds were selected and the mixtures of several sodium-based compounds with Na{sub 2}CO{sub 3} were thermally analyzed by the TG/DTA studies. Unfortunately, the selected sodium-based compounds, NaBrO{sub 3}, NaClO{sub 3} and NaBF{sub 4}, decomposed before 600 .deg. C and did not react with Na{sub 2}CO{sub 3}. In the near future, further research will be performed to search other compounds for cleaning the solid reaction products.

sCO2 Power Cycles Summit Summary November 2017.

Energy Technology Data Exchange (ETDEWEB)

Mendez Cruz, Carmen Margarita; Rochau, Gary E.; Lance, Blake

2018-04-01

Over the past ten years, the Department of Energy (DOE) has helped to develop components and technologies for the Supercritical Carbon Dioxide (sCO2) power cycle capable of efficient operation at high temperatures and high efficiency. The DOE Offices of Fossil Energy, Nuclear Energy, and Energy Efficiency and Renewable Energy collaborated in the planning and execution of the sCO2 Power Cycle Summit conducted in Albuquerque, NM in November 2017. The summit brought together participants from government, national laboratories, research, and industry to engage in discussions regarding the future of sCO 2 Power Cycles Technology. This report summarizes the work involved in summit planning and execution, before, during, and after the event, including the coordination between three DOE offices and technical content presented at the event.

Experimental Results From a 2kW Brayton Power Conversion Unit

Science.gov (United States)

Hervol, David; Mason, Lee; Birchenough, Arthur

2003-01-01

This paper presents experimental test results from operation of a 2 kWe Brayton power conversion unit. The Brayton converter was developed for a solar dynamic power system flight experiment planned for the Mir Space Station in 1997. The flight experiment was cancelled, but the converter was tested at Glenn Research Center as part of the Solar Dynamic Ground Test Demonstration system which included a solar concentrator, heat receiver, and space radiator. In preparation for the current testing, the heat receiver was removed and replaced with an electrical resistance heater, simulating the thermal input of a steady-state nuclear source. The converter was operated over a full range of thermal input power levels and rotor speeds to generate an overall performance map. The converter unit will serve as the centerpiece of a Nuclear Electric Propulsion Testbed at Glenn. Future potential uses for the Testbed include high voltage electrical controller development, integrated electric thruster testing and advanced radiator demonstration testing to help guide high power Brayton technology development for Nuclear Electric Propulsion (NEP).

Materials, Turbomachinery and Heat Exchangers for Supercritical CO2 Systems

Energy Technology Data Exchange (ETDEWEB)

Anderson, Mark; Nellis, Greg; Corradini, Michael

2012-10-19

The objective of this project is to produce the necessary data to evaluate the performance of the supercritical carbon dioxide cycle. The activities include a study of materials compatibility of various alloys at high temperatures, the heat transfer and pressure drop in compact heat exchanger units, and turbomachinery issues, primarily leakage rates through dynamic seals. This experimental work will serve as a test bed for model development and design calculations, and will help define further tests necessary to develop high-efficiency power conversion cycles for use on a variety of reactor designs, including the sodium fast reactor (SFR) and very high-temperature gas reactor (VHTR). The research will be broken into three separate tasks. The first task deals with the analysis of materials related to the high-temperature S-CO{sub 2} Brayton cycle. The most taxing materials issues with regard to the cycle are associated with the high temperatures in the reactor side heat exchanger and in the high-temperature turbine. The system could experience pressures as high as 20MPa and temperatures as high as 650°C. The second task deals with optimization of the heat exchangers required by the S-CO{sub 2} cycle; the S-CO{sub 2} flow passages in these heat exchangers are required whether the cycle is coupled with a VHTR or an SFR. At least three heat exchangers will be required: the pre-cooler before compression, the recuperator, and the heat exchanger that interfaces with the reactor coolant. Each of these heat exchangers is unique and must be optimized separately. The most challenging heat exchanger is likely the pre-cooler, as there is only about a 40°C temperature change but it operates close to the CO{sub 2} critical point, therefore inducing substantial changes in properties. The proposed research will focus on this most challenging component. The third task examines seal leakage through various dynamic seal designs under the conditions expected in the S-CO{sub 2} cycle

Effect of geometrical shape of the working substance Gadolinium on the performance of a regenerative magnetic Brayton refrigeration cycle

International Nuclear Information System (INIS)

Diguet, Gildas; Lin, Guoxing; Chen, Jincan

2013-01-01

Based on Mean Field Theory (MFT), the entropy of magnetic material Gadolinium (Gd), which is a function of the local magnetic field and temperature, is calculated and analyzed. This local magnetic field is the sum of the applied field H 0 plus the exchange field H W =λM and the demagnetizing field H d =−NM, where the demagnetizing factor N depends on the shape of magnetic materials. Hereby, the impacts of the demagnetizing factor N on the magnetic entropy, magnetic entropy change and main thermodynamics performance of a regenerative magnetic Brayton refrigeration cycle using Gd as the working substance are investigated and evaluated in detail. The results obtained underline the importance of the shape of the working substance used in magnetic refrigerators for room-temperature application; elongated materials provide better thermodynamics performance such as higher COP and net heat absorption. It is pointed out that for low external fields, the magnetic refrigerator ceased to be functional if flat materials were used. - Highlights: ► Gd entropy is calculated as a function of temperature and internal magnetic field. ► Magnetic Brayton cycle properties generally depend on the demagnetizing factor. ► Redundant heat transfer is highly sensitive to the demagnetizing factor. ► The net cooling quantity is highly sensitive to the demagnetizing factor. ► Coefficient of performance is dependant to the magnetic material shape.

Thermal performance analysis of Brayton cycle with waste heat recovery boiler for diesel engines of offshore oil production facilities

International Nuclear Information System (INIS)

Liu, Xianglong; Gong, Guangcai; Wu, Yi; Li, Hangxin

2016-01-01

Highlights: • Comparison of Brayton cycle with WHRB adopted in diesel engines with and without fans by thermal performance. • Waste heat recovery technology for FPSO. • The thermoeconomic analysis for the heat recovery for FPSO. - Abstract: This paper presents the theoretical analysis and on-site testing on the thermal performance of the waste heat recovery system for offshore oil production facilities, including the components of diesel engines, thermal boilers and waste heat boilers. We use the ideal air standard Brayton cycle to analyse the thermal performance. In comparison with the traditional design, the fans at the engine outlet of the waste heat recovery boiler is removed due to the limited space of the offshore platform. The cases with fan and without fan are compared in terms of thermal dynamics performance, energy efficiency and thermo-economic index of the system. The results show that the application of the WHRB increases the energy efficiency of the whole system, but increases the flow resistance in the duct. It is proved that as the waste heat recovery boiler takes the place of the thermal boiler, the energy efficiency of whole system without fan is slightly reduced but heat recovery efficiency is improved. This research provides an important guidance to improve the waste heat recovery for offshore oil production facilities.

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.

Detection Test for Leakage of CO2 into Sodium Loop

International Nuclear Information System (INIS)

Park, Sun Hee; Wi, Myung-Hwan; Min, Jae Hong

2015-01-01

This report is about the facility for the detection test for leakage of CO 2 into sodium loop. The facility for the detection test for leakage of CO 2 into sodium loop was introduced. The test will be carried out. Our experimental results are going to be expected to be used for approach methods to detect CO 2 leaking into sodium in heat exchangers. A sodium-and-carbon dioxide (Na-CO 2 ) heat exchanger is one of the key components for the supercritical CO 2 Brayton cycle power conversion system of sodium-cooled fast reactors (SFRs). A printed circuit heat exchanger (PCHE) is considered for the Na-CO 2 heat exchanger, which is known to have potential for reducing the volume occupied by the exchangers compared to traditional shell-and-tube heat exchangers. Among various issues about the Na- CO 2 exchanger, detection of CO 2 leaking into sodium in the heat exchanger is most important thing for its safe operation. It is known that reaction products from sodium and CO 2 such as sodium carbonate (Na 2 CO 3 ) and amorphous carbon are hardly soluble in sodium, which cause plug sodium channels. Detection technique for Na 2 CO 3 in sodium loop has not been developed yet. Therefore, detection of CO 2 and CO from reaction of sodium and CO 2 are proper to detect CO 2 leakage into sodium loop

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.

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.

1988-11-01

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.

Hydrogen production from coal gasification for effective downstream CO{sub 2} capture

Energy Technology Data Exchange (ETDEWEB)

Gnanapragasam, Nirmal V.; Reddy, Bale V.; Rosen, Marc A. [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology, 2000 Simcoe Street North, Oshawa, Ontario, L1H 7K4 (Canada)

2010-05-15

The coal gasification process is used in commercial production of synthetic gas as a means toward clean use of coal. The conversion of solid coal into a gaseous phase creates opportunities to produce more energy forms than electricity (which is the case in coal combustion systems) and to separate CO{sub 2} in an effective manner for sequestration. The current work compares the energy and exergy efficiencies of an integrated coal-gasification combined-cycle power generation system with that of coal gasification-based hydrogen production system which uses water-gas shift and membrane reactors. Results suggest that the syngas-to-hydrogen (H{sub 2}) system offers 35% higher energy and 17% higher exergy efficiencies than the syngas-to-electricity (IGCC) system. The specific CO{sub 2} emission from the hydrogen system was 5% lower than IGCC system. The Brayton cycle in the IGCC system draws much nitrogen after combustion along with CO{sub 2}. Thus CO{sub 2} capture and compression become difficult due to the large volume of gases involved, unlike the hydrogen system which has 80% less nitrogen in its exhaust stream. The extra electrical power consumption for compressing the exhaust gases to store CO{sub 2} is above 70% for the IGCC system but is only 4.5% for the H{sub 2} system. Overall the syngas-to-hydrogen system appears advantageous to the IGCC system based on the current analysis. (author)

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

International Nuclear Information System (INIS)

Tarlecki, Jason; Lior, Noam; Zhang Na

2007-01-01

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 (N 2 and H 2 ) 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

Brayton Power Conversion Unit Tested: Provides a Path to Future High-Power Electric Propulsion Missions

Science.gov (United States)

Mason, Lee S.

2003-01-01

Closed-Brayton-cycle conversion technology has been identified as an excellent candidate for nuclear electric propulsion (NEP) power conversion systems. Advantages include high efficiency, long life, and high power density for power levels from about 10 kWe to 1 MWe, and beyond. An additional benefit for Brayton is the potential for the alternator to deliver very high voltage as required by the electric thrusters, minimizing the mass and power losses associated with the power management and distribution (PMAD). To accelerate Brayton technology development for NEP, the NASA Glenn Research Center is developing a low-power NEP power systems testbed that utilizes an existing 2- kWe Brayton power conversion unit (PCU) from previous solar dynamic technology efforts. The PCU includes a turboalternator, a recuperator, and a gas cooler connected by gas ducts. The rotating assembly is supported by gas foil bearings and consists of a turbine, a compressor, a thrust rotor, and an alternator on a single shaft. The alternator produces alternating-current power that is rectified to 120-V direct-current power by the PMAD unit. The NEP power systems testbed will be utilized to conduct future investigations of operational control methods, high-voltage PMAD, electric thruster interactions, and advanced heat rejection techniques. The PCU was tested in Glenn s Vacuum Facility 6. The Brayton PCU was modified from its original solar dynamic configuration by the removal of the heat receiver and retrofitting of the electrical resistance gas heater to simulate the thermal input of a steady-state nuclear source. Then, the Brayton PCU was installed in the 3-m test port of Vacuum Facility 6, as shown. A series of tests were performed between June and August of 2002 that resulted in a total PCU operational time of about 24 hr. An initial test sequence on June 17 determined that the reconfigured unit was fully operational. Ensuing tests provided the operational data needed to characterize PCU

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

International Nuclear Information System (INIS)

Epiney, A.; Mikityuk, K.; Chawla, R.; Alpy, N.; Haubensack, D.; Malo, J.Y.

