WorldWideScience

Sample records for based heat works

  1. Performance evaluation of organic and titanium based working fluids for high-temperature heat pumps

    Energy Technology Data Exchange (ETDEWEB)

    Zamfirescu, C., E-mail: Calin.Zamfirescu@uoit.ca [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, ON, Canada L1H 74K (Canada); Dincer, I., E-mail: Ibrahim.Dincer@uoit.ca [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, ON, Canada L1H 74K (Canada); Naterer, G., E-mail: Greg.Naterer@uoit.ca [Faculty of Engineering and Applied Science, University of Ontario Institute of Technology (UOIT), 2000 Simcoe Street North, Oshawa, ON, Canada L1H 74K (Canada)

    2009-12-10

    In this paper, selected organic and titanium based fluids (biphenyl, biphenylmethane, naphthalene, isoquinoline, titanium tetrabromide and titanium tetraiodide) are assessed thermodynamically as potential working fluids for high temperature mechanical heat pumps. Various applications, such as thermo-chemical cycles for hydrogen production, chemical processes comprising endothermic reactions, steam generators and metallurgical processes, can benefit from such heat pumps as 'green' sources of high temperature heat. The environmental benefit occurs from avoiding fossil fuel heating and therefore reducing carbon dioxide and other pollutant emissions. Through heat pumps, a low-grade heat source from nuclear reactors, industrial waste, geothermal, etc. can be upgraded to high temperatures through a work-to-heat conversion. The work itself can originate from any source of renewable energy (wind, hydro, biomass, solar, etc.). In this paper, available thermo-physical parameters of the selected fluids are presented and appropriate equations of state are constructed to allow a heat pump thermodynamic analysis. Among these working fluids, only biphenyl, naphthalene, titanium tetrabromide and titanium tetraiodide have promising potential. For these fluids, a further parametric study is conducted to investigate the COP for a range of relevant operating conditions, in terms of temperature and pressure. The range of COP values is large, ranging from 1.9 to 7.3, depending on the fluid and temperature levels; the highest COP is obtained with TiI{sub 4}.

  2. Selection of organic Rankine cycle working fluid based on unit-heat-exchange-area net power

    Institute of Scientific and Technical Information of China (English)

    郭美茹; 朱启的; 孙志强; 周天; 周孑民

    2015-01-01

    To improve energy conversion efficiency, optimization of the working fluids in organic Rankine cycles (ORCs) was explored in the range of low-temperature heat sources. The concept of unit-heat-exchange-area (UHEA) net power, embodying the cost/performance ratio of an ORC system, was proposed as a new indicator to judge the suitability of ORC working fluids on a given condition. The heat exchange area was computed by an improved evaporator model without fixing the minimum temperature difference between working fluid and hot fluid, and the flow pattern transition during heat exchange was also taken into account. The maximum UHEA net powers obtained show that dry organic fluids are more suitable for ORCs than wet organic fluids to recover low-temperature heat. The organic fluid 1-butene is recommended if the inlet temperature of hot fluid is 353.15−363.15 K or 443.15−453.15 K, heptane is more suitable at 373.15−423.15 K, and R245ca is a good option at 483.15−503.15 K.

  3. Work Criteria Function of Irreversible Heat Engines

    Directory of Open Access Journals (Sweden)

    Mahmoud Huleihil

    2014-01-01

    Full Text Available The irreversible heat engine is reconsidered with a general heat transfer law. Three criteria known in the literature—power, power density, and efficient power—are redefined in terms of the work criteria function (WCF, a concept introduced in this study. The formulation enabled the suggestion and analysis of a unique criterion—the efficient power density (which accounts for the efficiency and power density. Practically speaking, the efficient power and the efficient power density could be defined on any order based on the WCF. The applicability of the WCF is illustrated for the Newtonian heat transfer law (n=1 and for the radiative law (n=4. The importance of WCF is twofold: it gives an explicit design and educational tool to analyze and to display graphically the different criteria side by side and thus helps in design process. Finally, the criteria were compared and some conclusions were drawn.

  4. Lunar Base Heat Pump

    Science.gov (United States)

    Walker, D.; Fischbach, D.; Tetreault, R.

    1996-01-01

    The objective of this project was to investigate the feasibility of constructing a heat pump suitable for use as a heat rejection device in applications such as a lunar base. In this situation, direct heat rejection through the use of radiators is not possible at a temperature suitable for lde support systems. Initial analysis of a heat pump of this type called for a temperature lift of approximately 378 deg. K, which is considerably higher than is commonly called for in HVAC and refrigeration applications where heat pumps are most often employed. Also because of the variation of the rejection temperature (from 100 to 381 deg. K), extreme flexibility in the configuration and operation of the heat pump is required. A three-stage compression cycle using a refrigerant such as CFC-11 or HCFC-123 was formulated with operation possible with one, two or three stages of compression. Also, to meet the redundancy requirements, compression was divided up over multiple compressors in each stage. A control scheme was devised that allowed these multiple compressors to be operated as required so that the heat pump could perform with variable heat loads and rejection conditions. A prototype heat pump was designed and constructed to investigate the key elements of the high-lift heat pump concept. Control software was written and implemented in the prototype to allow fully automatic operation. The heat pump was capable of operation over a wide range of rejection temperatures and cooling loads, while maintaining cooling water temperature well within the required specification of 40 deg. C +/- 1.7 deg. C. This performance was verified through testing.

  5. Work measurement in a quantum heat engine

    Science.gov (United States)

    Bariani, Francesco; Zhang, Keye; Dong, Ying; Meystre, Pierre

    2015-05-01

    We consider an optomechanical quantum heat engine operating on an Otto cycle for photon-phonon polaritons, the working substance of the engine. We discuss both the average value and quantum fluctuations of its work output, concentrating in particular on the effects of quantum non-adiabaticity due to the finite duration of the cycle. We also determine the quantum back-action of both absorptive and dispersive continuous measurements of the work, and quantify their impact on the Curzon-Ahlborn engine efficiency at maximum power and its fluctuations. We ackowledge financial support from National Basic Research Program of China, NSF, ARO and the DARPA QuaSAR programs

  6. Thermodynamic analysis of carbon dioxide blends with low GWP (global warming potential) working fluids-based transcritical Rankine cycles for low-grade heat energy recovery

    International Nuclear Information System (INIS)

    Carbon dioxide is a promising natural working fluid that can be used in transcritical Rankine cycles due to environmental and safety concerns. However, the high operation pressure has to be reduced and the relatively low efficiency of the system has to be increased. Traditional working fluids have been widely investigated to reclaim low-grade heat energy, and most of them have high GWPs (global warming potentials) or are flammable or even toxic. Consequently, to mitigate the above disadvantages, we studied zeotropic mixtures of carbon dioxide blends with 7 low GWP working fluids for use in a TRC (transcritical Rankine cycle) for low-grade heat conversion. The results revealed that these zeotropic mixtures can help improve the thermal efficiency of the TRC and decrease the operation pressure compared to that of pure CO2. Owing to the perfect thermal match in the heat transfer process, higher exergy efficiencies were achieved for the entire system when zeotropic mixtures were used than pure CO2. Maximum exergy efficiencies exist for the TRC at the corresponding optimal pressures for each mixture. Finally, the mixture CO2/R161 is recommended for small capacity instruments for its high efficiency, in spite of its high flammability; the mixtures CO2/R1234yf and CO2/R1234ze can be used in TRCs with larger capacities due to their lower flammability. - Highlights: • A TRC (transcritical Rankine cycle) using the blends of CO2 and low GWP working fluids is proposed. • The thermal efficiency is improved and the corresponding high operation pressure is reduced comparing to pure CO2. • The limitation condensation temperature of pure CO2 is solved with the proposed zeotropic mixtures. • The system exergy efficiency of mixtures-based TRC is improved in comparison with that of pure CO2. • Two kinds of zeotropic mixtures are proposed for the application of small and large scale TRCs respectively

  7. Visualization of working fluid flow in gravity assisted heat pipe

    Science.gov (United States)

    Nemec, Patrik; Malcho, Milan

    2015-05-01

    Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapor and vice versa help heat pipe to transport high heat flux. The article deal about construction and processes casing in heat pipe during operation. Experiment visualization of working fluid flow is performed with glass heat pipe filed with ethanol. The visualization of working fluid flow explains the phenomena as working fluid boiling, nucleation of bubbles, vapor flow, vapor condensation on the wall, vapor and condensate flow interaction, flow down condensate film thickness on the wall, occurred during the heat pipe operation.

  8. Visualization of working fluid flow in gravity assisted heat pipe

    Directory of Open Access Journals (Sweden)

    Nemec Patrik

    2015-01-01

    Full Text Available Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapor and vice versa help heat pipe to transport high heat flux. The article deal about construction and processes casing in heat pipe during operation. Experiment visualization of working fluid flow is performed with glass heat pipe filed with ethanol. The visualization of working fluid flow explains the phenomena as working fluid boiling, nucleation of bubbles, vapor flow, vapor condensation on the wall, vapor and condensate flow interaction, flow down condensate film thickness on the wall, occurred during the heat pipe operation.

  9. Distribution of heat flux by working fluid in loop heat pipe

    OpenAIRE

    Nemec Patrik; Malcho Milan

    2016-01-01

    The main topics of article are construction of loop heat pipe, thermal visualization of working fluid dynamics and research results interpretation. The work deals about heat flux transport by working fluid in loop heat pipe from evaporator to condenser evolution. The result of the work give us how the hydrodynamic and thermal processes which take place inside the loop of heat pipe affect on the overall heat transport by loop heat pipe at start-up and during operation.

  10. Distribution of heat flux by working fluid in loop heat pipe

    Directory of Open Access Journals (Sweden)

    Nemec Patrik

    2016-01-01

    Full Text Available The main topics of article are construction of loop heat pipe, thermal visualization of working fluid dynamics and research results interpretation. The work deals about heat flux transport by working fluid in loop heat pipe from evaporator to condenser evolution. The result of the work give us how the hydrodynamic and thermal processes which take place inside the loop of heat pipe affect on the overall heat transport by loop heat pipe at start-up and during operation.

  11. Distribution of heat flux by working fluid in loop heat pipe

    Science.gov (United States)

    Nemec, Patrik; Malcho, Milan

    2016-03-01

    The main topics of article are construction of loop heat pipe, thermal visualization of working fluid dynamics and research results interpretation. The work deals about heat flux transport by working fluid in loop heat pipe from evaporator to condenser evolution. The result of the work give us how the hydrodynamic and thermal processes which take place inside the loop of heat pipe affect on the overall heat transport by loop heat pipe at start-up and during operation.

  12. Renewable heating: how thinking big works

    Energy Technology Data Exchange (ETDEWEB)

    Holter, C. [SOLID (Austria)

    2005-10-01

    The Austrian company, SOLID, offers energy service contracts (ESCOs) and guaranteed results schemes to potential users of large solar thermal projects. Examples of its projects are used to demonstrate the benefits of such an approach. The solar collector (1407 m{sup 2}) at the Schwarzenegger Stadium in Graz is an example of the provision of district heating from solar power in combination with fossil fuel and run on an ESCO model. Several examples of the application of the guaranteed results scheme to multi-family housing illustrate how this model works; the projects use solar collectors ranging from 100 m{sup 2} to 430 m{sup 2}. SOLID supplies similar solar units to hotels and hospitals for domestic hot water (DHW) and space heating. A recent development by SOLID is the installation of solar cooling projects in a nine-storey office building in Kosovo (227 m{sup 2}) and a winery in Styria, Austria (100 m{sup 2}).

  13. Mathematical simulation of heat exchanger working conditions

    OpenAIRE

    Gavlas Stanislav; Ďurčanský Peter; Lenhard Richard; Jandačka Jozef

    2015-01-01

    One of the When designing a new heat exchanger it is necessary to consider all the conditions imposed on the exchanger and its desired properties. Most often the investigation of heat transfer is to find heat surface. When applying exchanger for proposed hot air engine, it will be a counter-flow heat exchanger of gas - gas type. Gas, which transfers the heat will be exhaust gas from the combustion of biomass. An important step in the design and verification is to analyze exchanger designed us...

  14. Working fluid flow visualization in gravity heat pipe

    Science.gov (United States)

    Nemec, Patrik; Malcho, Milan

    2016-03-01

    Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapour and vice versa help heat pipe to transport high heat flux. The article deal about gravity heat pipe construction and processes casing inside during heat pipe operation. Experiment working fluid flow visualization is performed with two glass heat pipes with different inner diameter (13 mm and 22 mm) and filled with water. The working fluid flow visualization explains the phenomena as a working fluid boiling, nucleation of bubbles, and vapour condensation on the wall, vapour and condensate flow interaction, flow down condensate film thickness on the wall occurred during the heat pipe operation.

  15. Working fluid flow visualization in gravity heat pipe

    Directory of Open Access Journals (Sweden)

    Nemec Patrik

    2016-01-01

    Full Text Available Heat pipe is device working with phase changes of working fluid inside hermetically closed pipe at specific pressure. The phase changes of working fluid from fluid to vapour and vice versa help heat pipe to transport high heat flux. The article deal about gravity heat pipe construction and processes casing inside during heat pipe operation. Experiment working fluid flow visualization is performed with two glass heat pipes with different inner diameter (13 mm and 22 mm and filled with water. The working fluid flow visualization explains the phenomena as a working fluid boiling, nucleation of bubbles, and vapour condensation on the wall, vapour and condensate flow interaction, flow down condensate film thickness on the wall occurred during the heat pipe operation.

  16. Simultaneous synthesis of work exchange networks with heat integration

    OpenAIRE

    Onishi, Viviani C.; Ravagnani, Mauro A.S.S.; Caballero Suárez, José Antonio

    2014-01-01

    The optimal integration of work and its interaction with heat can represent large energy savings in industrial plants. This paper introduces a new optimization model for the simultaneous synthesis of work exchange networks (WENs), with heat integration for the optimal pressure recovery of process gaseous streams. The proposed approach for the WEN synthesis is analogous to the well-known problem of synthesis of heat exchanger networks (HENs). Thus, there is work exchange between high-pressure ...

  17. Technical and economic working domains of industrial heat pumps: Part 2 - ammonia-water hybrid absorption-compression heat pumps

    DEFF Research Database (Denmark)

    Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix;

    2015-01-01

    The ammonia-water hybrid absorption-compression heat pump (HACHP) has been proposed as a relevant technology for industrial heat supply, especially for high sink temperatures and high temperature glides in the sink and source. This is due to the reduced vapour pressure and the non-isothermal phase...... change of the zeotropic mixture, ammonia-water. To evaluate to which extent these advantages can be translated into feasible heat pump solutions, the working domain of the HACHP is investigated based on technical and economic constraints. The HACHP working domain is compared to that of the best available...... vapour compression heat pump with natural working fluids. This shows that the HACHP increases the temperature lifts and heat supply temperatures that are feasible to produce with a heat pump. The HACHP is shown to be capable of delivering heat supply temperatures as high as 150 °C and temperature lifts...

  18. Membrane Based Heat Exchanger

    OpenAIRE

    Aarnes, Sofie Marie

    2012-01-01

    Reduction of the energy used to acclimatise buildings is a huge challenge simultaneously with the implementation of air tight low energy buildings. In residential buildings with several living units centralised air handling units are the most energy efficient system. However, in a centralised system there is important to avoid leakages of pollutions between the exhaust air and the supply air. This leads to that flat plate heat exchangers are used instead of the more energy efficient rotary he...

  19. Technical and economic working domains of industrial heat pumps: Part 2 - ammonia-water hybrid absorption-compression heat pumps

    OpenAIRE

    Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix; Reinholdt, L.; Elmegaard, Brian

    2015-01-01

    The ammonia-water hybrid absorption-compression heat pump (HACHP) has been proposed as a relevant technology for industrial heat supply, especially for high sink temperatures and high temperature glides in the sink and source. This is due to the reduced vapour pressure and the non-isothermal phase change of the zeotropic mixture, ammonia-water. To evaluate to which extent these advantages can be translated into feasible heat pump solutions, the working domain of the HACHP is investigated base...

  20. Working Fluids for Increasing Capacities of Heat Pipes

    Science.gov (United States)

    Chao, David F.; Zhang, Nengli

    2004-01-01

    A theoretical and experimental investigation has shown that the capacities of heat pipes can be increased through suitable reformulation of their working fluids. The surface tensions of all of the working fluids heretofore used in heat pipes decrease with temperature. As explained in more detail below, the limits on the performance of a heat pipe are associated with the decrease in the surface tension of the working fluid with temperature, and so one can enhance performance by reformulating the working fluid so that its surface tension increases with temperature. This improvement is applicable to almost any kind of heat pipe in almost any environment. The heat-transfer capacity of a heat pipe in its normal operating-temperature range is subject to a capillary limit and a boiling limit. Both of these limits are associated with the temperature dependence of surface tension of the working fluid. In the case of a traditional working fluid, the decrease in surface tension with temperature causes a body of the liquid phase of the working fluid to move toward a region of lower temperature, thus preventing the desired spreading of the liquid in the heated portion of the heat pipe. As a result, the available capillary-pressure pumping head decreases as the temperature of the evaporator end of the heat pipe increases, and operation becomes unstable. Water has widely been used as a working fluid in heat pipes. Because the surface tension of water decreases with increasing temperature, the heat loads and other aspects of performance of heat pipes that contain water are limited. Dilute aqueous solutions of long-chain alcohols have shown promise as substitutes for water that can offer improved performance, because these solutions exhibit unusual surface-tension characteristics: Experiments have shown that in the cases of an aqueous solution of an alcohol, the molecules of which contain chains of more than four carbon atoms, the surface tension increases with temperature when the

  1. Maximum work for Carnot-like heat engines with infinite heat source

    CERN Document Server

    Long, Rui

    2014-01-01

    An analysis of efficiency and its bounds at maximum work output for Carnot-like heat engines is conducted. The heat transfer processes are described by the linear law with time-dependent heat conductance. The upper bound of efficiency is found to be the CA efficiency,and is independent of the time duration completing each process and the time-dependent conductance. We prove that even the working medium exchanges heat sufficiently with the heat reservoirs, the work which could be extracted is finite and limited. The optimal temperature profiles in the heat exchanging processes are also analyzed. When the dimensionless contact times satisfy certain relations,the endoreversible model is recovered.

  2. Lunar base heat pump, phase 1

    Science.gov (United States)

    Goldman, Jeffrey H.; Harvey, A.; Lovell, T.; Walker, David H.

    1994-01-01

    This report describes the Phase 1 process and analysis used to select a refrigerant and thermodynamic cycle as the basis of a vapor compression heat pump requiring a high temperature lift, then to perform a preliminary design to implement the selected concept, including major component selection. Use of a vapor compression heat pump versus other types was based on prior work performed for the Electric Power Research Institute. A high lift heat pump is needed to enable a thermal control system to remove heat down to 275 K from a habitable volume when the external thermal environment is severe. For example, a long-term lunar base habitat will reject heat from a space radiator to a 325 K environment. The first step in the selection process was to perform an optimization trade study, quantifying the effect of radiator operating temperature and heat pump efficiency on total system mass; then, select the radiator operating temperature corresponding to the lowest system mass. Total system mass included radiators, all heat pump components, and the power supply system. The study showed that lunar night operation, with no temperature lift, dictated the radiator size. To operate otherwise would require a high mass penalty to store power. With the defined radiation surface, and heat pump performances assumed to be from 40 percent to 60 percent of the Carnot ideal, the optimum heat rejection temperature ranged from 387 K to 377 K, as a function of heat pump performance. Refrigerant and thermodynamic cycles were then selected to best meet the previously determined design conditions. The system was then adapted as a ground-based prototype lifting temperature to 360 K (versus 385 K for flight unit) and using readily available commercial-grade components. Over 40 refrigerants, separated into wet and dry compression behavioral types, were considered in the selection process. Refrigerants were initially screened for acceptable critical temperature. The acceptable refrigerants were

  3. Extracting work from a single heat bath through feedback

    OpenAIRE

    Abreu, D.; Seifert, U.

    2011-01-01

    Work can be extracted from a single heat bath if additional information is available. For the paradigmatic case of a Brownian particle in a harmonic potential, whose position has been measured with finite precision, we determine the optimal protocol for manipulating the center and stiffness of the potential in order to maximize this work in a finite-time process. The bound on this work imposed by a generalized second law inequality involving information can be reached only if both position an...

  4. Urban Heat Islands and Social Work: Opportunities for Intervention

    Directory of Open Access Journals (Sweden)

    Billy Hamilton

    2012-05-01

    Full Text Available The urban heat island (UHI, formed by surface modification of soil and vegetation, increases minimum nighttime temperatures within cities and causes heat-stress among dwellers. Children, elders and low-income persons are disproportionately burdened by the UHI. These populations often lack the necessary biological, economic and social resources to cope with or prevent heat stress. Because UHI’s are expected to increase with climate change, more social workers will be expected to serve the populations most affected by UHI. This paper addresses how the social work profession can play a role in efforts to address the effects of UHI’s on vulnerable populations.

  5. Technical and Economic Working Domains of Industrial Heat Pumps: Part 1 - Vapour Compression Heat Pumps

    DEFF Research Database (Denmark)

    Ommen, Torben Schmidt; Jensen, Jonas Kjær; Markussen, Wiebke Brix;

    2014-01-01

    A large amount of operational and economic constraints limit the applicability of heat pumps operated with natural working fluids. The limitations are highly dependent on the integration of heat source and sink streams. An evaluation of feasible operating conditions is carried out considering the...

  6. JOYO MK-III modification work on heat transport system. Working plan and plant control

    International Nuclear Information System (INIS)

    The MK-III project to improve the irradiation capability of the experimental fast reactor JOYO have been in underway since 1987. The increase of fast neutron flux and the enlargement of that field increase the reactor thermal rate from 100 MWt to 140 MWt. To increase cooling capacity of heat transport system, intermediate heat exchangers (IHXs), dump heat exchangers (DHXs), piping connecting to IHXs and DHXs, main motors on primary and secondary main circulation pumps were replaced. The replacement of these large components was carried out under following hard conditions. 1) Limitation of work space, 2) Fuel subassembly and molten sodium in the reactor vessel, 3) high radiation circumstances for primary cooling system, 4) treatment of radioactive sodium (radioactive sodium and corrosion product such as 60Co, 54Mn). There are little experiences of this kind of work in the world. Therefore the organization, working plan and safety management points were carefully examined and established, based on the previous experience of JOYO operation and maintenance, research and development results of safety treatment of sodium, experience of previous work on sodium facilities. Followings results were obtained and effectiveness was confirmed in the work. (1) Development of most suitable working plan derived from elements and full size mock up experiments, reduction of exposure time by workers training, reduction of radiation dose by installation of temporal radiation shielding were useful to reduce radiation dose. The usage of seal bag was useful to prevent the contamination spreading over. (2) The usage of seal bag, oxygen concentration monitoring in the seal bag, nitrogen concentration monitoring in the cooling system cover gas, low pressure control of cover gas were useful to reduce the inflow of oxygen to cooling system. (3) The bite cutting method for piping in air and press down cutting by roller cutter in the seal bag to prevent inflow of cutting piece, stopper insertion

  7. Influence of Heat Input, Working Fluid and Evacuation Level on the Performance of Pulsating Heat Pipe

    Directory of Open Access Journals (Sweden)

    K. Rama Narasimha

    2012-01-01

    Full Text Available An experimental study on pulsating heat pipe (PHP is presented in this work. A closed loop PHP with a single U turn is fabricated and tested. The transient and steady state experiments are conducted and operating temperatures are measured. The experiments are carried out for different working fluids, heat input and for different evacuation levels. The derived parameters include thermal resistance and heat transfer coefficient of PHP. The results of these experiments show an intermittent motion of the working fluid at lower heat input. The temperature difference between evaporator and condenser at steady state is found lower for acetone compared to water, ethanol and methanol. Lower value of thermal resistance and higher value of heat transfer coefficient are observed in case of acetone compared to water, ethanol and methanol. Lower values of temperature difference between evaporator and condenser and thermal resistance and higher value of heat transfer coefficient are observed at atmospheric conditions of operation of PHP compared to evacuation conditions. The Power Spectral Density Analysis is also carried out on the results of these experiments using FFT technique to analyse the pulsating motion of the fluid in a PHP. In the Power Spectral Density analysis, the frequency distribution of temperature variation in PHP was observed over a wider range, signifying the periodic motion in the fluid flow of the liquid slug and vapour plug. This characteristic frequency corresponded to the characteristic time for a couple of adjacent vapour plug and liquid slug passing through a specific local wall surface in a PHP.

  8. Work Fluctuation-Dissipation Trade-Off in Heat Engines.

    Science.gov (United States)

    Funo, Ken; Ueda, Masahito

    2015-12-31

    Reducing work fluctuation and dissipation in heat engines or, more generally, information heat engines that perform feedback control, is vital to maximize their efficiency. The same problem arises when we attempt to maximize the efficiency of a given thermodynamic task that undergoes nonequilibrium processes for arbitrary initial and final states. We find that the most general trade-off relation between work fluctuation and dissipation applicable to arbitrary nonequilibrium processes is bounded from below by the information distance characterizing how far the system is from thermal equilibrium. The minimum amount of dissipation is found to be given in terms of the relative entropy and the Renyi divergence, both of which quantify the information distance between the state of the system and the canonical distribution. We give an explicit protocol that achieves the fundamental lower bound of the trade-off relation.

  9. NUMERICAL AND EXPERIMENTAL ANALYSIS OF UNSTEADY WORK OF U-SHAPE BOREHOLE HEAT EXCHANGER

    Directory of Open Access Journals (Sweden)

    S. A. Filatau

    2014-01-01

    Full Text Available Unsteady numerical model of borehole heat exchanger heat regime was developed. General numerical modeling results are borehole heat flux, heat carrier inlet temperature and average soil temperature distribution. Proposed model is based on solution of heat conduction equation in transient plane axially symmetric formulation with boundary conditions for borehole heat exchanger and undisturbed soil domain. Solution method is finite difference method. Numerical model is verified with comparisons numerical results and experimental data from developed laboratory installation for simulation unsteady heat regime of horizontal positioned U-shape ground heat exchanger in sand medium.Cooling of water is organized in ground exchanger in experiment. Experiment includes two steps. Thermal properties of sand is determined at the first stage. Thermal conductivity of sand is determined by stationary plate method, thermal diffusivity is determined by regular regime method using cylindrical calorimeter. Determined properties are used further in processing of experimental results at second step for analysis of transient work of ground heat exchanger. Results of four experiments are analyzed with different duration and time behavior of mass flow and heat carrier temperature. Divergences of experimental and simulated results for temperature of heat carrier changes in the range 0,5–1,8 %, for sand temperature in the range 1,0–2,3 %, for heat flux in the range 3,6–5,4 %. Experimental results can be used for validation of other simulation methods of ground heat exchangers. Presented numerical model can be used for analyzing of heat supply systems with heat pumps.

  10. Work Output and Efficiency at Maximum Power of Linear Irreversible Heat Engines Operating with a Finite-Sized Heat Source

    Science.gov (United States)

    Izumida, Yuki; Okuda, Koji

    2014-05-01

    We formulate the work output and efficiency for linear irreversible heat engines working between a finite-sized hot heat source and an infinite-sized cold heat reservoir until the total system reaches the final thermal equilibrium state with a uniform temperature. We prove that when the heat engines operate at the maximum power under the tight-coupling condition without heat leakage the work output is just half of the exergy, which is known as the maximum available work extracted from a heat source. As a consequence, the corresponding efficiency is also half of its quasistatic counterpart.

  11. Work output and efficiency at maximum power of linear irreversible heat engines operating with a finite-sized heat source.

    Science.gov (United States)

    Izumida, Yuki; Okuda, Koji

    2014-05-01

    We formulate the work output and efficiency for linear irreversible heat engines working between a finite-sized hot heat source and an infinite-sized cold heat reservoir until the total system reaches the final thermal equilibrium state with a uniform temperature. We prove that when the heat engines operate at the maximum power under the tight-coupling condition without heat leakage the work output is just half of the exergy, which is known as the maximum available work extracted from a heat source. As a consequence, the corresponding efficiency is also half of its quasistatic counterpart.

  12. Technical and Economic Working Domains of Industrial Heat Pumps: Part 2 - Ammonia-Water Hybrid Absorption-Compression Heat Pumps

    DEFF Research Database (Denmark)

    Jensen, Jonas Kjær; Ommen, Torben Schmidt; Markussen, Wiebke Brix;

    2014-01-01

    compression heat pump with natural working fluids. This shows that the HACHP increases the temperature lifts and heat supply temperatures that are feasible to produce with a heat pump. The HACHP is shown to be capable of delivering heat supply temperatures as high as 140 XC and temperature lifts up to 60 K...

  13. WORKING PARK-FUEL CELL COMBINED HEAT AND POWER SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Allan Jones

    2003-09-01

    This report covers the aims and objectives of the project which was to design, install and operate a fuel cell combined heat and power (CHP) system in Woking Park, the first fuel cell CHP system in the United Kingdom. The report also covers the benefits that were expected to accrue from the work in an understanding of the full technology procurement process (including planning, design, installation, operation and maintenance), the economic and environmental performance in comparison with both conventional UK fuel supply and conventional CHP and the commercial viability of fuel cell CHP energy supply in the new deregulated energy markets.

  14. Thermoelectric Generation Using Waste Heat in Steel Works

    Science.gov (United States)

    Kuroki, Takashi; Kabeya, Kazuhisa; Makino, Kazuya; Kajihara, Takeshi; Kaibe, Hiromasa; Hachiuma, Hirokuni; Matsuno, Hidetoshi; Fujibayashi, Akio

    2014-06-01

    The steelmaking industry in Japan has significantly reduced its energy use for the past several decades and has kept the highest energy efficiency in the world. However, the steelmaking industry is strongly required to develop new technologies for further energy conservation in view of energy security, high and volatile energy prices, and climate change. One of the key technologies to achieve the requirement is waste heat recovery. This paper describes the thermoelectric generation (TEG) system using the waste heat in the steelmaking process. In this system, the TEG unit, which consists of 16 thermoelectric modules made of Bi-Te thermoelectric materials, generates the electrical power directly by converting the radiant heat released from hot steel products. Each thermoelectric module, whose size is 50 mm × 50 mm × 4.2 mm, generates 18 W when the hot-side temperature is 523 K and the cold-side is 303 K. Therefore, the output of the TEG unit is over 250 W. The performance and the durability of the system have been investigated under various operating conditions in steel works. The results of the verification tests in the JFE steel Corporation's continuous casting line will be discussed.

  15. Market survey of forest work tools and heating devices

    International Nuclear Information System (INIS)

    The TTS Institute has published internet pages where information has been 'gathered on the work tools, equipment, devices and machines needed by forest owners and people who use wood heating. The contact information of manufacturers and merchants for such tools and devices has also been provided. A link to the pages can be found at http://www.tts.fi. The pages are meant to be an aid for product buyers and also for advisory and research use. So far the pages are in trial use and are free of charge. They will be developed on the basis of feedback received. The TTS Institute internet pages operate primarily as a contact list where different product groups and contact information for product manufacturers and merchants can be found. The pages present limited information on the product since updating detailed product information would require intensive market monitoring and great work input. Furthermore, the objective is not to compete in the advertising market, but to publish independent information where the beneficiary is primarily the buyer. The contents of the pages are mainly limited to the products concerned with private forest owners and people who heat detached houses with wood, and information on those products. Information is collected and updated from public sources and also partly direct from the manufacturers and merchants. For clarity, the source of information will be mentioned. (orig.)

  16. Open district heating and marginal cost based heat pricing

    OpenAIRE

    Mäkelä, Henri

    2014-01-01

    Currently, an increasing usage of individual heating systems such as heat pumps and solar heat collectors, pose a challenge to the district heating market. However, individual heating technologies together with industrial processes produce excess heat, which can be utilized in district heating. The usage of excess heat can be seen as an opportuni-ty for new business strategies in district heating. The objective of this thesis was to simulate hourly district heat production in an open dist...

  17. Impact of the amount of working fluid in loop heat pipe to remove waste heat from electronic component

    Science.gov (United States)

    Smitka, Martin; Kolková, Z.; Nemec, Patrik; Malcho, M.

    2014-03-01

    One of the options on how to remove waste heat from electronic components is using loop heat pipe. The loop heat pipe (LHP) is a two-phase device with high effective thermal conductivity that utilizes change phase to transport heat. It was invented in Russia in the early 1980's. The main parts of LHP are an evaporator, a condenser, a compensation chamber and a vapor and liquid lines. Only the evaporator and part of the compensation chamber are equipped with a wick structure. Inside loop heat pipe is working fluid. As a working fluid can be used distilled water, acetone, ammonia, methanol etc. Amount of filling is important for the operation and performance of LHP. This work deals with the design of loop heat pipe and impact of filling ratio of working fluid to remove waste heat from insulated gate bipolar transistor (IGBT).

  18. Impact of the amount of working fluid in loop heat pipe to remove waste heat from electronic component

    Directory of Open Access Journals (Sweden)

    Smitka Martin

    2014-03-01

    Full Text Available One of the options on how to remove waste heat from electronic components is using loop heat pipe. The loop heat pipe (LHP is a two-phase device with high effective thermal conductivity that utilizes change phase to transport heat. It was invented in Russia in the early 1980’s. The main parts of LHP are an evaporator, a condenser, a compensation chamber and a vapor and liquid lines. Only the evaporator and part of the compensation chamber are equipped with a wick structure. Inside loop heat pipe is working fluid. As a working fluid can be used distilled water, acetone, ammonia, methanol etc. Amount of filling is important for the operation and performance of LHP. This work deals with the design of loop heat pipe and impact of filling ratio of working fluid to remove waste heat from insulated gate bipolar transistor (IGBT.

  19. Integrated Temperature Sensors based on Heat Diffusion

    NARCIS (Netherlands)

    Van Vroonhoven, C.P.L.

    2015-01-01

    This thesis describes the theory, design and implementation of a new class of integrated temperature sensors, based on heat diffusion. In such sensors, temperature is sensed by measuring the time it takes for heat to diffuse through silicon. An on-chip thermal delay can be determined by geometry and

  20. Entransy and exergy analyses for optimizations of heat-work conversion with carnot cycle

    Science.gov (United States)

    Han, Chul Ho; Kim, Kyoung Hoon

    2016-06-01

    The concept of entransy has been newly proposed in terms of the analogy between heat and electrical conduction and could be useful in analyzing and optimizing the heat-work conversion systems. This work presents comparative analyses of entransy and exergy for optimizations of heat-work conversion. The work production and heat transfer processes in Carnot cycle system are investigated with the formulations of exergy destruction, entransy loss, work entransy, entransy dissipation, and efficiencies for both cases of dumping and non-dumping of used source fluid. The effects of source and condensation temperatures on the system performance are systematically investigated for optimal condition of producing maximum work or work entransy.