2009-01-01

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)

Hollow Co2P nanoflowers organized by nanorods for ultralong cycle-life supercapacitors

KAUST Repository

Cheng, Ming

2017-08-24

Hollow Co2P nanoflowers (Co2P HNF) are successfully prepared via a one-step, template-free method. Microstructure analysis reveals that Co2P HNF is assembled by nanorods, possesses abundant mesopores and a amorphous carbon shell. Density functional theory calculation and electrochemical measurements demonstrate the high electrical conductivity of Co2P. Benefiting from the unique nanostructures, when employed as electrode material for supercapacitors, Co2P HNF exhibits a high specific capacitance, an outstanding rate capability, and an ultralong cycle stability. Furthermore,. the constructed Co2P HNF//AC ASC yields a high energy density of 30.5 Wh kg-1 at a power density of 850 W kg-1, along with an superior cycling performance (108.0% specific capacitance retained after 10000 cycles at 5 A g-1). These impressive results make Co2P HNF a promising candidate for supercapacitor applications.

An improved model to evaluate thermodynamic solar plants with cylindrical parabolic collectors and air turbine engines in open Joule–Brayton cycle

International Nuclear Information System (INIS)

Ferraro, Vittorio; Imineo, Francesco; Marinelli, Valerio

2013-01-01

An improved model to analyze the performance of solar plants operating with cylindrical parabolic collectors and atmospheric air as heat transfer fluid in an open Joule–Brayton cycle is presented. In the new model, the effect of the incident angle modifier is included, to take into account the variation of the optical efficiency with the incidence angle of the irradiance, and the effect of the reheating of the fluid also has been studied. The analysis was made for two operating modes of the plants: with variable air flow rate and constant inlet temperature to the turbine and with constant flow rate and variable inlet temperature to the turbine, with and without reheating of the fluid in the solar field. When reheating is used, the efficiency of the plant is increased. The obtained results show a good performance of this type of solar plant, in spite of its simplicity; it is able to compete well with other more complex plants operating with different heat transfer fluids. - Highlights: ► An improved model to calculate an innovative CPS solar plant is presented. ► The plant works with air in an open Joule–Brayton cycle. ► The reheating of the air increases the thermodynamic efficiency. ► The plant is very simple and competes well with other more complex solar plants

Second law analysis of the transcritical CO2 refrigeration cycle

International Nuclear Information System (INIS)

Fartaj, Amir; Ting, David S.-K.; Yang, Wendy W.

2004-01-01

Because of the global warming impact of HFCs, the use of natural refrigerants has received worldwide attention. Efficient use of refrigerants is of pressing concern to the present automotive and HVAC industries. The natural refrigerant, carbon dioxide (CO 2 ), exhibits promise for use in automotive air conditioning systems, in particular the transcritical CO 2 refrigeration cycle. The objective of this work is to identify the main factors that affect CO 2 system performance. A second law of thermodynamic analysis on the entire CO 2 refrigeration cycle is conducted so that the effectiveness of the components of the system can be deduced and ranked, allowing future efforts to focus on improving the components that have the highest potential for advancement. The analysis reveals that the compressor and the gas cooler exhibit the largest non-idealities within the system, and hence, efforts should be focused on improving these components

Rankine-Brayton engine powered solar thermal aircraft

Science.gov (United States)

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.

Rankline-Brayton engine powered solar thermal aircraft

Science.gov (United States)

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.

Hollow Co2P nanoflowers assembled from nanorods for ultralong cycle-life supercapacitors.

Science.gov (United States)

Cheng, Ming; Fan, Hongsheng; Xu, Yingying; Wang, Rongming; Zhang, Xixiang

2017-09-28

Hollow Co 2 P nanoflowers (Co 2 P HNFs) were successfully prepared via a one-step, template-free method. Microstructure analysis reveals that Co 2 P HNFs are assembled from nanorods and possess abundant mesopores and an amorphous carbon shell. Density functional theory calculations and electrochemical measurements demonstrate the high electrical conductivity of Co 2 P. Benefiting from the unique nanostructures, when employed as an electrode material for supercapacitors, Co 2 P HNFs exhibit a high specific capacitance, an outstanding rate capability, and an ultralong cycling stability. Furthermore, the constructed Co 2 P HNF//AC ASC exhibits a high energy density of 30.5 W h kg -1 at a power density of 850 W kg -1 , along with a superior cycling performance (108.0% specific capacitance retained after 10 000 cycles at 5 A g -1 ). These impressive results make Co 2 P HNFs a promising candidate for supercapacitor applications.

Efficiencies of subcritical and transcritical CO2 inverse cycles with and without an internal heat exchanger

International Nuclear Information System (INIS)

Zhang, F.Z.; Jiang, P.X.; Lin, Y.S.; Zhang, Y.W.

2011-01-01

An internal heat exchanger (IHX) is often used to improve the coefficient of performance (COP) of CO 2 inverse cycles. This paper presents a detailed analysis of the IHX's effect in CO 2 inverse cycles and finds suitable operating conditions for the IHX from a thermodynamic performance point of view. The results indicate that the COP is slightly reduced by an IHX in a CO 2 subcritical inverse cycle, so an IHX is not justified. However, for transcritical CO 2 inverse cycles, the compressor discharge pressures and CO 2 gas cooler outlet temperatures both have significant impacts on system performance. The analysis results for transcritical CO 2 inverse cycles show that a transition discharge pressure and a transition CO 2 gas cooler outlet temperature are objective existence above which the IHX improves the cycle performance. - Research highlights: → Find suitable operating conditions for the IHX. → Above transition CO2 gas cooler outlet temperature IHX improves cycle performance. → The IHX is not very useful for optimized space heating and refrigerating cycles.

Study of the first stages of oxidation of a ferritic-martensitic steel Fe-12Cr in CO2

International Nuclear Information System (INIS)

Bouhieda, S.

2012-01-01

In the framework of the development of Sodium Fast Reactors in France, supercritical carbon dioxide integrated in the Brayton cycle is proposed as new cycle energy conversion system to replace current steam generators. Ferritic-Martensitic steels with 9-12 wt% Cr are good candidates for heat exchanger application because they have good mechanical properties up to a temperature of 600 C, a high thermal conductivity, a low coefficient of thermal expansion and a lower cost than that of austenitic steels. However, it has been found that these steels present a high parabolic oxide growth rate and a strong carburization in the temperature and pressure conditions of the SC-CO 2 cycle (550 C, 250 bar). This study aims to investigate the influence of different parameters (impurities present in CO 2 , thermal ramp rate and surface state) on the oxidation mechanism of a Fe-12 Cr steel in CO 2 at 550 C. It has been shown that depending on these parameters, a thin protective oxide scale without any strong carburization can be obtained. A model is proposed to explain the experimental results. (author) [fr

Detection Test for Leakage of CO{sub 2} into Sodium Loop

Energy Technology Data Exchange (ETDEWEB)

Park, Sun Hee; Wi, Myung-Hwan; Min, Jae Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

This report is about the facility for the detection test for leakage of CO{sub 2} into sodium loop. The facility for the detection test for leakage of CO{sub 2} into sodium loop was introduced. The test will be carried out. Our experimental results are going to be expected to be used for approach methods to detect CO{sub 2} leaking into sodium in heat exchangers. A sodium-and-carbon dioxide (Na-CO{sub 2}) heat exchanger is one of the key components for the supercritical CO{sub 2} Brayton cycle power conversion system of sodium-cooled fast reactors (SFRs). A printed circuit heat exchanger (PCHE) is considered for the Na-CO{sub 2} heat exchanger, which is known to have potential for reducing the volume occupied by the exchangers compared to traditional shell-and-tube heat exchangers. Among various issues about the Na- CO{sub 2} exchanger, detection of CO{sub 2} leaking into sodium in the heat exchanger is most important thing for its safe operation. It is known that reaction products from sodium and CO{sub 2} such as sodium carbonate (Na{sub 2}CO{sub 3}) and amorphous carbon are hardly soluble in sodium, which cause plug sodium channels. Detection technique for Na{sub 2}CO{sub 3} in sodium loop has not been developed yet. Therefore, detection of CO{sub 2} and CO from reaction of sodium and CO{sub 2} are proper to detect CO{sub 2} leakage into sodium loop.

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.

Development of a 77K Reverse-Brayton Cryocooler with Multiple Coldheads, Phase I

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...

Metallic CoS2 nanowire electrodes for high cycling performance supercapacitors

Science.gov (United States)

Ren, Ren; Faber, Matthew S.; Dziedzic, Rafal; Wen, Zhenhai; Jin, Song; Mao, Shun; Chen, Junhong

2015-12-01

We report metallic cobalt pyrite (CoS2) nanowires (NWs) prepared directly on current collecting electrodes, e.g., carbon cloth or graphite disc, for high-performance supercapacitors. These CoS2 NWs have a variety of advantages for supercapacitor applications. Because the metallic CoS2 NWs are synthesized directly on the current collector, the good electrical connection enables efficient charge transfer between the active CoS2 materials and the current collector. In addition, the open spaces between the sea urchin structure NWs lead to a large accessible surface area and afford rapid mass transport. Moreover, the robust CoS2 NW structure results in high stability of the active materials during long-term operation. Electrochemical characterization reveals that the CoS2 NWs enable large specific capacitance (828.2 F g-1 at a scan rate of 0.01 V s-1) and excellent long term cycling stability (0-2.5% capacity loss after 4250 cycles at 5 A g-1) for pseudocapacitors. This example of metallic CoS2 NWs for supercapacitor applications expands the opportunities for transition metal sulfide-based nanostructures in emerging energy storage applications.

Study on expansion power recovery in CO2 trans-critical cycle

International Nuclear Information System (INIS)

Tian Hua; Ma Yitai; Li Minxia; Wang Wei

2010-01-01

Due to the ozone depletion potential and global warming potential of CFCs and HCFCs, CO 2 is considered as most potential alternative refrigerant. However, there are serious throttle losses and low system efficiency to CO 2 trans-critical cycle because of its low critical temperature and high operating pressure. The aim of this paper is to design an expander to recover expansion power in CO 2 trans-critical cycle. The theoretical analysis and calculation show that 14-23% of input power of compressor can be recovered. A prototype of rolling piston expander is designed and manufactured and its test facility is established. The test facility consists of CO 2 trans-critical cycle, the expander, the chilling water system and the cooling water system. The experimental results show that the recovery ratio and expander efficiency are affected by rotational speed, inlet temperature and mass flow of expander. The highest recovery ratio can reach to 0.145, which means 14.5% of input power of compressor can be recovered. The expander efficiency can reach to 45%.

Catalysts for long-life closed-cycle CO2 lasers

Science.gov (United States)

Schryer, David R.; Sidney, Barry D.; Miller, Irvin M.; Hess, Robert V.; Wood, George M.; Batten, Carmen E.; Burney, Lewis G.; Hoyt, Ronald F.; Paulin, Patricia A.; Brown, Kenneth G.

1987-01-01

Long-life, closed-cycle operation of pulsed CO2 lasers requires catalytic CO-O2 recombination both to remove O2, which is formed by discharge-induced CO2 decomposition, and to regenerate CO2. Platinum metal on a tin (IV) oxide substrate (Pt/SnO2) has been found to be an effective catalyst for such recombination in the desired temperature range of 25 to 100 C. This paper presents a description of ongoing research at NASA-LaRC on Pt/SnO2 catalyzed CO-O2 recombination. Included are studies with rare-isotope gases since rare-isotope CO2 is desirable as a laser gas for enhanced atmospheric transmission. Results presented include: (1) achievement of 98% to 100% conversion of a stoichiometric mixture of CO and O2 to CO2 for 318 hours (greater than 1 x 10 to the 6th power seconds), continuous, at a catalyst temperature of 60 C, and (2) development of a technique verified in a 30-hour test, to prevent isotopic scrambling when CO-18 and O-18(2) are reacted in the presence of a common-isotope Pt/Sn O-16(2) catalyst.

Passive Decay Heat Removal System Options for S-CO2 Cooled Micro Modular Reactor

International Nuclear Information System (INIS)

Moon, Jangsik; Jeong, Yong Hoon; Lee, Jeong Ik

2014-01-01

To achieve modularization of whole reactor system, Micro Modular Reactor (MMR) which has been being developed in KAIST took S-CO 2 Brayton power cycle. The S-CO 2 power cycle is suitable for SMR due to high cycle efficiency, simple layout, small turbine and small heat exchanger. These characteristics of S-CO 2 power cycle enable modular reactor system and make reduced system size. The reduced size and modular system motived MMR to have mobility by large trailer. Due to minimized on-site construction by modular system, MMR can be deployed in any electricity demand, even in isolated area. To achieve the objective, fully passive safety systems of MMR were designed to have high reliability when any offsite power is unavailable. In this research, the basic concept about MMR and Passive Decay Heat Removal (PDHR) system options for MMR are presented. LOCA, LOFA, LOHS and SBO are considered as DBAs of MMR. To cope with the DBAs, passive decay heat removal system is designed. Water cooled PDHR system shows simple layout, but has CCF with reactor systems and cannot cover all DBAs. On the other hand, air cooled PDHR system with two-phase closed thermosyphon shows high reliability due to minimized CCF and is able to cope with all DBAs. Therefore, the PDHR system of MMR will follows the air-cooled PDHR system and the air cooled system will be explored

Dependency of climate change and carbon cycle on CO2 emission pathways

International Nuclear Information System (INIS)

Nohara, Daisuke; Yoshida, Yoshikatsu; Misumi, Kazuhiro; Ohba, Masamichi

2013-01-01

Previous research has indicated that the response of globally average temperature is approximately proportional to cumulative CO 2 emissions, yet evidence of the robustness of this relationship over a range of CO 2 emission pathways is lacking. To address this, we evaluate the dependency of climate and carbon cycle change on CO 2 emission pathways using a fully coupled climate–carbon cycle model. We design five idealized pathways (including an overshoot scenario for cumulative emissions), each of which levels off to final cumulative emissions of 2000 GtC. The cumulative emissions of the overshoot scenario reach 4000 GtC temporarily, subsequently reducing to 2000 GtC as a result of continuous negative emissions. Although we find that responses of climatic variables and the carbon cycle are largely independent of emission pathways, a much weakened Atlantic meridional overturning circulation (AMOC) is projected in the overshoot scenario despite cessation of emissions. This weakened AMOC is enhanced by rapid warming in the Arctic region due to considerable temporary elevation of atmospheric CO 2 concentration and induces the decline of surface air temperature and decrease of precipitation over the northern Atlantic and Europe region. Moreover, the weakened AMOC reduces CO 2 uptake by the Atlantic and Arctic oceans. However, the weakened AMOC contributes little to the global carbon cycle. In conclusion, although climate variations have been found to be dependent on emission pathways, the global carbon cycle is relatively independent of these emission pathways, at least superficially. (letter)

Comparison of CFD results for a supercritical CO{sub 2} compressor with compressible and incompressible working fluids

Energy Technology Data Exchange (ETDEWEB)

Kim, Seong Gu; Baik, Seungjoon; Cho, Seong Kuk; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Kwon, Jinsu [Hanyang University, Seoul (Korea, Republic of)

2015-10-15

The authors compared flow parameters of S-CO{sub 2} compressor with various fluids to investigate fluid characteristic of S-CO{sub 2}, and performance of pump-derived type (shrouded impeller) compressor. The CFD results showed that the isentropic efficiency of CO{sub 2} case has a comparable performance in comparison to the water since S-CO{sub 2} has a meta-incompressible characteristic near the critical point. Because of the low rotating speed and non-optimized geometry of impeller, the pressure ratio of the compressor is low. However, the authors confirmed that this shrouded type impeller for S-CO{sub 2} compressor showed good performance as much as water case. This results will be reflected in the future S-CO{sub 2} compressor design. As the generation IV reactors are being researched, the supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle is identified as one of the promising power conversion cycles. The S-CO{sub 2} cycle has several advantages: high efficiency it has compact cycle components and simple layout. It can be also used for a power conversion system of sodium-cooled fast reactor (SFR) since it can eliminate potential safety issue of the sodium-water reactions. Moreover, the S-CO{sub 2} cycle can be used for small modular reactors (SMR) application since it occupies small footprint and it can designed as an economical dry-cooling system for SMRs. Design of a compressor is the major technical issue in development of S-CO{sub 2} cycle. Main purposes of this experiment are to accumulate operating experience of the S-CO{sub 2} loop, and to obtain fundamental data for the compressor design optimization near the critical point. However, inside the compressor, it is hard to know flow parameters by measurements. Therefore, the authors performed a CFD analysis to obtain useful flow parameters inside the compressor. The main goal of this paper is studying the flow parameters of pump-derived type compressor with S-CO{sub 2}, water, and air fluids to

The Effects of CO{sub 2} Pressure on Corrosion and Carburization Behaviors of Chromia-forming Austenitic Alloys

Energy Technology Data Exchange (ETDEWEB)

Lee, Ho Jung; Kim, Sung Hwan; Jang, Changheui [KAIST, Daejeon (Korea, Republic of)

2015-05-15

By applying S-CO{sub 2} cycle to SFR, the inherent safety could be improved by alleviating the concern of explosive reaction between high temperature steam and liquid sodium as well as increased thermal efficiency at 500-550 .deg. C compared to helium Brayton cycle. Meanwhile, from the material point of view, a compatibility such as corrosion and carburization of candidate materials in S-CO{sub 2} environment should be evaluated to assure the long-term integrity of IHX. It has been previously reported that Ni-base alloys and high-Cr Fe-base austenitic alloys showed a good corrosion resistance by the formation of thin chromia layer while carburization behaviors of those materials were not properly investigated. Corrosion and carburization behaviors of three chromia-forming austenitic alloys (Ni-base alloys and Alloy 800HT) were evaluated in S-CO{sub 2} (200 bar) and CO{sub 2} (1 bar) environment at 550.650 .deg. C for 1000 h. For all test materials, a good corrosion resistance was exhibited by the formation of thin chromia (Cr{sub 2}O{sub 3}) with small amount of minor oxides such as Mn1.5Cr1.5O{sub 4}, Al{sub 2}O{sub 3}, and TiO{sub 2}.

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.

Heat exchanger design for hot air ericsson-brayton piston engine

Science.gov (United States)

Ďurčanský, P.; Lenhard, R.; Jandačka, J.

2014-03-01

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.

Thermodynamic analysis of a new dual evaporator CO2 transcritical refrigeration cycle

Science.gov (United States)

Abdellaoui, Ezzaalouni Yathreb; Kairouani, Lakdar Kairouani

2017-03-01

In this work, a new dual-evaporator CO2 transcritical refrigeration cycle with two ejectors is proposed. In this new system, we proposed to recover the lost energy of condensation coming off the gas cooler and operate the refrigeration cycle ejector free and enhance the system performance and obtain dual-temperature refrigeration simultaneously. The effects of some key parameters on the thermodynamic performance of the modified cycle are theoretically investigated based on energetic and exergetic analysis. The simulation results for the modified cycle indicate more effective system performance improvement than the single ejector in the CO2 vapor compression cycle using ejector as an expander ranging up to 46%. The exergetic analysis for this system is made. The performance characteristics of the proposed cycle show its promise in dual-evaporator refrigeration system.

Thermodynamic analysis of a new dual evaporator CO2 transcritical refrigeration cycle

Directory of Open Access Journals (Sweden)

Abdellaoui Ezzaalouni Yathreb

2017-03-01

Full Text Available In this work, a new dual-evaporator CO2 transcritical refrigeration cycle with two ejectors is proposed. In this new system, we proposed to recover the lost energy of condensation coming off the gas cooler and operate the refrigeration cycle ejector free and enhance the system performance and obtain dual-temperature refrigeration simultaneously. The effects of some key parameters on the thermodynamic performance of the modified cycle are theoretically investigated based on energetic and exergetic analysis. The simulation results for the modified cycle indicate more effective system performance improvement than the single ejector in the CO2 vapor compression cycle using ejector as an expander ranging up to 46%. The exergetic analysis for this system is made. The performance characteristics of the proposed cycle show its promise in dual-evaporator refrigeration system.

Design of Supercritical Carbon Dioxide Compressor Testing Loop

Energy Technology Data Exchange (ETDEWEB)

Kim, Seong Gu; Lee, Jeong Ik; Ahn, Yoon Han; Lee, Je Kyoung [Korea Advanced Institute of Science and Technology, Daejeon (Korea, Republic of); Yoon, Ho Joon; Addad, Yacine [KUSTAR, Abu Dhabi (United Arab Emirates)

2012-05-15

For small and medium-sized reactors and Generation IV reactors such as sodium-cooled fast reactor are recently under development actively. The supercritical CO{sub 2} Brayton cycle is considered as an attractive cycle for the above mentioned nuclear systems. This is because the supercritical CO{sub 2} Brayton cycle (S-CO{sub 2} cycle) is especially effective to reduce the volume of power generation system, which occupies 1.5{approx}2 times more space than the primary nuclear system in general. Comparing to traditional water-vapor cycle and helium cycle, the S-CO{sub 2} system has relatively much less volume and component size. Therefore, S-CO{sub 2} cycle can be used for many purposes such as nuclear ship propulsion where volume requirement is strict, or a small nuclear reactor when it is constructed on geographically limited area

A preliminary study of a D-T tokamak fusion reactor with advanced blanket using the compact fusion advanced Brayton (CFAB) cycle

International Nuclear Information System (INIS)

Yoshikawa, K.; Ishikawa, M.; Umoto, J.; Fukuyama, A.; Mitarai, O.; Okamoto, M.; Sekimoto, H.; Nagatsu, M.

1995-01-01

Preliminary key issues for a synchrotron radiation-enhanced compact fusion advanced Brayton (CFAB) cycle fusion reactor similar to the CFAR (compact fusion advanced Rankine) cycle reactor are presented. These include plasma operation windows as a function of the first wall reflectivity and related issues, to estimate an allowance for deterioration of the first wall reflectivity due to dpa effects. It was found theoretically that first wall reflectivities down to 0.8 are still adequate for operation at an energy confinement scaling of 3 times Kaye-Goldston. Measurements of the graphite first wall reflectivities at Nagoya University indicate excellent reflectivities in excess of 90% for CC-312, PCC-2S, and PD-330S in the submillimeter regime, even at high temperatures in excess of 1000K. Some engineering issues inherent to the CFAB cycle are also discussed briefly in comparison with the CFAR cycle which uses hazardous limited-resource materials but is capable of using mercury as coolant for high heat removal. The CFAB cycle using helium coolant is found to achieve higher net plant conversion efficiencies in excess 60% using a non-equilibrium magnetohydrodynamic disk generator in the moderate pressure range, even at the cost of a relatively large pumping power, and at the penalty of high temperature materials, although excellent heat removal characteristics in the moderate pressure range need to be guaranteed in the future. (orig.)