  1. Urban Heat Islands and Social Work: Opportunities for Intervention

    OpenAIRE

    Billy Hamilton; Christina L. Erickson

    2012-01-01

    The urban heat island (UHI), formed by surface modification of soil and vegetation, increases minimum nighttime temperatures within cities and causes heat-stress among dwellers. Children, elders and low-income persons are disproportionately burdened by the UHI. These populations often lack the necessary biological, economic and social resources to cope with or prevent heat stress. Because UHI’s are expected to increase with climate change, more social workers will be expected to serve the pop...

  2. Base fluid in improving heat transfer for EV car battery

    Science.gov (United States)

    Bin-Abdun, Nazih A.; Razlan, Zuradzman M.; Shahriman, A. B.; Wan, Khairunizam; Hazry, D.; Ahmed, S. Faiz; Adnan, Nazrul H.; Heng, R.; Kamarudin, H.; Zunaidi, I.

    2015-05-01

    This study examined the effects of base fluid (as coolants) channeling inside the heat exchanger in the process of the increase in thermal conductivity between EV car battery and the heat exchanger. The analysis showed that secondary cooling system by means of water has advantages in improving the heat transfer process and reducing the electric power loss on the form of thermal energy from batteries. This leads to the increase in the efficiency of the EV car battery, hence also positively reflecting the performance of the EV car. The present work, analysis is performed to assess the design and use of heat exchanger in increasing the performance efficiency of the EV car battery. This provides a preface to the use this design for nano-fluids which increase and improve from heat transfer.

  3. Is there a layer deep in the Earth that uncouples heat from mechanical work?

    Directory of Open Access Journals (Sweden)

    S. J. Burns

    2014-02-01

    Full Text Available The thermal expansion coefficient is presented as the coupling between heat energy and mechanical work. It is shown that when heat and work are uncoupled then very unusual material properties occurs: for example, acoustic p waves are not damped and heat is not generated from mechanical motion. It is found that at pressures defined by the bulk modulus divided by the Anderson–Grüneisen parameter, then the thermal expansion coefficient approaches zero in linear-elastic models. Very large pressures always reduce thermal expansion coefficients; the importance of a very small or even negative thermal expansion coefficient is discussed in relation to physical processes deep in the core and mantle of Earth. Models of the thermal expansion coefficients based on interatomic potentials which are always relegated to isometric conditions preclude any changes in volume due to temperature changes. However, it is known that the pressures in the Earth are large enough to effectively reduce thermal expansion coefficients to near zero which decouples heat from mechanical work.

  4. Utilization of the waste heat of a steel work

    Science.gov (United States)

    Kaier, U.; Breymayer, W.

    1982-08-01

    The use of waste heat of a Siemens-Martin furnace for the production of high pressure steam for a brewery and for a domestic heating network was evaluated. A review of the different possible uses of the high pressure steam, e.g., for heating, for electricity generating, or for cooling, and the actual cost of electricity and fuel and of the domestic heating cost of the already existing network, was made. Cost of the production of steam is calculated, and due to the possible breakdown or maintenance stopping of the Siemens-Martin furnace, cost of the equipment of the boiler with oil or gas burners was evaluated. It is proved that the economical justification for the use of this waste heat doesn't exist.

  5. Technical and economic working domains of industrial heat pumps: Part 1 - single stage vapour compression heat pumps

    OpenAIRE

    Ommen, Torben Schmidt; Jensen, Jonas Kjær; Markussen, Wiebke Brix; Reinholdt, Lars; Elmegaard, Brian

    2015-01-01

    A large amount of operational and economic constraints limit the applicability of heat pumps operated with natural working fluids. The limitations are highly dependent on the integration of heat source and sink streams. An evaluation of feasible operating conditions was carried out considering the constraints of available refrigeration equipment and a requirement of a positive net present value of the investment. Six heat pump systems were considered, corresponding to an upper limit of the si...

  6. Making Work: Demonstrating Thermodynamic Concepts with Solar-Powered Wax and Rubber Heat Engines

    Science.gov (United States)

    Appleyard, S. J.

    2007-01-01

    Construction details are provided for simple heat engines that use candle wax and elastomers as working substances. The engines are constructed using common household materials and can be easily constructed in a school classroom or at home. They work reliably and are useful tools for demonstrating the conversion of heat to mechanical work. They…

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

    Indian Academy of Sciences (India)

    Yuehong Bi; Lingen Chen; Fengrui Sun

    2010-03-01

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

  8. Demonstration testing and evaluation of in situ soil heating. Treatability study work plan, Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Sresty, G.C.

    1994-07-07

    A Treatability Study planned for the demonstration of the in situ electromagnetic (EM) heating process to remove organic solvents is described in this Work Plan. The treatability study will be conducted by heating subsurface vadose-zone soils in an organic plume adjacent to the Classified Burial Ground K-1070-D located at K-25 Site, Oak Ridge. The test is scheduled to start during the fourth quarter of FY94 and will be completed during the first quarter of FY95. The EM heating process for soil decontamination is based on volumetric heating technologies developed during the `70s for the recovery of fuels from shale and tar sands by IIT Research Institute (IITRI) under a co-operative program with the US Department of Energy (DOE). Additional modifications of the technology developed during the mid `80s are currently used for the production of heavy oil and waste treatment. Over the last nine years, a number of Government agencies (EPA, Army, AF, and DOE) and industries sponsored further development and testing of the in situ heating and soil decontamination process for the remediation of soils containing hazardous organic contaminants. In this process the soil is heated in situ using electrical energy. The contaminants are removed from the soil due to enhanced vaporization, steam distillation and stripping. IITRI will demonstrate the EM Process for in situ soil decontamination at K-25 Site under the proposed treatability study. Most of the contaminants of concern are volatile organics which can be removed by heating the soil to a temperature range of 85 to 95 C. The efficiency of the treatment will be determined by comparing the concentration of contaminants in soil samples. Samples will be obtained before and after the demonstration for a measurement of the concentration of contaminants of concern.

  9. Implementing Evidence-Based Social Work Practice

    Science.gov (United States)

    Mullen, Edward J.; Bledsoe, Sarah E.; Bellamy, Jennifer L.

    2008-01-01

    Recently, social work has been influenced by new forms of practice that hold promise for bringing practice and research together to strengthen the scientific knowledge base supporting social work intervention. The most recent new practice framework is evidence-based practice. However, although evidence-based practice has many qualities that might…

  10. Real-Time Personalized Monitoring to Estimate Occupational Heat Stress in Ambient Assisted Working

    Directory of Open Access Journals (Sweden)

    Pablo Pancardo

    2015-07-01

    Full Text Available Ambient Assisted Working (AAW is a discipline aiming to provide comfort and safety in the workplace through customization and technology. Workers’ comfort may be compromised in many labor situations, including those depending on environmental conditions, like extremely hot weather conduces to heat stress. Occupational heat stress (OHS happens when a worker is in an uninterrupted physical activity and in a hot environment. OHS can produce strain on the body, which leads to discomfort and eventually to heat illness and even death. Related ISO standards contain methods to estimate OHS and to ensure the safety and health of workers, but they are subjective, impersonal, performed a posteriori and even invasive. This paper focuses on the design and development of real-time personalized monitoring for a more effective and objective estimation of OHS, taking into account the individual user profile, fusing data from environmental and unobtrusive body sensors. Formulas employed in this work were taken from different domains and joined in the method that we propose. It is based on calculations that enable continuous surveillance of physical activity performance in a comfortable and healthy manner. In this proposal, we found that OHS can be estimated by satisfying the following criteria: objective, personalized, in situ, in real time, just in time and in an unobtrusive way. This enables timely notice for workers to make decisions based on objective information to control OHS.

  11. Working cycles of devices based on bistable carbon nanotubes

    Science.gov (United States)

    Shklyaev, Oleg; Mockensturm, Eric; Crespi, Vincent; Carbon Nanotubes Collaboration

    2013-03-01

    Shape-changing nanotubes are an example of variable-shape sp2 carbon-based systems where the competition between strain and surface energies can be moderated by an externally controllable stimuli such as applied voltage, temperature, or pressure of gas encapsulated inside the tube. Using any of these stimuli one can transition a bistable carbon nanotube between the collapsed and inflated states and thus perform mechanical work. During the working cycle of such a device, energy from an electric or heat source is transferred to mechanical energy. Combinations of these stimuli allow the system to convert energy between different sources using the bistable shape-changing tube as a mediator. For example, coupling a bistable carbon nanotube to the heat and charge reservoirs can enable energy transfer between heat and electric forms. The developed theory can be extended to other nano-systems which change configurations in response to external stimuli.

  12. Life Cycle Assessment of Electricity Generation from Low Temperature Waste Heat : The Influence of Working Fluid

    OpenAIRE

    Bai, Lijun

    2012-01-01

    In the metallurgical industry and in refineries and process industries, there is significant amount of waste heat, it is a challenged field to do the research for producing electricity from the energy of waste heat. Traditionallay, Organic Rankine Cycle(ORC)is used for generating electricity from low temperature heat source. Recently researchers are focusing on the supercritical Rankine cycle which uses CO2 as working fluid for which is more environmental friendly working fluid, possilbe redu...

  13. Thermodynamic properties of lithium chloride ammonia complexes under heat pump type II working conditions

    Energy Technology Data Exchange (ETDEWEB)

    Van der Pal, M.; Veldhuis, J.B.J. [ECN Efficiency and Infrastructure, Petten (Netherlands)

    2010-12-15

    Heat pumps type II can be used for upgrading industrial waste heat to above pinch temperatures, with a typical lift from 130C to 180C. At ECN such a heat pump is developed based on the reaction of ammonia with lithium chloride and magnesium chloride as respectively the low and high temperature salt. The thermodynamic properties of these salts are required to determine temperature lift and coefficient of performance. This paper presents the behavior of the low temperature salt, lithium chloride, under typical working conditions with temperatures ranging from ambient temperature to 150C and ammonia pressures ranging from 0.3 to 30 bars. Measurements using an HPDSC, an autoclave and a custom-made ammonia pressure cell have been conducted to determine the pressure-temperature lines and their corresponding enthalpy and entropy values for lithium chloride ammonia complexes. The results show a direct transformation of lithium chloride mono-ammonia to lithium chloride tri-ammonia complex for ammonia pressures up to 4 bars and temperatures up to 90C. At higher temperatures and pressures a stable, intermediate ammonia complex, lithium chloride di-ammonia complex, is formed. Under these conditions also a liquid phase has been observed. The latter can greatly affect the heat pump performance, both positive (no lattice degradation) as negative (escape from matrix, form impenetrable film)

  14. Entransy and Exergy Analyses for Optimizations of Heat-Work Conversion with Carnot Cycle

    Institute of Scientific and Technical Information of China (English)

    Chul Ho Han; Kyoung Hoon Kim

    2016-01-01

    The concept of entransy has been newly proposed in terms of the analogy between heat and electrical conduction and could be useful in analyzing and optimizing the heat-work conversion systems.This work presents comparative analyses of entransy and exergy for optimizations of heat-work conversion.The work production and heat transfer processes in Carnot cycle system are investigated with the formulations of exergy destruction,entransy loss,work entransy,entransy dissipation,and efficiencies for both cases of dumping and non-dumping of used source fluid.The effects of source and condensation temperatures on the system performance are systematically investigated for optimal condition of producing maximum work or work entransy.

  15. Technical and economic working domains of industrial heat pumps: Part 1 - single stage vapour compression heat pumps

    DEFF Research Database (Denmark)

    Ommen, Torben Schmidt; Jensen, Jonas Kjær; Markussen, Wiebke Brix;

    2015-01-01

    A large amount of operational and economic constraints limit the applicability of heat pumps operated with natural working fluids. The limitations are highly dependent on the integration of heat source and sink streams. An evaluation of feasible operating conditions was carried out considering...... the constraints of available refrigeration equipment and a requirement of a positive net present value of the investment. Six heat pump systems were considered, corresponding to an upper limit of the sink temperature of 120 °C. For each set of heat sink and source temperatures the best available technology...... was determined. The results showed that four different heat pump systems propose the best available technology at different parts of the complete domain. Ammonia systems presented the best available technology at low sink outlet temperature. At high temperature difference between sink in- and outlet...

  16. Ventilation Heat Recovery from Wood-Burning Domestic Flues. A Theoretical Analysis Based on a Triple Concentric Tube Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Lionel Druette

    2013-01-01

    Full Text Available This paper presents a new air-heating system concept for energy-efficient dwellings. It is a system designed to heat a low-energy building by coupling a heat-recovery ventilation system with a three-fluid heat exchanger located on the chimney of a wood-pellet stove. The proposed work focuses on the heat transfer that occurs between flue gases, the ventilation air and the combustion air within a triple concentric tube heat exchanger with no insulation at its outer surface. The main objective is to predict outlet temperature for the specific geometry of the heat exchanger studied here. Thus, the governing differential equations are derived for a counter-co-current flow arrangement of the three fluids. Then analytical solutions for the steady-state temperature distribution are obtained as well as the amount of heat transferred to the outside. An expression for the effectiveness of the heat exchanger is also proposed. Based on these results, calculations are performed on a case study to predict the fluid temperature distribution along the heat exchanger. Finally, a parametric study is carried out on this case study to assess the influence of the relevant parameters on the effectiveness of the heat exchanger. In addition, computation of heat losses to the outside justifies whether insulation is needed.

  17. Working in Australia's heat: health promotion concerns for health and productivity.

    Science.gov (United States)

    Singh, Sudhvir; Hanna, Elizabeth G; Kjellstrom, Tord

    2015-06-01

    This exploratory study describes the experiences arising from exposure to extreme summer heat, and the related health protection and promotion issues for working people in Australia. Twenty key informants representing different industry types and occupational groups or activities in Australia provided semi-structured interviews concerning: (i) perceptions of workplace heat exposure in the industry they represented, (ii) reported impacts on health and productivity, as well as (iii) actions taken to reduce exposure or effects of environmental heat exposure. All interviewees reported that excessive heat exposure presents a significant challenge for their industry or activity. People working in physically demanding jobs in temperatures>35°C frequently develop symptoms, and working beyond heat tolerance is common. To avoid potentially dangerous health impacts they must either slow down or change their work habits. Such health-preserving actions result in lost work capacity. Approximately one-third of baseline work productivity can be lost in physically demanding jobs when working at 40°C. Employers and workers consider that heat exposure is a 'natural hazard' in Australia that cannot easily be avoided and so must be accommodated or managed. Among participants in this study, the locus of responsibility for coping with heat lay with the individual, rather than the employer. Heat exposure during Australian summers commonly results in adverse health effects and productivity losses, although quantification studies are lacking. Lack of understanding of the hazardous nature of heat exposure exacerbates the serious risk of heat stress, as entrenched attitudinal barriers hamper amelioration or effective management of this increasing occupational health threat. Educational programmes and workplace heat guidelines are required. Without intervention, climate change in hot countries, such as Australia, can be expected to further exacerbate heat-related burden of disease and loss

  18. A helium based pulsating heat pipe for superconducting magnets

    Science.gov (United States)

    Fonseca, Luis Diego; Miller, Franklin; Pfotenhauer, John

    2014-01-01

    This study was inspired to investigate an alternative cooling system using a helium-based pulsating heat pipes (PHP), for low temperature superconducting magnets. In addition, the same approach can be used for exploring other low temperature applications. The advantages of PHP for transferring heat and smoothing temperature profiles in various room temperature applications have been explored for the past 20 years. An experimental apparatus has been designed, fabricated and operated and is primarily composed of an evaporator and a condenser; in which both are thermally connected by a closed loop capillary tubing. The main goal is to measure the heat transfer properties of this device using helium as the working fluid. The evaporator end of the PHP is comprised of a copper winding in which heat loads up to 10 watts are generated, while the condenser is isothermal and can reach 4.2 K via a two stage Sumitomo RDK408A2 GM cryocooler. Various experimental design features are highlighted. Additionally, performance results in the form of heat transfer and temperature characteristics are provided as a function of average condenser temperature, PHP fill ratio, and evaporator heat load. Results are summarized in the form of a dimensionless correlation and compared to room temperature systems. Implications for superconducting magnet stability are highlighted.

  19. Determination Of Heat Load By Wet Bulb Globe Temperature In Working Environment

    Science.gov (United States)

    Králiková, Ružena; Maďoranová, Marieta

    2015-07-01

    Thermal load on people in general depends on the heat production in the human organism as a result of physical activity as well as environmental conditions which are affected by transfer of heat between human and the surrounding area. The resulting effect of metabolic exchanges which occur in work activities is the thermal load of organism. The paper deals with the evaluation of microclimatic conditions of the working environment of workers, who are exposed to the hot environment during their work.

  20. Investigation on incomplete condensation of non-azeotropic working fluids in high temperature heat pumps

    International Nuclear Information System (INIS)

    In order to improve high temperature heat pumps (HTHP), firstly, after theoretical analysis is conducted about the heat transfer of non-azeotropic working fluids in the condenser, the possibility of incomplete condensation of non-azeotropic working fluids in the condenser of a HTHP is presented. Secondly, an experimental plan is designed to study the phenomenon, and many working conditions experiments (flow rate, temperature and frequency are changed) are done on a water-to-water heat pump unit. Finally, the incomplete condensation is found, and some relationships are presented between the phenomenon and the parameters, which are helpful to improve the control strategy of the HTHP

  1. Performance of a quantum heat engine cycle working with harmonic oscillator systems

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    A cycle model of an irreversible heat engine working with harmonic systems is established in this paper. Based on the equation of motion of an operator in the Heisenberg picture and semi-group approach, the first law of thermodynamics for a harmonic system and the time evolution of the system are obtained. The general expressions for several important parameters, such as the work, efficiency, power output, and rate of entropy production are derived. By means of numerical analysis, the optimally operating regions and the optimal values of performance parameters of the cycle are determined under the condition of maximum power output. At last, some special cases, such as high temperature limit and frictionless case, are dis-cussed in brief.

  2. Performance of a quantum heat engine cycle working with harmonic oscillator systems

    Institute of Scientific and Technical Information of China (English)

    WANG JianHui; HE JiZhou; MAO ZhiYuan

    2007-01-01

    A cycle model of an irreversible heat engine working with harmonic systems is established in this paper. Based on the equation of motion of an operator in the Heisenberg picture and semi-group approach, the first law of thermodynamics for a harmonic system and the time evolution of the system are obtained. The general expressions for several important parameters, such as the work, efficiency, power output, and rate of entropy production are derived. By means of numerical analysis, the optimally operating regions and the optimal values of performance parameters of the cycle are determined under the condition of maximum power output. At last, some special cases, such as high temperature limit and frictionless case, are discussed in brief.

  3. Effect of working fluids on thermal performance of closed loop pulsating heat pipe

    Science.gov (United States)

    Kolková, Zuzana; Malcho, Milan

    2014-08-01

    Improving the performance of electrical components needs higher heat removal from these systems. One of the solutions available is to use a sealed heat pipe with a throbbing filling, where development meets the current requirements for intensification of heat removal and elimination of moving parts cooling systems. Heat pipes operate using phase change working fluid, and it is evaporation and condensation. They have a meandering shape and are characterized by high intensity of heat transfer, high durability and reliability. Advantage of these tubes is that it is not necessary to create the internal capillary structure for transporting liquid and they need any pump to the working fluid circulation. They have a simple structure, low cost, high performance, and they can be used for various structural applications. The choice of working fluid volume and performance affects thermal performance. Distilled water, ethanol and acetone were used in the performance ranges 0-80%.

  4. Effect of working fluids and internal diameters on thermal performance of vertical and horizontal closed-loop pulsating heat pipes with multiple heat sources

    OpenAIRE

    Kammuang-Lue Niti; Sakulchangsatjatai Phrut; Terdtoon Pradit

    2016-01-01

    Some electrical applications have a number of heat sources. The closed-loop pulsating heat pipe (CLPHP) is applied to transfer heat from these devices. Since the CLPHP primarily transfers heat by means of the working fluid’s phase change in a capillary tube, the thermal performance of the CLPHP significantly depends on the working fluid type and the tube’s internal diameter. In order to provide the fundamental information for manufacturers of heat exchanger...

  5. Evidence-Based Clearinghouses in Social Work

    Science.gov (United States)

    Soydan, Haluk; Mullen, Edward J.; Alexandra, Laine; Rehnman, Jenny; Li, You-Ping

    2010-01-01

    Objectives: The purpose of this article is to describe several evidence-based clearinghouses focused on social work and related intervention outcomes, placing them in the context of how such clearinghouses can contribute to research dissemination to foster effective, evidence-based practice. Method: The study employed an analysis of data provided…

  6. Binary blend of carbon dioxide and fluoro ethane as working fluid in transcritical heat pump systems

    Directory of Open Access Journals (Sweden)

    Zhang Xian-Ping

    2015-01-01

    Full Text Available As an eco-friendly working fluid, carbon dioxide or R744 is expected to substitute for the existing working fluids used in heat pump systems. It is, however, challenged by the much higher heat rejection pressure in transcritical cycle compared with the traditional subcritical cycle using freons. There exists a worldwide tendency to utilize blend refrigerants as alternatives. Therefore, a new binary blend R744/R161 in this research is proposed in order to decrease the heat rejection pressure. Meanwhile, on mixing R744 with R161, the flammability and explosivity of R161 can be suppressed because of the extinguishing effect of R744. A transcritical thermodynamic model is developed, and then the system performances of heat pump using R744/R161 blend are investigated and compared with those of pure R744 system under the same operation conditions. The variations of heat rejection pressure, heating coefficient of performance, unit volumetric heating capacity, discharge temperature of compressor and the mass fraction of R744/R161 are researched. The results show that R744/R161 mixture can reduce the heat rejection pressure of transcritical heat pump system.

  7. Open system trajectories specify fluctuating work but not heat

    Science.gov (United States)

    Talkner, Peter; Hänggi, Peter

    2016-08-01

    Based on the explicit knowledge of a Hamiltonian of mean force, the classical statistical mechanics and equilibrium thermodynamics of open systems in contact with a thermal environment at arbitrary interaction strength can be formulated. Yet, even though the Hamiltonian of mean force uniquely determines the equilibrium phase space probability density of a strongly coupled open system, the knowledge of this probability density alone is insufficient to determine the Hamiltonian of mean force, needed in constructing the underlying statistical mechanics and thermodynamics. We demonstrate that under the assumption that the Hamiltonian of mean force is known, an extension of thermodynamic structures from the level of averaged quantities to fluctuating objects (i.e., a stochastic thermodynamics) is possible. However, such a construction undesirably also involves a vast ambiguity. This situation is rooted in the eminent lack of a physical guiding principle allowing us to distinguish a physically meaningful theory out of a multitude of other equally conceivable ones.

  8. MHD natural convection flow along a vertical wavy surface with heat generation and pressure work

    Science.gov (United States)

    Alim, M. A.; Kabir, K. H.; Andallah, L. S.

    2016-07-01

    In this paper, the influence of pressure work on MHD natural convection flow of viscous incompressible fluid along a uniformly heated vertical wavy surface with heat generation has been investigated. The governing boundary layer equations are first transformed into a non-dimensional form using suitable set of dimensionless variables. The resulting nonlinear system of partial differential equations are mapped into the domain of a vertical flat plate and then solved numerically employing the implicit finite difference method, known as Keller-box scheme. The numerical results for the velocity profiles, temperature profiles, skin friction coefficient, the rate of heat transfers, the streamlines and the isotherms are shown graphically and skin friction coefficient and rate of heat transfer have been shown in tabular form for different values of the selective set of parameters consisting of pressure work parameter Ge, the magnetic parameter M, Prandtl number Pr, heat generation parameter Q and the amplitude of the wavy surface.

  9. Atmospheric dynamics. Constrained work output of the moist atmospheric heat engine in a warming climate.

    Science.gov (United States)

    Laliberté, F; Zika, J; Mudryk, L; Kushner, P J; Kjellsson, J; Döös, K

    2015-01-30

    Incoming and outgoing solar radiation couple with heat exchange at Earth's surface to drive weather patterns that redistribute heat and moisture around the globe, creating an atmospheric heat engine. Here, we investigate the engine's work output using thermodynamic diagrams computed from reanalyzed observations and from a climate model simulation with anthropogenic forcing. We show that the work output is always less than that of an equivalent Carnot cycle and that it is constrained by the power necessary to maintain the hydrological cycle. In the climate simulation, the hydrological cycle increases more rapidly than the equivalent Carnot cycle. We conclude that the intensification of the hydrological cycle in warmer climates might limit the heat engine's ability to generate work.

  10. Municipal water-based heat pump heating and/or cooling systems: Findings and recommendations. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Bloomquist, R.G. [Washington, State Univ., Pullman, WA (United States); Wegman, S. [South Dakota Utilities Commission (United States)

    1998-04-01

    The purpose of the present work was to determine if existing heat pump systems based on municipal water systems meet existing water quality standards, to analyze water that has passed through a heat pump or heat exchanger to determine if corrosion products can be detected, to determine residual chlorine levels in municipal waters on the inlet as well as the outlet side of such installations, to analyses for bacterial contaminants and/or regrowth due to the presence of a heat pump or heat exchanger, to develop and suggest criteria for system design and construction, to provide recommendations and specifications for material and fluid selection, and to develop model rules and regulations for the installation, operation, and monitoring of new and existing systems. In addition, the Washington State University (WSU) has evaluated availability of computer models that would allow for water system mapping, water quality modeling and system operation.

  11. Performance Study of Solar Heat Pipe with Different Working Fluids and Fill Ratios

    Science.gov (United States)

    Harikrishnan, S. S.; Kotebavi, Vinod

    2016-09-01

    This paper elaborates on the testing of solar heat pipes using different working fluids, fill ratios and tilt angles. Methanol, Acetone and water are used as working fluids, with fill ratios 25%, 50%, 75% and 100%. Experiments were carried out at 600 and 350 inclinations. Heat pipe condenser section is placed inside a water basin containing 200ml of water. The evaporator section is exposed to sunlight where the working fluid gets heated and it becomes vapour and moves towards the condenser section. In the condenser section the heat is given to the water in the basin and the vapour becomes liquid and comes back to the evaporator section due to gravitational force. Two modes of experiments are carried out: 1) using a parabolic collector and 2) using heat pipe with evacuated tubes. On comparative study, optimum fill ratio is been found to be 25% in every case and acetone exhibited slightly more efficiency than methanol and water. As far as the heat pipe orientation is concerned, 600 inclination of the heat pipe showed better performance than 350

  12. Working fluids of a low-temperature geothermally-powered Rankine cycle for combined power and heat generation system

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel combined power and heat generation system was investigated in this study. This system consists of a low-temperature geothermally-powered organic Rankine cycle (ORC) subsystem, an intermediate heat exchanger and a commercial R134a-based heat pump subsystem. The advantages of the novel combined power and heat generation system are free of using additional cooling water circling system for the power generation subsystem as well as maximizing the use of thermal energy in the low-temperature geothermal source. The main purpose is to identify suitable working fluids (wet, isentropic and dry flu-ids) which may yield high PPR (the ratio of power produced by the power generation subsystem to power consumed by the heat pump subsystem) value and QQR (the ratio of heat supplied to the user to heat produced by the geothermal source) value. Parameters under investigation were evaporating temperature, PPR value and QQR value. Results indicate that there exits an optimum evaporating temperature to maximize the PPR value and minimize the QQR value at the same time for individual fluid. And dry fluids show higher PPR values but lower QQR values. NH3 and R152a outstand among wet fluids. R134a out-stands among isentropic fluids. R236ea, R245ca, R245fa, R600 and R600a outstand among dry fluids. R236ea shows the highest PPR value among the recommended fluids.

  13. Personalized recommendation based on heat bidirectional transfer

    Science.gov (United States)

    Ma, Wenping; Feng, Xiang; Wang, Shanfeng; Gong, Maoguo

    2016-02-01

    Personalized recommendation has become an increasing popular research topic, which aims to find future likes and interests based on users' past preferences. Traditional recommendation algorithms pay more attention to forecast accuracy by calculating first-order relevance, while ignore the importance of diversity and novelty that provide comfortable experiences for customers. There are some levels of contradictions between these three metrics, so an algorithm based on bidirectional transfer is proposed in this paper to solve this dilemma. In this paper, we agree that an object that is associated with history records or has been purchased by similar users should be introduced to the specified user and recommendation approach based on heat bidirectional transfer is proposed. Compared with the state-of-the-art approaches based on bipartite network, experiments on two benchmark data sets, Movielens and Netflix, demonstrate that our algorithm has better performance on accuracy, diversity and novelty. Moreover, this method does better in exploiting long-tail commodities and cold-start problem.

  14. Work-Based Learning Symposium Proceedings 2009

    OpenAIRE

    Sheridan, Irene; Linehan, Margaret

    2009-01-01

    Prof. Michael Ward Head, Department of Food Business and Development, University College Cork I am honoured to have been invited to chair this morning’s session. My day job is here in UCC where I’m the Professor and Head of the Department of Food Business and Development and the Director of the Centre for Cooperative Studies. I’ve a particular interest in this work-based learning symposium because I, with my colleagues in both the department and the centre, have been involved in Work...

  15. Performance analysis of an organic Rankine cycle with internal heat exchanger having zeotropic working fluid

    Directory of Open Access Journals (Sweden)

    Thoranis Deethayat

    2015-09-01

    Full Text Available In this study, performance of a 50 kW organic Rankine cycle (ORC with internal heat exchanger (IHE having R245fa/R152a zeotropic refrigerant with various compositions was investigated. The IHE could reduce heat rate at the ORC evaporator and better cycle efficiency could be obtained. The zeotropic mixture could reduce the irreversibilities during the heat exchanges at the ORC evaporator and the ORC condenser due to its gliding temperature; thus the cycle working temperatures came closer to the temperatures of the heat source and the heat sink. In this paper, effects of evaporating temperature, mass fraction of R152a and effectiveness of internal heat exchanger on the ORC performances for the first law and the second law of thermodynamics were considered. The simulated results showed that reduction of R245fa composition could reduce the irreversibilities at the evaporator and the condenser. The suitable composition of R245fa was around 80% mass fraction and below this the irreversibilities were nearly steady. Higher evaporating temperature and higher internal heat exchanger effectiveness also increased the first law and second law efficiencies. A set of correlations to estimate the first and the second law efficiencies with the mass fraction of R245fa, the internal heat exchanger effectiveness and the evaporating temperature were also developed.

  16. EFFECT OF WORKING FLUID AND FILLING RATIO ON PERFORMANCE OF A CLOSED LOOP PULSATING HEAT PIPE

    Directory of Open Access Journals (Sweden)

    E. R. BABU

    2016-06-01

    Full Text Available This paper presents preliminary experimental results on thermal performance of a closed loop pulsating heat pipe (CLPHP using copper tube having internal and external diameter with 2 mm and 3 mm respectively. For the experimentation, filling ratio (FR was varied from 30 % to 70% with 10% increments, four turns and different heat inputs of 10 to 22 W(Watts is supplied to PHP’s. The position of the PHP’s was vertical bottom heat mode. The length of evaporator, adiabatic and condenser section was maintained 55, 80, and 50 mm respectively. The working fluids are selected as Acetone, Methanol, Ethanol, CCL4 (Carbon Tetrachloride, and Benzene. In this study, characteristics of the thermal resistance and average evaporator temperatures at different heat input for various working fluids have been determined. The result shows that, the thermal resistance decreases rapidly with the increase of the heating input from 10 to 22 W. Further, slowly was extended on different working fluids as mentioned. From the experimental results, Acetone was found to be better working fluid as compared to other fluids.

  17. GIS based analysis of future district heating potential in Denmark

    DEFF Research Database (Denmark)

    Nielsen, Steffen; Möller, Bernd

    2013-01-01

    in Denmark have been mapped in a heat atlas which includes all buildings and their heat demands. This article focuses on developing a method for assessing the costs associated with supplying these buildings with DH. The analysis is based on the existing DH areas in Denmark. By finding the heat production...

  18. Analysis and assessment of a new organic Rankine based heat engine system with/without cogeneration

    International Nuclear Information System (INIS)

    A low-temperature heat driven heat engine is proposed as a cost-effective system for power and heat production for small scale applications. The external heat source allows flexibility in the design; the system may be coupled with various available renewable sources including biomass/biofuel/biogas combustion, geothermal heat, concentrated solar radiation, and industrial waste heat, by selecting appropriate off-the-shelf components from the HVAC (heating, ventilation, and air conditioning), refrigeration, and automotive industries for use in an ORC (organic Rankine cycle). A theoretical analysis and an experimental study are carried out for an ORC with R134a as the working fluid, utilizing a low-temperature heat source (Tsource < 150 °C), with focus on the expansion and boiling processes. The complete ORC model is comprised of models for the expander, working fluid pump, boiler, and condenser. Thermodynamic and heat transfer models are developed to calculate the local and averaged heat transfer coefficient of the working fluid throughout the boiling process, based on the geometry of the selected heat exchanger. Data collected for the experimental ORC test bench are used to validate the expander and boiler models. A case study is performed for the proposed ORC, for cogeneration of power and heat in a residential application. The results of the case study analysis for the proposed ORC system indicate a cycle efficiency of 0.05, exergy efficiency of 0.17, and energy and exergy cogeneration efficiency of 0.87, and 0.35, respectively. - Highlights: • Development and investigation of a scroll based Rankine heat engine operating with R134a. • Thermodynamic analyses of the system and its components. • Heat transfer analyses of boiler and condenser. • Dynamic analysis of expander. • Model validation through performed experiments on an ORC test bench

  19. COMBINED EFFECTS OF HEAT STRESS AND SHIFT WORK ON PHYSIOLOGICAL PARAMETERS IN FOUNDRY WORKERS

    Directory of Open Access Journals (Sweden)

    P.Nassiri

    1990-08-01

    Full Text Available In order to investigate the combined effects of shift work and heat stress on the physiological parameters, such as heart rate (HR and body temperature (BT, a hot-dry working environment was investigated for 53 workers in foundry workshops. In this study Wet Bulb Globe Temperature index (WBGT was measured and along with that simultaneously heart rate and oral temperature were checked in 3 shifts. The results indicated that the physiological responses of workers changed whenever the shift changed and the responses were increased by a corresponding increase in heat stress, index.