SO{sub 2} Retention by CaO-Based Sorbent Spent in CO{sub 2} Looping Cycles

Energy Technology Data Exchange (ETDEWEB)

Manovic, V.; Anthony, E.J.; Loncarevic, D.

2009-07-15

CaO-based looping cycles are promising processes for CO{sub 2} Capture from both syngas and flue gas. The technology is based on cyclical carbonation of CaO and regeneration of CaCO{sub 3} in a dual fluidized-bed reactor to produce a pure CO{sub 2} stream suitable for sequestration. Use of spent sorbent from CO{sub 2} looping cycles for SO{sub 2} capture is investigated. Three limestones were investigated: Kelly Rock (Canada), La Blanca (Spain), and Katowice (Poland, Upper Silesia). Carbonation/calcination cycles were performed in a tube furnace with both the original limestones and samples thermally pretreated for different times (i.e., sintered). The spent sorbent samples were sulfated in a thermogravimetric analyzer (TGA). The changes in the resulting sorbent pore structure were then investigated using mercury porosimetry. It has been shown that the sulfation rates of both thermally pretreated and spent sorbent samples are lower in comparison with those of the original samples. However, final conversions of both spent and pretreated sorbents after longer sulfation time were comparable or higher than those observed for the original sorbents under comparable conditions. Maximum sulfation levels strongly depend on sorbent porosity and pore surface area. The results showed that spent sorbent samples from CO{sub 2} looping cycles can be used as sorbents for SO{sub 2} retention in cases where significant porosity loss does not occur during CO{sub 2} reaction cycles. In the case of spent Kelly Rock and Katowice samples, sorbent particles are practically uniformly sulfated, achieving final conversions that are determined by the total pore volume available for the bulky CaSO{sub 4} product.

Different sorbents in calcium looping cycle for CO{sub 2} capture

Energy Technology Data Exchange (ETDEWEB)

Luo, Cong; Zheng, Ying; Ding, Ning [Huazhong Univ. of Science and Technology, Wuhan (China). State Key Lab. of Coal Combustion

2013-07-01

Cyclic CO{sub 2} capture using commercial pure micro CaCO{sub 3} and nano CaCO{sub 3} is investigated in this paper which focuses on the different characteristics two different sorbents during high temperature reactions. The results indicate that the nano CaCO{sub 3} sorbent has higher carbonation conversions and carbonation rates than the micro CaCO{sub 3} sorbent in the cyclic reactions. Furthermore, nano sorbent can retain its fast carbonation rates at the beginning dozens of seconds during each cycle. In contrast, the carbonation rates of micro sorbent diminish with the increase of cycle number. But, unfortunately, CaO derived from nano CaCO3 sorbent sinter much easily. Its grains, which are composed of numerous spherical nanocrystallites, experience dramatic morphological changes during high temperature reactions.

Evaluation Analysis of the CO2 Emission and Absorption Life Cycle for Precast Concrete in Korea

Directory of Open Access Journals (Sweden)

Taehyoung Kim

2016-07-01

Full Text Available To comply with recent international trends and initiatives, and in order to help achieve sustainable development, Korea has established a greenhouse gas (GHG emission reduction target of 37% (851 million tons of the business as usual (BAU rate by 2030. Regarding environmentally-oriented standards such as the IGCC (International Green Construction Code, there are also rising demands for the assessment on CO2 emissions during the life cycle in accordance with ISO (International Standardization Organization’s Standard 14040. At present, precast concrete (PC engineering-related studies primarily cover structural and construction aspects, including improvement of structural performance in the joint, introduction of pre-stressed concrete and development of half PC. In the manufacture of PC, steam curing is mostly used for the early-strength development of concrete. In steam curing, a large amount of CO2 is produced, causing an environmental problem. Therefore, this study proposes a method to assess CO2 emissions (including absorption throughout the PC life cycle by using a life cycle assessment (LCA method. Using the proposed assessment method, CO2 emissions during the life cycle of a precast concrete girder (PCG were assessed. In addition, CO2 absorption was assessed against a PCG using conventional carbonation and CO2 absorption-related models. As a result, the CO2 emissions throughout the life cycle of the PCG were 1365.6 (kg-CO2/1 PCG. The CO2 emissions during the production of raw materials among the CO2 emissions throughout the life cycle of the PCG were 1390 (kg-CO2/1 PCG, accounting for a high portion to total CO2 emissions (nearly 90%. In contrast, the transportation and manufacture stages were 1% and 10%, respectively, having little effect on total CO2 emissions. Among the use of the PCG, CO2 absorption was mostly decided by the CO2 diffusion coefficient and the amount of CO2 absorption by cement paste. The CO2 absorption by carbonation

Parametric studies on different gas turbine cycles for a high temperature gas-cooled reactor

International Nuclear Information System (INIS)

Wang Jie; Gu Yihua

2005-01-01

The high temperature gas-cooled reactor (HTGR) coupled with turbine cycle is considered as one of the leading candidates for future nuclear power plants. In this paper, the various types of HTGR gas turbine cycles are concluded as three typical cycles of direct cycle, closed indirect cycle and open indirect cycle. Furthermore they are theoretically converted to three Brayton cycles of helium, nitrogen and air. Those three types of Brayton cycles are thermodynamically analyzed and optimized. The results show that the variety of gas affects the cycle pressure ratio more significantly than other cycle parameters, however, the optimized cycle efficiencies of the three Brayton cycles are almost the same. In addition, the turbomachines which are required for the three optimized Brayton cycles are aerodynamically analyzed and compared and their fundamental characteristics are obtained. Helium turbocompressor has lower stage pressure ratio and more stage number than those for nitrogen and air machines, while helium and nitrogen turbocompressors have shorter blade length than that for air machine

Foil Bearing Coating Behavior in CO₂

Energy Technology Data Exchange (ETDEWEB)

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

2017-08-01

The Sandia S-CO₂ Recompression Closed Brayton Cycle (RCBC) utilizes a series of gas foil bearings in its turbine-alternator-compressors. At high shaft rotational speed these bearings allow the shaft to ride on a cushion of air. Conversely, during startup and shutdown, the shaft rides along the foil bearing surface. Low-friction coatings are used on bearing surfaces in order to facilitate rotation during these periods. An experimental program was initiated to elucidate the behavior of coated bearing foils in the harsh environments of this system. A test configuration was developed enabling long duration exposure tests, followed by a range of analyses relevant to their performance in a bearing. This report provides a detailed overview of this work. The results contained herein provide valuable information in selecting appropriate coatings for more advanced future bearing-rig tests at the newly established test facility in Sandia-NM.

Design of an efficient space constrained diffuser for supercritical CO2 turbines

Science.gov (United States)

Keep, Joshua A.; Head, Adam J.; Jahn, Ingo H.

2017-03-01

Radial inflow turbines are an arguably relevant architecture for energy extraction from ORC and supercritical CO 2 power cycles. At small scale, design constraints can prescribe high exit velocities for such turbines, which lead to high kinetic energy in the turbine exhaust stream. The inclusion of a suitable diffuser in a radial turbine system allows some exhaust kinetic energy to be recovered as static pressure, thereby ensuring efficient operation of the overall turbine system. In supercritical CO 2 Brayton cycles, the high turbine inlet pressure can lead to a sealing challenge if the rotor is supported from the rotor rear side, due to the seal operating at rotor inlet pressure. An alternative to this is a cantilevered layout with the rotor exit facing the bearing system. While such a layout is attractive for the sealing system, it limits the axial space claim of any diffuser. Previous studies into conical diffuser geometries for supercritical CO 2 have shown that in order to achieve optimal static pressure recovery, longer geometries of a shallower cone angle are necessitated when compared to air. A diffuser with a combined annular-radial arrangement is investigated as a means to package the aforementioned geometric characteristics into a limited space claim for a 100kW radial inflow turbine. Simulation results show that a diffuser of this design can attain static pressure rise coefficients greater than 0.88. This confirms that annular-radial diffusers are a viable design solution for supercritical CO2 radial inflow turbines, thus enabling an alternative cantilevered rotor layout.

Future ocean hypercapnia driven by anthropogenic amplification of the natural CO2 cycle

Science.gov (United States)

McNeil, Ben I.; Sasse, Tristan P.

2016-01-01

High carbon dioxide (CO2) concentrations in sea-water (ocean hypercapnia) can induce neurological, physiological and behavioural deficiencies in marine animals. Prediction of the onset and evolution of hypercapnia in the ocean requires a good understanding of annual variations in oceanic CO2 concentration, but there is a lack of relevant global observational data. Here we identify global ocean patterns of monthly variability in carbon concentration using observations that allow us to examine the evolution of surface-ocean CO2 levels over the entire annual cycle under increasing atmospheric CO2 concentrations. We predict that the present-day amplitude of the natural oscillations in oceanic CO2 concentration will be amplified by up to tenfold in some regions by 2100, if atmospheric CO2 concentrations continue to rise throughout this century (according to the RCP8.5 scenario of the Intergovernmental Panel on Climate Change). The findings from our data are broadly consistent with projections from Earth system climate models. Our predicted amplification of the annual CO2 cycle displays distinct global patterns that may expose major fisheries in the Southern, Pacific and North Atlantic oceans to hypercapnia many decades earlier than is expected from average atmospheric CO2 concentrations. We suggest that these ocean ‘CO2 hotspots’ evolve as a combination of the strong seasonal dynamics of CO2 concentration and the long-term effective storage of anthropogenic CO2 in the oceans that lowers the buffer capacity in these regions, causing a nonlinear amplification of CO2 concentration over the annual cycle. The onset of ocean hypercapnia (when the partial pressure of CO2 in sea-water exceeds 1,000 micro-atmospheres) is forecast for atmospheric CO2 concentrations that exceed 650 parts per million, with hypercapnia expected in up to half the surface ocean by 2100, assuming a high-emissions scenario (RCP8.5). Such extensive ocean hypercapnia has detrimental implications for

The seasonal cycle of pCO2 and CO2 fluxes in the Southern Ocean: diagnosing anomalies in CMIP5 Earth system models

Science.gov (United States)

Precious Mongwe, N.; Vichi, Marcello; Monteiro, Pedro M. S.

2018-05-01

The Southern Ocean forms an important component of the Earth system as a major sink of CO2 and heat. Recent studies based on the Coupled Model Intercomparison Project version 5 (CMIP5) Earth system models (ESMs) show that CMIP5 models disagree on the phasing of the seasonal cycle of the CO2 flux (FCO2) and compare poorly with available observation products for the Southern Ocean. Because the seasonal cycle is the dominant mode of CO2 variability in the Southern Ocean, its simulation is a rigorous test for models and their long-term projections. Here we examine the competing roles of temperature and dissolved inorganic carbon (DIC) as drivers of the seasonal cycle of pCO2 in the Southern Ocean to explain the mechanistic basis for the seasonal biases in CMIP5 models. We find that despite significant differences in the spatial characteristics of the mean annual fluxes, the intra-model homogeneity in the seasonal cycle of FCO2 is greater than observational products. FCO2 biases in CMIP5 models can be grouped into two main categories, i.e., group-SST and group-DIC. Group-SST models show an exaggeration of the seasonal rates of change of sea surface temperature (SST) in autumn and spring during the cooling and warming peaks. These higher-than-observed rates of change of SST tip the control of the seasonal cycle of pCO2 and FCO2 towards SST and result in a divergence between the observed and modeled seasonal cycles, particularly in the Sub-Antarctic Zone. While almost all analyzed models (9 out of 10) show these SST-driven biases, 3 out of 10 (namely NorESM1-ME, HadGEM-ES and MPI-ESM, collectively the group-DIC models) compensate for the solubility bias because of their overly exaggerated primary production, such that biologically driven DIC changes mainly regulate the seasonal cycle of FCO2.

Quasi-static Cycle Performance Analysis of Micro Modular Reactor for Heat Sink Temperature Variation

Energy Technology Data Exchange (ETDEWEB)

Cho, Seong Kuk; Lee, Jekyoung; Ahn, Yoonhan; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Cha, Jae Eun [KAERI, Daejeon (Korea, Republic of)

2015-10-15

A Supercritical CO{sub 2} (S-CO{sub 2}) cycle has potential for high thermal efficiency in the moderate turbine inlet temperature (450 - 750 .deg. C) and achieving compact system size because of small specific volume and simple cycle layouts. Owing to small specific volume of S-CO{sub 2} and the development of heat exchanger technology, it can accomplish complete modularization of the system. The previous works focused on the cycle performance analysis for the design point only. However, the heat sink temperature can be changed depending on the ambient atmosphere condition, i.e. weather, seasonal change. This can influence the compressor inlet temperature, which alters the cycle operating condition overall. To reflect the heat sink temperature variation, a quasi-static analysis code for a simple recuperated S-CO{sub 2} Brayton cycle has been developed by the KAIST research team. Thus, cycle performance analysis is carried out with a compressor inlet temperature variation in this research. In the case of dry air-cooling system, the ambient temperature of the local surrounding can affect the compressor inlet temperature. As the compressor inlet temperature increases, thermal efficiency and generated electricity decrease. As further works, the experiment of S-CO{sub 2} integral test loop will be performed to validate in-house codes, such as KAIST{sub T}MD and the quasi-static code.

Cost estimating Brayton and Stirling engines

Science.gov (United States)

Fortgang, H. R.

1980-01-01

Brayton and Stirling engines were analyzed for cost and selling price for production quantities ranging from 1000 to 400,000 units per year. Parts and components were subjected to indepth scrutiny to determine optimum manufacturing processes coupled with make or buy decisions on materials and small parts. Tooling and capital equipment costs were estimated for each detail and/or assembly. For low annual production volumes, the Brayton engine appears to have a lower cost and selling price than the Stirling Engine. As annual production quantities increase, the Stirling becomes a lower cost engine than the Brayton. Both engines could benefit cost wise if changes were made in materials, design and manufacturing process as annual production quantities increase.

Garrett solar Brayton engine/generator status

Science.gov (United States)

Anson, B.

1982-07-01

The solar advanced gas turbine (SAGT-1) is being developed by the Garrett Turbine Engine Company, for use in a Brayton cycle power conversion module. The engine is derived from the advanced gas turbine (AGT101) now being developd by Garrett and Ford Motor Company for automotive use. The SAGT Program is presently funded for the design, fabrication and test of one engine at Garrett's Phoenix facility. The engine when mated with a solar receiver is called a power conversion module (PCU). The PCU is scheduled to be tested on JPL's test bed concentrator under a follow on phase of the program. Approximately 20 kw of electrical power will be generated.

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.

Comparison between reverse Brayton and Kapitza based LNG boil-off gas reliquefaction system using exergy analysis

Science.gov (United States)

Kochunni, Sarun Kumar; Chowdhury, Kanchan

2017-02-01

LNG boil-off gas (BOG) reliquefaction systems in LNG carrier ships uses refrigeration devices which are based on reverse Brayton, Claude, Kapitza (modified Claude) or Cascade cycles. Some of these refrigeration devices use nitrogen as the refrigerants and hence nitrogen storage vessels or nitrogen generators needs to be installed in LNG carrier ships which consume space and add weight to the carrier. In the present work, a new configuration based on Kapitza liquefaction cycle which uses BOG itself as working fluid is proposed and has been compared with Reverse Brayton Cycle (RBC) on sizes of heat exchangers and compressor operating parameters. Exergy analysis is done after simulating at steady state with Aspen Hysys 8.6® and the comparison between RBC and Kapitza may help designers to choose reliquefaction system with appropriate process parameters and sizes of equipment. With comparable exergetic efficiency as that of an RBC, a Kaptiza system needs only BOG compressor without any need of nitrogen gas.

Energy analysis and design of mixed CO{sub 2}/steam gas turbine cycles

Energy Technology Data Exchange (ETDEWEB)

Bram, S; De Ruyck, J [Vrije Universiteit Brussel, Brussels (Belgium). Dept. of Mechanics

1995-06-01

The capturing and disposal of CO{sub 2} from power plant exhaust gases is a possible route for reducing CO{sub 2} emissions. The present paper investigates the full recirculation of exhaust gases in a gas turbine cycle, combined with the injection of steam or water. Such recirculation leads to an exhaust gas with very high CO{sub 2} concentration (95% or more). Different regenerative cycle layouts are proposed and analyzed for efficiency, exergy destruction and technical feasibility. Pinch Technology methods are next applied to find the best configuration for heat regeneration and injection of water. From this analysis, dual pressure evaporation with water injection in the intercooler emerges as an interesting option. 3 refs., 2 figs., 1 tab.

Experimental and CFD Analysis of Printed Circuit Heat Exchanger for Supercritical CO{sub 2} Power Cycle Application

Energy Technology Data Exchange (ETDEWEB)

Baik, Seungjoon; Kim, Hyeon Tae; Kim, Seong Gu; Lee, Jekyoung; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2015-10-15

The supercritical carbon dioxide (S-CO{sub 2}) power cycle has been suggested as an alternative for the SFR power generation system. First of all, relatively mild sodium-CO{sub 2} interaction can reduce the accident probability. Also the S-CO{sub 2} power conversion cycle can achieve high efficiency with SFR core thermal condition. Moreover, the S-CO{sub 2} power cycle can reduce cycle footprint due to high density of the working fluid. Recently, various compact heat exchangers have been studied for developing an optimal heat exchanger. In this paper, the printed circuit heat exchanger was selected for S-CO{sub 2} power cycle applications and was closely investigated experimentally and analytically. Recently, design and performance prediction of PCHE received attention due to its importance in high pressure power systems such as S-CO{sub 2} cycle. To evaluate a PCHE performance with CO{sub 2} to water, KAIST research team designed and tested a lab-scale PCHE. From the experimental data and CFD analysis, pressure drop and heat transfer correlations are obtained. For the CFD analysis, Ansys-CFX commercial code was utilized with RGP table implementation. In near future, the turbulence model sensitivity study will be followed.

Thermodynamic analysis and comparison between CO_2 transcritical power cycles and R245fa organic Rankine cycles for low grade heat to power energy conversion

International Nuclear Information System (INIS)

Li, L.; Ge, Y.T.; Luo, X.; Tassou, S.A.

2016-01-01

Highlights: • CO_2 is a promising working fluid to be applied in low-grade power generation systems. • Thermodynamic models of CO_2 transcritical power cycles (T-CO_2) and R245fa ORC were developed. • Energy and exergy analyses were carried out for T-CO_2 and R245fa ORC systems. • Optimal system designs are existed for both T-CO_2 and R245fa ORC systems. - Abstract: In this paper, a theoretical study is conducted to investigate and compare the performance of CO_2 transcritical power cycles (T-CO_2) and R245fa organic Rankine cycles (ORCs) using low-grade thermal energy to produce useful shaft or electrical power. Each power cycle consists of typical Rankine cycle components, such as a working fluid pump, gas generator or evaporator, turbine with electricity generator, air cooled condenser and recuperator (internal heat exchanger). The thermodynamic models of both cycles have been developed and are applied to calculate and compare the cycle thermal and exergy efficiencies at different operating conditions and control strategies. The simulation results show that the system performances for both cycles vary with different operating conditions. When the heat source (waste heat) temperature increases from 120 °C to 260 °C and heat sink (cooling air) temperature is reduced from 20 °C to 0 °C, both thermal efficiencies of R245fa ORC and T-CO_2 with recuperator can significantly increase. On the other hand, R245fa ORC and T-CO_2 exergy efficiencies increase with lower heat sink temperatures and generally decrease with higher heat source temperatures. In addition, with the same operating conditions and heat transfer assumptions, the thermal and exergy efficiencies of R245fa ORCs are both slightly higher than those of T-CO_2. However, the efficiencies of both cycles can be enhanced by installing a recuperator in each system at specified operating conditions. Ultimately, optimal operating states can be predicted, with particular focus on the working fluid expander

Life Cycle CO2 Assessment by Block Type Changes of Apartment Housing

Directory of Open Access Journals (Sweden)

Cheonghoon Baek

2016-08-01

Full Text Available The block type and structural systems in buildings affect the amount of building materials required as well as the CO2 emissions that occur throughout the building life cycle (LCCO2. The purpose of this study was to assess the life cycle CO2 emissions when an apartment housing with ‘flat-type’ blocks (the reference case was replaced with more sustainable ‘T-type’ blocks with fewer CO2 emissions (the alternative case maintaining the same total floor area. The quantity of building materials used and building energy simulations were analyzed for each block type using building information modeling techniques, and improvements in LCCO2 emission were calculated by considering high-strength concrete alternatives. By changing the bearing wall system of the ‘flat-type’ block to the ‘column and beam’ system of the ‘T-type’ block, LCCO2 emissions of the alternative case were 4299 kg-CO2/m2, of which 26% was at the construction stage, 73% was as the operational stage and 1% was at the dismantling and disposal stage. These total LCCO2 emissions were 30% less than the reference case.

Preliminary Study of Printed Circuit Heat Exchanger (PCHE) for various power conversion systems for SMART

Energy Technology Data Exchange (ETDEWEB)

Kwon, Jinsu; Baik, Seungjoon; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of)

2016-10-15

The steam-Rankine cycle was the most widely used power conversion system for a nuclear power plant. The size of the heat exchanger is important for the modulation. Such a challenge was conducted by Kang et al. They change the steam generator type for the SMART from helical type heat exchanger to Printed Circuit Heat Exchanger (PCHE). Recently, there has been a growing interest in the supercritical carbon dioxide (S-CO{sub 2}) Brayton cycle as the most promising power conversion system. The reason is high efficiency with simple layout and compact power plant due to small turbomachinery and compact heat exchanger technology. That is why the SCO{sub 2} Brayton cycle can enhance the existing advantages of Small Modular Reactor (SMR) like SMART, such as reduction in size, capital cost, and construction period. Thermal hydraulic and geometric parameters of a PCHE for the S-CO{sub 2} power cycle coupled to SMART. The results show that the water - CO{sub 2} printed circuit heat exchanger size is smaller than printed circuit steam generator for the superheated steam Rankine cycle. This results show the potential benefit of using the S-CO-2 Brayton power cycle to a water-cooled small modular reactor.

Properties of noble gases and binary mixtures for closed Brayton Cycle applications

International Nuclear Information System (INIS)

Tournier, Jean-Michel P.; El-Genk, Mohamed S.