  20. Worked problems in heat, thermodynamics and kinetic theory for physics students

    CERN Document Server

    Pincherle, L; Green, L L

    2013-01-01

    Worked Problems in Heat, Thermodynamics and Kinetic Theory for Physics Students is a complementary to textbooks in physics. This book is a collection of exercise problems that have been part of tutorial classes in heat and thermodynamics at the University of London. This collection of exercise problems, with answers that are fully worked out, deals with various topics. This book poses problems covering the definition of temperature such as calculating the assigned value of the temperature of boiling water under specific conditions. This text also gives example of problems dealing with the fir

  1. Ablation Properties of the Carbon-Based Composites Used in Artificial Heat Source Under Fire Accident

    Institute of Scientific and Technical Information of China (English)

    TANG; Xian; HUANG; Jin-ming; ZHOU; Shao-jian; LUO; Zhi-fu

    2012-01-01

    <正>The ablation properties of the carbon-based composites used in artificial heat source under fire accident were investigated by the arc heater. In this work, we tested the carbon-based composites referring to Fig. 1. Their linear/mass ablation ratio and ablation morphologies were studied. The results showed that the carbon-based composites used in artificial heat source behaved well

  2. Physiological characteristics under the influence of heat stress working in the hot environment, (4)

    International Nuclear Information System (INIS)

    There is a possibility that physical and mental stress appears under hot environmental condition for the cause of wearing protection suits on reactor maintenance work. It is important to reduce heat stress rapidly and effectively. This paper mentioned following about the results of static state and simulation work done by testees with or without protection suits under 25 kinds of temperatures and wind velocities in a artificial climate chamber. (1) the correlation between ambient temperatures or wind velocities and subjective symptoms without protection suits. (2) the correlation between ambient temperatures or wind velocities and skin temperatures without protection suits. (3) investigation of the parts of body affecting subjective symptoms. (4) the correlation between ambient temperatures or wind velocities and skin temperatures at working with protection suits. (5) working out countermeasures of recovery from heat stress with the index of skin temperatures and subjective symptoms. (author)

  3. Acclimation to moderate heat adequately prepares individuals for work in a hotter environment

    NARCIS (Netherlands)

    Jonkman, A.G.; Linnane, D.M.; Weller, A.S.; Daanen, H.A.M.

    2007-01-01

    This work was funded by the Human Sciences Domain of the UK Ministry of Defence Scientific Research Programme. Optimising the preparation of individuals to perform exercise in a hot environment is typically achieved by implementing a programme of heat acclimation (HA). It is well-established that HA

  4. Enhanced technical and economic working domains of industrial heat pumps operated in series

    DEFF Research Database (Denmark)

    Ommen, Torben; Jensen, Jonas Kjær; Markussen, Wiebke Brix;

    2015-01-01

    By operating heat pumps (HPs) in series, it is possible to obtain closer match between working fluid and sink- and source streams, resulting in higher coefficient of performance (COP). For industrial HPs, it was found that serial connection of either two or three units results in an increase in COP...

  5. Development of new heat pump cloth drum dryer with CO2 as working fluid

    OpenAIRE

    Elnan, Åsmund

    2011-01-01

    Since early the early 20th century the electrical tumble dryer became an appliance to dry clothes. During many years of improvements different configurations to solve issues on decreased drying time and more energy efficient solutions has been performed. Several different configurations have been developed; air vented dryers, condensing dryers and the most recent heat pump dryers. The heat pumps in drying technology became the next solution based on improved drying time and decreased energy c...

  6. A new heating system based on coupled air source absorption heat pump for cold regions: Energy saving analysis

    International Nuclear Information System (INIS)

    Highlights: • A double-stage coupled air source absorption heat pump (ASAHP) is proposed. • The coupled ASAHP exhibits stable and high performance in very cold regions. • Energy-saving rate of the coupled ASAHP in all the typical cities is above 20%. - Abstract: Energy consumption for heating and domestic hot water is very high. The heating system based on an air source absorption heat pump (ASAHP) had been assessed to have great energy saving potential. However, the single-stage ASAHP exhibits poor performance when the outdoor air temperature is very low. A double-stage coupled ASAHP is proposed to improve the energy-saving potential of single-stage ASAHP in cold regions. The heating capacity and primary energy efficiency (PEE) of the proposed system operated in both coupled mode and single-stage mode are simulated under various working conditions. The building load and primary energy consumption of different heating systems applied in cold regions are analyzed comparatively to investigate the energy-saving potential of the coupled ASAHP. Results show that the coupled ASAHP exhibits stable PEE and provides high heating capacity in very cold conditions. The energy-saving rate of the coupled ASAHP in all the typical cities is above 20%. In addition, the energy-saving potential of the single-stage ASAHP in severely cold areas can be improved obviously by coupled ASAHP, with an improvement of 7.73% in Harbin

  7. Analysis of the location for peak heating in CHP based combined district heating systems

    International Nuclear Information System (INIS)

    Combined heat and power (CHP) is the main technology for providing the base load of district heating in China. However, CHP is not efficient for providing the peak load; instead, a peak boiler with high efficiency could be used to compensate the peak load. This paper studies how the location of the peak boiler can affect the energy efficiency and economic performance of such CHP based combined district heating system. Firstly, the connection mode and the control strategy for different peak heating locations are analyzed. Then the effect of the peak boiler's location on the initial investment of the network and the cost for distributing heat is studied. The objective is to place the peak boiler in a location where the overall costs are the smallest. Following this rule, the results indicate that the peak boiler should be located at the CHP plant if that allows using cheaper ‘self-use electricity’ in CHP for distributing the heat. However, if the market electricity price is used everywhere, or if energy efficiency is more emphasized, the location of the peak boiler should be closer to the users with dense heat loads. - Highlights: • Location for peak heating in the CHP based combined DH system is studied. • Regulation or control strategies for combined DH are summarized. • The heat load duration curve for combined DH is demonstrated. • Network design for combined DH with peak boiler outside of the CHP is analyzed

  8. Optimal design of the heat pipe using TLBO (teaching–learning-based optimization) algorithm

    International Nuclear Information System (INIS)

    Heat pipe is a highly efficient and reliable heat transfer component. It is a closed container designed to transfer a large amount of heat in system. Since the heat pipe operates on a closed two-phase cycle, the heat transfer capacity is greater than for solid conductors. Also, the thermal response time is less than with solid conductors. The three major elemental parts of the rotating heat pipe are: a cylindrical evaporator, a truncated cone condenser, and a fixed amount of working fluid. In this paper, a recently proposed new stochastic advanced optimization algorithm called TLBO (Teaching–Learning-Based Optimization) algorithm is used for single objective as well as multi-objective design optimization of heat pipe. It is easy to implement, does not make use of derivatives and it can be applied to unconstrained or constrained problems. Two examples of heat pipe are presented in this paper. The results of application of TLBO algorithm for the design optimization of heat pipe are compared with the NPGA (Niched Pareto Genetic Algorithm), GEM (Grenade Explosion Method) and GEO (Generalized External optimization). It is found that the TLBO algorithm has produced better results as compared to those obtained by using NPGA, GEM and GEO algorithms. - Highlights: • The TLBO (Teaching–Learning-Based Optimization) algorithm is used for the design and optimization of a heat pipe. • Two examples of heat pipe design and optimization are presented. • The TLBO algorithm is proved better than the other optimization algorithms in terms of results and the convergence

  9. CO2-based mixtures as working fluids for geothermal turbines.

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Steven Alan; Conboy, Thomas M.; Ames, David E.

    2012-01-01

    Sandia National Laboratories is investigating advanced Brayton cycles using supercritical working fluids for application to a variety of heat sources, including geothermal, solar, fossil, and nuclear power. This work is centered on the supercritical CO{sub 2} (S-CO{sub 2}) power conversion cycle, which has the potential for high efficiency in the temperature range of interest for these heat sources and is very compact-a feature likely to reduce capital costs. One promising approach is the use of CO{sub 2}-based supercritical fluid mixtures. The introduction of additives to CO{sub 2} alters the equation of state and the critical point of the resultant mixture. A series of tests was carried out using Sandia's supercritical fluid compression loop that confirmed the ability of different additives to increase or lower the critical point of CO{sub 2}. Testing also demonstrated that, above the modified critical point, these mixtures can be compressed in a turbocompressor as a single-phase homogenous mixture. Comparisons of experimental data to the National Institute of Standards and Technology (NIST) Reference Fluid Thermodynamic and Transport Properties (REFPROP) Standard Reference Database predictions varied depending on the fluid. Although the pressure, density, and temperature (p, {rho}, T) data for all tested fluids matched fairly well to REFPROP in most regions, the critical temperature was often inaccurate. In these cases, outside literature was found to provide further insight and to qualitatively confirm the validity of experimental findings for the present investigation.

  10. Maximum power output of a class of irreversible non-regeneration heat engines with a non-uniform working fluid and linear phenomenological heat transfer law

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Maximum power output of a class of irreversible non-regeneration heat engines with non-uniform working fluid,in which heat transfers between the working fluid and the heat reservoirs obey the linear phenomenological heat transfer law [q ∝Δ(T-1)],are studied in this paper. Optimal control theory is used to determine the upper bounds of power of the heat engine for the lumped-parameter model and the distributed-parameter model,respectively. The results show that the maximum power output of the heat engine in the distributed-parameter model is less than or equal to that in the lumped-parameter model,which could provide more realistic guidelines for real heat engines. Analytical solutions of the maximum power output are obtained for the irreversible heat engines working between constant temperature reservoirs. For the irreversible heat engine operating between variable temperature reservoirs,a numerical example for the lumped-parameter model is provided by numerical calculation. The effects of changes of reservoir’s temperature on the maximum power of the heat engine are analyzed. The obtained results are,in addition,compared with those obtained with Newtonian heat transfer law [q ∝Δ(T)].

  11. Effect of working fluids and internal diameters on thermal performance of vertical and horizontal closed-loop pulsating heat pipes with multiple heat sources

    Directory of Open Access Journals (Sweden)

    Kammuang-Lue Niti

    2016-01-01

    Full Text Available Some electrical applications have a number of heat sources. The closed-loop pulsating heat pipe (CLPHP is applied to transfer heat from these devices. Since the CLPHP primarily transfers heat by means of the working fluid’s phase change in a capillary tube, the thermal performance of the CLPHP significantly depends on the working fluid type and the tube’s internal diameter. In order to provide the fundamental information for manufacturers of heat exchangers, this study on the effect of working fluids and internal diameters has been conducted. Three electrical plate heaters were installed on the CLPHP as the heat sources. The experiments were conducted by varying the working fluid to be R123, ethanol, and water, and the internal diameter to be 1.0 mm, 1.5 mm, and 2.0 mm. For each set of the same working fluid and internal diameter, the input heat fluxes of the heat sources were also made to vary within six different patterns. It can be concluded that when the latent heat of evaporation increases - in the case of vertical CLPHP - and when the dynamic viscosity of the liquid increases - in the case of horizontal CLPHP - the thermal performance decreases. Moreover, when the internal diameter increases, the thermal performance increases for both of vertical and horizontal CLPHPs.

  12. CFD Based Evaluation Of Effectiveness Of Counter Flow Heat Exchanger

    Directory of Open Access Journals (Sweden)

    Gurpreet Kour

    2014-04-01

    Full Text Available Engineers are continually being asked to improve effectiveness of heat transfer equipments. These requests may arise as a result of the need to increase profitability or accommodate capital limitations. Processes which use heat transfer equipment i.e. heat exchanger must frequently be improved for these reasons. Artifical roughness is important technique for enhancing the effectiveness of heat exchanger. In this work effectiveness of smooth as well as roughened tube in heat exchanger is theoretically investigated by using ring type roughness geometry. The performance obtained is then compared with smooth tube. Ringed tube has a significant effect on effectiveness of heat exchanger. The effectiveness is 3.2 times as compared with plane tube was reported. The effectiveness found to be increased with increasing roughness and decreasing pitch between the rings.

  13. Information Work Support Based on Activity Data

    OpenAIRE

    Schmidt, Benedikt

    2013-01-01

    In industrial and post industrial nations like Germany and the USA more than a quarter of the workforce mainly works with information. Most of the work done by these information workers is the production, supervision and dissemination of information at computer workplaces. Information workers frequently works on multiple tasks in parallel. Few guidelines regulate and structure the work process. Therefore, the successful execution of the work requires a high degree of individual planning. ...

  14. Synthetic heat carrier oil compositions based on polyalkylene glycols

    International Nuclear Information System (INIS)

    The results of syntheses of heat carrier oils based on polyalkylene glycols (PAGs) using suitable additives have been reported. Polyalkylene glycols have been prepared by heating diethylene glycol, propylene oxide, glycols, adipic acid and 2-ethyhexanol in the presence of KOH and stannyl octoate as catalyst in the molar ratio to give proper physical properties and viscosity-temperature index. The prepared PAGs have been taken as basic components for heat carrier oil compositions. In order to improve the thermal stability and viscosity indices, as well as other specifications, anti-oxidant and anti-foaming additives were added to the base material to reach optimum compositions. Thermal stability, mass loss on vaporization at 250 oC, 350 oC and changing the specifications after heating at 300 oC for 10 h have also been investigated. The obtained heat carrier oils showed comparable improved properties in comparison with commercially available heat carriers

  15. Demonstration testing and evaluation of in situ soil heating. Treatability study work plan (Revision 2)

    International Nuclear Information System (INIS)

    A Treatability Study planned for the demonstration of the in situ electromagnetic (EM) heating process to remove organic solvents is described in this Work Plan. The treatability study will be conducted by heating subsurface vadose-zone soils in an organic plume adjacent to the Classified Burial Ground K-1070-D located at K-25 Site, Oak Ridge. The test is scheduled to start during the fourth quarter of FY94 and will be completed during the first quarter of FY95. Over the last nine years, a number of Government agencies (EPA, Army, AF, and DOE) and industries sponsored further development and testing of the in situ heating and soil decontamination process for the remediation of soils containing hazardous organic contaminants. In this process the soil is heated in situ using electrical energy. The contaminants are removed from the soil due to enhanced vaporization, steam distillation and stripping. IITRI will demonstrate the EM Process for in situ soil decontamination at K-25 Site under the proposed treatability study. Most of the contaminants of concern are volatile organics which can be removed by heating the soil to a temperature range of 85 degrees to 95 degrees C. The efficiency of the treatment will be determined by comparing the concentration of contaminants in soil samples. Samples will be obtained before and after the demonstration for a measurement of the concentration of contaminants of concern. This document is a Treatability Study Work Plan for the demonstration program. The document contains a description of the proposed treatability study, background of the EM heating process, description of the field equipment, and demonstration test design

  16. Demonstration testing and evaluation of in situ soil heating. Treatability study work plan (Revision 2)

    Energy Technology Data Exchange (ETDEWEB)

    Sresty, G.C.

    1994-12-30

    A Treatability Study planned for the demonstration of the in situ electromagnetic (EM) heating process to remove organic solvents is described in this Work Plan. The treatability study will be conducted by heating subsurface vadose-zone soils in an organic plume adjacent to the Classified Burial Ground K-1070-D located at K-25 Site, Oak Ridge. The test is scheduled to start during the fourth quarter of FY94 and will be completed during the first quarter of FY95. Over the last nine years, a number of Government agencies (EPA, Army, AF, and DOE) and industries sponsored further development and testing of the in situ heating and soil decontamination process for the remediation of soils containing hazardous organic contaminants. In this process the soil is heated in situ using electrical energy. The contaminants are removed from the soil due to enhanced vaporization, steam distillation and stripping. IITRI will demonstrate the EM Process for in situ soil decontamination at K-25 Site under the proposed treatability study. Most of the contaminants of concern are volatile organics which can be removed by heating the soil to a temperature range of 85{degrees} to 95{degrees}C. The efficiency of the treatment will be determined by comparing the concentration of contaminants in soil samples. Samples will be obtained before and after the demonstration for a measurement of the concentration of contaminants of concern. This document is a Treatability Study Work Plan for the demonstration program. The document contains a description of the proposed treatability study, background of the EM heating process, description of the field equipment, and demonstration test design.

  17. Utilization of Low Temperature Heat in Coal based Power Plants

    OpenAIRE

    Sisic, Elmir

    2013-01-01

    Carbon Capture and Storage aims at capturing and storing carbon emissions from large point sources underground. One of three main ways of implementing CCS is in coal based power plants is the pressurized oxy-combustion, an advanced form of oxy-combustion. There are different approaches in designing the heat cycle with CCS. Included in the design is the acid condenser, a heat exchanger which utilizes the low temperature and latent heat of the flue gas for preheating purposes. The objective of ...

  18. Model-based control of district heating supply temperature

    Energy Technology Data Exchange (ETDEWEB)

    Saarinen, Linn

    2010-11-15

    A model-based control strategy for the supply temperature to a district heating network was tested during three weeks at Idbaecken's CHP plant. The aim was to increase the electricity efficiency by a lower supply temperature, without risking the delivery reliability of heat to the district heating customers. Simulations and tests showed that at high loads, the mean supply temperature could be reduced by 4 deg C and the electricity production could be increased by 2.5%

  19. Heat integration of an Olefins Plant: Pinch Analysis and mathematical optimization working together

    Directory of Open Access Journals (Sweden)

    M. Beninca

    2011-03-01

    Full Text Available This work explores a two-step, complexity reducing methodology, to analyze heat integration opportunities of an existing Olefins Plant, identify and quantify reduction of energy consumption, and propose changes of the existing heat exchanger network to achieve these goals. Besides the analysis of plant design conditions, multiple operational scenarios were considered to propose modifications for handling real plant operation (flexibility. On the strength of plant complexity and large dimension, work methodology was split into two parts: initially, the whole plant was evaluated with traditional Pinch Analysis tools. Several opportunities were identified and modifications proposed. Modifications were segregated to represent small and independent portions of the original process. One of them was selected to be re-analyzed, considering two scenarios. Reduction of problem dimension allowed mathematical methodologies (formulation with decomposition, applying LP, MILP and NLP optimization methods to synthesize flexible networks to be applied, generating a feasible modification capable of fulfilling the proposed operational scenarios.

  20. Linear irreversible heat engines based on local equilibrium assumptions

    Science.gov (United States)

    Izumida, Yuki; Okuda, Koji

    2015-08-01

    We formulate an endoreversible finite-time Carnot cycle model based on the assumptions of local equilibrium and constant energy flux, where the efficiency and the power are expressed in terms of the thermodynamic variables of the working substance. By analyzing the entropy production rate caused by the heat transfer in each isothermal process during the cycle, and using the endoreversible condition applied to the linear response regime, we identify the thermodynamic flux and force of the present system and obtain a linear relation that connects them. We calculate the efficiency at maximum power in the linear response regime by using the linear relation, which agrees with the Curzon-Ahlborn (CA) efficiency known as the upper bound in this regime. This reason is also elucidated by rewriting our model into the form of the Onsager relations, where our model turns out to satisfy the tight-coupling condition leading to the CA efficiency.

  1. Cardiac strain of confectionery worker in relation to heat exposure during regular work shift

    Directory of Open Access Journals (Sweden)

    Rajib Biswas

    2011-01-01

    Full Text Available Context: In India, a wide variety of occupations are performed in adverse indoor working environment. Work physiological studies in these jobs are scanty as compared to investigations done on more arduous outdoor occupations. Aims and Objectives: Physiological strain of workers engaged in sweet making activities was assessed in terms of cardiac strain indices in relation to heat stress. Setting and Design: 33 full-time workers from eastern India were compared for cardiac strain profile obtained during summer and winter during their regular work shift. A comparison was also done in between younger (n=12 and older (n=16 subjects. Materials and Methods : Working heart rate (WHR was recorded continuously during work. The pulse deceleration index (PDI was obtained from recovery heart rate (RHR. Net cardiac cost (NCC and relative cardiac cost (RCC were the main indices used to evaluate physical strain. Thermal stress assessed from wet bulb globe temperature (WBGT. Statistical Analysis: Students′ t-test and Wilcoxon signed rank paired tests were used for comparing physiological responses. Values were considered significant when P < 0.05. Results: Work load was significantly higher in summer for all workers. RCC of younger workers in winter and summer ranged between 18% and 26%. This was significantly lower as compared to the RCC of older workers which was 27% in winter and 30% in summer. The physiological workload appeared to be moderate in nature. The WBGT index was above the recommended range in summer for both the groups. Older workers showed a no recovery pattern in terms of recovery pulse that indicated toward a cumulative stress which may be attributed to a combined effect of heat and work in summer and extra amount of work performed in winter season. Conclusion: The physical workload is aggravated with various ergonomic stressors present in the work place. An ergonomic intervention has been indicated as further scope of this study.

  2. INDUSTRIAL CARBON DIOXIDE HEAT PUMP STATION WITH EVAPORATORS WORKING AT VARIOUS TEMPERATURE LEVELS AND AT VARIABLE LOAD

    Directory of Open Access Journals (Sweden)

    Sit M.L.

    2010-08-01

    Full Text Available The block diagram of an industrial carbon dioxide heat pump working in a supercritical cycle, with two evaporators included in parallel working at different temperature levels (mainly for wine-making factories is developed. Heat pump is intended for simultaneous production of heat and cold and works at variable thermal loading. It is shown, how an ejector inclusion in the heat pump scheme provides growth of its thermal efficiency. The way of construction of the hydraulic scheme and a control system provides full controllability of the thermal pump.

  3. Reprint of : Three-terminal heat engine and refrigerator based on superlattices

    Science.gov (United States)

    Choi, Yunjin; Jordan, Andrew N.

    2016-08-01

    We propose a three-terminal heat engine based on semiconductor superlattices for energy harvesting. The periodicity of the superlattice structure creates an energy miniband, giving an energy window for allowed electron transport. We find that this device delivers a large power, nearly twice than the heat engine based on quantum wells, with a small reduction of efficiency. This engine also works as a refrigerator in a different regime of the system's parameters. The thermoelectric performance of the refrigerator is analyzed, including the cooling power and coefficient of performance in the optimized condition. We also calculate phonon heat current through the system and explore the reduction of phonon heat current compared to the bulk material. The direct phonon heat current is negligible at low temperatures, but dominates over the electronic at room temperature and we discuss ways to reduce it.

  4. Work-based resources as moderators of the relationship between work hours and satisfaction with work-family balance.

    Science.gov (United States)

    Valcour, Monique

    2007-11-01

    This study reports an investigation of the relationships of work hours, job complexity, and control over work time to satisfaction with work-family balance. Based on data from a sample of 570 telephone call center representatives, a moderated hierarchical regression analysis revealed that work hours were negatively related to satisfaction with work-family balance, consistent with the resource drain perspective. Job complexity and control over work time were positively associated with satisfaction with work-family balance. Control over work time moderated the relationship such that as work hours rose, workers with low control experienced a decline in work-family balance satisfaction, while workers with high control did not. Results encourage greater research attention to work characteristics, such as job complexity and control over work time, and skills that represent resources useful to the successful integration of work and family demands.

  5. A general framework to select working fluid and configuration of ORCs for low-to-medium temperature heat sources

    International Nuclear Information System (INIS)

    Highlights: • General guidelines are proposed to select ORC working fluid and cycle layout. • Distance between critical and heat source temperature for optimal fluid selection. • Separate contributions of cycle efficiency and heat recovery factor. - Abstract: The selection of the most suitable working fluid and cycle configuration for a given heat source is a fundamental step in the search for the optimum design of Organic Rankine Cycles. In this phase cycle efficiency and heat source recovery factor lead to opposite design choices in the achievement of maximum system efficiency and, in turn, maximum power output. In this work, both separate and combined effects of these two performance factors are considered to supply a thorough understanding of the compromise resulting in maximum performance. This goal is pursued by carrying out design optimizations of four different ORC configurations operating with twenty-seven working fluids and recovering heat from sensible heat sources in the temperature range 120–180 °C. Optimum working fluids and thermodynamic parameters are those which simultaneously allow high cycle efficiency and high heat recovery from the heat source to be obtained. General guidelines are suggested to reach this target for any system configuration. The distance between fluid critical temperature and inlet temperature of the heat source is found to play a key role in predicting the optimum performance of all system configurations regardless of the inlet temperature of the heat source

  6. Analogy between gambling and measurement-based work extraction

    Science.gov (United States)

    Vinkler, Dror A.; Permuter, Haim H.; Merhav, Neri

    2016-04-01

    In information theory, one area of interest is gambling, where mutual information characterizes the maximal gain in wealth growth rate due to knowledge of side information; the betting strategy that achieves this maximum is named the Kelly strategy. In the field of physics, it was recently shown that mutual information can characterize the maximal amount of work that can be extracted from a single heat bath using measurement-based control protocols, i.e. using ‘information engines’. However, to the best of our knowledge, no relation between gambling and information engines has been presented before. In this paper, we briefly review the two concepts and then demonstrate an analogy between gambling, where bits are converted into wealth, and information engines, where bits representing measurements are converted into energy. From this analogy follows an extension of gambling to the continuous-valued case, which is shown to be useful for investments in currency exchange rates or in the stock market using options. Moreover, the analogy enables us to use well-known methods and results from one field to solve problems in the other. We present three such cases: maximum work extraction when the probability distributions governing the system and measurements are unknown, work extraction when some energy is lost in each cycle, e.g. due to friction, and an analysis of systems with memory. In all three cases, the analogy enables us to use known results in order to obtain new ones.

  7. Heat exposure, cardiovascular stress and work productivity in rice harvesters in India: implications for a climate change future.

    Science.gov (United States)

    Sahu, Subhashis; Sett, Moumita; Kjellstrom, Tord

    2013-01-01

    Excessive workplace heat exposures create well-known risks of heat stroke, and it limits the workers' capacity to sustain physical activity. There is very limited evidence available on how these effects reduce work productivity, while the quantitative relationship between heat and work productivity is an essential basis for climate change impact assessments. We measured hourly heat exposure in rice fields in West Bengal and recorded perceived health problems via interviews of 124 rice harvesters. In a sub-group (n = 48) heart rate was recorded every minute in a standard work situation. Work productivity was recorded as hourly rice bundle collection output. The hourly heat levels (WBGT = Wet Bulb Globe Temperature) were 26-32°C (at air temperatures of 30-38°C), exceeding international standards. Most workers reported exhaustion and pain during work on hot days. Heart rate recovered quickly at low heat, but more slowly at high heat, indicating cardiovascular strain. The hourly number of rice bundles collected was significantly reduced at WBGT>26°C (approximately 5% per°C of increased WBGT). We conclude that high heat exposure in agriculture caused heat strain and reduced work productivity. This reduction will be exacerbated by climate change and may undermine the local economy.

  8. Magnesium based metal hydride reactor incorporating helical coil heat exchanger: Simulation study and optimal design

    International Nuclear Information System (INIS)

    Highlights: • A new 3D modeling for Mg-based metal hydride reactor is proposed. • Hydriding kinetics of Mg-based alloys is modeled based on the experimental data. • Helical coil heat exchanger has better heat transfer effect than traditional one. • The reactor with smaller non-dimensional pitch has favorable performance. - Abstract: Magnesium based metal hydride has been viewed as one of the most commonly-used materials in the practical applications of hydrogen energy systems. The heat and mass transfer processes have significant effects on the hydrogen storage performance of magnesium based metal hydride reactors. Incorporating helical coil heat exchanger into the reactor could be an effective way to improve the performance of heat and mass transfer. In this work, a new three-dimensional model for magnesium based metal hydride reactor with helical coil heat exchanger is proposed and solved using the commercial software package COMSOL Multiphysics V3.5a. The comparison of hydrogen storage behaviors between the reactors incorporating the traditional straight pipe and new helical coil heat exchangers is firstly conducted based on the numerical simulation. The comparison results show that the helical coil heat exchanger has better effect on improving the characteristics of reactor than the straight pipe heat exchanger due to its secondary circulation. The effects of key parameters, including the initial conditions, heat transfer coefficients of heat transfer fluid and helical coil geometry on the characteristics of reactor with the helical coil heat exchanger are also analyzed systematically. It is discovered that larger initial hydrogen pressure and lower initial temperature are beneficial to the improvement of hydrogen absorption kinetics, because of the greater driving force for the hydriding reaction. The results of optimal design suggest that smaller non-dimensional pitch, the ratio of helical pitch to helical diameter, improves the heat and mass transfer

  9. Design of heat pipe heat exchanger used in communication base station%通信基站用热管换热器的设计

    Institute of Scientific and Technical Information of China (English)

    鲍玲玲; 王景刚; 王晓明

    2011-01-01

    热管及热管换热器凭借着其优良的传热特性得到了日益广泛的应用.分析了通信基站用重力热管换热器的工作原理及特点,结合通信基站实例,利用VB语言编写了重力热管换热器的计算程序,设计了一款结构和性能较合理的重力热管换热器.%Heat pipe and heat pipe heat exchanger have good heat transfer characteristics,therefore they obtain increasing application. Analyses the characteristics and working principle of the heat pipe heat exchanger used in communication base station,with a communication base station example,and based on VB compiling language,makes the calculation program for gravitation heat pipe heat exchanger and designs a gravitation heat pipe heat exchanger with adequate structure and performance.

  10. The neural bases of orthographic working memory

    Directory of Open Access Journals (Sweden)

    Jeremy Purcell

    2014-04-01

    First, these results reveal a neurotopography of OWM lesion sites that is well-aligned with results from neuroimaging of orthographic working memory in neurally intact participants (Rapp & Dufor, 2011. Second, the dorsal neurotopography of the OWM lesion overlap is clearly distinct from what has been reported for lesions associated with either lexical or sublexical deficits (e.g., Henry, Beeson, Stark, & Rapcsak, 2007; Rapcsak & Beeson, 2004; these have, respectively, been identified with the inferior occipital/temporal and superior temporal/inferior parietal regions. These neurotopographic distinctions support the claims of the computational distinctiveness of long-term vs. working memory operations. The specific lesion loci raise a number of questions to be discussed regarding: (a the selectivity of these regions and associated deficits to orthographic working memory vs. working memory more generally (b the possibility that different lesion sub-regions may correspond to different components of the OWM system.

  11. The concepts of work and heat and the first and second laws of thermodynamics

    CERN Document Server

    de Abreu, Rodrigo

    2012-01-01

    A simple and effective approach to thermodynamics is suggested, which solves the major difficulties in the traditional presentation of the subject. The internal energy is introduced from the behavior of deformable bodies, whereas the importance of keeping in mind the microscopic picture is emphasized. A straightforward model is used to show that the internal energy depends on the volume and entropy, from where the relationship between mechanics and thermodynamics is immediate, mechanics corresponding to isentropic thermodynamics. The questions of evolution to equilibrium and irreversibility are studied under the light of the action of the "dynamic force", which has a dissipative character. The present formulation leads to a discussion and clarification of the physical meaning of various thermodynamic quantities, such as pressure, temperature, work and heat. The adiabatic piston problem is analyzed, as a paradigmatic case where the notions of "adiabatic" and "heat transfer" are often ill-defined.

  12. Sulfur Based Thermochemical Heat Storage for Baseload Concentrated Solar Power Generation

    Energy Technology Data Exchange (ETDEWEB)

    wong, bunsen

    2014-11-20

    This project investigates the engineering and economic feasibility of supplying baseload power using a concentrating solar power (CSP) plant integrated with sulfur based thermochemical heat storage. The technology stores high temperature solar heat in the chemical bonds of elemental sulfur. Energy is recovered as high temperature heat upon sulfur combustion. Extensive developmental and design work associated with sulfur dioxide (SO2) disproportionation and sulfuric acid (H2SO4) decomposition chemical reactions used in this technology had been carried out in the two completed phases of this project. The feasibility and economics of the proposed concept was demonstrated and determined.

  13. Teaching Standards-Based Group Work Competencies to Social Work Students: An Empirical Examination

    Science.gov (United States)

    Macgowan, Mark J.; Vakharia, Sheila P.

    2012-01-01

    Objectives: Accreditation standards and challenges in group work education require competency-based approaches in teaching social work with groups. The Association for the Advancement of Social Work with Groups developed Standards for Social Work Practice with Groups, which serve as foundation competencies for professional practice. However, there…

  14. Writing Assignments Based on Literary Works.

    Science.gov (United States)

    Matthews, Dorothy, Ed.

    1985-01-01

    The literature selections serving as the basis for writing assignments in the articles in this journal issue range from time-honored English classics ("Beowulf,""Sir Gawain and the Green Knight") and American standards ("A Farewell to Arms,""The Scarlet Letter") to contemporary fiction. The articles deal with works by women writers (Shirley…

  15. Proliferation resistance of plutonium based on decay heat

    International Nuclear Information System (INIS)

    Proliferation resistance of plutonium can be enhanced by increasing the decay heat of plutonium. For example, it can be enhanced by increasing the isotopic fraction of 238Pu, which has the largest decay heat among plutonium isotopes, produced by transmutation of Minor Actinides (Protected Plutonium Production: P3). In the present paper, proliferation resistance of plutonium was evaluated based on decay heat with physical assessment model. As a summary of the evaluation, new criteria to evaluate proliferation resistance of plutonium based on its isotopic composition from the view point of decay heat were suggested. The present methodology and the criteria were applied to evaluate the impact of P3 by the transmutation of Minor Actinides in fast breeder reactor blanket on proliferation resistance of plutonium. (author)

  16. Heat unit-based crop coefficient for grapefruit trees

    International Nuclear Information System (INIS)

    The onset and rate of sap moving up the branches of grapefruit (Citrus paradisi Macfadyen) trees were monitored hourly using portable sap flow sensors at Waddell, Arizona. Hourly reference evapotranspiration (ETo) estimates were calculated using data from a nearby weather station. Crop water use was estimated from soil moisture measurements using a neutron probe. These data were used to first delineate the upper and lower temperature threshold values for the determination of heat units. A heat unit-based crop coefficient was then derived from a correlation of the crop coefficient with heat units over a crop year. The heat unit-based crop coefficient was found to be similar to crop coefficients derived by other reseachers

  17. Work, Train, Win: Work-Based Learning Design and Management for Productivity Gains. OECD Education Working Papers, No. 135

    Science.gov (United States)

    Kis, Viktoria

    2016-01-01

    Realising the potential of work-based learning schemes as a driver of productivity requires careful design and support. The length of work-based learning schemes should be adapted to the profile of productivity gains. A scheme that is too long for a given skill set might be unattractive for learners and waste public resources, but a scheme that is…

  18. Liquid Salt Heat Exchanger Technology for VHTR Based Applications

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Mark; Sridhara, Kumar; Allen, Todd; Peterson, Per

    2012-10-11

    The objective of this research is to evaluate performance of liquid salt fluids for use as a heat carrier for transferring high-temperature process heat from the very high-temperature reactor (VHTR) to chemical process plants. Currently, helium is being considered as the heat transfer fluid; however, the tube size requirements and the power associated with pumping helium may not be economical. Recent work on liquid salts has shown tremendous potential to transport high-temperature heat efficiently at low pressures over long distances. This project has two broad objectives: To investigate the compatibility of Incoloy 617 and coated and uncoated SiC ceramic composite with MgCl2-KCl molten salt to determine component lifetimes and aid in the design of heat exchangers and piping; and, To conduct the necessary research on the development of metallic and ceramic heat exchangers, which are needed for both the helium-to-salt side and salt-to-process side, with the goal of making these heat exchangers technologically viable. The research will consist of three separate tasks. The first task deals with material compatibility issues with liquid salt and the development of techniques for on-line measurement of corrosion products, which can be used to measure material loss in heat exchangers. Researchers will examine static corrosion of candidate materials in specific high-temperature heat transfer salt systems and develop an in situ electrochemical probe to measure metallic species concentrations dissolved in the liquid salt. The second task deals with the design of both the intermediate and process side heat exchanger systems. Researchers will optimize heat exchanger design and study issues related to corrosion, fabrication, and thermal stresses using commercial and in-house codes. The third task focuses integral testing of flowing liquid salts in a heat transfer/materials loop to determine potential issues of using the salts and to capture realistic behavior of the salts in a

  19. Characterization of zeolite-based coatings for adsorption heat pumps

    CERN Document Server

    Freni, Angelo; Bonaccorsi, Lucio; Chmielewski, Stefanie; Frazzica, Andrea; Calabrese, Luigi; Restuccia, Giovanni

    2015-01-01

    This book proposes a radically new approach for characterizing thermophysical and mechanical properties of zeolite-based adsorbent coatings for Adsorptive Heat Transformers (AHT). It presents a developed standard protocol for the complete characterization of advanced coated adsorbers. Providing an in-depth analysis of the different procedures necessary for evaluating the performance of adsorbers, it also presents an analysis of their stability under the hydrothermal and mechanical stresses during their entire life cycle. Adsorptive Heat Transformers (AHT), especially adsorption chillers and

  20. Single-Sided Electromagnetic Induction Heating Based on IGBT

    OpenAIRE

    Song Wang; Guangda Li; Xiaokun Li

    2014-01-01

    A single-sided induction heating system based on IGBT is proposed. The system includes the series resonant circuit, control circuit, and auxiliary circuit. The main circuit includes rectifier, filter, inverter, and resonant circuit. A drive circuit is designed for IGBT combing some protection circuits. We have a simulation of the single-sided induction heating system in ANSYS. The simulation results are compared with the experimental results. The performance of the system is promising. And al...

  1. Why activity-based costing works.

    Science.gov (United States)

    Gabram, S G; Mendola, R A; Rozenfeld, J; Gamelli, R L

    1997-01-01

    With advancing technology and the quest for delineating the true cost of a procedure or diagnostic test, cost accounting techniques are being re-explored in the health care setting. Activity-based costing (ABC), adopted from other businesses, is one such example that has applications in the health industry. The purpose of this paper is to enhance the understanding of health care costs among physician providers, emphasizing a new approach--activity-based costing. PMID:10169347

  2. Why activity-based costing works.

    Science.gov (United States)

    Gabram, S G; Mendola, R A; Rozenfeld, J; Gamelli, R L

    1997-01-01

    With advancing technology and the quest for delineating the true cost of a procedure or diagnostic test, cost accounting techniques are being re-explored in the health care setting. Activity-based costing (ABC), adopted from other businesses, is one such example that has applications in the health industry. The purpose of this paper is to enhance the understanding of health care costs among physician providers, emphasizing a new approach--activity-based costing.

  3. Multiple Days of Heat Exposure on Firefighters' Work Performance and Physiology.

    Directory of Open Access Journals (Sweden)

    Brianna Larsen

    Full Text Available This study assessed the accumulated effect of ambient heat on the performance of, and physiological and perceptual responses to, intermittent, simulated wildfire fighting tasks over three consecutive days. Firefighters (n = 36 were matched and allocated to either the CON (19°C or HOT (33°C condition. They performed three days of intermittent, self-paced simulated firefighting work, interspersed with physiological testing. Task repetitions were counted (and converted to distance or area to determine work performance. Participants were asked to rate their perceived exertion and thermal sensation after each task. Heart rate, core temperature (Tc, and skin temperature (Tsk were recorded continuously throughout the simulation. Fluids were consumed ad libitum. Urine volume was measured throughout, and urine specific gravity (USG analysed, to estimate hydration. All food and fluid consumption was recorded. There was no difference in work output between experimental conditions. However, significant variation in performance responses between individuals was observed. All measures of thermal stress were elevated in the HOT, with core and skin temperature reaching, on average, 0.24 ± 0.08°C and 2.81 ± 0.20°C higher than the CON group. Participants' doubled their fluid intake in the HOT condition, and this was reflected in the USG scores, where the HOT participants reported significantly lower values. Heart rate was comparable between conditions at nearly all time points, however the peak heart rate reached each circuit was 7 ± 3% higher in the CON trial. Likewise, RPE was slightly elevated in the CON trial for the majority of tasks. Participants' work output was comparable between the CON and HOT conditions, however the performance change over time varied significantly between individuals. It is likely that the increased fluid replacement in the heat, in concert with frequent rest breaks and task rotation, assisted with the regulation of

  4. Ultrasonic test application in geothermal heat exchangers and civil works to monitor the grout integrity (TUC)

    Science.gov (United States)

    Mandrone, Giuseppe; Comina, Cesare; Giuliani, Andrea

    2013-04-01

    The working of a vertical geothermal probe, realized with a pipe U-tubes of high-density-polyethylene (HDPE) inserted in a grouted boreholes, is linked to the possibility to exchange heat with the surrounding soil. The concrete material useful for the borehole heat exchangers allows to satisfy a double purpose: sealing the polyethylene pipes from groundwater in the event of loss and increasing the thermal properties of the whole probe to provide a greater interaction with the underground. If this operation is not performed properly, the complete system may not satisfy the required heat demand, even with a well dimensioned installation, wasting the value of the entire carried out work. This paper offers to a wide group of professional actors a possible ultrasonic method of a draft and economically sustainable investigation for the identification of defects that could be present in the cementation realized inside a geothermal probe, but also in the realization of sonic piles. The instrument used for this type of test (TUC - Test Ultrasonic Cementation) has been designed and tested by the technicians of AG3, a Spin Off Company of Torino University, in collaboration with 3DM Electric and PASI companies, then subjected to patenting procedure (Patent Pending TO2011A000036). The main innovative feature of this approach has been the miniaturization of the equipment, able to investigate the geothermal probes with U-tubes with standard dimension (the maximum overall dimensions of the instruments detectors is 26 mm), maintaining a sampling rate appropriate to investigate the cementation and the early centimetres of the surrounding soil. The processing of the recorded data was performed by a dedicated Matlab software. In the first part of the article is presented the calibration process, that it was carried out through ad hoc creation of two situations likely to be investigated, while in the second part the paper reports the results obtained by the application of the TUC

  5. Performance analysis of the single-stage absorption heat transformer using a new working pair composed of ionic liquid and water

    International Nuclear Information System (INIS)

    The performance simulation of a single-stage absorption heat transformer using a new working pair composed of ionic liquids, 1-ethyl-3-methylimidazolium dimethylphosphate, and water (H2O + [EMIM][DMP]), was performed based on the thermodynamic properties of the new working pair and on the mass and energy balance for each component of the system. In order to evaluate the new working pair, the simulation results were compared with those of aqueous solution of lithium bromide (H2O + LiBr), Trifluoroethanol (TFE) + tetraethylenglycol dimethylether (E181). The results indicate that when generation, evaporation, condensing and absorption temperatures are 90 °C, 90 °C, 35 °C and 130 °C, the coefficients of performance of the single-stage absorption heat transformer using H2O + LiBr, H2O + [EMIM][DMP] and TFE + E181 as working pairs will reach 0.494, 0.481 and 0.458 respectively. And the corresponding exergy efficiency will reach 0.64, 0.62 and 0.59, respectively. Meanwhile the available heat outputs for per unit mass of refrigerant are 2466 kJ/kg, 2344 kJ/kg and 311 kJ/kg, respectively. The above excellent cycle performance together with the advantages of negligible vapor pressure, no crystallization and more weak corrosion tendency to iron-steel materials may make the new working pair better suited for the industrial absorption heat transformer. - Highlights: ► The cycle performance of the single-stage absorption heat transformer was simulated. ► Water and 1-ethyl-3-methylimidazolium dimethylphosphate was used as new working pair. ► Water and 1-ethyl-3-methylimidazolium dimethylphosphate are entirely miscible. ► The COP and exergy efficiency for this new working pairs were 0.481 and 0.62. ► The new working pairs has potential application to absorption heat transformer.

  6. Heating of thermoplastic-based unidirectional composite prepregs

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.; Weber, M.E.; Charrier, J.M. (McGill Univ., Montreal (Canada))

    1989-04-01

    Thermoplastic-based prepregs offer a potential for faster manufacture of composite products than with thermoset-based prepregs. The winding or controlled placement of thermoplastic-based prepreg tapes requires the rapid heating of the moving tape, just prior to its contact with the substrate on the mandrel. In the case of complex shapes, geometrical constraints and significant variations in tape speeds in the course of manufacture, make it particularly desirable to be able to model the heating process. A mathematical model and its experimental verification for convection/conduction heat transfer to and through either a homogeneous thermoplastic material, or thermoplastic-based unidirectional composites featuring glass, aramid and carbon fibers, is discussed. 12 refs.

  7. Water Based Phase Change Material Heat Exchanger Development

    Science.gov (United States)

    Hansen, Scott W.; Sheth, Ribik B.; Atwell, Matt; Cheek, Ann; Agarwal, Muskan; Hong, Steven; Patel, Aashini,; Nguyen, Lisa; Posada, Luciano

    2014-01-01

    In a cyclical heat load environment such as low Lunar orbit, a spacecraft’s radiators are not sized to reject the full heat load requirement. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a “topper” to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HXs do not use a consumable, thereby leading to reduced launch mass and volume requirements. Studies conducted in this paper investigate utilizing water’s high latent heat of formation as a PCM, as opposed to traditional waxes, and corresponding complications surrounding freezing water in an enclosed volume. Work highlighted in this study is primarily visual and includes understanding ice formation, freeze front propagation, and the solidification process of water/ice. Various test coupons were constructed of copper to emulate the interstitial pin configuration (to aid in conduction) of the proposed water PCM HX design. Construction of a prototypic HX was also completed in which a flexible bladder material and interstitial pin configurations were tested. Additionally, a microgravity flight was conducted where three copper test articles were frozen continuously during microgravity and 2-g periods and individual water droplets were frozen during microgravity.

  8. Performance-Based Rewards and Work Stress

    Science.gov (United States)

    Ganster, Daniel C.; Kiersch, Christa E.; Marsh, Rachel E.; Bowen, Angela

    2011-01-01

    Even though reward systems play a central role in the management of organizations, their impact on stress and the well-being of workers is not well understood. We review the literature linking performance-based reward systems to various indicators of employee stress and well-being. Well-controlled experiments in field settings suggest that certain…

  9. 混合工质太阳能平板热管集热器的传热性能%Heat Transfer Performance ofthe Flat Plate Heat Pipe Solar Collector with Mixture Working Fluid

    Institute of Scientific and Technical Information of China (English)

    杜胜华; 苏海鹏

    2014-01-01

    介绍了平板热管的基本结构与原理,在分析乙二醇及其混合工质的热物理学特性的基础上,建立平板热管的物理与数学模型。采用数值计算模拟方法,分析了混合工质平板热管集热器的传热性能,研究了集热器的效率、温升和启动性能随工作时间的变化规律。研究表明,乙二醇水混合工质平板热管集热器适宜于低温寒冷地区,具有较高的集热性能。%The basic structure and principle of flat plate heat pipe were introduced based on thermal physics characteristics analysis of ethylene glycol and mixtures , physical and mathematical models of flat plate heat pipe were established.By the numerical simulation method , the heat transfer performance of the flat heat pipe heat collector with mixture working fluid was analyzed , and the efficiency , temperature collector up and starting performance by time were studied.It showed that flat heat pipe heat collector with ethylene glycol water mixture was suitable for cold area , and the heat collecting performance was high.

  10. Graph based model to support nurses' work.

    Science.gov (United States)

    Benedik, Peter; Rajkovič, Uroš; Sušteršič, Olga; Prijatelj, Vesna; Rajkovič, Vladislav

    2014-01-01

    Health care is a knowledge-based community that critically depends on knowledge management activities in order to ensure quality. Nurses are primary stakeholders and need to ensure that their information and knowledge needs are being met in such ways that enable them, to improve the quality and efficiency of health care service delivery for all subjects of health care. This paper describes a system to help nurses to create nursing care plan. It supports focusing nurse's attention on those resources/solutions that are likely to be most relevant to their particular situation/problem in nursing domain. System is based on multi-relational property graph representing a flexible modeling construct. Graph allows modeling a nursing domain (ontology) and the indices that partition domain into an efficient, searchable space where the solution to a problem is seen as abstractly defined traversals through its vertices and edges. PMID:24943559

  11. Subscale Water Based Phase Change Material Heat Exchanger Development

    Science.gov (United States)

    Sheth, Rubik; Hansen, Scott

    2016-01-01

    Supplemental heat rejection devices are required in many spacecraft as the radiators are not sized to meet the full heat rejection demand. One means of obtaining additional heat rejection is through the use of phase change material heat exchangers (PCM HX's). PCM HX's utilize phase change to store energy in unfavorable thermal environments (melting) and reject the energy in favorable environments (freezing). Traditionally, wax has been used as a PCM on spacecraft. However, water is an attractive alternative because it is capable of storing about 40% more energy per unit mass due to its higher latent heat of fusion. The significant problem in using water as a PCM is its expansion while freezing, leading to structural integrity concerns when housed in an enclosed heat exchanger volume. Significant investigation and development has taken place over the past five years to understand and overcome the problems associated with water PCM HX's. This paper reports on the final efforts by Johnson Space Center's Thermal Systems Branch to develop a water based PCM HX. The test article developed and reported on is a subscale version of the full-scale water-based PCM HX's constructed by Mezzo Technologies. The subscale unit was designed by applying prior research on freeze front propagation and previous full-scale water PCM HX development. Design modifications to the subscale unit included use of urethane bladder, decreased aspect ratio, perforated protection sheet, and use of additional mid-plates. Testing of the subscale unit was successful and 150 cycles were completed without fail.

  12. Solar water heating system for a lunar base

    Science.gov (United States)

    Somers, Richard E.; Haynes, R. Daniel

    1992-01-01

    An investigation of the feasibility of using a solar water heater for a lunar base is described. During the investigation, computer codes were developed to model the lunar base configuration, lunar orbit, and heating systems. Numerous collector geometries, orientation variations, and system options were identified and analyzed. The results indicate that the recommended solar water heater could provide 88 percent of the design load and would not require changes in the overall lunar base design. The system would give a 'safe-haven' water heating capability and use only 7 percent to 10 percent as much electricity as an electric heating system. As a result, a fixed position photovoltaic array can be reduced by 21 sq m.

  13. Work-Based Learning, Identity and Organisational Culture

    Science.gov (United States)

    Ahlgren, Linda; Tett, Lyn

    2010-01-01

    This paper discusses the ways in which employers view the contribution of work-based learning, how participating learners' experience the provision offered to them and how far work-based programmes can contribute to changing the discourse about learning from one of deficit to one of strengths. It draws on two complementary studies of work based…

  14. Method of Heating a Foam-Based Catalyst Bed

    Science.gov (United States)

    Fortini, Arthur J.; Williams, Brian E.; McNeal, Shawn R.

    2009-01-01

    A method of heating a foam-based catalyst bed has been developed using silicon carbide as the catalyst support due to its readily accessible, high surface area that is oxidation-resistant and is electrically conductive. The foam support may be resistively heated by passing an electric current through it. This allows the catalyst bed to be heated directly, requiring less power to reach the desired temperature more quickly. Designed for heterogeneous catalysis, the method can be used by the petrochemical, chemical processing, and power-generating industries, as well as automotive catalytic converters. Catalyst beds must be heated to a light-off temperature before they catalyze the desired reactions. This typically is done by heating the assembly that contains the catalyst bed, which results in much of the power being wasted and/or lost to the surrounding environment. The catalyst bed is heated indirectly, thus requiring excessive power. With the electrically heated catalyst bed, virtually all of the power is used to heat the support, and only a small fraction is lost to the surroundings. Although the light-off temperature of most catalysts is only a few hundred degrees Celsius, the electrically heated foam is able to achieve temperatures of 1,200 C. Lower temperatures are achievable by supplying less electrical power to the foam. Furthermore, because of the foam s open-cell structure, the catalyst can be applied either directly to the foam ligaments or in the form of a catalyst- containing washcoat. This innovation would be very useful for heterogeneous catalysis where elevated temperatures are needed to drive the reaction.

  15. Effect of cold work on initiation stage crack growth rate of nickel based alloys

    International Nuclear Information System (INIS)

    To investigate the effect of cold work on initiation stage crack growth rates of nickel based alloy, initiation stage crack growth rates were measured for simulated PWR primary water conditions using flat type specimens which were prepared from three different heats of alloy 600 and then 20 and 40% cold worked. Almost all data showed the stress had an increasing linear dependency on crack growth rate ; however there was some scattering of data and some materials showed a different tendency. Since yield strength was increased by cold work, for the same stress, the initiation stage crack growth rates were restrained or were not changed significantly by cold work. (author)

  16. Flow visualization of silicon-based micro pulsating heat pipes

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Two sets of silicon-based micro pulsating heat pipes(SMPHPs) with trapezoidal cross section having hydraulic diameters of 352 μm(#1) and 394 μm(#2) respectively were fabricated for the first time using MEMS technology.With FC-72 as the working fluid,the start-up,steady operation state,as well as flow patterns were investigated using a CCD camera.It was found that the start-up process of these two SMPHPs was rather rapid.At the start-up period,no nucleation was observed,and the vapor plugs at the evaporator U-bends were formed mainly due to the breakup of liquid slugs.At the steady operation state,self-sustained oscillation with large amplitudes dominated the flow behavior when the inclination angle varied from 10° to 90°,but the nucleate boiling and bulk circulation were observed only in SMPHP #2.While bubbly,slug/plug,annular/semi-annular,and wavy-annular flows were observed in both two SMPHPs,the injection flow only appeared in SMPHP #2.

  17. Assessing Energy Efficiency of Compression Heat Pumps in Drying Processes when Zeotropic Hydrocarbon Mixtures are Used as Working Agents

    Directory of Open Access Journals (Sweden)

    Shurayts Alexander

    2016-01-01

    Full Text Available Presents the results of studies of innovative materials in the field of renewable energy.The paper proposes a design and a formula for assessing energy efficiency of the heat pump air dryer, which uses zeotropic hydrocarbon mixtures of saturated hydrocarbons as a working agent and applies the principle of a counter-current heat exchanger with a variable temperature of both the working and the drying agents. Energy efficiency of the heat pump is achieved by means of obtaining a greater part of heat from renewable energy sources, in this case by cooling the air and condensing the water vapors in the heat pump. A conducted analysis identified correlations in establishing the marginal real coefficient of performance of the compression heat pump dryer running on zeotropic hydrocarbon mixtures and operating a cycle with variable temperatures of both the working and the drying agent in the evaporator and the condenser of the heat pump. According to the established correlations, the marginal real coefficient of performance of the compression heat pump dryers running on zeotropic hydrocarbon mixtures of 40 mol% of R600a and 60 mol% of R601 is 1.92 times higher than that of the same dryers running on only R600 (n-butane.

  18. Inter-conversion of Work and Heat With Plasma Electric Fields

    International Nuclear Information System (INIS)

    Thermodynamics of a model system where a group of cold charged particles locally confined in a volume VP within a warm plasma of temperature T and fixed volume V (VP<< V) is presented. Various thermodynamic functions of the model e.g., Helmhotz free energy, internal energy, entropy, electrostatic pressure of charged particles are calculated from first principles. In the homogeneous limit, an equation of state for the ES pressure of charged particles is derived and the internal energy is shown to consist solely of the thermal energy of the back ground plasma. Finally, the direct conversion of plasma heat into mechanical work is demonstrated via a Striling like engine cycle involving ES isothermal compression of plasma electric fields.

  19. Quantum heat engine cycle working with a strongly correlated electron system

    Institute of Scientific and Technical Information of China (English)

    WANG HaiLong; PAN Hui; WANG RongMing

    2012-01-01

    A new model of a quantum heat engine (QHE) cycle is established,in which the working substance consists of an interacting electrons system.One of our purposes is to test the validity of the second law of thermodynamics by this model,which is more general than the spin-1/2 antiferromagnetic Heisenberg model since it would recover the spin model when the on-site Coulomb interaction U is strong enough.On the basis of quantum mechanics and the first law of thermodynamics,we show no violation of the second law of thermodynamics during the cycle.We further study the performance characteristics of the cycle by investigating in detail the optimal relations of efficiency and dimensionless power output.We find that the efficiency of our engine can be expressed as η=1 - t22/t21 in the large-U limit,which is valid even for a four sites QHE.

  20. Embedded water-based surface heating part 2: experimental validation

    DEFF Research Database (Denmark)

    Karlsson, Henrik

    2010-01-01

    (o) 2, n(o) GEC/DST-94.050R, CSTB, France.) experimentally derived reference data for the specific setup. This article constitutes an attempt to experimentally validate the numerical simulation tool that was recently developed by Karlsson (Karlsson H (2010) Embedded water-based surface heating, part 1......The transient operation of an embedded water-based floor heating system has been studied by means of a numerical simulation tool. Prior to this study, Caccavelli and Richard (Caccavelli D, Richard P (1994) Etude portant sur le dimensionnement d'un plancher chauffant a eau chaude en CIC. Rapport n......: hybrid 3D numerical model. Journal of Building Physics 33: 357-391). The thermal response of the system is tested in both long (16 h) and short (30 min) cycle experiments where the water flow alters between on and off. Temperature distribution, within the floor construction, and the heat exchange process...

  1. Performance Evaluation of a Helical Coil Heat Exchanger Working under Supercritical Conditions in a Solar Organic Rankine Cycle Installation

    Directory of Open Access Journals (Sweden)

    Marija Lazova

    2016-06-01

    Full Text Available Worldwide interest in low grade heat valorization using organic Rankine cycle (ORC technologies has increased significantly. A new small-scale ORC with a net capacity of 3 kW was efficiently integrated with a concentrated solar power technology for electricity generation. The excess heat source from Photovoltaic (PV collectors with a maximum temperature of 100 °C was utilized through a supercritical heat exchanger that uses R-404A as working medium. By ensuring supercritical heat transfer leads to a better thermal match in the heat exchanger and improved overall cycle efficiency. A helical coil heat exchanger was designed by using heat transfer correlations from the literature. These heat transfer correlations were derived for different conditions than ORCs and their estimated uncertainty is ~20%. In order to account for the heat transfer correlation uncertainties this component was oversized by 20%. Next, a prototype was built and installed in an integrated concentrated photovoltaic/thermal (CPV/T/Rankine system. The results from the measurements show that for better estimation of the sizing of the heat exchanger a more accurate correlation is required in order to design an optimal configuration and thus employ cheaper components.

  2. Experimental and numerical investigation of a cross flow air-to-water heat pipe-based heat exchanger used in waste heat recovery

    OpenAIRE

    J. Ramos; Chong, A.; Jouhara, H

    2016-01-01

    This paper applies CFD modelling and numerical calculations to predict the thermal performance of a cross flow heat pipe based heat exchanger. The heat exchanger under study transfers heat from air to water and it is equipped with six water-charged wickless heat pipes, with a single-pass flow pattern on the air side (evaporator) and two flow passes on the water side (condenser). For the purpose of CFD modelling, the heat pipes were considered as solid devices of a known thermal conductivity w...

  3. The scientific base of heating water by microwave

    Science.gov (United States)

    Akdoǧan, Ender; ćiftçi, Muharrem

    2016-03-01

    This article is based on the master thesis [4] related to our invention which was published in World Intellectual Property Organization (WO/2011/048506) as a microwave water heater. In the project, a prototype was produced to use microwave in industrial heating. In order to produce the prototype, the most appropriate material kind for microwave-water experiments was determined by a new energy loss rate calculation technique. This new energy loss calculation is a determinative factor for material permeability at microwave frequency band (1-100 GHz). This experimental series aim to investigate the rationality of using microwave in heating industry. Theoretically, heating water by microwave (with steady frequency 2.45 GHz) is analyzed from sub-molecular to Classical Mechanic results of heating. In the study, we examined Quantum Mechanical base of heating water by microwave experiments. As a result, we derived a Semi-Quantum Mechanical equation for microwave-water interactions and thus, Wien displacement law can be derived to verify experimental observations by this equation.

  4. 基于复合热源的热泵型空调器%Heat pump air conditioner based on multiple heat sources

    Institute of Scientific and Technical Information of China (English)

    吴国珊; 凌勋

    2012-01-01

    It is proposed that the air-water multiple heat sources could be the heat source of heat pump air conditioner. Based on the current study condition, the heat pump air conditioner which has a air/family waste water multiple heat source is preliminary designed. The working cycle and characteristics of the air conditioner are analyzed by using the thermodynamic principle. The results show that the refrigeration performance of the heat pump air conditioner is better than that of air source heat pump air conditioner, the heating performance and the situation which the outdoor heat exchanger frosts are improved.%提出将空气-水作为热泵型空调器的复合热源.根据当前的研究状况,初步设计空气-水复合热源热泵型空调器,利用热力学原理分析该空调器的工作循环和特点,结果表明该空调器的制冷性能高于空气源热泵空调器,制热和室外换热器结霜状况得到一定改善.

  5. Diamond-based heat spreaders for power electronic packaging applications

    Science.gov (United States)

    Guillemet, Thomas

    As any semiconductor-based devices, power electronic packages are driven by the constant increase of operating speed (higher frequency), integration level (higher power), and decrease in feature size (higher packing density). Although research and innovation efforts have kept these trends continuous for now more than fifty years, the electronic packaging technology is currently facing a challenge that must be addressed in order to move toward any further improvements in terms of performances or miniaturization: thermal management. Thermal issues in high-power packages strongly affect their reliability and lifetime and have now become one of the major limiting factors of power modules development. Thus, there is a strong need for materials that can sustain higher heat flux levels while safely integrating into the electronic package architecture. In such context, diamond is an attractive candidate because of its outstanding thermal conductivity, low thermal expansion, and high electrical resistivity. Its low heat capacity relative to metals such as aluminum or copper makes it however preferable for heat spreading applications (as a heat-spreader) rather than for dissipating the heat flux itself (as a heat sink). In this study, a dual diamond-based heat-spreading solution is proposed. Polycrystalline diamond films were grown through laser-assisted combustion synthesis on electronic substrates (in the U.S) while, in parallel, diamond-reinforced copper-matrix composite films were fabricated through tape casting and hot pressing (in France). These two types of diamond-based heat-spreading films were characterized and their microstructure and chemical composition were related to their thermal performances. Particular emphasize was put on the influence of interfaces on the thermal properties of the materials, either inside a single material (grain boundaries) or between dissimilar materials (film/substrate interface, matrix/reinforcement interface). Finally, the packaging

  6. Electricity eliminates rust from district heat pipes. The new deoxidation method works on radiators

    Energy Technology Data Exchange (ETDEWEB)

    Sonninen, R.; Leisio, C.

    1996-11-01

    Oxygen dissolving in district heating water through district heat pipes and pipe joints made of plastic corrodes many small and medium-size district heating systems, resulting in heat cuts in the buildings connected to these systems. IN some cases, corrosion products have even circulated back to district heating power plants, thus hampering heat generation in the worst of cases. People residing in blocks of flats where some radiator components are made of plastic also face a similar problem, though on a smaller scale. A small and efficient electrochemical deoxidation cell has now been invented to eliminate this nuisance, which occurs particularly in cold winter weather. (orig.)

  7. Potential escalation of heat-related working costs with climate and socioeconomic changes in China.

    Science.gov (United States)

    Zhao, Yan; Sultan, Benjamin; Vautard, Robert; Braconnot, Pascale; Wang, Huijun J; Ducharne, Agnes

    2016-04-26

    Global climate change will increase the frequency of hot temperatures, impairing health and productivity for millions of working people and raising labor costs. In mainland China, high-temperature subsidies (HTSs) are allocated to employees for each working day in extremely hot environments, but the potential heat-related increase in labor cost has not been evaluated so far. Here, we estimate the potential HTS cost in current and future climates under different scenarios of socioeconomic development and radiative forcing (Representative Concentration Pathway), taking uncertainties from the climate model structure and bias correction into account. On average, the total HTS in China is estimated at 38.6 billion yuan/y (US $6.22 billion/y) over the 1979-2005 period, which is equivalent to 0.2% of the gross domestic product (GDP). Assuming that the HTS standards (per employee per hot day) remain unchanged throughout the 21st century, the total HTS may reach 250 billion yuan/y in the 2030s and 1,000 billion yuan/y in 2100. We further show that, without specific adaptation, the increased HTS cost is mainly determined by population growth until the 2030s and climate change after the mid-21st century because of increasingly frequent hot weather. Accounting for the likely possibility that HTS standards follow the wages, the share of GDP devoted to HTS could become as high as 3% at the end of 21st century. PMID:27044089

  8. Atucha I nuclear power plant: repair works in QK02W01 moderator system heat exchanger

    International Nuclear Information System (INIS)

    Atucha I nuclear power plant moderator system operates with highly radioactive heavy water, a pressure of 115 Bar and temperatures of about 200 C degrees. In March 2000, an increasing leakage of heavy water to the conventional thermal circuit was detected, conducting the plant to a shut down. The development of a number of actions and measures were taken, in order to plug this leakage. The leakage was found in a heat exchanger, which is located in a place of difficult access, with a high radiological yield and which, according to design, it was not considered to be mechanically repaired. It is a U bend tubes heat exchanger, weighting about 20 tons, and with a heavy water flow of 800 tons/h on the primary circuit, and 950 tons/h of ordinary water on the secondary side. Foreseeing this event, it had been designed and constructed special equipment and procedures, by means of a contract, with the Company INVAP SA. Repair works were carried out within a period of eighty-six (86) days, from which, forty five days were used to repair the component itself. A considerable amount of time was used to prepare simulators and the training of personnel. Due to the high radiological yield and the strict care of radiological standards, it was necessary the participation of 300 persons, integrating a collective dose of 4,86 Sv-m. It was necessary the construction of platforms and auxiliary stairs so as to make the work place accessible, as well as lifting and movement devices for heavy components, since this area does not have such kind of facilities. Welding and cutting machines remote controlled as well as manipulators which operated in front of the exchanger tube sheet were used. The aim was the reduction of dose values as much as possible. Special shielding were developed and in some cases it was necessary the adoption of drastic measures such as the cutting of bolts or pipes. The failure was detected and the tube was plugged. Also were plugged those tubes with wall thickness

  9. Prediction of heat transfer of nanofluid on critical heat flux based on fractal geometry

    Institute of Scientific and Technical Information of China (English)

    Xiao Bo-Qi

    2013-01-01

    Analytical expressions for nucleate pool boiling heat transfer of nanofluid in the critical heat flux (CHF) region are derived taking into account the effect of nanoparticles moving in liquid based on the fractal geometry theory.The proposed fractal model for the CHF of nanofluid is explicitly related to the average diameter of the nanoparticles,the volumetric nanoparticle concentration,the thermal conductivity of nanoparticles,the fractal dimension of nanoparticles,the fractal dimension of active cavities on the heated surfaces,the temperature,and the properties of the fluid.It is found that the CHF of nanofluid decreases with the increase of the average diameter of nanoparticles.Each parameter of the proposed formulas on CHF has a clear physical meaning.The model predictions are compared with the existing experimental data,and a good agreement between the model predictions and experimental data is found.The validity of the present model is thus verified.The proposed fractal model can reveal the mechanism of heat transfer in nanofluid.

  10. Continued Water-Based Phase Change Material Heat Exchanger Development

    Science.gov (United States)

    Hansen, Scott W.; Sheth, Rubik B.; Poynot, Joe; Giglio, Tony; Ungar, Gene K.

    2015-01-01

    In a cyclical heat load environment such as low Lunar orbit, a spacecraft's radiators are not sized to meet the full heat rejection demands. Traditionally, a supplemental heat rejection device (SHReD) such as an evaporator or sublimator is used to act as a "topper" to meet the additional heat rejection demands. Utilizing a Phase Change Material (PCM) heat exchanger (HX) as a SHReD provides an attractive alternative to evaporators and sublimators as PCM HX's do not use a consumable, thereby leading to reduced launch mass and volume requirements. In continued pursuit of water PCM HX development two full-scale, Orion sized water-based PCM HX's were constructed by Mezzo Technologies. These HX's were designed by applying prior research on freeze front propagation to a full-scale design. Design options considered included bladder restraint and clamping mechanisms, bladder manufacturing, tube patterns, fill/drain methods, manifold dimensions, weight optimization, and midplate designs. Two units, Units A and B, were constructed and differed only in their midplate design. Both units failed multiple times during testing. This report highlights learning outcomes from these tests and are applied to a final sub-scale PCM HX which is slated to be tested on the ISS in early 2017.