2008-01-01

A review is conducted of the properties of the noble gases, helium, neon, argon, krypton and xenon, and their binary mixtures at pressures from 0.1 to 20 MPa and temperatures up to 1400 K. An extensive database of experimental measurements is compiled and used to develop semi-empirical properties correlations. The correlations accurately account for the effects of pressure and temperature on the thermodynamic and transport properties of these gases for potential uses in space (∼2 MPa and up to 1400 K) and terrestrial (∼7.0 MPa and up to 1200 K) applications of Closed Brayton Cycle (CBC). The developed correlations are based on the Chapman-Enskog kinetic theory for dilute gases, and on the application of the law of corresponding states to account for the dependence of properties on pressure. The correlations use the critical temperature and density of the gases as scaling parameters, and their predictions are compared with the compiled database. At temperatures ≥400 K and pressures ≤2 MPa in CBC space power systems, He and Ne, and the binary mixtures of He-Xe and He-Kr with molecular weights ≤40 g/mole behave essentially like a perfect gas, and the error of neglecting the effect of pressure on their compressibility factor, specific heats and transport properties is ≤1%. At a typical operating pressure of 7.0 MPa and up to 1200 K in terrestrial CBC power plants, neglecting the effect of pressure can result in ∼4% error in the properties of noble gases and the binary mixtures of He-Xe and He-Kr with molecular weights ≤40 g/mole, and as much as 20% error for pure argon. Therefore, when operating at pressures >2.0 MPa and/or using noble gases or binary mixtures with molecular weights > 40 g/mole, the present correlations should be used to accurately predict the thermodynamic and transport properties

The use of gas based energy conversion cycles for sodium fast reactors

International Nuclear Information System (INIS)

Saez, M.; Haubensack, D.; Alpy, N.; Gerber, A.; Daid, F.

2008-01-01

In the frame of Sodium Fast Reactors, CEA, AREVA and EDF are involved in a substantial effort providing both significant expertise and original work in order to investigate the interest to use a gas based energy conversion cycle as an alternative to the classical steam cycle. These gas cycles consist in different versions of the Brayton cycle, various types of gas being considered (helium, nitrogen, argon, separately or mixed, sub or supercritical carbon dioxide) as well as various cycle arrangements (indirect, indirect / combined cycles). The interest of such cycles is analysed in details by thermodynamic calculations and cycle optimisations. The objective of this paper is to provide a comparison between gas based energy conversion cycles from the viewpoint of the overall plant efficiency. Key factors affecting the Brayton cycle efficiency include the turbine inlet temperature, compressors and turbine efficiencies, recuperator effectiveness and cycle pressure losses. A nitrogen Brayton cycle at high pressure (between 100 and 180 bar) could appear as a potential near-term solution of classical gas power conversion system for maximizing the plant efficiency. At long-term, supercritical carbon dioxide Brayton cycle appears very promising for Sodium Fast Reactors, with a potential of high efficiency using even at a core outlet temperature of 545 deg. C. (authors)

Cycle Design of Reverse Brayton Cryocooler for HTS Cable Cooling Using Exergy Analysis

Science.gov (United States)

Gupta, Sudeep Kumar; Ghosh, Parthasarathi

2017-02-01

The reliability and price of cryogenic refrigeration play an important role in the successful commercialization of High Temperature Superconducting (HTS) cables. For cooling HTS cable, sub-cooled liquid nitrogen (LN2) circulation system is used. One of the options to maintain LN2 in its sub-cooled state is by providing refrigeration with the help of Reverse Brayton Cryo-cooler (RBC). The refrigeration requirement is 10 kW for continuously sub-cooling LN2 from 72 K to 65 K for cooling 1 km length of HTS cable [1]. In this paper, a parametric evaluation of RBC for sub-cooling LN2 has been performed using helium as a process fluid. Exergy approach has been adopted for this analysis. A commercial process simulator, Aspen HYSYS® V8.6 has been used for this purpose. The critical components have been identified and their exergy destruction and exergy efficiency have been obtained for a given heat load condition.

Brayton rotating units for space reactor power systems

Energy Technology Data Exchange (ETDEWEB)

Gallo, Bruno M.; El-Genk, Mohamed S. [Institute for Space and Nuclear Power Studies and Chemical and Nuclear Engineering Dept., The Univ. of New Mexico, Albuquerque, NM 87131 (United States)

2009-09-15

Designs and analyses models of centrifugal-flow compressor and radial-inflow turbine of 40.8kW{sub e} Brayton Rotating Units (BRUs) are developed for 15 and 40 g/mole He-Xe working fluids. Also presented are the performance results of a space power system with segmented, gas cooled fission reactor heat source and three Closed Brayton Cycle loops, each with a separate BRU. The calculated performance parameters of the BRUs and the reactor power system are for shaft rotational speed of 30-55 krpm, reactor thermal power of 120-471kW{sub th}, and turbine inlet temperature of 900-1149 K. With 40 g/mole He-Xe, a power system peak thermal efficiency of 26% is achieved at rotation speed of 45 krpm, compressor and turbine inlet temperatures of 400 and 1149 K and 0.93 MPa at exit of the compressor. The corresponding system electric power is 122.4kW{sub e}, working fluid flow rate is 1.85 kg/s and the pressure ratio and polytropic efficiency are 1.5% and 86.3% for the compressor and 1.42% and 94.1% for the turbine. For the same nominal electrical power of 122.4kW{sub e}, decreasing the molecular weight of the working fluid (15 g/mole) decreases its flow rate to 1.03 kg/s and increases the system pressure to 1.2 MPa. (author)

CO{sub 2} capture behavior of shell during calcination/carbonation cycles

Energy Technology Data Exchange (ETDEWEB)

Li, Y.J.; Zhao, C.S.; Chen, H.C.; Duan, L.B.; Chen, X.P. [School of Energy and Environment, Southeast University, Nanjing (China)

2009-08-15

The cyclic carbonation performances of shells as CO{sub 2} sorbents were investigated during multiple calcination/carbonation cycles. The carbonation kinetics of the shell and limestone are similar since they both exhibit a fast kinetically controlled reaction regime and a diffusion controlled reaction regime, but their carbonation rates differ between these two regions. Shell achieves the maximum carbonation conversion for carbonation at 680-700 C. The mactra veneriformis shell and mussel shell exhibit higher carbonation conversions than limestone after several cycles at the same reaction conditions. The carbonation conversion of scallop shell is slightly higher than that of limestone after a series of cycles. The calcined shell appears more porous than calcined limestone, and possesses more pores >230 nm, which allow large CO{sub 2} diffusion-carbonation reaction rates and higher conversion due to the increased surface area of the shell. The pores of the shell that are greater than 230 nm do not sinter significantly. The shell has more sodium ions than limestone, which probably leads to an improvement in the cyclic carbonation performance during the multiple calcination/carbonation cycles. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

Eigendecomposition model of resistance temperature detector with applications to S-CO{sub 2} cycle sensing

Energy Technology Data Exchange (ETDEWEB)

Heifetz, Alexander, E-mail: aheifetz@anl.gov; Vilim, Richard

2017-01-15

Highlights: • Developed eigendecomposition model of resistance temperature detector (RTD) in a fluid. • Showed that RTD time constant primarily depends on the rate of heat transfer from the fluid to the outer wall of RTD. • Showed that RTD time constant can be calculated as the sum of reciprocal eigenvalues of the heat transfer matrix. • Calculated time constant of thermowell-mounted RTD sensor at the hot side of the precooler in the S-CO{sub 2} cycle. - Abstract: Super-critical carbon dioxide (S-CO{sub 2}) is a promising thermodynamic cycle for advanced nuclear reactors and solar energy conversion applications. Dynamic control of the proposed recompression S-CO{sub 2} cycle is accomplished with input from resistance temperature detector (RTD) measurements of the process fluid. One of the challenges in practical implementation of S-CO{sub 2} cycle is high corrosion rate of component and sensor materials. In this paper, we develop a mathematical model of RTD sensing using eigendecomposition model of radial heat transfer in a layered long cylinder. We show that the value of RTD time constant primarily depends on the rate of heat transfer from the fluid to the outer wall of RTD. We also show that for typical material properties, RTD time constant can be calculated as the sum of reciprocal eigenvalues of the heat transfer matrix. Using the computational model and a set of RTD and CO{sub 2} fluid thermo-physical parameter values, we calculate the value of time constant of thermowell-mounted RTD sensor at the hot side of the precooler in the S-CO{sub 2} cycle. The eigendecomposition model of RTD will be used in future studies to model sensor degradation and its impact on control of S-CO{sub 2}.

Thermodynamic simulation of CO{sub 2} capture for an IGCC power plant using the calcium looping cycle

Energy Technology Data Exchange (ETDEWEB)

Li, Y. [National Engineering Laboratory for Coal-Burning Pollutant Emission Reduction, Shandong University, Jinan (China); Zhao, C.; Ren, Q. [School of Energy and Environment, Southeast University, Nanjing (China)

2011-06-15

A CO{sub 2} capture process for an integrated gasification combined cycle (IGCC) power plant using the calcium looping cycle was proposed. The CO{sub 2} capture process using natural and modified limestone was simulated and investigated with the software package Aspen Plus. It incorporated a fresh feed of sorbent to compensate for the decay in CO{sub 2} capture activity during long-term cycles. The sorbent flow ratios have significant effect on the CO{sub 2} capture efficiency and net efficiency of the CO{sub 2} capture system. The IGCC power plant, using the modified limestone, exhibits higher CO{sub 2} capture efficiency than that using the natural limestone at the same sorbent flow ratios. The system net efficiency using the natural and modified limestones achieves 41.7% and 43.1%, respectively, at the CO{sub 2} capture efficiency of 90% without the effect of sulfation. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Quantum thermodynamic cycles and quantum heat engines. II.

Science.gov (United States)

Quan, H T

2009-04-01

We study the quantum-mechanical generalization of force or pressure, and then we extend the classical thermodynamic isobaric process to quantum-mechanical systems. Based on these efforts, we are able to study the quantum version of thermodynamic cycles that consist of quantum isobaric processes, such as the quantum Brayton cycle and quantum Diesel cycle. We also consider the implementation of the quantum Brayton cycle and quantum Diesel cycle with some model systems, such as single particle in a one-dimensional box and single-mode radiation field in a cavity. These studies lay the microscopic (quantum-mechanical) foundation for Szilard-Zurek single-molecule engine.

Preliminary design study of an alternate heat source assembly for a Brayton isotope power system

Science.gov (United States)

Strumpf, H. J.

1978-01-01

Results are presented for a study of the preliminary design of an alternate heat source assembly (HSA) intended for use in the Brayton isotope power system (BIPS). The BIPS converts thermal energy emitted by a radioactive heat source into electrical energy by means of a closed Brayton cycle. A heat source heat exchanger configuration was selected and optimized. The design consists of a 10 turn helically wound Hastelloy X tube. Thermal analyses were performed for various operating conditions to ensure that post impact containment shell (PICS) temperatures remain within specified limits. These limits are essentially satisfied for all modes of operation except for the emergency cooling system for which the PICS temperatures are too high. Neon was found to be the best choice for a fill gas for auxiliary cooling system operation. Low cycle fatigue life, natural frequency, and dynamic loading requirements can be met with minor modifications to the existing HSA.

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.

Parametric optimization design for supercritical CO2 power cycle using genetic algorithm and artificial neural network

International Nuclear Information System (INIS)

Wang Jiangfeng; Sun Zhixin; Dai Yiping; Ma Shaolin

2010-01-01

Supercritical CO 2 power cycle shows a high potential to recover low-grade waste heat due to its better temperature glide matching between heat source and working fluid in the heat recovery vapor generator (HRVG). Parametric analysis and exergy analysis are conducted to examine the effects of thermodynamic parameters on the cycle performance and exergy destruction in each component. The thermodynamic parameters of the supercritical CO 2 power cycle is optimized with exergy efficiency as an objective function by means of genetic algorithm (GA) under the given waste heat condition. An artificial neural network (ANN) with the multi-layer feed-forward network type and back-propagation training is used to achieve parametric optimization design rapidly. It is shown that the key thermodynamic parameters, such as turbine inlet pressure, turbine inlet temperature and environment temperature have significant effects on the performance of the supercritical CO 2 power cycle and exergy destruction in each component. It is also shown that the optimum thermodynamic parameters of supercritical CO 2 power cycle can be predicted with good accuracy using artificial neural network under variable waste heat conditions.