  11. Technoeconomic analysis of a biomass based district heating system

    International Nuclear Information System (INIS)

    This paper discussed a proposed biomass-based district heating system to be built for the Pictou Landing First Nation Community in Nova Scotia. The community centre consists of 6 buildings and a connecting arcade. The methodology used to size and design heating, ventilating and air conditioning (HVAC) systems, as well as biomass district energy systems (DES) were discussed. Annual energy requirements and biomass fuel consumption predictions were presented, along with cost estimates. A comparative assessment of the system with that of a conventional oil fired system was also conducted. It was suggested that the design and analysis methodology could be used for any similar application. The buildings were modelled and simulated using the Hourly Analysis Program (HAP), a detailed 2-in-1 software program which can be used both for HVAC system sizing and building energy consumption estimation. A techno-economics analysis was conducted to justify the viability of the biomass combustion system. Heating load calculations were performed assuming that the thermostat was set constantly at 22 degrees C. Community centre space heating loads due to individual envelope components for 3 different scenarios were summarized, as the design architecture for the buildings was not yet finalized. It was suggested that efforts should be made to ensure air-tightness and insulation levels of the interior arcade glass wall. A hydronic distribution system with baseboard space heating units was selected, comprising of a woodchip boiler, hot water distribution system, convective heating units and control systems. The community has its own logging operation which will provide the wood fuel required by the proposed system. An outline of the annual allowable harvest covered by the Pictou Landing Forestry Management Plan was presented, with details of proposed wood-chippers for the creation of biomass. It was concluded that the woodchip combustion system is economically preferable to the

  12. Facilitating Chemistry Teachers to Implement Inquiry-Based Laboratory Work

    Science.gov (United States)

    Cheung, Derek

    2008-01-01

    Science teachers generally find inquiry-based laboratory work very difficult to manage. This research project aimed at facilitating chemistry teachers to implement inquiry-based laboratory work in Hong Kong secondary schools. The major concerns of seven chemistry teachers were identified. They were most concerned about the lack of class time,…

  13. WORK BASED HIGHER LEARNING FOR THE DANISH TOURISM SECTOR

    DEFF Research Database (Denmark)

    Lindegaard, Klaus; Voergård-Olesen, Rikke Karen

    2012-01-01

    The paper reports on an investigation of the business needs for work based higher learning in the Danish tourism sector and the match with the supply of higher education, emphasizing opportunities and barriers for work based learning (WBL) in the Danish University System. The Danish tourism secto...

  14. Magnetocaloric heat-pump cycles based on the AF-F transition in Fe-Rh alloys

    Energy Technology Data Exchange (ETDEWEB)

    Annaorazov, M.P. E-mail: annaoraz@bahcesehir.edu.trannaoraz@hotmail.com; Uenal, M.; Nikitin, S.A.; Tyurin, A.L.; Asatryan, K.A

    2002-10-01

    The proposal involves a heat-pumping scheme based upon the first-order antiferromagnetism-ferromagnetism transition in FeRh alloy. Using the model S-T diagram for this alloy, the heat-pump cycles, are drawn up based on the transition latent heat absorption and emission when the transition is induced by applying magnetic field. The calculated values of heat coefficient {phi} for the cycles are {approx}39 at {delta}T=5 K and {approx}30 at {delta}T=10 K, where {delta}T is the difference between the temperature surrounding and that of the heat receiver. These values are achieved using the comparatively low magnetic fields of {approx}2x10{sup 6} A m{sup -1}. The high values of {phi}, together with high value of cooling capacity, make it possible to consider Fe-Rh alloys as an effective magnetic heat-pump working body near the room temperature.

  15. Characteristics of heat transfer from the working medium to the case of an axial-flow compressor

    Science.gov (United States)

    Lokai, V. I.; Karimova, A. G.; Prokopev, V. I.

    The heat transfer from the working medium to the case of an axial-flow compressor is investigated experimentally over a wide range of rpm (7000-17,000), air flow rates, and radial clearances between the case and the rotor. A nonuniform distribution of heat transfer coefficients over different parts of the case is observed for all the operating conditions investigated. Maximum heat transfer coefficients have been measured over the rotor near the exit; somewhat lower heat transfer coefficients have been recorded in the radial clearance behind the rotor; and still lower heat transfer coefficients have been observed at the ends of the interblade channels of the guide vanes and in the radial clearance behind them.

  16. Cardiac tissue ablation with catheter-based microwave heating.

    Science.gov (United States)

    Rappaport, C

    2004-11-01

    The common condition of atrial fibrillation is often treated by cutting diseased cardiac tissue to disrupt abnormal electrical conduction pathways. Heating abnormal tissue with electromagnetic power provides a minimally invasive surgical alternative to treat these cardiac arrhythmias. Radio frequency ablation has become the method of choice of many physicians. Recently, microwave power has also been shown to have great therapeutic benefit in medical treatment requiring precise heating of biological tissue. Since microwave power tends to be deposited throughout the volume of biological media, microwave heating offers advantages over other heating modalities that tend to heat primarily the contacting surface. It is also possible to heat a deeper volume of tissue with more precise control using microwaves than with purely thermal conduction or RF electrode heating. Microwave Cardiac Ablation (MCA) is used to treat heart tissue that allows abnormal electrical conduction by heating it to the point of inactivation. Microwave antennas that fit within catheter systems can be positioned close to diseased tissue. Specialized antenna designs that unfurl from the catheter within the heart can then radiate specifically shaped fields, which overcome problems such as excessive surface heating at the contact point. The state of the art in MCA is reviewed in this paper and a novel catheter-based unfurling wide aperture antenna is described. This antenna consists of the centre conductor of a coaxial line, shaped into a spiral and insulated from blood and tissue by a non-conductive fluid filled balloon. Initially stretched straight inside a catheter for transluminal guiding, once in place at the cardiac target, the coiled spiral antenna is advanced into the inflated balloon. Power is applied in the range of 50-150 W at the reserved industrial, scientific and medical (ISM) frequency of 915 MHz for 30-90 s to create an irreversible lesion. The antenna is then retracted back into the

  17. Effects of Stress Work on MHD Natural Convection Flow along a Vertical Wavy Surface with Joule Heating

    Directory of Open Access Journals (Sweden)

    Kazi Humayun Kabir

    2015-01-01

    Full Text Available An analysis is presented to investigate the influences of viscous and pressure stress work on MHD natural convection flow along a uniformly heated vertical wavy surface. The governing equations are first modified and then transformed into dimensionless non-similar equations by using set of suitable transformations. The transformed boundary layer equations are solved numerically using the implicit finite difference method, known as Keller-box scheme. Numerical results for the velocity profiles, temperature profiles, skin friction coefficient, the rate of heat transfers, streamlines and isotherms are shown graphically. Some results of skin friction, rate of heat transfer are presented in tabular form for selected values of physical parameters.

  18. The Gravitational Heat Exchanger

    OpenAIRE

    De Aquino, Fran

    2015-01-01

    The heat exchangers are present in many sectors of the economy. They are widely used in Refrigerators, Air-conditioners, Engines, Refineries, etc. Here we show a heat exchanger that works based on the gravity control. This type of heat exchanger can be much more economic than the conventional heat exchangers.

  19. Optimizations of a model external combustion engine for maximum work output with generalized radiative heat transfer law

    Directory of Open Access Journals (Sweden)

    Kang Ma, Lingen Chen, Fengrui Sun

    2011-07-01

    Full Text Available The generalized radiative heat transfer law is introduced into a model external combustion engine with a movable piston, and effects of heat transfer laws on the optimizations of the engine for maximum work output are investigated in this paper. Numerical examples for the optimizations with linear phenomenological (n=-1, Newton’s (n=1, square (n=2, cubic (n=3 and radiative (n=4 heat transfer laws are provided, respectively, and the obtained results are compared with each other. The results show that work output and efficiency of the optimal fully cyclic operation and optimal semi-cyclic operation decrease with the increase of heat conductance, and the work output, compression ratio and efficiency of the optimal semi-cyclic operation are larger than those of optimal fully cyclic operation. Although all of the curves of volume versus time of the optimal fully cyclic operation and the Euler-Lagrange (E-L arcs of the optimal semi-cyclic operation are nearly sinusoidal and consist of three stages with the five heat transfer laws, the curves with different heat transfer laws are different.

  20. Finite Volume Based Computer Program for Ground Source Heat Pump System

    Energy Technology Data Exchange (ETDEWEB)

    Menart, James A. [Wright State University

    2013-02-22

    This report is a compilation of the work that has been done on the grant DE-EE0002805 entitled ?Finite Volume Based Computer Program for Ground Source Heat Pump Systems.? The goal of this project was to develop a detailed computer simulation tool for GSHP (ground source heat pump) heating and cooling systems. Two such tools were developed as part of this DOE (Department of Energy) grant; the first is a two-dimensional computer program called GEO2D and the second is a three-dimensional computer program called GEO3D. Both of these simulation tools provide an extensive array of results to the user. A unique aspect of both these simulation tools is the complete temperature profile information calculated and presented. Complete temperature profiles throughout the ground, casing, tube wall, and fluid are provided as a function of time. The fluid temperatures from and to the heat pump, as a function of time, are also provided. In addition to temperature information, detailed heat rate information at several locations as a function of time is determined. Heat rates between the heat pump and the building indoor environment, between the working fluid and the heat pump, and between the working fluid and the ground are computed. The heat rates between the ground and the working fluid are calculated as a function time and position along the ground loop. The heating and cooling loads of the building being fitted with a GSHP are determined with the computer program developed by DOE called ENERGYPLUS. Lastly COP (coefficient of performance) results as a function of time are provided. Both the two-dimensional and three-dimensional computer programs developed as part of this work are based upon a detailed finite volume solution of the energy equation for the ground and ground loop. Real heat pump characteristics are entered into the program and used to model the heat pump performance. Thus these computer tools simulate the coupled performance of the ground loop and the heat pump

  1. Recovery Act: Finite Volume Based Computer Program for Ground Source Heat Pump Systems

    Energy Technology Data Exchange (ETDEWEB)

    James A Menart, Professor

    2013-02-22

    This report is a compilation of the work that has been done on the grant DE-EE0002805 entitled Finite Volume Based Computer Program for Ground Source Heat Pump Systems. The goal of this project was to develop a detailed computer simulation tool for GSHP (ground source heat pump) heating and cooling systems. Two such tools were developed as part of this DOE (Department of Energy) grant; the first is a two-dimensional computer program called GEO2D and the second is a three-dimensional computer program called GEO3D. Both of these simulation tools provide an extensive array of results to the user. A unique aspect of both these simulation tools is the complete temperature profile information calculated and presented. Complete temperature profiles throughout the ground, casing, tube wall, and fluid are provided as a function of time. The fluid temperatures from and to the heat pump, as a function of time, are also provided. In addition to temperature information, detailed heat rate information at several locations as a function of time is determined. Heat rates between the heat pump and the building indoor environment, between the working fluid and the heat pump, and between the working fluid and the ground are computed. The heat rates between the ground and the working fluid are calculated as a function time and position along the ground loop. The heating and cooling loads of the building being fitted with a GSHP are determined with the computer program developed by DOE called ENERGYPLUS. Lastly COP (coefficient of performance) results as a function of time are provided. Both the two-dimensional and three-dimensional computer programs developed as part of this work are based upon a detailed finite volume solution of the energy equation for the ground and ground loop. Real heat pump characteristics are entered into the program and used to model the heat pump performance. Thus these computer tools simulate the coupled performance of the ground loop and the heat pump. The

  2. Computational heat transfer analysis and combined ANN–GA optimization of hollow cylindrical pin fin on a vertical base plate

    Indian Academy of Sciences (India)

    C Balachandar; S Arunkumar; M Venkatesan

    2015-09-01

    In the devices like laptops, microprocessors, the electric circuits generate heat while performing work which necessitates the use of fins. In the present work, the heat transfer characteristics of hollow cylindrical pin fin array on a vertical rectangular base plate is studied using commercial CFD code ANSYS FLUENT© . The hollow cylindrical pin fins are arranged inline. The heat transfer augmentation is studied for different parameters such as inner radius, outer radius, height of the fins and number of pin fins. The base plate is supplied with a constant heat flux in the range of 20–500W. The base plate dimensions are kept constant. The base plate temperature is predicted using Artificial Neural Network (ANN) by training the network based on the results of numerical simulation. The trained ANN is used to analyse the fin in terms of enhanced heat transfer and weight reduction when compared to solid pin fin. Optimization of the hollow cylindrical pin fin parameters to obtain maximum heat transfer from the base plate is carried out using Genetic Algorithm (GA) applied on the trained neural network. The analysis using the numerical simulation and neural network shows that the hollow fins provide an increased heat transfer and a weight reduction of about 90% when compared to solid cylindrical pin fins.

  3. A Framework for Interactive Work Design based on Digital Work Analysis and Simulation

    CERN Document Server

    Ma, Liang; Fu, Huanzhang; Guo, Yang; Chablat, Damien; Bennis, Fouad; 10.1002/hfm.20178

    2010-01-01

    Due to the flexibility and adaptability of human, manual handling work is still very important in industry, especially for assembly and maintenance work. Well-designed work operation can improve work efficiency and quality; enhance safety, and lower cost. Most traditional methods for work system analysis need physical mock-up and are time consuming. Digital mockup (DMU) and digital human modeling (DHM) techniques have been developed to assist ergonomic design and evaluation for a specific worker population (e.g. 95 percentile); however, the operation adaptability and adjustability for a specific individual are not considered enough. In this study, a new framework based on motion tracking technique and digital human simulation technique is proposed for motion-time analysis of manual operations. A motion tracking system is used to track a worker's operation while he/she is conducting a manual handling work. The motion data is transferred to a simulation computer for real time digital human simulation. The data ...

  4. Design, Fabrication and Testing of Two Different Laboratory Prototypes of CSI-based Induction Heating Units

    Science.gov (United States)

    Roy, M.; Sengupta, M.

    2012-09-01

    Induction heating is a non-contact heating process which became popular due to its energy efficiency. Current source inverter (CSI) based induction heating units are commonly used in the industry. Most of these CSIs are thyristor based, since thyristors of higher ratings are easily available. These being load commutated apparatus a start-up circuit is needed to initiate commutation. In this paper the design and fabrication of two laboratory prototypes have been presented. The first one, a SCR-based CSI fed controlled induction heating unit (IHU), has been tested with two different types of start-up procedures. Thereafter the fabrication and performance of another IGBT-based CSI is compared with the thyristor-based CSI for a 2 kW, 10 kHz application. These two types of CSIs are fully fabricated in laboratory along with the IHU. Performance analysis and simulation of two different CSIs has been done by using SequelGUI2. The triggering pulses for the inverter devices (for both CSI devices as well as auxilliary thyristor of start-up circuit) have been generated and closed-loop control has been done in FPGA platform built around an Altera make cyclone EPIC12Q240C processor which can be programmed using Quartus II software. Close agreement between simulated and experimental results highlight the accuracy of the experimental work.

  5. HEAT EXPOSURE ASSESSMENT IN THE WORKING ENVIRONMENT OF A GLASS MANUFACTURING UNIT

    Directory of Open Access Journals (Sweden)

    M. Pourmahabadian, M. Adelkhah, K. Azam

    2008-04-01

    Full Text Available Heat stress is a common health problem throughout industry. Any heat stress evaluation requires some exposure assessment of climatic conditions, especially air temperature, humidity, and speed, along with the average temperature of the solid surroundings. In this paper workplace environmental climatic parameters were measured and then evaluated by Wet Bulb Globe Temperature, Corrected Effective Temperature, Heat Stress Index, and Allowable Exposure Time indices among 40 workers in a glass manufacturing unit in Tehran. Also, the effect of available heat control devices on heat stress indices was investigated. The results of this study showed that the obtained heat stress index in individual section and press units is exceeded from 100 (in individual section unit: 302.6, in press unit: 283.6. Also, it is found that the mean average of allowable exposure time in individual section and press units were 13.15 and 12.26 minutes exposure for one hour, respectively. No significant relationship was found between environmental parameters in three parts of body regions (height of head, abdomen and ankle except for measured air velocity in both units (P<0.007. Positive correlation was found between wet bulb globe temperature, corrected effective temperature and heat stress index indices, but negative correlation was found between allowable exposure time and other indices. Mann Whitney non-parametric test revealed significant relationships in wet bulb globe temperature, corrected effective temperature, heat stress index and allowable exposure time indices when metallic shield was used as heat absorber.

  6. Performance of ammonia–water based cycles for power generation from low enthalpy heat sources

    International Nuclear Information System (INIS)

    Cost efficient power generation from low temperature heat sources requires an optimal usage of the available heat. In addition to the ORC (Organic Rankine Cycles), cycles with ammonia and water as working fluid show promising results regarding efficiency. Due to their non-isothermal phase change, mixtures can adapt well to a liquid heat source temperature profile and reduce the exergetic losses. In this analysis thermodynamic calculations on the layouts of two existing ammonia–water cycles are compared: a geothermal power plant based on a Siemens’ patent and a modified lab plant based on a patent invented by Kalina (KCS-34). The difference between the two cycles is the position of the internal heat recovery. Cycle simulations were carried out at defined boundary conditions in order to identify optimal operation parameters. For the selected heat source of 393.15 K (hot water) the ammonia mass fraction between 80% and 90% results in the best performance in both configurations. In general, the layout of Siemens achieves a slightly better efficiency compared to the KCS-34. Compared to an ORC using R245fa as working fluid, the exergetic efficiency can be increased by the ammonia/water based cycles by approximately 25%. - Highlights: • Two NH3/H2O based cycles based on existing plants are analyzed and compared. • A simple KCS-34 focuses on a high enthalpy difference at the turbine. • The Kalina cycle of a Siemens patent KC SG1 runs on a high vapor mass flow. • The layout of the KC SG1 shows slightly better results compared to the KCS-34. • NH3/H2O cycles show an efficiency increase compared to a regular ORC with R245fa

  7. Heat pump-based geothermal energy. Technical and economic study. The costs of heat-pump-based geothermal energy

    International Nuclear Information System (INIS)

    This study aims at identifying the financial basis on which actors of a geothermal project for heating, cooling and hot water production can rely. It also aims at describing the three main technical solutions for very-low-energy geothermal: horizontal sensors, vertical probes, and geothermal doublets on aquifer. After a presentation of the adopted methodology and of the different economic, thermal and technical hypotheses, the respective costs of these technical solutions are assessed and a comparison between these systems and conventional energies is reported. The economic study is performed for different markets: individual housing, collective housing, and office building. Different aspects of each operation are studied: underground works (drilling) and surface equipment (heat pump and support). Investment, maintenance and operational costs are analysed

  8. Phonon Boltzmann equation-based discrete unified gas kinetic scheme for multiscale heat transfer

    CERN Document Server

    Guo, Zhaoli

    2016-01-01

    Numerical prediction of multiscale heat transfer is a challenging problem due to the wide range of time and length scales involved. In this work a discrete unified gas kinetic scheme (DUGKS) is developed for heat transfer in materials with different acoustic thickness based on the phonon Boltzmann equation. With discrete phonon direction, the Boltzmann equation is discretized with a second-order finite-volume formulation, in which the time-step is fully determined by the Courant-Friedrichs-Lewy (CFL) condition. The scheme has the asymptotic preserving (AP) properties for both diffusive and ballistic regimes, and can present accurate solutions in the whole transition regime as well. The DUGKS is a self-adaptive multiscale method for the capturing of local transport process. Numerical tests for both heat transfers with different Knudsen numbers are presented to validate the current method.

  9. Titanium based flat heat pipes for computer chip cooling

    Science.gov (United States)

    Soni, Gaurav; Ding, Changsong; Sigurdson, Marin; Bozorgi, Payam; Piorek, Brian; MacDonald, Noel; Meinhart, Carl

    2008-11-01

    We are developing a highly conductive flat heat pipe (called Thermal Ground Plane or TGP) for cooling computer chips. Conventional heat pipes have circular cross sections and thus can't make good contact with chip surface. The flatness of our TGP will enable conformal contact with the chip surface and thus enhance cooling efficiency. Another limiting factor in conventional heat pipes is the capillary flow of the working fluid through a wick structure. In order to overcome this limitation we have created a highly porous wick structure on a flat titanium substrate by using micro fabrication technology. We first etch titanium to create very tall micro pillars with a diameter of 5 μm, a height of 40 μm and a pitch of 10 μm. We then grow a very fine nano structured titania (NST) hairs on all surfaces of the pillars by oxidation in H202. In this way we achieve a wick structure which utilizes multiple length scales to yield high performance wicking of water. It's capable of wicking water at an average velocity of 1 cm/s over a distance of several cm. A titanium cavity is laser-welded onto the wicking substrate and a small quantity of water is hermetically sealed inside the cavity to achieve a TGP. The thermal conductivity of our preliminary TGP was measured to be 350 W/m-K, but has the potential to be several orders of magnitude higher.

  10. Organizational and Employee Interests in Programs of Work Based Learning.

    Science.gov (United States)

    Costley, Carol

    2001-01-01

    A study of two university centers that operate in-house work-based learning programs for employers showed that employees gained considerable benefits, although there were tensions between their self-development needs and organizational needs. Organizations increased the intellectual capital of the work force but needed better ways to manage…

  11. Experimental and computational investigation of a MEMS-based boiler for waste heat recovery

    International Nuclear Information System (INIS)

    Highlights: • A microboiler with capillary channels for low temperature energy harvesting. • Complete thermodynamic analysis is completed. • The boiler is designed for minimum thermal losses. • Capability of capillary channels to pump at various pressure is investigated. - Abstract: Thermodynamically limited processes make waste heat abundant in availability. An Organic Rankine Cycle (ORC) steam powered micro system designed to scavenge waste heat from various sources (transportation, industries or solar) is presented. The key boiler component is fabricated and characterized in this work. The system design has been inspired by the various efforts implemented in development of micro heat recovery devices and engines. The complete system consists of three individual micro components (1) boiler, (2) free piston expander and (3) superheater. Specifically, design, fabrication techniques, test setup and results of the miniaturized boiler are presented in this paper. A key design feature of the boiler is the inclusion of capillary channels for fluid flow from the surrounding reservoirs to the heated area. The pressurized steam is created by the boiler as a result of phase transformation of the working fluid. This pressurized steam can be utilized to drive another MEMS device (PZT membranes, turbines, thermoelectric, etc.) to generate power. In this upgraded boiler design, radial capillary channels and a thin film glass steamdome were considered to improve the operating efficiency. These inclusions enhanced capillary flow, energy absorption via phase change, mass flow rate and operating pressure. The power inputs of 1.8 W and 2.7 W were selected to simulate and characterize the boiler performance based on real-world waste heat source temperatures. For these power inputs, the maximum power absorption efficiency demonstrated by the boiler via phase change of the working fluid was approximately 88%. The peak operating pressure demonstrated by the boiler was 8.5 k

  12. Design-based practice: a new perspective for social work.

    Science.gov (United States)

    Cohen, Burton J

    2011-10-01

    Evidence-based practice (EBP) has emerged as an alternative to traditional social work practice and has ignited a new round in the decades-old debate about the relationship between knowledge and practice in the field. This article identifies several limitations inherent in the EBP perspective and argues that it would be unfortunate if EBP were to become the new paradigm for social work practice and education. It also presents a new perspective for social work called design-based practice (DBP), which is based on the work of Herbert Simon and Mary Parker Follett, and compares this perspective with EBP and authority-based practice. DBP rests on the belief that knowledge is derived from experience and interactions between practitioners and clients and that professional practice should be primarily concerned with "how things ought to be."

  13. The Heat Is on: An Inquiry-Based Investigation for Specific Heat

    Science.gov (United States)

    Herrington, Deborah G.

    2011-01-01

    A substantial number of upper-level science students and practicing physical science teachers demonstrate confusion about thermal equilibrium, heat transfer, heat capacity, and specific heat capacity. The traditional method of instruction, which involves learning the related definitions and equations, using equations to solve heat transfer…

  14. Exploring policy options for a transition to sustainable heating system diffusion using an agent-based simulation

    International Nuclear Information System (INIS)

    Change in home heating to more efficient and renewable systems is important for a sound climate policy. The present paper aims to identify potential interventions for the uptake of wood-pellet heating in Norway using an agent-based model (ABM). The theoretically based, empirically founded, agent-based simulation demonstrates that financial support, i.e., a stable wood-pellet price, and technical development, i.e., functional reliability improvement, have to be established all at the same time for a successful wood-pellet market to start. Furthermore, a soft intervention through persuading households to use environmentally beneficial heating system is not a promising driver for wood-pellet diffusion. Limitations and suggestions for future work are also discussed. - Research highlights: → The theoretically based, empirically founded, agent-based simulation is applied to investigate potential policy options toward diffusion of wood-pellet heating in Norway. → Relative advantages are necessary for wood-pellet heating to be adopted, consistent with Diffusion of Innovation theory (). → Simultaneous development is also required for further uptake of wood-pellet heating, supporting the existing empirical hypothesis by . → Persuading households to use environmentally friendly heating system is not a promising driver, in line with empirical finding of , who investigated psychological factors underlying the adoption of wood-pellet heating.

  15. Exploring policy options for a transition to sustainable heating system diffusion using an agent-based simulation

    Energy Technology Data Exchange (ETDEWEB)

    Maya Sopha, Bertha, E-mail: bertha.sopha@ntnu.n [Industrial Ecology Programme and Department of Energy and Process Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway); Kloeckner, Christian A. [Department of Psychology, Section for Risk Psychology, Environment and Safety (RIPENSA), Norwegian University of Science and Technology, NO-7491 Trondheim (Norway); Hertwich, Edgar G. [Industrial Ecology Programme and Department of Energy and Process Engineering, Norwegian University of Science and Technology, NO-7491 Trondheim (Norway)

    2011-05-15

    Change in home heating to more efficient and renewable systems is important for a sound climate policy. The present paper aims to identify potential interventions for the uptake of wood-pellet heating in Norway using an agent-based model (ABM). The theoretically based, empirically founded, agent-based simulation demonstrates that financial support, i.e., a stable wood-pellet price, and technical development, i.e., functional reliability improvement, have to be established all at the same time for a successful wood-pellet market to start. Furthermore, a soft intervention through persuading households to use environmentally beneficial heating system is not a promising driver for wood-pellet diffusion. Limitations and suggestions for future work are also discussed. - Research highlights: {yields} The theoretically based, empirically founded, agent-based simulation is applied to investigate potential policy options toward diffusion of wood-pellet heating in Norway. {yields} Relative advantages are necessary for wood-pellet heating to be adopted, consistent with Diffusion of Innovation theory (). {yields} Simultaneous development is also required for further uptake of wood-pellet heating, supporting the existing empirical hypothesis by . {yields} Persuading households to use environmentally friendly heating system is not a promising driver, in line with empirical finding of , who investigated psychological factors underlying the adoption of wood-pellet heating.

  16. It's Too Hot! It's Too Cold!--Understanding How Heat Works

    Science.gov (United States)

    Roman, Harry T.

    2012-01-01

    Engineers often measure temperature for a wide variety of applications and assessments. This article describes how STEM educators can use thermometers or temperature sensors to help students understand how heat disperses through fluids, both air and water. It also provides hands-on learning about air and water heating systems. (Contains 4 figures.)

  17. Waste Contaminants at Military Bases Working Group report

    International Nuclear Information System (INIS)

    The Waste Contaminants at Military Bases Working Group has screened six prospective demonstration projects for consideration by the Federal Advisory Committee to Develop On-Site Innovative Technologies (DOIT). These projects include the Kirtland Air Force Base Demonstration Project, the March Air Force Base Demonstration Project, the McClellan Air Force Base Demonstration Project, the Williams Air Force Base Demonstration Project, and two demonstration projects under the Air Force Center for Environmental Excellence. A seventh project (Port Hueneme Naval Construction Battalion Center) was added to list of prospective demonstrations after the September 1993 Working Group Meeting. This demonstration project has not been screened by the working group. Two additional Air Force remediation programs are also under consideration and are described in Section 6 of this document. The following information on prospective demonstrations was collected by the Waste Contaminants at Military Bases Working Group to assist the DOIT Committee in making Phase 1 Demonstration Project recommendations. The remainder of this report is organized into seven sections: Work Group Charter's mission and vision; contamination problems, current technology limitations, and institutional and regulatory barriers to technology development and commercialization, and work force issues; screening process for initial Phase 1 demonstration technologies and sites; demonstration descriptions -- good matches;demonstration descriptions -- close matches; additional candidate demonstration projects; and next steps

  18. Conceptual fusion reactor designs based on the laser heat solenoid

    International Nuclear Information System (INIS)

    The feasibility of the laser heated solenoid (LHS) as an approach to fusion and fusion-fission commercial power generation has been examined. The LHS concept is based on magnetic confinement of a long slender plasma column which is partly heated by the axially directed beam from a powerful long wavelength laser. As a pure fusion concept, the LHS configurations studied so far are characterized by fairly difficult engineering constraints, particularly on the magnet, a large laser, and a marginally acceptable system energy balance. As a fusion-fission system, however, the LHS is capable of a very attractive energy balance, has much more relaxed engineering constraints, requires a relatively modest laser, and as such holds great potential as a power generator and fissile fuel breeding scheme

  19. Laser-heating-based active optics for synchrotron radiation applications

    CERN Document Server

    Yang, Fugui; Zhang, Xiaowei

    2016-01-01

    Active optics has attracted considerable interest from researchers in synchrotron radiation facilities, because of its capacity for x-ray wavefront correction. Here, we report a novel and efficient technique for correcting or modulating a mirror surface profile based on laser-heating-induced thermal expansion. An experimental study of the characteristics of the surface thermal deformation response indicates that the power of a milliwatt laser yields a bump height as low as sub-nanometer scale, and that variation of the spot size modulates the response function width effectively. In addition, the capacity of the laser-heating technique for free-form surface modulation is demonstrated via a surface correction experiment. The developed method is a promising new approach towards effective x-ray active optics coupled with at-wavelength metrology techniques.

  20. Work.

    Science.gov (United States)

    Haines, Annette M.

    2003-01-01

    Draws upon Maria Montessori's writings to examine work as a universal human tendency throughout life. Discusses the work of adaptation of the infant, work of "psycho-muscular organism" for the preschooler, work of the imagination for the elementary child, community work of the adolescent, and work of the adult. Asserts that Montessorians' role is…

  1. Satellite and ground-based sensors for the Urban Heat Island analysis in the city of Rome

    DEFF Research Database (Denmark)

    Fabrizi, Roberto; Bonafoni, Stefania; Biondi, Riccardo

    2010-01-01

    In this work, the trend of the Urban Heat Island (UHI) of Rome is analyzed by both ground-based weather stations and a satellite-based infrared sensor. First, we have developed a suitable algorithm employing satellite brightness temperatures for the estimation of the air temperature belonging...

  2. Methods of increasing net work output of organic Rankine cycles for low-grade waste heat recovery with a detailed analysis using a zeotropic working fluid mixture and scroll expander

    Science.gov (United States)

    Woodland, Brandon Jay

    performance to cost ratio of this machine lends significant credence to the economic viability of small-scale, low-temperature ORCs. The experimental campaign covered two heat source temperatures, the full range of pump and expander speeds, a full range of heat source and heat sink fluid flow rates, and various charge levels for the three working fluids. This resulted in 366 steady-state measurements. The steady state measurements are used to develop a detailed ORC model. The model is based on multi-fluid performance maps for the pump and expander and a robust moving-boundary heat exchanger model. It is validated against the measured data and predicts the net power output of the tested ORC with a mean absolute percent error of 7.16%. Comparisons made with the detailed model confirm the predictions of the design-stage model. Using a conservative estimate of the condenser fan power, 19.1% improvement of the ZRC over the baseline ORC is indicated for a source temperature of 80 °C. For a 100 °C source temperature, 13.8% improvement is indicated. A key feature of the detailed ORC model is that it calculates the charge inventory of the working fluid in each heat exchanger and line set. Total system charge can also be specified as a model input. The model can represent the total charge well for R134a at low measured charge levels. As the measured charge level increases, the model becomes less accurate. Reasons for the deviation of the model at higher charge are investigated. It is expected that a charge tuning scheme could be employed to improve the accuracy of model-predicted charge.

  3. Cogeneration heating system based on ejector heat pumps%基于喷射式热泵的热电联产供热系统

    Institute of Scientific and Technical Information of China (English)

    徐翔; 王远超; 张博

    2014-01-01

    There are two serious problems in the combined heat and power system:with the increase of heating area and quality, the heating is insufficient; the heavy discharge of low-grade thermal energy in the circulating cooling water wastes energy seriously. A novel system is presented based on ejector heat pumps (EDH-CHP) to solve the two problems by improving the heating capacity of the district heating system. It recycles the waste heat from circulating cooling water for district heating, and increases the heating capacity of the existing heating network by increasing the temperature difference between the water streams supplying and returning the original heating network. Compared with a traditional system, the new one has an additional ejector heat pump in the heating station, named HP1, and another ejector heat pump in the heating substation, named HP2. Thermodynamic analysis and experimental study are carried out for the two ejector heat pumps. The results show that both HP1 and HP2 can improve the performance of district heating under normal working conditions. Experimental results show that the COP of HP1 can reach 1.4-1.9 and the temperature of returning water in the original network can be decreased to 35℃ in HP2. A typical case study shows that the EDH-CHP system can improve the heating capacity of the existing heating network by 50% by adding 30% steam consumption, or improve the heating capacity of the existing heating network by 9% at the same steam consumption, or decrease the energy consumption by 6%at the same heating capacity.%热电联产面临着两个严重问题:供热面积与质量的增加导致供热不足;电厂凝汽器循环冷却水存在大量低品质热量浪费。为同时解决这两个问题,提出了一种利用喷射式热泵强化集中供热的新型EDH-CHP系统。该系统从循环冷却水中回收余热,并将余热应用于集中供热;另外通过增大供热一次网的供回水温差提高原一次网的供热

  4. ESTIMATION OF WORKING CONDITIONS OF FOUNDRY WORKERS BY INFRARED (HEAT RADIATION

    Directory of Open Access Journals (Sweden)

    A. M. Lazarenkov

    2010-01-01

    Full Text Available The description of infrared radiations, their influence on human organism is given. The results of investigation of infrared (heat radiation intensity on the workers in foundries are given.

  5. Pipeline heating method based on optimal control and state estimation

    Energy Technology Data Exchange (ETDEWEB)

    Vianna, F.L.V. [Dept. of Subsea Technology. Petrobras Research and Development Center - CENPES, Rio de Janeiro, RJ (Brazil)], e-mail: fvianna@petrobras.com.br; Orlande, H.R.B. [Dept. of Mechanical Engineering. POLI/COPPE, Federal University of Rio de Janeiro - UFRJ, Rio de Janeiro, RJ (Brazil)], e-mail: helcio@mecanica.ufrj.br; Dulikravich, G.S. [Dept. of Mechanical and Materials Engineering. Florida International University - FIU, Miami, FL (United States)], e-mail: dulikrav@fiu.edu

    2010-07-01

    In production of oil and gas wells in deep waters the flowing of hydrocarbon through pipeline is a challenging problem. This environment presents high hydrostatic pressures and low sea bed temperatures, which can favor the formation of solid deposits that in critical operating conditions, as unplanned shutdown conditions, may result in a pipeline blockage and consequently incur in large financial losses. There are different methods to protect the system, but nowadays thermal insulation and chemical injection are the standard solutions normally used. An alternative method of flow assurance is to heat the pipeline. This concept, which is known as active heating system, aims at heating the produced fluid temperature above a safe reference level in order to avoid the formation of solid deposits. The objective of this paper is to introduce a Bayesian statistical approach for the state estimation problem, in which the state variables are considered as the transient temperatures within a pipeline cross-section, and to use the optimal control theory as a design tool for a typical heating system during a simulated shutdown condition. An application example is presented to illustrate how Bayesian filters can be used to reconstruct the temperature field from temperature measurements supposedly available on the external surface of the pipeline. The temperatures predicted with the Bayesian filter are then utilized in a control approach for a heating system used to maintain the temperature within the pipeline above the critical temperature of formation of solid deposits. The physical problem consists of a pipeline cross section represented by a circular domain with four points over the pipe wall representing heating cables. The fluid is considered stagnant, homogeneous, isotropic and with constant thermo-physical properties. The mathematical formulation governing the direct problem was solved with the finite volume method and for the solution of the state estimation problem

  6. Performance characteristic of thermosyphon heat pipe at radiant heat source

    Science.gov (United States)

    Hrabovský, Peter; Papučík, Štefan; Kaduchová, Katarína

    2016-06-01

    This article discusses about device, which is called heat pipe. This device is with heat source with radiant heat source. Heat pipe is device with high efficiency of heat transfer. The heat pipe, which is describe in this article is termosyphon heat pipe. The experiment with termosyphon heat pipe get a result. On the base of result, it will be in future to create mathematical model in Ansys. Thermosyphon heat pipe is made of copper and distilled water is working fluid. The significance of this experiment consists in getting of the heat transfer and performance characteristic. On the basis of measured and calculated data can be constructed the plots.

  7. The Netherlands. Complex ground source heat drilling for horticultural works; Niederlande. Komplexe Erdwaermebohrung fuer Gartenbaubetriebe

    Energy Technology Data Exchange (ETDEWEB)

    Kilian, Dieter [DrillTec GUT GmbH, Deggendorf (Germany)

    2012-11-01

    For the past six months, the Dutch gardening industry looked to Honselersdijk near Rotterdam with great expectations. There, five market gardening businesses planned to heat their greenhouses with geothermal heat instead of natural gas. After technically complex drilling operations, hot water is now flowing at a rate of up to 50 litres per second; the drilling project remained fascinating to the last for everybody involved.

  8. Teaching about Faith-Based Organizations in the Social Work Curriculum: Perspectives of Social Work Educators

    Science.gov (United States)

    Pandya, Samta P.

    2016-01-01

    Faith-based organizations (FBOs) have an important presence in contemporary civil society and have gained further prominence through their repertoire of social welfare and services. This study engaged social work educators (n = 316) across nine countries to examine their perceptions of including discourses on faith and FBOs in the social work…

  9. Work-Based Learning and Academic Skills. IEE Working Paper No. 15.

    Science.gov (United States)

    Hughes, Katherine L.; Moore, David Thornton; Bailey, Thomas R.

    The claim that work-based experience improves students' academic performance was examined through a study of the academic progress of 25 high school and community college student interns employed in various health care workplaces. Data were collected from the following activities: (1) review of the literature on academic reinforcement and academic…

  10. What is the future of work based learning in VET?

    DEFF Research Database (Denmark)

    Jørgensen, Christian Helms

    Dual systems of vocational education and training that build on the tradition of apprenticeship have many attractive qualities, seen from a political perspective. VET systems that comprise a significant amount of work-based training, provide a valuable alternative for young people who chose...... not to pursue an academic career. Countries with strong apprenticeship systems tend to have less youth unemployment and a smoother transition to the labour market than others. Furthermore, from a learning perspective, the outcomes of work-based training and informal learning are enhanced when they are combined...... with formal education in a dual system. But historically in many countries, apprenticeship has given way to school-based forms of VET and dual systems are only dominant in a limited number of countries. Furthermore, the integration of work-based training in an educational programme involves many challenges...

  11. Optimization of heat transfer utilizing graph based evolutionary algorithms

    International Nuclear Information System (INIS)

    This paper examines the use of graph based evolutionary algorithms (GBEAs) for optimization of heat transfer in a complex system. The specific case examined in this paper is the optimization of heat transfer in a biomass cookstove utilizing three-dimensional computational fluid dynamics to generate the fitness function. In this stove hot combustion gases are used to heat a cooking surface. The goal is to provide an even spatial temperature distribution on the cooking surface by redirecting the flow of combustion gases with baffles. The variables in the optimization are the position and size of the baffles, which are described by integer values. GBEAs are a novel type of EA in which a topology or geography is imposed on an evolving population of solutions. The choice of graph controls the rate at which solutions can spread within the population, impacting the diversity of solutions and convergence rate of the EAs. In this study, the choice of graph in the GBEAs changes the number of mating events required for convergence by a factor of approximately 2.25 and the diversity of the population by a factor of 2. These results confirm that by tuning the graph and parameters in GBEAs, computational time can be significantly reduced

  12. Energy-efficient miniature-scale heat pumping based on shape memory alloys

    Science.gov (United States)

    Ossmer, Hinnerk; Wendler, Frank; Gueltig, Marcel; Lambrecht, Franziska; Miyazaki, Shuichi; Kohl, Manfred

    2016-08-01

    Cooling and thermal management comprise a major part of global energy consumption. The by far most widespread cooling technology today is vapor compression, reaching rather high efficiencies, but promoting global warming due to the use of environmentally harmful refrigerants. For widespread emerging applications using microelectronics and micro-electro-mechanical systems, thermoelectrics is the most advanced technology, which however hardly reaches coefficients of performance (COP) above 2.0. Here, we introduce a new approach for energy-efficient heat pumping using the elastocaloric effect in shape memory alloys. This development is mainly targeted at applications on miniature scales, while larger scales are envisioned by massive parallelization. Base materials are cold-rolled textured Ti49.1Ni50.5Fe0.4 foils of 30 μm thickness showing an adiabatic temperature change of +20/‑16 K upon superelastic loading/unloading. Different demonstrator layouts consisting of mechanically coupled bridge structures with large surface-to-volume ratios are developed allowing for control by a single actuator as well as work recovery. Heat transfer times are in the order of 1 s, being orders of magnitude faster than for bulk geometries. Thus, first demonstrators achieve values of specific heating and cooling power of 4.5 and 2.9 W g‑1, respectively. A maximum temperature difference of 9.4 K between heat source and sink is reached within 2 min. Corresponding COP on the device level are 4.9 (heating) and 3.1 (cooling).

  13. Energy-efficient miniature-scale heat pumping based on shape memory alloys

    Science.gov (United States)

    Ossmer, Hinnerk; Wendler, Frank; Gueltig, Marcel; Lambrecht, Franziska; Miyazaki, Shuichi; Kohl, Manfred

    2016-08-01

    Cooling and thermal management comprise a major part of global energy consumption. The by far most widespread cooling technology today is vapor compression, reaching rather high efficiencies, but promoting global warming due to the use of environmentally harmful refrigerants. For widespread emerging applications using microelectronics and micro-electro-mechanical systems, thermoelectrics is the most advanced technology, which however hardly reaches coefficients of performance (COP) above 2.0. Here, we introduce a new approach for energy-efficient heat pumping using the elastocaloric effect in shape memory alloys. This development is mainly targeted at applications on miniature scales, while larger scales are envisioned by massive parallelization. Base materials are cold-rolled textured Ti49.1Ni50.5Fe0.4 foils of 30 μm thickness showing an adiabatic temperature change of +20/-16 K upon superelastic loading/unloading. Different demonstrator layouts consisting of mechanically coupled bridge structures with large surface-to-volume ratios are developed allowing for control by a single actuator as well as work recovery. Heat transfer times are in the order of 1 s, being orders of magnitude faster than for bulk geometries. Thus, first demonstrators achieve values of specific heating and cooling power of 4.5 and 2.9 W g-1, respectively. A maximum temperature difference of 9.4 K between heat source and sink is reached within 2 min. Corresponding COP on the device level are 4.9 (heating) and 3.1 (cooling).

  14. Nano-Al Based Energetics: Rapid Heating Studies and a New Preparation Technique

    Science.gov (United States)

    Sullivan, Kyle; Kuntz, Josh; Gash, Alex; Zachariah, Michael

    2011-06-01

    Nano-Al based thermites have become an attractive alternative to traditional energetic formulations due to their increased energy density and high reactivity. Understanding the intrinsic reaction mechanism has been a difficult task, largely due to the lack of experimental techniques capable of rapidly and uniform heating a sample (~104- 108 K/s). The current work presents several studies on nano-Al based thermites, using rapid heating techniques. A new mechanism termed a Reactive Sintering Mechanism is proposed for nano-Al based thermites. In addition, new experimental techniques for nanocomposite thermite deposition onto thin Pt electrodes will be discussed. This combined technique will offer more precise control of the deposition, and will serve to further our understanding of the intrinsic reaction mechanism of rapidly heated energetic systems. An improved mechanistic understanding will lead to the development of optimized formulations and architectures. This work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  15. Metal-Organic Frameworks in Adsorption-Driven Heat Pumps: The Potential of Alcohols as Working Fluids.

    Science.gov (United States)

    de Lange, Martijn F; van Velzen, Benjamin L; Ottevanger, Coen P; Verouden, Karlijn J F M; Lin, Li-Chiang; Vlugt, Thijs J H; Gascon, Jorge; Kapteijn, Freek

    2015-11-24

    A large fraction of global energy is consumed for heating and cooling. Adsorption-driven heat pumps and chillers could be employed to reduce this consumption. MOFs are often considered to be ideal adsorbents for heat pumps and chillers. While most published works to date on this topic have focused on the use of water as a working fluid, the instability of many MOFs to water and the fact that water cannot be used at subzero temperatures pose certain drawbacks. The potential of using alcohol-MOF pairs in adsorption-driven heat pumps and chillers is investigated. To this end, 18 different selected MOF structures in combination with either methanol or ethanol as a working fluid are considered, and their potential is assessed on the basis of adsorption measurements and thermodynamic efficiencies. If alcohols are used instead of water, then (1) adsorption occurs at lower relative pressures for methanol and even lower pressure for ethanol, (2) larger pores can be utilized efficiently, as hysteresis is absent for pores smaller than 3.4 nm (2 nm for water), (3) larger pore sizes need to be employed to ensure the desired stepwise adsorption, (4) the effect of (polar/apolar) functional groups in the MOF is far less pronounced, (5) the energy released or taken up per cycle is lower, but heat and mass transfer may be enhanced, (6) stability of MOFs seems to be less of an issue, and (7) cryogenic applications (e.g., ice making) become feasible. From a thermodynamic perspective, UiO-67, CAU-3, and ZIF-8 seem to be the most promising MOFs for both methanol and ethanol as working fluids. Although UiO-67 might not be completely stable, both CAU-3 and ZIF-8 have the potential to be applied, especially in subzero-temperature adsorption chillers (AC).

  16. Maximum efficiency of ideal heat engines based on a small system: correction to the Carnot efficiency at the nanoscale.

    Science.gov (United States)

    Quan, H T

    2014-06-01

    We study the maximum efficiency of a heat engine based on a small system. It is revealed that due to the finiteness of the system, irreversibility may arise when the working substance contacts with a heat reservoir. As a result, there is a working-substance-dependent correction to the Carnot efficiency. We derive a general and simple expression for the maximum efficiency of a Carnot cycle heat engine in terms of the relative entropy. This maximum efficiency approaches the Carnot efficiency asymptotically when the size of the working substance increases to the thermodynamic limit. Our study extends Carnot's result of the maximum efficiency to an arbitrary working substance and elucidates the subtlety of thermodynamic laws in small systems.

  17. Decent work on industrial enterprise based the approach competentive

    OpenAIRE

    Humeniuk, Nataliia

    2013-01-01

    The article proves that achieving decent work possible under the coordination purposes of the enterprise with the goals of employees on the basis of explicit requirements as to such employees to the production process. In connection with the proposed use of the competency approach to create such a system of priorities, and the control scheme of responsibility includes managing staff, working conditions and social processes. Based on the generalization of human resource management processes pr...

  18. Design of plate directional heat transmission structure based on layered thermal metamaterials

    Directory of Open Access Journals (Sweden)

    L. K. Sun

    2016-02-01

    Full Text Available Invisibility cloaks based on transformation optics are often closed structures; however, such a structure limits the kinds of objects that can be placed in the cloak. In this work, we adopt a transformation thermodynamics approach to design an “open cloak”, called a plate directional heat transmission structure, which is capable of guiding heat fluxes to the flank region of the metamaterial device. The most fascinating and unique feature of the device is that the lower surface can remain at a lower temperature compared with the SiO2 aerogel thermal insulation material. Our results are expected to markedly enhance capabilities in thermal protection, thermal-energy utilization, and domains beyond. In addition to the theoretical analysis, the present design is demonstrated in numerical simulations based on finite element calculations.

  19. Design of plate directional heat transmission structure based on layered thermal metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Sun, L. K.; Yu, Z. F.; Huang, J., E-mail: slk-0-1999@163.com [China Aerodynamics Research and Development Center, Mianyang 621000 (China)

    2016-02-15

    Invisibility cloaks based on transformation optics are often closed structures; however, such a structure limits the kinds of objects that can be placed in the cloak. In this work, we adopt a transformation thermodynamics approach to design an “open cloak”, called a plate directional heat transmission structure, which is capable of guiding heat fluxes to the flank region of the metamaterial device. The most fascinating and unique feature of the device is that the lower surface can remain at a lower temperature compared with the SiO{sub 2} aerogel thermal insulation material. Our results are expected to markedly enhance capabilities in thermal protection, thermal-energy utilization, and domains beyond. In addition to the theoretical analysis, the present design is demonstrated in numerical simulations based on finite element calculations.

  20. Performance Analysis and Working Fluid Selection of a Supercritical Organic Rankine Cycle for Low Grade Waste Heat Recovery

    Directory of Open Access Journals (Sweden)

    Yourong Li

    2012-08-01

    Full Text Available The performance analysis of a supercritical organic Rankine cycle system driven by exhaust heat using 18 organic working fluids is presented. Several parameters, such as the net power output, exergy efficiency, expander size parameter (SP, and heat exchanger requirement of evaporator and the condenser, were used to evaluate the performance of this recovery cycle and screen the working fluids. The results reveal that in most cases, raising the expander inlet temperature is helpful to improve the net power output and the exergy efficiency. However, the effect of the expander inlet pressure on those parameters is related to the expander inlet temperature and working fluid used. Either lower expander inlet temperature and pressure, or higher expander inlet temperature and pressure, generally makes the net power output more. Lower expander inlet temperature results in larger total heat transfer requirement and expander size. According to the screening criteria of both the higher output and the lower investment, the following working fluids for the supercritical ORC system are recommended: R152a and R143a.

  1. Collaborative work model based on peer-to-peer network

    Institute of Scientific and Technical Information of China (English)

    JIANG Jian-zhong; FU Li; ZHANG Xuan-peng; XU Chuan-yun

    2007-01-01

    In this paper, we incorporated peer-to-peer (P2P) concept with agent technology and put forward a collaborative work model based on peer-to-peer network (P2PCWM) after investigating into business demands of modern enterprises and problems prevailing in mainstream collaborative work systems based on central server. Theoretically, the P2PCWM can effectively overcome the problems in a conventional system with a central server and meet the practical demands of modern businesses. It is distinguished from other systems by its features of equality, openness, promptness, fairness, expandability and convenience.

  2. Construction and testing of ceramic fabric heat pipe with water working fluid

    Science.gov (United States)

    Antoniak, Zenen I.; Webb, Brent J.; Bates, James M.; Cooper, Matthew F.

    1991-01-01

    A prototype ceramic fabric/titanium water heat pipe has been constructed and tested; it transported 25 to 80 W of power at 423 K. Component development and testing is continuing with the aim of providing an improved prototype, with a 38 micron stainless steel liner covered by a biaxially-braided Nextel (trademark) sleeve that is approximately 300 microns thick. This fabric has been tested to 800 K, and its emittance is about 0.5 at that temperature. Advanced versions of the water heat pipe will probably require a coating over the ceramic fabric in order to increase this emittance to the 0.8 to 0.9 range.

  3. Thermoset polyester-based superhydrophobic microchannels for nanofluid heat transfer applications

    Science.gov (United States)

    Chung, Chia-Yang; Warkiani, Majid E.; Mesgari, Sara; Rosengarten, Gary; Taylor, Robert

    2015-12-01

    Both microchannels and nanofluids have shown promise to enhance convective heat transfer. However, the major drawback of these two technologies is their significant increase of pumping pressure due to increased frictional drag (for high surface area microchannels) or increased viscoelastic frictional drag (for nanofluids). It is possible to decrease frictional drag, and overcome this drawback, by implementing superhydrophobic surfaces to create slip with the channel wall. In this work, surface microstructures fabricated from the thermoset polyester (TPE) were used to create superhydrophobic surfaces which are capable of reducing the frictional drag in channel flow and thus, reduce the pumping pressure. Preliminary experimental results of superhydrophobic microchannels with rib-and-cavity microstructures aligned transversely and longitudinally to the flow direction were studied with both distilled water and water-based multi-walled carbon nanotube (MWCNT) nanofluid as the working fluids. While pressure drop reduction of superhydrophobic surfaces and heat transfer enhancement of nanofluids were shown, it was observed that heat transfer degradation occurred at higher flow rates with MWCNT nanofluid as the working fluid due to the precipitation of nanoparticles.

  4. A Working Memory Test Battery: Java-Based Collection of Seven Working Memory Tasks

    Directory of Open Access Journals (Sweden)

    James M Stone

    2015-06-01

    Full Text Available Working memory is a key construct within cognitive science. It is an important theory in its own right, but the influence of working memory is enriched due to the widespread evidence that measures of its capacity are linked to a variety of functions in wider cognition. To facilitate the active research environment into this topic, we describe seven computer-based tasks that provide estimates of short-term and working memory incorporating both visuospatial and verbal material. The memory span tasks provided are; digit span, matrix span, arrow span, reading span, operation span, rotation span, and symmetry span. These tasks are built to be simple to use, flexible to adapt to the specific needs of the research design, and are open source. All files can be downloaded from the project website http://www.cognitivetools.uk and the source code is available via Github.

  5. Defect characterisation based on heat diffusion using induction thermography testing

    Science.gov (United States)

    He, Yunze; Pan, Mengchun; Luo, Feilu

    2012-10-01

    Pulsed eddy current (PEC) thermography (a.k.a. induction thermography) has been successfully applied to detect defects (corrosion, cracks, impact, and delamination) in metal alloy and carbon fiber reinforced plastic. During these applications, the defect detection mechanism is mainly investigated based on the eddy current interaction with defect. In this paper, defect characterisation for wall thinning defect and inner defect in steel is investigated based on heat diffusion. The paper presents the PEC thermography testing, which integrates the reflection mode and transmission mode by means of configuring two cameras on both sides of sample. The defect characterisation methods under transmission mode and reflection mode are investigated and compared through 1D analytical analysis, 3D numerical studies, and experimental studies. The suitable detection mode for wall thinning and inner defects quantification is concluded.

  6. Heat pump without particle transport or external work on the medium achieved by differential thermostatting of the phase space.

    Science.gov (United States)

    Patra, Puneet Kumar; Bhattacharya, Baidurya

    2016-03-01

    We propose a mechanism that enables heat flow from a colder region to a hotter region without necessitating either particle transport or external work on the conductor, thereby bypassing the compressor part of a classical heat pump cycle. Our mechanism relies on thermostatting the kinetic and configurational temperatures of the same particle differently. We keep the two ends of a conductor, which in the present study is a single dimensional ϕ(4) chain, at the same kinetic temperature T(0), but at different configurational temperatures--one end hotter and the other end colder than T(0). While external energy is needed within the thermostatted regions to achieve this differential thermostatting, no external work is performed on the system itself. We show that the mechanism satisfies the statistical form of the second law of thermodynamics (the fluctuation theorem). The proposed mechanism reveals two interesting findings: (i) contrary to traditional thermodynamics where only the kinetic temperature is thought to govern heat conduction, configurational temperature can also play an important role, and (ii) the relative temperature difference between the kinetic and configurational variables governs the direction of heat flow. The challenge, however, is in developing experimental techniques to thermostat the kinetic and configurational variables of the same particle at different values.

  7. Heat pump without particle transport or external work on the medium achieved by differential thermostatting of the phase space.

    Science.gov (United States)

    Patra, Puneet Kumar; Bhattacharya, Baidurya

    2016-03-01

    We propose a mechanism that enables heat flow from a colder region to a hotter region without necessitating either particle transport or external work on the conductor, thereby bypassing the compressor part of a classical heat pump cycle. Our mechanism relies on thermostatting the kinetic and configurational temperatures of the same particle differently. We keep the two ends of a conductor, which in the present study is a single dimensional ϕ(4) chain, at the same kinetic temperature T(0), but at different configurational temperatures--one end hotter and the other end colder than T(0). While external energy is needed within the thermostatted regions to achieve this differential thermostatting, no external work is performed on the system itself. We show that the mechanism satisfies the statistical form of the second law of thermodynamics (the fluctuation theorem). The proposed mechanism reveals two interesting findings: (i) contrary to traditional thermodynamics where only the kinetic temperature is thought to govern heat conduction, configurational temperature can also play an important role, and (ii) the relative temperature difference between the kinetic and configurational variables governs the direction of heat flow. The challenge, however, is in developing experimental techniques to thermostat the kinetic and configurational variables of the same particle at different values. PMID:27078485

  8. Heating and Cooling. A Resource Unit for Teachers. Learning in Science Project. Working Paper No. 38.

    Science.gov (United States)

    Schollum, Brendan; And Others

    The major focus of this unit is on changes where substances do not, from the scientific viewpoint, actually change into other substances. For example, substances may expand or contract upon heating or change form (such as ice to water). Part 1 provides a 12-item instrument to enable teachers to check their own ideas about this topic and to clarify…

  9. EXERGY-BASED ECOLOGICAL ANALYSIS OF GENERALIZED IRREVERSIBLE HEAT PUMP SYSTEM

    Directory of Open Access Journals (Sweden)

    GOVIND MAHESHWARI

    2011-10-01

    Full Text Available A reverse Carnot cycle forms the basis of all heat-pump cycles in providing heating and cooling loads. The optimal exergy-based Ecological analysis of an irreversible Heat-pump system with the losses of heat resistance, heat leak and internal irreversibility has been carried out by taking into account Exergy based ecological function (E as an objective in the viewpoint of Finite-Time-Thermodynamics (FTT or Entropy Generation Minimization (EGM. Exergy is defined here as the power required minus the lost power. The effects of irreversibilities along with internal heat leakage on coefficient on the performance of the system are investigated. The exergy based Ecological function decreases steadily with irreversibilites and heat leakages in the system. COP in such a system increases with the cycle temperature ratio. If a heat pump cycle is optimized with above mentioned criterion, there is a trade-off between its coefficient of Performance and the heating load it provides.

  10. Synthesis of Flexible Heat Exchanger Networks with Stream Splits Based on Rangers of Stream Supply Temperatures and Heat Capacity Flowrates

    Institute of Scientific and Technical Information of China (English)

    李志红; 罗行; 华贵; W.Roetzel

    2004-01-01

    A new superstructure model of heat exchanger networks (HEN) with stream splits based on rangers of streams supply temperatures and heat capacity flow rates is presented. The simultaneous optimal mathematical model of flexible HEN synthesis is established too. Firstly, the streams with rangers of supply temperatures and/or the streams with the rangers of heat capacity flow rates are pretreated; Secondly, several rules are proposed to establish the superstructure model of HEN with splits and the simultaneous optimal mathematical model of flexible HEN; Thirdly, the improving genetic algorithm is applied to solve the mathematical model established at the second step effectively, and the original optimal structure of HEN based on the maximum operation limiting condition can be obtained easily; Finally, the rules of heat exchange unit merged and the heat load of heat exchanger relaxed are presented, the flexible configuration of HEN satisfied the operation condition between the upper and down bounds of supply temperature and heat capacity flow rates can be obtained based on the original optimal structure of HEN by means of these rules. A case study demonstrates the method presented in this paper is effective

  11. Model Based Diagnosis of an Air Source Heat Pump

    OpenAIRE

    Alfredsson, Sandra

    2011-01-01

    The purpose of a heat pump is to control the temperature of an enclosed space. This is done by using heat exchange with a heat source, for example water, air, or ground. In the air source heat pump that has been studied during this master thesis, a refrigerant exchanges heat with the outdoor air and with a water distribution system. The heat pump is controlled through the circuit containing the refrigerant and it is therefore crucial that this circuit is functional. To ensure this, a diagnosi...

  12. Vegetable Oil-Based Metal Working Fluids-A Review

    Directory of Open Access Journals (Sweden)

    Vaibhav Koushik A.V

    2012-06-01

    Full Text Available Metal working fluids are widely employed to increase the machining productivity and quality of metal cutting, but their usage poses a great threat to ecology and health of workers in the industry. Therefore, a need arose to identify eco-friendly and hazard free alternatives to conventional mineral oil based metal working fluids. Vegetable oils have become identified world over as a potential source of environmentally favorable metal working fluids due to a combination of biodegradability, renewability and excellent lubrication performance. Low oxidation and thermal stability, poor low temperature behavior, however limit their potential application as metal working lubricants and has become the thrust area of research of scientists and tribologists world over.

  13. Social Work Students' Perceptions of Team-Based Learning

    Science.gov (United States)

    Macke, Caroline; Taylor, Jessica Averitt; Taylor, James E.; Tapp, Karen; Canfield, James

    2015-01-01

    This study sought to examine social work students' perceptions of Team-Based Learning (N = 154). Aside from looking at overall student perceptions, comparative analyses examined differences in perceptions between BSW and MSW students, and between Caucasian students and students of color. Findings for the overall sample revealed favorable…

  14. Enhancing Social Work Education through Team-Based Learning

    Science.gov (United States)

    Gillespie, Judy

    2012-01-01

    Group learning strategies are used extensively in social work education, despite the challenges and negative outcomes regularly experienced by students and faculty. Building on principles of cooperative learning, team-based learning offers a more structured approach that maximizes the benefits of cooperative learning while also offering…

  15. WWW-based environments for collaborative group work

    NARCIS (Netherlands)

    Collis, Betty

    1998-01-01

    Since 1994, we have been involved in the design and use of a series of WWW-based environments to support collaborative group work for students in a technical university in The Netherlands. These environments, and the course re-design that accompanies each new environment, began in April 1994 and con

  16. Work-based Learning as Critical Social Pedagogy.

    Science.gov (United States)

    Wagner, Regine; Childs, Merilyn; Houlbrook, Mick

    2001-01-01

    Presents economic responsiveness and critical social pedagogy as the main forces in work-based learning. Describes research of Australia's Research Centre for Learning and Social Transformation, which is guided by principles of accessibility, shared knowledge production, and multidisciplinary learning. (Contains 41 references.) (SK)

  17. Mobile Communication and Work Practices in Knowledge-based Organizations

    Directory of Open Access Journals (Sweden)

    Pertti Hurme

    2005-01-01

    Full Text Available This paper examines the role of mobile communication, mobile tools and work practices in the context of organizations, especially knowledge-based organizations. Today, organizations are highly complex and diverse. Not surprisingly, various solutions to incorporating mobile tools and mobile communication in organizations have been devised. Challenges to technological development and research on mobile communication are presented.

  18. A Society Based on Work. Information Series No. 270.

    Science.gov (United States)

    Carnevale, Anthony Patrick

    American society is based on work. The industrial revolution exposed a growing proportion of the population to unemployment, underemployment, and dislocation. Early theoreticians believed that unemployment was a temporary labor market imbalance that would correct itself with downward wage adjustments. John Maynard Keynes, on the other hand, argued…

  19. Role of hippocampal dentate gyrus neurons in the protective effects of heat shock factor 1 on working memory

    Institute of Scientific and Technical Information of China (English)

    Min Peng; Xiongzhao Zhu; Ming Cheng; Xiangyi Chen; Shuqiao Yao

    2011-01-01

    Increasing evidence suggests that heat shock factor 1 exerts endogenous protective effects on working memory under conditions of chronic psychological stress. However, the precise underlying mechanisms remain poorly understood. This study examined the protective factors affecting working memory in heat shock transcription factor 1 gene knockout mice. The results indicated that the number of correct T maze alternations decreased following mild chronic psychological stress in knockout mice. This change was accompanied by a decrease in neurogenesis and an increase in neuronal apoptosis in the hippocampal dentate gyrus. The number of correct T maze alternations was positively correlated with neurogenesis in hippocampal dentate gyrus, and negatively correlated with neuronal apoptosis. In wild type mice, no significant difference was detected in the number of correct T maze alternations or neuronal apoptosis in hippocampal dentate gyrus. These results indicate that the heat shock factor 1 gene has an endogenous protective role in working memory during mild chronic psychological stress associated with dentate gyrus neuronal apoptosis.Moreover, dentate gyrus neurogenesis appears to participate in the protective mechanism.

  20. Organic rankine cycle coupled to a solar pond by direct-contact heat exchange - selection of a working fluid

    Science.gov (United States)

    Wright, J. D.

    1982-06-01

    Heat from a solar pond may be used to drive an organic Rankine cycle and produce electricity. Due to the inherent low efficiency of low temperature cycles, large amounts of heat must be transferred, and heat exchangers may account for up to 50% of the plant cost. Use of a direct contact boiler, in which the organic fluid is bubbled through a stream of pond brine, may reduce the plant cost by about 25%. The choice of a working fluid affects plant efficiency, turbine cost, and the loss rate of the organic fluid. Low vapor pressure fluids maximize cycle efficiency by minimizing pumping requirements, but require a larger turbine. Efficiency affects the size and cost of the entire plant and low pressure fluids are preferred. The saturated and halogenated hydrocarbons were evaluated for use as working fluids. It is found that the working fluid is best suited to this application, because of high efficiency, low solubility in the pond, and a reasonable turbine cost.

  1. Solar process heat. Citations from the NTIS data base

    Science.gov (United States)

    Hundemann, A. S.

    1980-04-01

    Feasibility, design, cost, and economic potential of solar process heat are discussed. Potential applications to industries using hot water or steam and to heat used for dehydration processes in agriculture are covered. Contains 60 abstracts.

  2. Activity-based computing for medical work in hospitals

    DEFF Research Database (Denmark)

    Bardram, Jakob Eyvind

    2009-01-01

    . In a hospital, the challenges arising from the management of parallel activities and interruptions are amplified because multitasking is now combined with a high degree of mobility, collaboration, and urgency. The article presents the empirical and theoretical background for activity-based computing, its......Studies have revealed that people organize and think of their work in terms of activities that are carried out in pursuit of some overall objective, often in collaboration with others. Nevertheless, modern computer systems are typically single-user oriented, that is, designed to support individual...... tasks such as word processing while sitting at a desk. This article presents the concept of Activity-Based Computing (ABC), which seeks to create computational support for human activities. The ABC approach has been designed to address activity-based computing support for clinical work in hospitals...

  3. Postponement of incipient collapse due to work-induced heat stress by limited cooling

    Science.gov (United States)

    Blockley, W. V.

    1973-01-01

    Four subjects completed five treadmill training sessions under comfortable to cool conditions and were calibrated to find an optimum combination of speed and grade on the treadmill which would produce a metabolic rate of 2000 Btu-hr. Dressed in an Apollo liquid cooling garment, each man underwent a total of four experiments in which the rate of heat extraction from the liquid cooling garment was adjusted to an amount which would cause a storage within the body of 1000 Btu/hr. Physiological measurements included skin temperature at 9 locations, rectal and ear canal probes, and heart rate. The increases in tolerance time for the various subjects and the various methods of emergency cooling, ranged from a low of six minutes to a high of 48 minutes, or from 8 to 102% of the baseline tolerance times. The largest gains were achieved in a subject whose tolerance endpoint was atypical, and whose baseline heat tolerance was unsually low.

  4. Efficiency, Power and Period of a model quantum heat engine working in a finite time

    Science.gov (United States)

    Bekele, Mulugeta; Dima, Tolasa A.; Alemye, Mekuannent; Chegeno, Warga

    We take a spin-half quantum particle undergoing Carnot type cyclic process in a finite time assisted by two heat reservoirs and an external magnetic field. We find that the power of the heat engine is maximum at a particular period of the cyclic process and efficiency at the maximum power is at least half of the Carnot efficiency. We further apply the Omega-criterion for a figure of merit representing a compromise between useful power and lost power determining the corresponding efficiency for the optimization criterion to be at least three fourth of the Carnot efficiency. The authers are thankful to the International Science programme, IPS, Uppsala, Sweden for their support to our research lab.

  5. THE INFLUENCE OF DIFFERENT DESIGN PARAMETERS AND WORKING CONDITIONS ON CHARACTERISTICS OF HEAT METERS

    Institute of Scientific and Technical Information of China (English)

    LIU Yong-hui; DU Guang-sheng; LIU Zheng-gang; WANG You-yuan

    2009-01-01

    In this article, the UDF technology in Fluent software is used to simulate three-dimensional flow fields and to obtain various flow parameters. The standard k-ε model and the RNG k-εmodel are both used to calculate the inner flow field of the basal meter, and a comparison of the calculated results between two models shows that RNG k-εmodel is more effective for calculations of the inner flow of rotary wing mechanism. The influence of tip clearance on the characteristics of the basal meter is studied. The influence of the bottom ribs on the heat meter is evaluated by the numerical simulation method. This article also simulates the flow of disturbance located at the inlet of the basal meter, and shows that a swirl located at the front of the basal meter can affect the stability of the heat meter.

  6. Women working at university restaurants: life and work conditions and gender-based violence

    Directory of Open Access Journals (Sweden)

    Kelly Cristina Maxima Pereira Venancio

    2013-10-01

    Full Text Available This is an exploratory and descriptive study with a quantitative approach that aimed to understand the social production and reproduction processes of women working at university restaurants and the occurrence and the magnitude of gender-based violence committed against them by their intimate partners. The data were collected through semi-structured interviews. The analysis categories used were social production and reproduction, gender and gender-based violence. The interviewees held a subordinate social position during the productive and reproductive periods of their lives. Approximately 70% reported having experienced gender-based violence from an intimate partner (66% psychological violence, 36.3% physical violence and 28.6% sexual violence. Most of the health problems resulting from violence were related to mental health. The results indicate that the situation requires immediate interventions, mostly guided by the instrumentalization of these women and the support by the state and the university as appropriate to address violence.

  7. Modelling of robotic work cells using agent based-approach

    Science.gov (United States)

    Sękala, A.; Banaś, W.; Gwiazda, A.; Monica, Z.; Kost, G.; Hryniewicz, P.