Extension of the supercritical carbon dioxide brayton cycle to low reactor power operation: investigations using the coupled anl plant dynamics code-SAS4A/SASSYS-1 liquid metal reactor code system

International Nuclear Information System (INIS)

Moisseytsev, A.; Sienicki, J.J.

2012-01-01

Significant progress has been made on the development of a control strategy for the supercritical carbon dioxide (S-CO 2 ) Brayton cycle enabling removal of power from an autonomous load following Sodium-Cooled Fast Reactor (SFR) down to decay heat levels such that the S-CO 2 cycle can be used to cool the reactor until decay heat can be removed by the normal shutdown heat removal system or a passive decay heat removal system such as Direct Reactor Auxiliary Cooling System (DRACS) loops with DRACS in-vessel heat exchangers. This capability of the new control strategy eliminates the need for use of a separate shutdown heat removal system which might also use supercritical CO 2 . It has been found that this capability can be achieved by introducing a new control mechanism involving shaft speed control for the common shaft joining the turbine and two compressors following reduction of the load demand from the electrical grid to zero. Following disconnection of the generator from the electrical grid, heat is removed from the intermediate sodium circuit through the sodium-to-CO 2 heat exchanger, the turbine solely drives the two compressors, and heat is rejected from the cycle through the CO 2 -to-water cooler. To investigate the effectiveness of shaft speed control, calculations are carried out using the coupled Plant Dynamics Code-SAS4A/SASSYS-1 code for a linear load reduction transient for a 1000 MWt metallic-fueled SFR with autonomous load following. No deliberate motion of control rods or adjustment of sodium pump speeds is assumed to take place. It is assumed that the S-CO 2 turbomachinery shaft speed linearly decreases from 100 to 20% nominal following reduction of grid load to zero. The reactor power is calculated to autonomously decrease down to 3% nominal providing a lengthy window in time for the switchover to the normal shutdown heat removal system or for a passive decay heat removal system to become effective. However, the calculations reveal that the

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

directly for industrial purposes. Furthermore, the ABC can be split on the compression side and part of the flow can be directed to a reversed Brayton cycle producing cold air. The cold airflow can in turn be used for air conditioning or industrial duties. The idea of a trigenerative ABC (TriABC) is presented in the report. An ABC concept producing electricity, heat and cold in small-scale installation, can be an attractive alternative for local power production. Environmental advantages, as reduced CO2 emission and CFC-free heat pump, should be recognised. To explore the expected potential of the ABC and TriABC, it is necessary to conduct a feasibility study among the Swedish municipalities and industries. The design of the resulting specified ABC/TriABC system can be best performed in co-operation with gas turbine manufacturers.

Conceptual Design Study of a Closed Brayton Cycle Turbogenerator for Space Power Thermal-To-Electric Conversion System

Science.gov (United States)

Hansen, Jeff L.

2000-01-01

A conceptual design study was completed for a 360 kW Helium-Xenon closed Brayton cycle turbogenerator. The selected configuration is comprised of a single-shaft gas turbine engine coupled directly to a high-speed generator. The engine turbomachinery includes a 2.5:1 pressure ratio compression system with an inlet corrected flow of 0.44 kg/sec. The single centrifugal stage impeller discharges into a scroll via a vaned diffuser. The scroll routes the air into the cold side sector of the recuperator. The hot gas exits a nuclear reactor radiator at 1300 K and enters the turbine via a single-vaned scroll. The hot gases are expanded through the turbine and then diffused before entering the hot side sector of the recuperator. The single shaft design is supported by air bearings. The high efficiency shaft mounted permanent magnet generator produces an output of 370 kW at a speed of 60,000 rpm. The total weight of the turbogenerator is estimated to be only 123 kg (less than 5% of the total power plant) and has a volume of approximately 0.11 cubic meters. This turbogenerator is a key element in achieving the 40 to 45% overall power plant thermal efficiency.

Coupled nutrient cycling determines tropical forest trajectory under elevated CO2.

Science.gov (United States)

Bouskill, N.; Zhu, Q.; Riley, W. J.

2017-12-01

Tropical forests have a disproportionate capacity to affect Earth's climate relative to their areal extent. Despite covering just 12 % of land surface, tropical forests account for 35 % of global net primary productivity and are among the most significant of terrestrial carbon stores. As atmospheric CO2 concentrations increase over the next century, the capacity of tropical forests to assimilate and sequester anthropogenic CO2 depends on limitation by multiple factors, including the availability of soil nutrients. Phosphorus availability has been considered to be the primary factor limiting metabolic processes within tropical forests. However, recent evidence points towards strong spatial and temporal co-limitation of tropical forests by both nitrogen and phosphorus. Here, we use the Accelerated Climate Modeling for Energy (ACME) Land Model (ALMv1-ECA-CNP) to examine how nutrient cycles interact and affect the trajectory of the tropical forest carbon sink under, (i) external nutrient input, (ii) climate (iii) elevated CO2, and (iv) a combination of 1-3. ALMv1 includes recent theoretical advances in representing belowground competition between roots, microbes and minerals for N and P uptake, explicit interactions between the nitrogen and phosphorus cycles (e.g., phosphatase production and nitrogen fixation), the dynamic internal allocation of plant N and P resources, and the integration of global datasets of plant physiological traits. We report nutrient fertilization (N, P, N+P) predictions for four sites in the tropics (El Verde, Puerto Rico, Barro Colorado Island, Panama, Manaus, Brazil and the Osa Peninsula, Coast Rica) to short-term nutrient fertilization (N, P, N+P), and benchmarking of the model against a meta-analysis of forest fertilization experiments. Subsequent simulations focus on the interaction of the carbon, nitrogen, and phosphorus cycles across the tropics with a focus on the implications of coupled nutrient cycling and the fate of the tropical

Performance comparison of two low-CO2 emission solar/methanol hybrid combined cycle power systems

International Nuclear Information System (INIS)

Li, Yuanyuan; Zhang, Na; Lior, Noam

2015-01-01

Highlights: • Two novel solar hybrid combined cycle systems have been proposed and analyzed. • The power systems integrate solar-driven thermo-chemical conversion and CO 2 capture. • Exergy efficiency of about 55% and specific CO 2 emissions of 34 g/kW h are predicted. • Systems CO 2 emissions are 36.8% lower compared to a combined cycle with CO 2 capture. • The fossil fuel demand is ∼30% lower with a solar share of ∼20%. - Abstract: Two novel hybrid combined cycle power systems that use solar heat and methanol, and integrate CO 2 capture, are proposed and analyzed, one based on solar-driven methanol decomposition and the other on solar-driven methanol reforming. The high methanol conversion rates at relatively low temperatures offer the advantage of using the solar heat at only 200–300 °C to drive the syngas production by endothermic methanol conversions and its conversion to chemical energy. Pre-combustion decarbonization is employed to produce CO 2 -free fuel from the fully converted syngas, which is then burned to produce heat at the high temperature for power generation in the proposed advanced combined cycle systems. To improve efficiency, the systems’ configurations were based on the principle of cascade use of multiple heat sources of different temperatures. The thermodynamic performance of the hybrid power systems at its design point is simulated and evaluated. The results show that the hybrid systems can attain an exergy efficiency of about 55%, and specific CO 2 emissions as low as 34 g/kW h. Compared to a gas/steam combined cycle with flue gas CO 2 capture, the proposed solar-assisted system CO 2 emissions are 36.8% lower, and a fossil fuel saving ratio of ∼30% is achievable with a solar thermal share of ∼20%. The system integration predicts high efficiency conversion of solar heat and low-energy-penalty CO 2 capture, with the additional advantage that solar heat is at relatively low temperature where its collection is cheaper and

Coiled Tube Gas Heaters For Nuclear Gas-Brayton Power Conversion

Energy Technology Data Exchange (ETDEWEB)

Peterson, Per F.

2018-03-31

This project developed an alternative design for heat exchangers for application to heating supercritical carbon dioxide (S-CO₂) or air for power conversion. We have identified an annular coiled tube bundle configuration–where hot sodium enters tubes from multiple vertical inlet manifold pipes, flows in a spiral pattern radially inward and downward, and then exits into an equal number of vertical outlet manifold pipes–as a potentially attractive option. The S-CO₂ gas or air flows radially outward through the tube bundle. Coiled tube gas heaters (CTGHs) are expected to have excellent thermal shock, long-term thermal creep, in-service inspection, and reparability characteristics, compared to alternative options. CTGHs have significant commonality with modern nuclear steam generators. Extensive experience exists with the design, manufacture, operation, in-service inspection and maintenance of nuclear steam generators. The U.S. Nuclear Regulatory Commission also has extensive experience with regulatory guidance documented in NUREG 0800. CTGHs leverage this experience and manufacturing capability. The most important difference between steam generators and gas-Brayton cycles such as the S-CO₂ cycle is that the heat exchangers must operate with counter flow with high effectiveness to minimize the pinch-point temperature difference between the hot liquid coolant and the heated gas. S-CO₂-cycle gas heaters also operate at sufficiently elevated temperatures that time dependent creep is important and allowable stresses are relatively low. Designing heat exchangers to operate in this regime requires configurations that minimize stresses and stress concentrations. The cylindrical tubes and cylindrical manifold pipes used in CTGHs are particularly effective geometries. The first major goal of this research project was to develop and experimentally validate a detailed, 3-D multi-phase (gas-solid-liquid) heat transport model for

Cycling-induced degradation of LiCoO2 thin-film cathodes at elevated temperature

International Nuclear Information System (INIS)

Van Sluytman, J.S.; West, W.C.; Whitacre, J.F.; Alamgir, F.M.; Greenbaum, S.G.

2006-01-01

The cycle life of LiCoO 2 -based all solid-state thin-film cells has been studied at room temperature, and at elevated temperatures of 50, 100, and 150 deg. C. X-ray diffraction, as well as Raman analysis, has been used to complement the electrochemical data in examining structural and chemical changes. XRD and Raman spectroscopy data indicate that elevated temperature soaks of the thin-film batteries in the quiescent state causes no discernable changes in the LiCoO 2 cathode layer. However, when the thin-film batteries are cycled at elevated temperatures, decreases in average grain size of the LiCoO 2 film occur with dramatic concomitant charge and discharge capacity loss

SP-100/Brayton power system concepts

International Nuclear Information System (INIS)

Owen, D.F.

1989-01-01

Use of closed Brayton cycle (CBC) power conversion technology has been investigated for use with SP-100 reactors for space power systems. The CBC power conversion technology is being developed by Rockwell International under the Dynamic Isotype Power System (DIPS) and Space Station Freedom solar dynamic power system programs to provide highly efficient power conversion with radioisotype and solar collector heat sources. Characteristics including mass, radiator area, thermal power, and operating temperatures for systems utilizing SP-100 reactor and CBC power conversion technology were determined for systems in the 10-to 100-kWe power range. Possible SP-100 reactor/CBC power system configurations are presented. Advantages of CBC power conversion technology with regard to reactor thermal power, operating temperature, and development status are discussed

Research on catalysts for long-life closed-cycle CO2 laser oaperation

Science.gov (United States)

Sidney, Barry D.; Schryer, David R.; Upchurch, Billy T.; Hess, Robert V.; Wood, George M.