    2016-08-01

    In the case of modern manufacturing systems the requirements, both according the scope and according characteristics of technical procedures are dynamically changing. This results in production system organization inability to keep up with changes in a market demand. Accordingly, there is a need for new design methods, characterized, on the one hand with a high efficiency and on the other with the adequate level of the generated organizational solutions. One of the tools that could be used for this purpose is the concept of agent systems. These systems are the tools of artificial intelligence. They allow assigning to agents the proper domains of procedures and knowledge so that they represent in a self-organizing system of an agent environment, components of a real system. The agent-based system for modelling robotic work cell should be designed taking into consideration many limitations considered with the characteristic of this production unit. It is possible to distinguish some grouped of structural components that constitute such a system. This confirms the structural complexity of a work cell as a specific production system. So it is necessary to develop agents depicting various aspects of the work cell structure. The main groups of agents that are used to model a robotic work cell should at least include next pattern representatives: machine tool agents, auxiliary equipment agents, robots agents, transport equipment agents, organizational agents as well as data and knowledge bases agents. In this way it is possible to create the holarchy of the agent-based system.

  8. Sobre a primeira lei da termodinâmica: as diferenciais do calor e do trabalho On the first law of thermodynamics: heat and work differentials

    Directory of Open Access Journals (Sweden)

    Joaquim Anacleto

    2007-04-01

    Full Text Available We treat some subtleties concerning the First Law of Thermodynamics and discuss the inherent difficulties, namely the interpretation of the heat and the work differentials. By proposing a new differential equation for the First Law, which is written using both system and neighborhood variables, we overcome the mentioned difficulties and establish a criterion for the definition of heat and work.

  9. Mobile work platform for initial lunar base construction

    Science.gov (United States)

    Brazell, James W.; Maclaren, Brice K.; Mcmurray, Gary V.; Williams, Wendell M.

    1992-01-01

    Described is a system of equipment intended for site preparation and construction of a lunar base. The proximate era of lunar exploration and the initial phase of outpost habitation are addressed. Drilling, leveling, trenching, and cargo handling are within the scope of the system's capabilities. The centerpiece is a three-legged mobile work platform, named SKITTER. Using standard interfaces, the system is modular in nature and analogous to the farmer's tractor and implement set. Conceptually somewhat different from their Earthbound counterparts, the implements are designed to take advantage of the lunar environment as well as the capabilities of the work platform. The proposed system is mechanically simple and weight efficient.

  10. SOLAR ABSORBING COOLING SYSTEMS BASED ON MULTISTAGE HEAT-MASS-TRANSFER DEVICES

    Directory of Open Access Journals (Sweden)

    Doroshenko A.V.

    2014-08-01

    Full Text Available The article presents the worked out schematics for the alternative refrigeration systems and of air-conditioning systems, based on the use of absorbing cycle and of the sunny energy for the regeneration (renewals of absorbent solution. We use here the cascade principle of construction of all heat-mass-transfer apparatus with variation of both the temperature level and the growth of absorbent concentration on the cascade stages. The heat-mass-transfer equipment as a part of the drying and cooling units is standardized and is executed by means of multistage monoblock compositions from poly-meric materials. The preliminary analysis of possibilities of the sunny systems in application to the tasks of cooling of environment and air-conditioning systems is carried out.

  11. Synchrotron-based FTIR spectromicroscopy: Cytotoxicity and heating considerations

    Energy Technology Data Exchange (ETDEWEB)

    Holman, Hoi-Ying N.; Martin, Michael C.; McKinney, Wayne R.

    2002-12-13

    Synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectromicroscopy is a newly emerging bioanalytical and imaging tool. This unique technique provides mid-infrared (IR) spectra, hence chemical information, with high signal-to-noise at spatial resolutions as fine as 3 to 10 microns. Thus it enables researchers to locate, identify, and track specific chemical events within an individual living mammalian cell. Mid-IR photons are too low in energy (0.05 - 0.5 eV) to either break bonds or to cause ionization. In this review, we show that the synchrotron IR beam has no detectable effects on the short- and long-term viability, reproductive integrity, cell-cycle progression, and mitochondrial metabolism in living human cells, and produces only minimal sample heating (< 0.5 degrees C). These studies have established an important foundation for SR-FTIR spectromicroscopy in biological and biomedical research.

  12. Synchrotron-based FTIR spectromicroscopy Cytotoxicity and heating considerations

    CERN Document Server

    Holman, H Y N; McKinney, W R

    2002-01-01

    Synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectromicroscopy is a newly emerging bioanalytical and imaging tool. This unique technique provides mid-infrared (IR) spectra, hence chemical information, with high signal-to-noise at spatial resolutions as fine as 3 to 10 microns. Thus it enables researchers to locate, identify, and track specific chemical events within an individual living mammalian cell. Mid-IR photons are too low in energy (0.05 - 0.5 eV) to either break bonds or to cause ionization. In this review, we show that the synchrotron IR beam has no detectable effects on the short- and long-term viability, reproductive integrity, cell-cycle progression, and mitochondrial metabolism in living human cells, and produces only minimal sample heating (< 0.5 degrees C). These studies have established an important foundation for SR-FTIR spectromicroscopy in biological and biomedical research.

  13. Characterization of Bimetallic Castings with an Austenitic Working Surface Layer and an Unalloyed Cast Steel Base

    Science.gov (United States)

    Wróbel, Tomasz

    2014-05-01

    The paper presents the technology of bimetallic castings based on the founding method of layer coating directly in the cast process of the so-called method of mold cavity preparation. The prepared castings consist of two fundamental parts, i.e., the base and the working surface layer. The base part of the bimetallic casting is typical foundry material, i.e., unalloyed cast steel, whereas the working layer is a plate of austenitic alloy steel sort X2CrNi 18-9. The quality of the joint between the base part and the working layer was evaluated on the basis of ultrasonic non-destructive testing and structure examinations containing metallographic macro- and microscopic studies with the use of a light microscope (LOM) with microhardness measurements and a scanning electron microscope (SEM) with microanalysis of the chemical composition (energy dispersive spectroscopy—EDS). On the basis of the obtained results it was confirmed that the decisive phenomena needed to create a permanent joint between the two components of the bimetallic casting are carbon and heat transport in the direction from the high-carbon and hot base material which was poured into the mold in the form of liquid metal to the low-carbon and cold material of the working layer which was placed in the mold cavity in the form of a monolithic insert.

  14. Strengthening health workforce capacity through work-based training

    Directory of Open Access Journals (Sweden)

    Matovu Joseph KB

    2013-01-01

    Full Text Available Abstract Background Although much attention has been given to increasing the number of health workers, less focus has been directed at developing models of training that address real-life workplace needs. Makerere University School of Public Health (MakSPH with funding support from the Centers for Disease Control and Prevention (CDC developed an eight-month modular, in-service work-based training program aimed at strengthening the capacity for monitoring and evaluation (M&E and continuous quality improvement (CQI in health service delivery. Methods This capacity building program, initiated in 2008, is offered to in-service health professionals working in Uganda. The purpose of the training is to strengthen the capacity to provide quality health services through hands-on training that allows for skills building with minimum work disruptions while encouraging greater involvement of other institutional staff to enhance continuity and sustainability. The hands-on training uses practical gaps and challenges at the workplace through a highly participatory process. Trainees work with other staff to design and implement ‘projects’ meant to address work-related priority problems, working closely with mentors. Trainees’ knowledge and skills are enhanced through short courses offered at specific intervals throughout the course. Results Overall, 143 trainees were admitted between 2008 and 2011. Of these, 120 (84% from 66 institutions completed the training successfully. Of the trainees, 37% were Social Scientists, 34% were Medical/Nursing/Clinical Officers, 5.8% were Statisticians, while 23% belonged to other professions. Majority of the trainees (80% were employed by Non-Government Organizations while 20% worked with the public health sector. Trainees implemented 66 projects which addressed issues such as improving access to health care services; reducing waiting time for patients; strengthening M&E systems; and improving data collection and

  15. Evaluating Work-Based Learning: Insights from an Illuminative Evaluation Study of Work-Based Learning in a Vocational Qualification

    Science.gov (United States)

    van Rensburg, Estelle

    2008-01-01

    This article outlines an illuminative evaluation study of the work-based module in a vocational qualification in Animal Health offered for the paraveterinary industry by a distance education institution in South Africa. In illuminative evaluation, a programme is studied by qualitative methods to gain an in-depth understanding of its "instructional…

  16. SPECTRAL data-based estimation of soil heat flux

    Science.gov (United States)

    Singh, R.K.; Irmak, A.; Walter-Shea, Elizabeth; Verma, S.B.; Suyker, A.E.

    2011-01-01

    Numerous existing spectral-based soil heat flux (G) models have shown wide variation in performance for maize and soybean cropping systems in Nebraska, indicating the need for localized calibration and model development. The objectives of this article are to develop a semi-empirical model to estimate G from a normalized difference vegetation index (NDVI) and net radiation (R n) for maize (Zea mays L.) and soybean (Glycine max L.) fields in the Great Plains, and present the suitability of the developed model to estimate G under similar and different soil and management conditions. Soil heat fluxes measured in both irrigated and rainfed fields in eastern and south-central Nebraska were used for model development and validation. An exponential model that uses NDVI and Rn was found to be the best to estimate G based on r2 values. The effect of geographic location, crop, and water management practices were used to develop semi-empirical models under four case studies. Each case study has the same exponential model structure but a different set of coefficients and exponents to represent the crop, soil, and management practices. Results showed that the semi-empirical models can be used effectively for G estimation for nearby fields with similar soil properties for independent years, regardless of differences in crop type, crop rotation, and irrigation practices, provided that the crop residue from the previous year is more than 4000 kg ha-1. The coefficients calibrated from particular fields can be used at nearby fields in order to capture temporal variation in G. However, there is a need for further investigation of the models to account for the interaction effects of crop rotation and irrigation. Validation at an independent site having different soil and crop management practices showed the limitation of the semi-empirical model in estimating G under different soil and environment conditions. ?? 2011 American Society of Agricultural and Biological Engineers ISSN 2151-0032.

  17. Risk based on quality, environmental and occupational safety in heat treatment processes

    Directory of Open Access Journals (Sweden)

    T. Karkoszka

    2014-10-01

    Full Text Available Growing competition on the market forces the organisations to be more technological and organisational flexibility, both in the range of ensuring the products’ quality and minimising the affect the surrounding environment as well as limiting the threats of the work safety. The studies proposed the way of consistent risk management of the operational discrepancies, based on the operational control, aiming at confirming the consistency of the key characteristics with the fixed operational criteria. The applied method guarantees avoiding the estimated risk, as unaccepted, and supervising and keeping on the even level the risk classified as the accepted one, which was used in the processes of the heat treatment.

  18. AN EXPERIMENTAL STUDY ON HEAT TRANSPORT CAPABILITY OF A TWO PHASE THERMOSYPHON CHARGED WITH DIFFERENT WORKING FLUIDS

    Directory of Open Access Journals (Sweden)

    M. Kannan

    2014-01-01

    Full Text Available In the present investigation a two phase thermosyphon has been fabricated to investigate the effect of operating parameters on the heat transport capability. The system consists of evaporator section, adiabatic section and condenser section with thermocouples located on the wall of thermosyphon. Electric heater was fixed on the bottom of the evaporator section and water jacket for cooling the condenser was placed on the top of the condenser section of the thermosyphon. The experiments were conducted with three different thermosyphons with inner diameters of 6.7, 9.5 and 12 mm. The variation of heat transport capability of the thermosyphon was studied for the input heat transfer rate ranging from 0 to 1200 W for various filling ratios and with operating temperature from 30 to 70°C. Water, methanol, ethanol and acetone were used as working fluids. The maximum heat transport capability was found to be high for water compared to other fluids such as ethanol, methanol and acetone at the operating temperatures higher than 40°C.

  19. FINITE ELEMENT TECHNIQUE FOR SOLUTION OF THERMO-CONTACT PROBLEMS AND ITS APPLICATION IN NUMERICAL ANALYSIS OF DEVICES WORKING WITH INDUCTION HEATING

    Directory of Open Access Journals (Sweden)

    M.G. Pantelyat

    2016-09-01

    Full Text Available Purpose. To develop an effective approach for the numerical solution of transient thermo-contact problems and present a typical example of its utilization regarding devices working on the principle of thermoelasticity produced by induction heating and specific technological processes intended for assembly and disassembly of systems containing shrink fits. Methodology. A finite element technique for solution of 2D multiphysics (electromagnetic, thermal and structural problems is developed, taking into account temperature dependences of material properties and continuous variations of the contact surfaces. Modeling of the contact interaction between two parts is based on the concept of a special contact finite element having no thickness. The functional for the temperature problem is supplemented with components corresponding to the thermal conductivity of this contact layer. The heat generated due to mutual sliding of both parts can also be taken into account, but the heat capacity (specific heat of the contact layer is neglected. Using a special 1D 4-node finite elements a system of equations for the description of the thermo-contact problem is obtained. Originality. Relatively simple analytical formulae for calculation of the contact thermal resistances occurring in specific parts of electrical machines are known. The paper offers an alternative approach for the numerical solution of transient thermo-contact problems based on the concept of a special 1D contact finite element having no thickness. Results. The presented technique is applied for the computer simulation of assembly and disassembly of a shrink fit using induction heating. Conclusions regarding the choice of technological modes are made. Comparative computations for drills made from hard alloy and alloyed tool steel are carried out.

  20. Work-based learning in health care environments.

    Science.gov (United States)

    Spouse, J

    2001-03-01

    In reviewing contemporary literature and theories about work-based learning, this paper explores recent trends promoting life-long learning. In the process the paper reviews and discusses some implications of implementing recent policies and fostering le arning in health care practice settings. Recent Government policies designed to provide quality health care services and to improve staffing levels in the nursing workforce, have emphasized the importance of life-long learning whilst learning-on-the-job and the need to recognize and credit experiential learning. Such calls include negotiation of personal development plans tailored to individual educational need and context-sensitive learning activities. To be implemented effectively, this policy cann ot be seen as a cheap option but requires considerable financial resourcing for preparation of staff and the conduct of such activities. Successful work-based learning requires investment in staff at all levels as well as changes to staffing structures in organizations and trusts; changes designed to free people up to work and learn collaboratively. Creating an organizational environment where learning is prized depends upon a climate of trust; a climate where investigation and speculation are fostered and where time is protected for engaging in discussions about practice. Such a change may be radical for many health care organizations and may require a review of current policies and practices ensuring that they include education at all levels. The nature of such education also requires reconceptualizing. In the past, learning in practice settings was seen as formal lecturing or demonstration, and relied upon behaviourist principles of learning. Contemporary thinking suggests effective learning in work-settings is multi-faceted and draws on previously acquired formal knowledge, contextualizes it and moulds it according to situations at hand. Thinking about work-based learning in this way raises questions about how such

  1. Students’ Self-Assessment in Project-Based Work

    Directory of Open Access Journals (Sweden)

    Alvyda Liuolienė

    2014-12-01

    Full Text Available The article aims at exploring the benefits of self-assessment as it is an important skill for lifelong learning and for critical reflection on one’s own performance. The authors of the article focus on students’ self-assessment of their language proficiency skills and achievements in working on projects. Students’ reflection on their learning has numerous benefits, such as motivation, self-direction, greater responsibility, decreased intimidation and fear of the audience, development of critical thinking, etc. The paper presents the analysis of a questionnaire based on the research of respondents’ self-evaluation of working on the project. The study has aimed at finding out the students’ attitude towards project-based learning and their assessment of their personal progress in respect of the development of their language proficiency skills.

  2. An experimental study on the performance of closed loop pulsating heat pipe (CLPHP) with methanol as a working fluid

    Science.gov (United States)

    Rahman, Md. Lutfor; Nourin, Farah Nazifa; Salsabil, Zaimaa; Yasmin, Nusrat; Ali, Mohammad

    2016-07-01

    Thermal control is an important topic for thermal management of small electrical and electronic devices. Closed loop pulsating heat pipe (CLPHP) arises as the best solution for thermal control. The aim of this experimental study is to search a CLPHP of better thermal performance for cooling different electrical and electronic devices. In this experiment, methanol is used as working fluid. The effect of using methanol as a working fluid is studied on thermal performance in different filling ratios and angles of inclination. A copper capillary tube is used where the inner diameter is 2mm,outer diameter is 2.5mm and 250mm long. The CLPHP has 8 loops where the evaporation section is 50mm, adiabatic section is 120mm and condensation section is 80mm. The experiment is done using FR of 40%-70% with 10% of interval and angles of inclination 0° (vertical), 30°, 45°, 60° varying heat input. The results are compared on the basis of evaporator temperature, condenser temperature and their differences, thermal resistance, heat transfer co-efficient, power input and pulsating time. The results demonstrate the effect of methanol in different filling ratios and angles of inclination. M ethanol shows better performance at 30° inclination with 40% FR.

  3. Effects of vacuum heat treatment on the photoelectric work function and surface morphology of multilayered silver–metal electrical contacts

    International Nuclear Information System (INIS)

    Contact materials used for electrical breakers are often made with silver alloys. Mechanical and thermodynamical properties as well as electron emission of such complicated alloys present a lack of reliable and accurate experimental data. This paper deals mainly with electron work function (EWF) measurements about silver–metal (Ag–Me) electrical contacts (Ag–Ni (60/40) and Ag–W (50/50)), before and after surface heat treatments at 513 K–873 K, under UHV conditions (residual gas pressure of 1.4 × 10−7 mbar). The electron work function (EWF) of silver alloyed contacts was measured photoelectrically, using both Fowler's method of isothermal curves and linearized Fowler plots. An interesting fact brought to light by this investigation is that after vacuum heat treatments, the diffusion and/or evaporation phenomena, affecting the atomic composition of the alloy surface, somehow confine the EWF of the silver–nickel alloy, Φ(Ag–Ni), determined at room temperature in interval]Φ(Ag), Φ(Ni) [=] 4.26 eV, 4.51 eV[. Surface analysis of two specimens before and after heating showed a significant increase of tungsten atomic proportion on the contact surface for Ag–W contacts after VH treatments. A multilayer model, taking into account the strong intergranular and volume segregation gives a good interpretation of the obtained results.

  4. Effects of vacuum heat treatment on the photoelectric work function and surface morphology of multilayered silver–metal electrical contacts

    Energy Technology Data Exchange (ETDEWEB)

    Akbi, Mohamed, E-mail: akbi_mohamed@umbb.dz [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France); Department of Physics, Faculty of Sciences, University of Boumerdes (UMBB), Independence Avenue, 35000 Boumerdes (Algeria); Bouchou, Aïssa [Faculty of Physics, University of Algiers (USTHB), B.P. 32, El-Alia, Bab-Ezzouar, 16111 Algiers (Algeria); Zouache, Noureddine [Laboratoire “Arc Electrique et Plasmas Thermiques”, CNRS, UPRES-A 6069, 24, Avenue des Landais, F-63177 Aubière Cedex (France)

    2014-06-01

    Contact materials used for electrical breakers are often made with silver alloys. Mechanical and thermodynamical properties as well as electron emission of such complicated alloys present a lack of reliable and accurate experimental data. This paper deals mainly with electron work function (EWF) measurements about silver–metal (Ag–Me) electrical contacts (Ag–Ni (60/40) and Ag–W (50/50)), before and after surface heat treatments at 513 K–873 K, under UHV conditions (residual gas pressure of 1.4 × 10{sup −7} mbar). The electron work function (EWF) of silver alloyed contacts was measured photoelectrically, using both Fowler's method of isothermal curves and linearized Fowler plots. An interesting fact brought to light by this investigation is that after vacuum heat treatments, the diffusion and/or evaporation phenomena, affecting the atomic composition of the alloy surface, somehow confine the EWF of the silver–nickel alloy, Φ(Ag–Ni), determined at room temperature in interval]Φ(Ag), Φ(Ni) [=] 4.26 eV, 4.51 eV[. Surface analysis of two specimens before and after heating showed a significant increase of tungsten atomic proportion on the contact surface for Ag–W contacts after VH treatments. A multilayer model, taking into account the strong intergranular and volume segregation gives a good interpretation of the obtained results.

  5. Optimized chemical composition, working and heat treatment condition for resistance to irradiation assisted stress corrosion cracking of cold worked 316 and high-chromium austenitic stainless steel

    International Nuclear Information System (INIS)

    The authors have reported that the primary water stress corrosion cracking (PWSCC) in baffle former bolts made of austenitic stainless steels for PWR after long-term operation is caused by irradiation-induced grain boundary segregation. The resistance to PWSCC of simulated austenitic stainless steels whose chemical compositions are simulated to the grain boundary chemical composition of 316 stainless steel after irradiation increased with decrease of the silicon content, increases of the chromium content, and precipitation of M23C6 carbides at the grain boundaries. In order to develop resistance to irradiation assisted stress corrosion cracking in austenitic stainless steels, optimized chemical compositions and heat treatment conditions for 316CW and high-chromium austenitic stainless steels for PWR baffle former bolts were investigated. For 316CW stainless steel, ultra-low-impurities and high-chromium content are beneficial. About 20% cold working before aging and after solution treatment has also been recommended to recover sensitization and make M23C6 carbides coherent with the matrix at the grain boundaries. Heating at 700 to 725degC for 20 to 50 h was selected as a suitable aging procedure. Cold working of 5 to 10% after aging produced the required mechanical properties. The optimized composition of the high-chromium austenitic stainless steel contents 30% chromium, 30% nickel, and ultra-low impurity levels. This composition also reduces the difference between its thermal expansion coefficient and that of 304 stainless steel for baffle plates. Aging at 700 to 725degC for longer than 40 h and cold working of 10 to 15% after aging were selected to meet mechanical property specifications. (author)

  6. Novel work-based learning courses in analytical sciences

    OpenAIRE

    Williams, Ruth; Velasco, Maria

    2010-01-01

    The Open University (OU) is well known for the delivery of world class distance education. From 2010, the OU offers a new Foundation Degree in Analytical Sciences, developed to enhance the skills base of the workforce in analytical laboratories. It allows students to earn and learn simultaneously without taking time off. Students are sponsored by their employer and supported by an OU tutor throughout the four years of part-time study. 25 per cent of the degree comprises two work-based learni...

  7. MEMS-Based Boiler Operation from Low Temperature Heat Transfer and Thermal Scavenging

    Directory of Open Access Journals (Sweden)

    Leland Weiss

    2012-04-01

    Full Text Available Increasing world-wide energy use and growing population growth presents a critical need for enhanced energy efficiency and sustainability. One method to address this issue is via waste heat scavenging. In this approach, thermal energy that is normally expelled to the environment is transferred to a secondary device to produce useful power output. This paper investigates a novel MEMS-based boiler designed to operate as part of a small-scale energy scavenging system. For the first time, fabrication and operation of the boiler is presented. Boiler operation is based on capillary action that drives working fluid from surrounding reservoirs across a heated surface. Pressure is generated as working fluid transitions from liquid to vapor in an integrated steamdome. In a full system application, the steam can be made available to other MEMS-based devices to drive final power output. Capillary channels are formed from silicon substrates with 100 µm widths. Varying depths are studied that range from 57 to 170 µm. Operation of the boiler shows increasing flow-rates with increasing capillary channel depths. Maximum fluid mass transfer rates are 12.26 mg/s from 170 µm channels, an increase of 28% over 57 µm channel devices. Maximum pressures achieved during operation are 229 Pa.

  8. ANALYSIS OF HEAT TRANSFER OF WORK ROLL COOLING IN HOT ROLLING

    Directory of Open Access Journals (Sweden)

    Marcio Rodrigo Solimani

    2013-10-01

    Full Text Available The roll cooling in Hot Rolling of flats directly affects two fundamental characteristics of the rolls:.the durability due to surface degradation. The other is the thermal expansion, which affects the shape and dimensions of the strip. Cooling is done by water jets that need to be properly adjusted. The determination of heat transfer coefficients is essential to optimize the process and thus increase its durability and quality of the strip. Results of experimental and numerical effects of cooling using a water jet fan-shaped on a prototype roll at temperatures between 50°C and 350°C are performed. Water pressure, nozzle type and the position along the length of the fan-shaped (center and edge influence the efficiency of roll cooling. The maximum value found in the coefficient of heat transfer was 6.0 kW/m2°C, and a 14.3% difference between the center and end of the jet fan-shaped is observed.

  9. Thermal effusivity measurement based on analysis of 3D heat flow by modulated spot heating using a phase lag matrix with a combination of thermal effusivity and volumetric heat capacity

    Science.gov (United States)

    Ohta, Hiromichi; Hatori, Kimihito; Matsui, Genzou; Yagi, Takashi; Miyake, Shugo; Okamura, Takeo; Endoh, Ryo; Okada, Ryo; Morishita, Keisuke; Yokoyama, Shinichiro; Taguchi, Kohei; Kato, Hideyuki

    2016-11-01

    The study goal was to establish a standard industrial procedure for the measurement of thermal effusivity by a thermal microscope (TM), using a periodic heating method with a thermoreflectance (TR) technique. To accomplish this goal, a working group was organized that included four research institutes. Each institute followed the same procedure: a molybdenum (Mo) film was sputtered on the surface of Pyrex, yttria-stabilized zirconia (YSZ), alumina (Al2O3), Germanium (Ge), and silicon (Si) samples, and then the phase lag of the laser intensity modulation was measured by the resultant surface temperature. A procedure was proposed to calibrate the effect of 3D heat flow, based on the analytical solution of the heat conduction equation, and thermal effusivity was measured. The derived values show good agreement with literature values. As a result, the TM calibration procedure can be recommended for practical use in measuring the thermal effusivity in a small region of the materials.

  10. 甲醇水溶液脉动热管的传热特性%Heat transfer characteristics of pulsating heat pipe with aqueous methanol as working fluid

    Institute of Scientific and Technical Information of China (English)

    王迅; 李达; 李云昭

    2014-01-01

    The experiments on heat transfer characteristics of the start-up and steady operation processes of pulsating heat pipe were conducted using three working fluids at various inclination angles and heat inputs. Water,methanol,and aqueous methanol were used as working fluid with 50%fill ratio. The characteristics were compared and analyzed between aqueous methanol,water,methanol in the start-up and steady operation processes. The type of start-up for aqueous methanol was gradual start-up at low heat inputs and different inclination angles. Start-up time span of aqueous methanol was longer than that of methanol,but shorter than that of water. In a steady operation process,the temperature of aqueous methanol in heating section was lower than that of methanol,and fluctuation of temperature was larger. Aqueous methanol showed the best thermal performance among them at low and medium heat inputs. The minimum thermal resistances of aqueous methanol were 0.38℃/W and 0.3℃/W at the angle 45°and 90°,respectively.%以体积分数为50%的甲醇水溶液为工质,充液率为50%,对不同倾角和加热功率条件下环路脉动热管的启动性能和稳定运行时的传热性能进行了实验研究。对比分析了甲醇水溶液、无水甲醇和水的传热效果,探讨了甲醇水溶液与水、无水甲醇在启动过程中启动时间、启动温度以及稳定运行时传热热阻、热冷端温差的变化特点。结果表明,在低加热功率条件下,甲醇水溶液45°和90°倾角下的启动方式均为温度渐变型,甲醇水溶液的启动时间比无水甲醇长,但比水短。稳定运行时,甲醇水溶液在90°倾角下加热段温度低于甲醇,且波动较大。在低、中加热功率条件下,甲醇水溶液传热性能优于水和无水甲醇,甲醇水溶液在45°和90°倾角下的最小热阻值分别为0.38℃/W和0.3℃/W。

  11. Base-Bleed Effect on X-33 Aerospike Plume Induced Base-Heating Environment During Power-Pack Out

    Science.gov (United States)

    Wang, Tee-See; Droege, Alan; D'Agostino, Mark; Lee, Young-Ching; Williams, Robert

    2003-01-01

    A computational heat transfer methodology was developed to study the dual-engine linear aerospike plume induced base-heating environment during one power-pack out, in ascent flight. One power-pack out results in reduction of power levels for both engines. That, in turn, reduces the amount of base-bleed and changes the distribution of base-bleed on the two pillows. Hence, the concern of increased base-heating during power-pack out. The thermo-flowfield of the entire vehicle was computed. The computational methodology for the convective heating is based on a three-dimensional, finite-volume, viscous, chemically reacting, and pressure-based computational fluid dynamics formulation. The computational methodology for the radiative heating is based on a three-dimensional, finite-volume, and spectral-line-based weighted-sum-of-gray-gases absorption computational radiation heat transfer formulation. A separate radiation model was used for diagnostic purposes. The computational methodology was systematically benchmarked. In this study, near-base radiative heat fluxes were computed and they compared well with those measured from an installed linear aerospike engine tests. The base-heating environment of 18 trajectory points selected from three power-pack out ascent scenarios was computed and is presented here. The power-pack out condition has the most impact on convective base-heating when it happens early in flight. The some of its impact comes from the asymmetric and reduced base-bleed.

  12. Development of seasonal heat storage based on stable supercooling of a sodium acetate water mixture

    DEFF Research Database (Denmark)

    Furbo, Simon; Fan, Jianhua; Andersen, Elsa;

    2012-01-01

    . • The reliability of the supercooling was elucidated for the heat storage modules for different operation conditions. • The reliability of a cooling method used to start solidification of the supercooled sodium acetate water mixture was elucidated. The method is making use of boiling CO2 in a small tank in good......A number of heat storage modules for seasonal heat storages based on stable supercooling of a sodium acetate water mixture have been tested by means of experiments in a heat storage test facility. The modules had different volumes and designs. Further, different methods were used to transfer heat...... to and from the sodium acetate water mixture in the modules. By means of the experiments: • The heat exchange capacity rates to and from the sodium acetate water mixture in the heat storage modules were determined for different volume flow rates. • The heat content of the heat storage modules were determined...

  13. Thermal-hydraulic characteristics and performance of 3D wavy channel based printed circuit heat exchanger

    International Nuclear Information System (INIS)

    CFD study is done here to propose an efficient PCHE (Printed Circuit Heat Exchanger) model; used as a recuperator in International Thermonuclear Experimental Reactor (ITER). 3D steady state conjugate heat-transfer numerical simulations are done; considering the variation of thermo-physical properties as a function of temperature. Helium is used as a working fluid and alloy 617 as solid substrate. The study is done for various angle of bend (θ = 0°(straight), 5°, 10° and 15°) and Reynolds number (Re = 350, 700, 1400 and 2100). Various types of flow patterns, within one wavy-section, are presented to analyze thermal-hydraulic characteristics. Thermal hydraulic performance parameters are presented for the various wavy-sections as well as within a section; and for the complete PCHE model. Heat transfer enhancement as compared to pressure penalty is higher for the wavy channel; and increases with increasing Re and θ. Wavy as compared to plane channel based PCHE is demonstrated here to give better thermal-hydraulic performance. A detailed characteristics as well as performance-parameters for thermal hydraulics in a 3D wavy channel based PCHE model − not found in the literature − is presented here. - Highlights: • Studied effect of Reynolds number and angle of bend. • Analyzed thermal-hydraulic characteristics, by various types of flow pat-terns. • Demonstrated an increase in local heat flux due to change in the flow-direction. • Demonstrated better performance of wavy as compared to plane channel based PCHE. • Proposed correlation for friction factor and Nusselt number

  14. Mathematical Simulation of Temperature Profiles within Microwave Heated Wood Made for Wood-Based Nano composites

    International Nuclear Information System (INIS)

    High intensive microwave pretreatment is a new method to modify wood for the fabrication of wood-based nano composites. Based on the physical law on heat transfer, a mathematical model to describe the temperature profiles within wood heated by high intensive microwave was established and simulated in this research. The results showed that the temperature profiles within wood were related to microwave heating methods; The temperature inside wood firstly increased and then gradually decreased along the direction of microwave transmission when the unilateral microwave heating was applied, and the temperature difference along the thickness direction of wood was very significant; The temperature with wood firstly increased and then gradually decreased from the wood surface to interior when the bilateral microwave heating was applied. Compared with the unilateral microwave heating, bilateral microwave heating is a better microwave heating method for the more uniform wood microwave pretreatment.

  15. Thermo-Economic Analysis of Zeotropic Mixtures and Pure Working Fluids in Organic Rankine Cycles for Waste Heat Recovery

    Directory of Open Access Journals (Sweden)

    Florian Heberle

    2016-03-01

    Full Text Available We present a thermo-economic analysis of an Organic Rankine Cycle (ORC for waste heat recovery. A case study for a heat source temperature of 150 °C and a subcritical, saturated cycle is performed. As working fluids R245fa, isobutane, isopentane, and the mixture of isobutane and isopentane are considered. The minimal temperature difference in the evaporator and the condenser, as well as the mixture composition are chosen as variables in order to identify the most suitable working fluid in combination with optimal process parameters under thermo-economic criteria. In general, the results show that cost-effective systems have a high minimal temperature difference ΔTPP,C at the pinch-point of the condenser and a low minimal temperature difference ΔTPP,E at the pinch-point of the evaporator. Choosing isobutane as the working fluid leads to the lowest costs per unit exergy with 52.0 €/GJ (ΔTPP,E = 1.2 K; ΔTPP,C = 14 K. Considering the major components of the ORC, specific costs range between 1150 €/kW and 2250 €/kW. For the zeotropic mixture, a mole fraction of 90% isobutane leads to the lowest specific costs per unit exergy. A further analysis of the ORC system using isobutane shows high sensitivity of the costs per unit exergy for the selected cost estimation methods and for the isentropic efficiency of the turbine.

  16. Heat pipes. Citations from the NTIS data base

    Science.gov (United States)

    Reed, W. E.

    1980-04-01

    Theory, design, fabrication, testing, and operation of heat pipes are presented in these Federally sponsored research reports. Applications are described in the areas of heating and air conditioning, power generation, electronics cooling, spacecraft, nuclear reactors, cooling engines, and thermodynamics. This updated bibliography contains 70 abstracts, all of which are new entries to the previous edition.

  17. Is flexible work precarious? A study based on the 4th European survey of working conditions 2005

    OpenAIRE

    Tangian, Andranik S.

    2007-01-01

    The analysis of interaction of flexibility and precariousness of work shows that the more flexible employment, the more it is precarious. For this purpose, two families of indices, of flexible work and of precarious work, are defined basing on the Fourth European Survey of Working Conditions 2005 by the European Foundation for the Improvement of Living and Working Conditions (2007a). Two methodologies of constructing composite indicators are applied, of the Hans Böckler Foundation, and of the...