1987-01-01

Long-life, closed-cycle operation of pulsed CO2 lasers requires catalytic CO-O2 recombination both to remove O2, which is formed by discharge-induced CO2 decomposition, and to regenerate CO2. Platinum metal on a tin-oxide substrate (Pt/SnO2) has been found to be an effective catalyst for such recombination in the desired temperature range of 25 to 100 C. This paper presents a description of ongoing research at NASA-Langley on Pt/SnO2 catalyzed CO-O2 recombination. Included are studies with rare-isotope gases since rare-isotope CO2 is desirable as a laser gas for enhanced atmospheric transmission. Results presented include: (1) the effects of various catalyst pretreatment techniques on catalyst efficiency; (2) development of a technique, verified in a 30-hour test, to prevent isotopic scrambling when C(O-18) and (O-18)2 are reacted in the presence of a common-isotope Pt/Sn(O-16)2 catalyst; and (3) development of a mathematical model of a laser discharge prior to catalyst introduction.

Methodology of CO{sub 2} emission evaluation in the life cycle of office building facades

Energy Technology Data Exchange (ETDEWEB)

Taborianski, Vanessa Montoro; Prado, Racine T.A., E-mail: racine.prado@poli.usp.br

2012-02-15

The construction industry is one of the greatest sources of pollution because of the high level of energy consumption during its life cycle. In addition to using energy while constructing a building, several systems also use power while the building is operating, especially the air-conditioning system. Energy consumption for this system is related, among other issues, to external air temperature and the required internal temperature of the building. The facades are elements which present the highest level of ambient heat transfer from the outside to the inside of tall buildings. Thus, the type of facade has an influence on energy consumption during the building life cycle and, consequently, contributes to buildings' CO{sub 2} emissions, because these emissions are directly connected to energy consumption. Therefore, the aim is to help develop a methodology for evaluating CO{sub 2} emissions generated during the life cycle of office building facades. The results, based on the parameters used in this study, show that facades using structural glazing and uncolored glass emit the most CO{sub 2} throughout their life cycle, followed by brick facades covered with compound aluminum panels or ACM (Aluminum Composite Material), facades using structural glazing and reflective glass and brick facades with plaster coating. On the other hand, the typology of facade that emits less CO{sub 2} is brickwork and mortar because its thermal barrier is better than structural glazing facade and materials used to produce this facade are better than brickwork and ACM. Finally, an uncertainty analysis was conducted to verify the accuracy of the results attained. - Highlights: Black-Right-Pointing-Pointer We develop a methodology for evaluating CO{sub 2} emissions generated during the life cycle of office building facades. Black-Right-Pointing-Pointer This methodology is based in LCA. Black-Right-Pointing-Pointer We use an uncertainty analysis to verify the accuracy of the results

Thermal analysis of supercritical CO2 power cycles: Assessment of their suitability to the forthcoming sodium fast reactors

International Nuclear Information System (INIS)

Pérez-Pichel, G.D.; Linares, J.I.; Herranz, L.E.; Moratilla, B.Y.

2012-01-01

Highlights: ► This paper investigates the potential use of S-CO 2 cycles in SFRs. ► A wide range of configurations have been explored. ► It is feasible to reach a thermal efficiency as high as 43.5%. ► A sensitivity analysis together with an exergy study have been done. ► Potential use in SFRs of recompression S-CO 2 cycles for their balance of plant. - Abstract: Sodium fast reactors (SFRs) potential to meet Gen. IV requirements is broadly acknowledged worldwide. The scientific and technological experience accumulated by operating test reactors and, even, by running commercial reactors, makes them be considered as the closest Gen. IV option in the near future. In the past their balance of plant has been always based on Rankine cycles. This paper investigates the potential use of supercritical recompression CO 2 cycles (S-CO 2 ) in SFRs on the basis of the working parameters foreseen within the European Sodium Fast Reactor (ESFR) project. A wide range of configurations have been explored, from the simplest one to combined cycles (with organic Rankine cycles, ORC), and a comparison has been set in terms of thermal efficiency. As a result, it has been found out that the most basic configuration could reach a thermal efficiency as high as 43.31%, which is comparable to that obtained through super-critical Rankine cycles proposed elsewhere. A sensitivity analysis together with an exergy study of this configuration, pointed the pre-cooler and IHX Na–CO 2 as key components in the cycle performance. These results highlight a main conclusion: the potential use in SFRs of recompression S-CO 2 cycles for their balance of plant, whenever a sound and extensive database is built-up on S-CO 2 turbo-machinery and IHX performance.

Performance comparison of different thermodynamic cycles for an innovative central receiver solar power plant

Science.gov (United States)

Reyes-Belmonte, Miguel A.; Sebastián, Andrés; González-Aguilar, José; Romero, Manuel

2017-06-01

The potential of using different thermodynamic cycles coupled to a solar tower central receiver that uses a novel heat transfer fluid is analyzed. The new fluid, named as DPS, is a dense suspension of solid particles aerated through a tubular receiver used to convert concentrated solar energy into thermal power. This novel fluid allows reaching high temperatures at the solar receiver what opens a wide range of possibilities for power cycle selection. This work has been focused into the assessment of power plant performance using conventional, but optimized cycles but also novel thermodynamic concepts. Cases studied are ranging from subcritical steam Rankine cycle; open regenerative Brayton air configurations at medium and high temperature; combined cycle; closed regenerative Brayton helium scheme and closed recompression supercritical carbon dioxide Brayton cycle. Power cycle diagrams and working conditions for design point are compared amongst the studied cases for a common reference thermal power of 57 MWth reaching the central cavity receiver. It has been found that Brayton air cycle working at high temperature or using supercritical carbon dioxide are the most promising solutions in terms of efficiency conversion for the power block of future generation by means of concentrated solar power plants.

Solar Cycle Variations of SABER CO2 and MLS H2O in the Mesosphere and Lower Thermosphere Region

Science.gov (United States)

Salinas, C. C. J.; Chang, L. C.; Liang, M. C.; Qian, L.; Yue, J.; Russell, J. M., III; Mlynczak, M. G.

2017-12-01

This work aims to present the solar cycle variations of SABER CO2 and MLS H2O in the Mesosphere and Lower Thermosphere region. These observations are then compared to SD-WACCM outputs of CO2 and H2O in order to understand their physical mechanisms. After which, we attempt to model their solar cycle variations using the default TIME-GCM and the TIME-GCM with MERRA reanalysis as lower-boundary conditions. Comparing the outputs of the default TIME-GCM and TIME-GCM with MERRA will give us insight into the importance of solar forcing and lower atmospheric forcing on the solar cycle variations of CO2 and H2O. The solar cycle influence in the parameters are calculated by doing a multiple linear regression with the F10.7 index. The solar cycle of SABER CO2 is reliable above 1e-2 mb and below 1e-3 mb. Preliminary results from the observations show that SABER CO2 has a stronger negative anomaly due to the solar cycle over the winter hemisphere. MLS H2O is reliable until 1e-2. Preliminary results from the observations show that MLS H2O also has a stronger negative anomaly due to the solar cycle over the winter hemisphere. Both SD-WACCM and the default TIME-GCM reproduce these stronger anomalies over the winter hemisphere. An analysis of the tendency equations in SD-WACCM and default TIME-GCM then reveal that for CO2, the stronger winter anomaly may be attributed to stronger downward transport over the winter hemisphere. For H2O, an analysis of the tendency equations in SD-WACCM reveal that the stronger winter anomaly may be attributed to both stronger downward transport and stronger photochemical loss. On the other hand, in the default TIME-GCM, the stronger winter anomaly in H2O may only be attributed to stronger downward transport. For both models, the stronger downward transport is attributed to enhanced stratospheric polar winter jet during solar maximum. Future work will determine whether setting the lower boundary conditions of TIME-GCM with MERRA will improve the match

Relative estimates of TCA cycle pool size from 14CO2 production profiles

International Nuclear Information System (INIS)

Kelleher, J.K.; Cesta, M.L.; Holleran, A.L.

1986-01-01

In metabolic and isotopic steady state, the rate of 14 CO 2 production by TCA cycle intermediates labeled at different positions is linear. However, before the system reaches isotopic steady state, the rate of 14 CO 2 production is non-linear. The x-intercept extrapolated from the linear phase indicates the turnover rate of all metabolic pools the tracer must pass through. By exposing identical systems to 14 C succinate labeled in different positions, the contribution of TCA cycle pools to the non-linear phase may be considered. Specifically, the extrapolated x-intercept for [2,3 14 C] succinate will be greater than the x-intercept for [1,4 14 C] succinate if the TCA cycle pools are a contributing factor to the non-linear phase. The authors have used this method to analyze pyruvate oxidation in AS 30D hepatoma cells. They found that the extrapolated x-intercepts for the two tracers were identical. This indicates that the non-linear phase resulted from equilibration of the tracer with pools prior to entering the TCA cycle, i.e. lactate. Using this technique, it may be possible to estimate the variations in TCA cycle pool sizes in vivo

Low CO2-emissions hybrid solar combined-cycle power system with methane membrane reforming

International Nuclear Information System (INIS)

Li, Yuanyuan; Zhang, Na; Cai, Ruixian

2013-01-01

Based on the principle of cascade utilization of multiple energy resources, a gas-steam combined cycle power system integrated with solar thermo-chemical fuel conversion and CO 2 capture has been proposed and analyzed. The collected solar heat at 550 °C drives the endothermic methane reforming and is converted to the produced syngas chemical exergy, and then released as high-temperature thermal energy via combustion for power generation, achieving its high-efficiency heat-power conversion. The reforming reaction is integrated with a hydrogen separation membrane, which continuously withdraws hydrogen from the reaction zone and enables nearly full methane conversion. The CO 2 enriched gas being concentrated in the retentate zone is collected and processed with pre-combustion decarbonization. The system is thermodynamically simulated using the ASPEN PLUS code. The results show that with 91% CO 2 captured, the specific CO 2 emission is 25 g/kWh. An exergy efficiency of 58% and thermal efficiency of 51.6% can be obtained. A fossil fuel saving ratio of 31.2% is achievable with a solar thermal share of 28.2%, and the net solar-to-electricity efficiency based on the gross solar heat incident on the collector is about 36.4% compared with the same gas-steam combined cycle system with an equal CO 2 removal ratio obtained by post-combustion decarbonization. - Highlights: ► A solar-assisted hybrid combined cycle power system has been proposed and analyzed. ► The system integrates power generation with solar-driven reforming and CO 2 capture. ► solar heat upgrading and high-efficiency heat-to-power conversion are achieved. ► membrane reforming enables high CH 4 conversion and pre-combustion CO 2 capture. ► The system thermodynamic performances have been investigated and compared

The Martian hydrologic cycle - Effects of CO2 mass flux on global water distribution

Science.gov (United States)

James, P. B.

1985-01-01

The Martian CO2 cycle, which includes the seasonal condensation and subsequent sublimation of up to 30 percent of the planet's atmosphere, produces meridional winds due to the consequent mass flux of CO2. These winds currently display strong seasonal and hemispheric asymmetries due to the large asymmetries in the distribution of insolation on Mars. It is proposed that asymmetric meridional advection of water vapor on the planet due to these CO2 condensation winds is capable of explaining the observed dessication of Mars' south polar region at the current time. A simple model for water vapor transport is used to verify this hypothesis and to speculate on the effects of changes in orbital parameters on the seasonal water cycle.

Reactivation properties of carbide slag as a CO{sub 2} sorbent during calcination/carbonation cycles

Energy Technology Data Exchange (ETDEWEB)