  18. The effects of moderate heat stress and open-plan office noise distraction on office work

    DEFF Research Database (Denmark)

    Witterseh, Thomas; Wyon, David; Clausen, Geo

    2002-01-01

    Thirty subjects clothed for comfort at 22 deg.C performed simulated office work for 3 hours at 22/26/30 deg.C (7.4 g/kg dry air, i.e. 45/35/28 %RH) in quiet and recorded open-plan office noise (55 dBA) conditions. Warmth decreased perceived air quality (P......Thirty subjects clothed for comfort at 22 deg.C performed simulated office work for 3 hours at 22/26/30 deg.C (7.4 g/kg dry air, i.e. 45/35/28 %RH) in quiet and recorded open-plan office noise (55 dBA) conditions. Warmth decreased perceived air quality (P...

  19. Work-based identity and work engagement as potential antecedents of task performance and turnover intention: Unravelling a complex relationship

    Directory of Open Access Journals (Sweden)

    F. Chris Bothma

    2012-01-01

    Full Text Available Orientation: Work-based identity, used as a reference to the self, is the answer to the question ’Who am I at work?’ Work-related identities, derived from different social foci through identity formation processes, have as behavioural guides a significant influence on employee behaviour, which, in turn has an impact on work outcomes. Engagement, presented in different conceptualisations, is viewed by practitioners and academic researchers as an important antecedent of employee behaviour.Research purpose: The main purpose of the study was to investigate whether work-based identity and work engagement differed (in combination with personal alienation, helping behaviour and burnout as potential antecedents (amongst numerous others of task performance and turnover intention.Research design: A census-based sampling approach amongst 23 134 employees in the employment of an ICT company yielded a sample of 2429 usable questionnaires. Scales used in the study were the Maslach Burnout Inventory (MBI-HSS-20, Utrecht Work Engagement Scale (UWES, Work-based Identity, Personal Alienation, Helping Behaviour, Turnover Intention and Task Performance Scales.Main findings: The findings indicate that work-based identity and work engagement give similar appearing results as potential predictors of turnover intention and task performance. Practical/managerial implications: Reducing withdrawal behaviours and enhancing work performance are everyday challenges for organisations. Interventions focused on enhancing work-based identity and work engagement in the work environment should have a meaningful impact when these behaviours need to be addressed.Contribution/value-add: Work-based identity as a multidimensional construct has the potential, with further refinement, to become a valuable construct that can play a leading role in future work engagement research.

  20. District heating and gas engine heat pump: Economic analysis based on a case study

    Energy Technology Data Exchange (ETDEWEB)

    Lazzarin, R.; Noro, M. [Department of Management and Engineering, University of Padova, Stradella, S. Nicola, 3, 36100 Vicenza (Italy)

    2006-02-01

    'S. Nicola' HVAC plant in Vicenza features innovative and significant energy savings characteristics. It has been set up by a gas engine heat pump (coupled to two condensing boilers) whose performances are here evaluated during three years of operation. Due to a grid expansion, the University received the offer of being connected to the district heating grid. This possibility that is often considered advantageous was economically evaluated. As a result of this, a significant increasing of the building annual energy bill was demonstrated in case of acceptance. (author)

  1. The Effect of Fabric Type of Common Iranian Working Clothes on the Induced Cardiac and Physiological Strain Under Heat Stress.

    Science.gov (United States)

    Parvari, Roh Allah; Aghaei, Habib Allah; Dehghan, Habibollah; Khademi, Abolfazl; Maracy, Mohammad Reza; Dehghan, Somayeh Farhang

    2015-01-01

    The present study compared the effect of fabric type of working clothes on heat strain responses in different levels of physical workload and under different kinds of weather conditions. Four kinds of working clothing fabric that are greatly popular in Iranian industry were assessed on 18 healthy male at 2 environments: hot and humid (dry temperature [DBt]: 35°C and relative humidity [RH]: 70%) and hot and dry (DBt: 40°C and RH: 40%). The physiological responses such as heart rate and core body temperature were reported. It was found that there were no significant differences between different types of clothing fabric on cardiac and physiological parameters. It can be recommended that 100% cotton clothing ensemble during low-workload activities and 30.2% cotton-69.8% polyester clothing ensemble during moderate-workload activities is used for Iranian workers to maintain the cardiac and physiological strains as low as possible.

  2. Application of the Second Law Analysis to a Heat Exchanger Working with Ethanol/Water Ice Slurry

    Directory of Open Access Journals (Sweden)

    Christophe Peuvrel

    2004-12-01

    Full Text Available The use of ice slurries as secondary refrigerants is a very promising technology. The aim of this paper is to evaluate the contribution of second law analysis to the study of a phase changing secondary refrigerant in cooling systems. The first step of the work presented here consists of two parts: the first involves the calculation of enthalpies and entropies and the second is an entropy/exergy analysis of a heat exchanger. This work attempts to provide a thermodynamic criterion in order to choose the kind of fluid and the inflow conditions that are more suitable for a particular application. It presents the establishment of the method and the results that have been obtained for an ethyl alcohol-water mixture.

  3. Mathematical Simulation of Temperature Profiles within Microwave Heated Wood Made for Wood-Based Nanocomposites

    OpenAIRE

    Xianjun Li; Yongfeng Luo; Hongbin Chen; Xia He; Jianxiong Lv; Yiqiang Wu

    2013-01-01

    High intensive microwave pretreatment is a new method to modify wood for the fabrication of wood-based nanocomposites. Based on the physical law on heat transfer, a mathematical model to describe the temperature profiles within wood heated by high intensive microwave was established and simulated in this research. The results showed that the temperature profiles within wood were related to microwave heating methods; The temperature inside wood firstly increased and then gradually decreased al...

  4. Spike-based population coding and working memory.

    Directory of Open Access Journals (Sweden)

    Martin Boerlin

    2011-02-01

    Full Text Available Compelling behavioral evidence suggests that humans can make optimal decisions despite the uncertainty inherent in perceptual or motor tasks. A key question in neuroscience is how populations of spiking neurons can implement such probabilistic computations. In this article, we develop a comprehensive framework for optimal, spike-based sensory integration and working memory in a dynamic environment. We propose that probability distributions are inferred spike-per-spike in recurrently connected networks of integrate-and-fire neurons. As a result, these networks can combine sensory cues optimally, track the state of a time-varying stimulus and memorize accumulated evidence over periods much longer than the time constant of single neurons. Importantly, we propose that population responses and persistent working memory states represent entire probability distributions and not only single stimulus values. These memories are reflected by sustained, asynchronous patterns of activity which make relevant information available to downstream neurons within their short time window of integration. Model neurons act as predictive encoders, only firing spikes which account for new information that has not yet been signaled. Thus, spike times signal deterministically a prediction error, contrary to rate codes in which spike times are considered to be random samples of an underlying firing rate. As a consequence of this coding scheme, a multitude of spike patterns can reliably encode the same information. This results in weakly correlated, Poisson-like spike trains that are sensitive to initial conditions but robust to even high levels of external neural noise. This spike train variability reproduces the one observed in cortical sensory spike trains, but cannot be equated to noise. On the contrary, it is a consequence of optimal spike-based inference. In contrast, we show that rate-based models perform poorly when implemented with stochastically spiking neurons.

  5. Heat, work and subtle fluids: a commentary on Joule (1850) ‘On the mechanical equivalent of heat’

    Science.gov (United States)

    Young, John

    2015-01-01

    James Joule played the major role in establishing the conservation of energy, or the first law of thermodynamics, as a universal, all-pervasive principle of physics. He was an experimentalist par excellence and his place in the development of thermodynamics is unarguable. This article discusses Joule's life and scientific work culminating in the 1850 paper, where he presented his detailed measurements of the mechanical equivalent of heat using his famous paddle-wheel apparatus. Joule's long series of experiments in the 1840s leading to his realisation that the conservation of energy was probably of universal validity is discussed in context with the work of other pioneers, notably Sadi Carnot, who effectively formulated the principle of the second law of thermodynamics a quarter of a century before the first law was accepted. The story of Joule's work is a story of an uphill struggle against a critical scientific establishment unwilling to accept the mounting evidence until it was impossible to ignore. His difficulties in attracting funding and publishing in reputable journals despite the quality of his work will resonate with many young scientists and engineers of the present day. This commentary was written to celebrate the 350th anniversary of the journal Philosophical Transactions of the Royal Society. PMID:25750152

  6. From Opinion-Based to Evidence-Based Social Work: The Swedish Case

    Science.gov (United States)

    Sundell, Knut; Soydan, Haluk; Tengvald, Karin; Anttila, Sten

    2010-01-01

    This article presents an account of Sweden's Institute for Evidence-Based Social Work Practice (IMS), located in Stockholm, Sweden. The article places IMS in the context of making Swedish social care services less opinion-based and more evidence-based. The institute is an example of how policy-driven processes promote the use of evidence-based…

  7. Heat transfer characteristics of the metal hydride vessel based on the plate-fin type heat exchanger

    Science.gov (United States)

    Oi, Tsutomu; Maki, Kohei; Sakaki, Yoshinori

    Heat transfer characteristics of the metal hydride vessel based on the plate-fin type heat exchanger were investigated. Metal hydride beds were filled with AB 2 type hydrogen-storage alloy's particles, Ti 0.42Zr 0.58Cr 0.78Fe 0.57Ni 0.2Mn 0.39Cu 0.03, with a storage capacity of 0.92 wt.%. Heat transfer model in the metal hydride bed based on the heat transfer mechanism for packed bed proposed by Kunii and co-workers is presented. The time-dependent hydrogen absorption/desorption rate and pressure in the metal hydride vessel calculated by the model were compared with the experimental results. During the hydriding, calculated hydrogen absorption rates agreed with measured ones. Calculated thermal equilibrium hydrogen pressures were slightly lower than the measured hydrogen pressures at the inlet of metal hydride vessel. Taking account of the pressure gradient between the inlet of metal hydride vessel and the metal hydride bed, it is considered that this discrepancy is reasonable. During the dehydriding, there were big differences between the calculated hydrogen desorption rates and measured ones. As calculated hydrogen desorption rates were lower than measured ones, there were big differences between the calculated thermal equilibrium hydrogen pressures and the measured hydrogen pressures at the inlet of metal hydride vessel. It is considered that those differences are due to the differences of the heat transfer characteristics such as thermal conductivity of metal hydride particles and porosity between the assumed and actual ones. It is important to obtain the heat transfer characteristics such as thermal conductivity of metal hydride particles and porosity both during the hydriding and dehydriding to design a metal hydride vessel.

  8. Optimum load distribution between heat sources based on the Cournot model

    Science.gov (United States)

    Penkovskii, A. V.; Stennikov, V. A.; Khamisov, O. V.

    2015-08-01

    One of the widespread models of the heat supply of consumers, which is represented in the "Single buyer" format, is considered. The methodological base proposed for its description and investigation presents the use of principles of the theory of games, basic propositions of microeconomics, and models and methods of the theory of hydraulic circuits. The original mathematical model of the heat supply system operating under conditions of the "Single buyer" organizational structure provides the derivation of a solution satisfying the market Nash equilibrium. The distinctive feature of the developed mathematical model is that, along with problems solved traditionally within the bounds of bilateral relations of heat energy sources-heat consumer, it considers a network component with its inherent physicotechnical properties of the heat network and business factors connected with costs of the production and transportation of heat energy. This approach gives the possibility to determine optimum levels of load of heat energy sources. These levels provide the given heat energy demand of consumers subject to the maximum profit earning of heat energy sources and the fulfillment of conditions for formation of minimum heat network costs for a specified time. The practical realization of the search of market equilibrium is considered by the example of a heat supply system with two heat energy sources operating on integrated heat networks. The mathematical approach to the solution search is represented in the graphical form and illustrates computations based on the stepwise iteration procedure for optimization of levels of loading of heat energy sources (groping procedure by Cournot) with the corresponding computation of the heat energy price for consumers.

  9. Effects of ventilation behaviour on indoor heat load based on test reference years

    Science.gov (United States)

    Rosenfelder, Madeleine; Koppe, Christina; Pfafferott, Jens; Matzarakis, Andreas

    2016-02-01

    Since 2003, most European countries established heat health warning systems to alert the population to heat load. Heat health warning systems are based on predicted meteorological conditions outdoors. But the majority of the European population spends a substantial amount of time indoors, and indoor thermal conditions can differ substantially from outdoor conditions. The German Meteorological Service (Deutscher Wetterdienst, DWD) extended the existing heat health warning system (HHWS) with a thermal building simulation model to consider heat load indoors. In this study, the thermal building simulation model is used to simulate a standardized building representing a modern nursing home, because elderly and sick people are most sensitive to heat stress. Different types of natural ventilation were simulated. Based on current and future test reference years, changes in the future heat load indoors were analyzed. Results show differences between the various ventilation options and the possibility to minimize the thermal heat stress during summer by using an appropriate ventilation method. Nighttime ventilation for indoor thermal comfort is most important. A fully opened window at nighttime and the 2-h ventilation in the morning and evening are more sufficient to avoid heat stress than a tilted window at nighttime and the 1-h ventilation in the morning and the evening. Especially the ventilation in the morning seems to be effective to keep the heat load indoors low. Comparing the results for the current and the future test reference years, an increase of heat stress on all ventilation types can be recognized.

  10. Monitoring of Building Heating and Cooling Systems Based on Geothermal Heat Pump in Galicia (Spain

    Directory of Open Access Journals (Sweden)

    Iglesias M.

    2012-10-01

    Full Text Available In November 2009 was signed an agreement between Galicia’s Government and EnergyLab to develop a project related with the geothermal heatpumps (hereafter, GSHP technology. That project consisted in replacing the existing thermal equipment generators (diesel boilers and air-water heat pumps by GSHP systems in representative public buildings: two nursery schools, a university library, a health centre and a residential building. This new systems will reach the demands of existing heating, cooling and domestic hot water (hereafter, DHW. These buildings can serve as examples of energy and economic savings that can offer this technology. We will show detailed analysis of the GSHP facilities monitored, since the starting-up of them. Which includes: COP’s, EER’s, energy consumption, operating costs, operation hours of the system, economic and emissions comparative, geothermal exchange evolution graphs, environmental conditions evolution graphs (temperature and demands, etc. The results presented show an example of the important benefits of the GSHP technology and the significant savings that can offer its implementation for heating, cooling and DHW production.

  11. Monitoring of Building Heating and Cooling Systems Based on Geothermal Heat Pump in Galicia (Spain)

    Science.gov (United States)

    Iglesias, M.; Rodriguez, J.; Franco, D.

    2012-10-01

    In November 2009 was signed an agreement between Galicia's Government and EnergyLab to develop a project related with the geothermal heatpumps (hereafter, GSHP) technology. That project consisted in replacing the existing thermal equipment generators (diesel boilers and air-water heat pumps) by GSHP systems in representative public buildings: two nursery schools, a university library, a health centre and a residential building. This new systems will reach the demands of existing heating, cooling and domestic hot water (hereafter, DHW). These buildings can serve as examples of energy and economic savings that can offer this technology. We will show detailed analysis of the GSHP facilities monitored, since the starting-up of them. Which includes: COP's, EER's, energy consumption, operating costs, operation hours of the system, economic and emissions comparative, geothermal exchange evolution graphs, environmental conditions evolution graphs (temperature and demands), etc. The results presented show an example of the important benefits of the GSHP technology and the significant savings that can offer its implementation for heating, cooling and DHW production. Note to the reader: The article number has been corrected on web pages on November 22, 2013.

  12. Effects of composition, heat treatment and cold work on structure and properties of alloy 800

    International Nuclear Information System (INIS)

    The creep characteristics of alloy 800 at temperatures around 6000C are greatly affected by the composition and treatments in the final stages of manufacture. Short-term and creep properties of alloy 800 at 6000C are described for six melts covering the carbon range 0.054-0.078%, the titanium range 0.23-0.57% and the aluminium range 0.17-0.52%. The properties are related to the alloy chemistry and the microstructure. It is shown that homogeneously nucleated γ'-precipitates are the main cause of low ductility in alloy 800 but there is also some influence of, for instance, grain boundary M23C6 films and discontinuous precipitation of Ni3Ti or M23C6 in grain boundaries. The extent of γ'-precipitation is controlled primarily by the (Ti+Al)-content. To avoid γ' and ensure a high creep ductility the (Ti+Al)-content should be limited to 0.70-0.75% for alloy 800 with a carbon content of 0.054-0.078% and solution annealed at 11500C. A lower solution temperature will reduce the matrix Ti-content and push the allowed total (Ti+Al)-content upwards. The effect of grain size is such that a coarse-grained material becomes more brittle than a fine-grained one. Cold work of up to 10% will enhance the creep-rupture strength but reduce the ductility

  13. Plastic variational principle based on the least work consumption principle

    Institute of Scientific and Technical Information of China (English)

    唐松花; 罗迎社; 周筑宝; 王智超

    2008-01-01

    Plastic variational principles are foundation to solve the boundary-value problems of plastic mechanics with the variational method(or energy method) and finite element method.The most convenient way of establishing different kinds of variational principles is to set up the extreme principle related to the studied problem.Based on a general new extreme principle-the Least work consumption principle,the variational principles of the rigid-plastic and rigid-viscoplastic material were derived.In comparison with existing methods,the method in this paper is more clear and direct,and the physical meaning is clear-cut.This method can offer a new way for establishing other kinds of variational principles.

  14. Facilitated Work Based Learning - analyseret i et pragmatisk perspektiv

    DEFF Research Database (Denmark)

    Thomassen, Anja Overgaard

    Ph.d.-afhandlingen behandler, med afsæt i John Deweys (1859-1952) pragmatisme, Facilitated Work Based Learning (FWBL) der er en tilgang til efter/videreuddannelse. På baggrund af konkrete uddannelsesforløb gennemført ud fra FWBL analyseres de udfordringer der opstår omkring gennemførelse af...... samarbejde mellem virksomhed og universitet. Især rettes blikket mod den udfordring, at uddannelsesforløbet gennemføres i en virksomhedskontekst og ikke på en uddannelsesinstitution. Ligeledes behandles det, hvilke udfordringer der kan opstå, når personer med forskellige erfaring og erhvervsmæssig baggrund...

  15. Quality of Work and Team- and Project Based Work Practices in Engineering

    DEFF Research Database (Denmark)

    Buch, Anders; Andersen, Vibeke

    2015-01-01

    It is the aim of this paper to investigate teamwork amongst professionals in engineering consultancy companies in order to discern how teamwork affects the collaboration and work practices of the professionals and eventually their quality of work. The paper investigates how professional engineering...... ractices are enacted in two engineering consultancy companies in Denmark where ‘teamwork’ has been or is an ideal for organizing work....

  16. Influence of pre-heating on the surface modification of powder-metallurgy processed cold-work tool steel during laser surface melting

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Heat-treatment protocol for laser surface melting of cold-work tool steel is proposed. • The laser melted steel surface is hardened, and morphologically modified. • The pre-heating of substrate creates a crack-and pore-free steel surface. • The optimum pre-heating temperature is determined to be 350 °C. • Using pre-heating the quantity of retained austenite is reduced. - Abstract: In this study we determine the optimal parameters for surface modification using the laser surface melting of powder-metallurgy processed, vanadium-rich, cold-work tool steel. A combination of steel pre-heating, laser surface melting and a subsequent heat treatment creates a hardened and morphologically modified surface of the selected high-alloy tool steel. The pre-heating of the steel prior to the laser surface melting ensures a crack- and pore-free modified surface. Using a pre-heating temperature of 350 °C, the extremely fine microstructure, which typically evolves during the laser-melting, became slightly coarser and the volume fraction of retained austenite was reduced. In the laser-melted layer the highest values of microhardness were achieved in the specimens where a subsequent heat treatment at 550 °C was applied. The performed thermodynamic calculations were able to provide a very valuable assessment of the liquidus temperature and, especially, a prediction of the chemical composition as well as the precipitation and dissolution sequence for the carbides

  17. Experimental validation of an inverse heat conduction based non-intrusive thermal sensor

    International Nuclear Information System (INIS)

    A non-conventional sensor based on inverse heat transfer (IHT) technique, which present minimum surface intrusion has already been developed (patented at IIT Kanpur). The sensor is based on Levenberg-Marquardt algorithm and method of minimization of least square error. In the present study, validation of the sensor for dropwise condensation is presented. The experiments are performed on a vertical test plate for two different mass flow rates and two cooling water temperature conditions. The estimated heat flux using IHT technique matches very well with heat flux calculated using two thermocouples data, and with average heat flux obtained from the condensate mass collected. (author)

  18. GIS Based Analysis of future district heating potential in Denmark

    DEFF Research Database (Denmark)

    Nielsen, Steffen; Möller, Bernd

    2012-01-01

    The physical placement of buildings is important when determining the future potential for district heating (DH). Good locations for DH are mainly determined by having a large heat demand within a certain area combined with an access to local resources. In Denmark, the placement of buildings and...... finding the heat production cost within these areas, and adding transmission and distribution costs, the economic feasibility of supplying areas with DH is found. The result of the analysis is that the DH potential differs from area to area. In many areas it is economically feasible to expand DH, while in...... others production costs and grid losses should be reduced for DH expansions to be feasible. Including transmission and distribution costs into the calculation, gives an idea about where the boundaries for DH are. These boundaries are not static, but changes under different conditions....

  19. The management of heat stress for the firefighter: a review of work conducted on behalf of the Toronto Fire Service.

    Science.gov (United States)

    McLellan, Tom M; Selkirk, Glen A

    2006-07-01

    This report provides a summary of research conducted through a grant provided by the Workplace Safety Insurance Board of Ontario. The research was divided into two phases; first, to define safe work limits for firefighters wearing their protective clothing and working in warm environments; and, the second, to examine strategies to reduce the thermal burden and extend the operational effectiveness of the firefighter. For the first phase, subjects wore their protective ensemble and carried their self-contained breathing apparatus (SCBA) and performed very light, light, moderate or heavy work at 25 degrees C, 30 degrees C or 35 degrees C. Thermal and evaporative resistance coefficients were obtained from thermal manikin testing that allowed the human physiological responses to be compared with modeled data. Predicted continuous work times were then generated using a heat strain model that established limits for increases in body temperature to 38.0 degrees C, 38.5 degrees C and 39.0 degrees C. Three experiments were conducted for the second phase of the project. The first study revealed that replacing the duty uniform pants that are worn under the bunker pants with shorts reduced the thermal strain for activities that lasted longer than 60 min. The second study examined the importance of fluid replacement. The data revealed that fluid replacement equivalent to at least 65% of the sweat lost increased exposure time by 15% compared with no fluid replacement. The last experiment compared active and passive cooling. Both the use of a mister or forearm and hand submersion in cool water significantly increased exposure time compared with passive cooling that involved only removing most of the protective clothing. Forearm and hand submersion proved to be most effective and produced dramatic increases in exposure time that approximated 65% compared with the passive cooling procedure. When the condition of no fluid replacement and passive cooling was compared with fluid

  20. Development of high-aspect-ratio microchannel heat exchanger based on multi-tool milling process

    Institute of Scientific and Technical Information of China (English)

    潘敏强; 李金恒; 汤勇

    2008-01-01

    A high-aspect-ratio microchannel heat exchanger based on multi-tool milling process was developed. Several slotting cutters were stacked together for simultaneously machining several high-aspect-ratio microchannels with manifold structures. On the basis of multi-tool milling process, the structural design of the manifold side height, microchannel length, width, number, and interval were analyzed. The heat transfer performances of high-aspect-ratio microchannel heat exchangers with two different manifolds were investigated by experiments, and the influencing factors were analyzed. The results indicate that the magnitude of heat transfer area per unit volume dominates the heat transfer performances of plate-type micro heat exchanger, while the velocity distribution between microchannels has little effects on the heat transfer performances.

  1. Heat Dissipation for Microprocessor Using Multiwalled Carbon Nanotubes Based Liquid

    Directory of Open Access Journals (Sweden)

    Bui Hung Thang

    2013-01-01

    Full Text Available Carbon nanotubes (CNTs are one of the most valuable materials with high thermal conductivity (2000 W/m·K compared with thermal conductivity of Ag 419 W/m·K. This suggested an approach in applying the CNTs in thermal dissipation system for high power electronic devices, such as computer processor and high brightness light emitting diode (HB-LED. In this work, multiwalled carbon nanotubes (MWCNTs based liquid was made by COOH functionalized MWCNTs dispersed in distilled water with concentration in the range between 0.2 and 1.2 gram/liter. MWCNT based liquid was used in liquid cooling system to enhance thermal dissipation for computer processor. By using distilled water in liquid cooling system, CPU’s temperature decreases by about 10°C compared with using fan cooling system. By using MWCNT liquid with concentration of 1 gram/liter MWCNTs, the CPU’s temperature decreases by 7°C compared with using distilled water in cooling system. Theoretically, we also showed that the presence of MWCNTs reduced thermal resistance and increased the thermal conductivity of liquid cooling system. The results have confirmed the advantages of the MWCNTs for thermal dissipation systems for the μ-processor and other high power electronic devices.

  2. Heat dissipation for microprocessor using multiwalled carbon nanotubes based liquid.

    Science.gov (United States)

    Hung Thang, Bui; Trinh, Pham Van; Chuc, Nguyen Van; Khoi, Phan Hong; Minh, Phan Ngoc

    2013-01-01

    Carbon nanotubes (CNTs) are one of the most valuable materials with high thermal conductivity (2000 W/m · K compared with thermal conductivity of Ag 419 W/m · K). This suggested an approach in applying the CNTs in thermal dissipation system for high power electronic devices, such as computer processor and high brightness light emitting diode (HB-LED). In this work, multiwalled carbon nanotubes (MWCNTs) based liquid was made by COOH functionalized MWCNTs dispersed in distilled water with concentration in the range between 0.2 and 1.2 gram/liter. MWCNT based liquid was used in liquid cooling system to enhance thermal dissipation for computer processor. By using distilled water in liquid cooling system, CPU's temperature decreases by about 10°C compared with using fan cooling system. By using MWCNT liquid with concentration of 1 gram/liter MWCNTs, the CPU's temperature decreases by 7°C compared with using distilled water in cooling system. Theoretically, we also showed that the presence of MWCNTs reduced thermal resistance and increased the thermal conductivity of liquid cooling system. The results have confirmed the advantages of the MWCNTs for thermal dissipation systems for the μ -processor and other high power electronic devices.

  3. Large Eddy/Reynolds-Averaged Navier-Stokes Simulations of CUBRC Base Heating Experiments

    Science.gov (United States)

    Salazar, Giovanni; Edwards, Jack R.; Amar, Adam J.

    2012-01-01

    ven with great advances in computational techniques and computing power during recent decades, the modeling of unsteady separated flows, such as those encountered in the wake of a re-entry vehicle, continues to be one of the most challenging problems in CFD. Of most interest to the aerothermodynamics community is accurately predicting transient heating loads on the base of a blunt body, which would result in reduced uncertainties and safety margins when designing a re-entry vehicle. However, the prediction of heat transfer can vary widely depending on the turbulence model employed. Therefore, selecting a turbulence model which realistically captures as much of the flow physics as possible will result in improved results. Reynolds Averaged Navier Stokes (RANS) models have become increasingly popular due to their good performance with attached flows, and the relatively quick turnaround time to obtain results. However, RANS methods cannot accurately simulate unsteady separated wake flows, and running direct numerical simulation (DNS) on such complex flows is currently too computationally expensive. Large Eddy Simulation (LES) techniques allow for the computation of the large eddies, which contain most of the Reynolds stress, while modeling the smaller (subgrid) eddies. This results in models which are more computationally expensive than RANS methods, but not as prohibitive as DNS. By complimenting an LES approach with a RANS model, a hybrid LES/RANS method resolves the larger turbulent scales away from surfaces with LES, and switches to a RANS model inside boundary layers. As pointed out by Bertin et al., this type of hybrid approach has shown a lot of promise for predicting turbulent flows, but work is needed to verify that these models work well in hypersonic flows. The very limited amounts of flight and experimental data available presents an additional challenge for researchers. Recently, a joint study by NASA and CUBRC has focused on collecting heat transfer data

  4. Optimal waste heat recovery Rankine based for heavy duty applications

    OpenAIRE

    Grelet, Vincent; Reiche, Thomas; Guillaume, Ludovic; Lemort, Vincent

    2014-01-01

    Even in nowadays engines which can reach 45% of efficiency a high amount of energy is released as heat to the ambient. The increase in oil prices compels manufacturers to focus on new solutions to improve fuel efficiency of truck powertrain such as Waste Heat Recovery Systems (WHRS). Over last few years a lot of studies have proven that there are a lot of hurdles (cooling margin, expansion machines, …) for a perfect match of such a system on a vehicle. The objective of this study is to define...

  5. CFD simulation of direct contact condensation with ANSYS CFX using surface renewal theory based heat transfer coefficients

    Energy Technology Data Exchange (ETDEWEB)

    Wanninger, Andreas; Ceuca, Sabin Cristian; Macian-Juan, Rafael [Technische Univ. Muenchen, Garching (Germany). Dept. of Nuclear Engineering

    2013-07-01

    Different approaches for the calculation of Direct Contact Condensation (DCC) using Heat Transfer Coefficients (HTC) based on the Surface Renewal Theory (SRT) are tested using the CFD simulation tool ANSYS CFX. The present work constitutes a preliminary study of the flow patterns and conditions observed using different HTC models. A complex 3D flow pattern will be observed in the CFD simulations as well as a strong coupling between the condensation rate and the two-phase flow dynamics. (orig.)

  6. HEAT PUMP STATION WITH CARBON DIOXIDE AS A WORKING FLUID ENERGY EFFICIENCY GROWTH IN COMBINED DISTRICT HEATING SYSTEM DUE TO ITS CONTROL SYSTEM OPTIMIZATION

    Directory of Open Access Journals (Sweden)

    Sit B.M.

    2008-04-01

    Full Text Available A diagram of the heat pump station (HPS for the central heat supply station of the district heating system, which gets the power from the CHP plant is examined. A block diagram of the control of the system and compressor pressure control system are examined. The description of the control laws of evaporator at the variable heat load of the HPS and control laws of the gas cooler taking into account the goal of achieving the maximum of COP of HPS is shown as well.

  7. Asymmetric Base-Bleed Effect on Aerospike Plume-Induced Base-Heating Environment During Power-Pack Out

    Science.gov (United States)

    Wang, Ten-See; Droege, Alan; D'Agostino, Mark; Lee, Young-Ching; Williams, Robert

    2003-01-01

    A computational heat transfer design methodology was developed to study tbe dual-engine linear aerospike plume-induced base-heating environment during one power-pack out, in ascent flight. It includes a three-dimensional, finite volume, viscous, chemically reacting, and pressure-based computational fluid dynamics formulation, a special base-bleed boundary condition, and a three-dimensional, finite volume, and spectral-line-based weighted-sum-of-gray-gases absorption computational radiation heat transfer formulation. A separate radiation model was used for diagnostic purposes. The computational methodology was systematically benchmarked. in this study, near-base radiative heat fluxes were computed, and they compared well with those measured during static linear aerospike engine tests. The base-heating environment of 18 trajectory points secected from three power-pack out scenarios was computed. The computed asymmetric base-heating physics were analyzed. The power-pack out condition has the most impact on convective base heating when it happens early in flight. The soume of its impact comes from the asymmetric and reduced base bleed.

  8. Model-based analysis and simulation of regenerative heat wheel

    DEFF Research Database (Denmark)

    Wu, Zhuang; Melnik, Roderick V. N.; Borup, F.

    2006-01-01

    of mathematical models for the thermal analysis of the fluid and wheel matrix. The effect of heat conduction in the direction of the fluid flow is taken into account and the influence of variations in rotating speed of the wheel as well as other characteristics (ambient temperature, airflow and geometric size...

  9. Air Conditioning, Heating, and Refrigeration. Competency-Based Curriculum Manual.

    Science.gov (United States)

    Gourley, Frank A., Jr.

    This manual was developed to serve as an aid to administrators and instructors involved with postsecondary air conditioning, heating, and refrigeration programs. The first of six chapters contains general information on program implementation, the curriculum design, facilities and equipment requirements, and textbooks and references. Chapter 2…

  10. Artificial Neural Networks-Based Software for Measuring Heat Collection Rate and Heat Loss Coefficient of Water-in-Glass Evacuated Tube Solar Water Heaters

    OpenAIRE

    Liu, Zhijian; Liu, Kejun; Li, Hao; Zhang, Xinyu; Jin, Guangya; Cheng, Kewei

    2015-01-01

    Measurements of heat collection rate and heat loss coefficient are crucial for the evaluation of in service water-in-glass evacuated tube solar water heaters. However, conventional measurement requires expensive detection devices and undergoes a series of complicated procedures. To simplify the measurement and reduce the cost, software based on artificial neural networks for measuring heat collection rate and heat loss coefficient of water-in-glass evacuated tube solar water heaters was devel...

  11. Thermodynamic and kinetic investigation of a chemical reaction-based miniature heat pump

    OpenAIRE

    Flueckiger, Scott M.; Volle, Fabien; Garimella, S V; Mongia, Rajiv K.

    2012-01-01

    Representative reversible endothermic chemical reactions (paraldehyde depolymerization and 2-proponal dehydrogenation) are theoretically assessed for their use in a chemical heat pump design for compact thermal management applications. Equilibrium and dynamic simulations are undertaken to explore the operation of the heat pump which upgrades waste heat from near room temperature by approximately 20 in a minimized system volume. A model is developed based on system mass and energy balances cou...

  12. Optimizing critical heat flux enhancement through nano-particle-based surface modifications

    International Nuclear Information System (INIS)

    Colloidal dispersions of nano-particles, also known as nano-fluids, have shown to yield significant Critical Heat Flux (CHF) enhancement. The CHF enhancement mechanism in nano-fluids is due to the buildup of a porous layer of nano-particles upon boiling. Unlike microporous coatings that had been studied extensively, nano-particles have the advantages of forming a thin layer on the substrate with surface roughness ranges from the sub-micron to several microns. By tuning the chemical properties it is possible to coat the nano-particles in colloidal dispersions onto the desired surface, as has been demonstrated in engineering thin film industry. Building on recent work conducted at MIT, this paper illustrates the maximum CHF enhancement that can be achieved based on existing correlations. Optimization of the CHF enhancement by incorporation of key factors, such as the surface wettability and roughness, will also be discussed. (authors)

  13. Reflexive Professionalism as a Second Generation of Evidence-Based Practice: Some Considerations on the Special Issue "What Works? Modernizing the Knowledge-Base of Social Work"

    Science.gov (United States)

    Otto, Hans-Uwe; Polutta, Andreas; Ziegler, Holger

    2009-01-01

    This article refers sympathetically to the thoughtful debates and positions in the "Research on Social Work Practice" ("RSWP"; Special Issue, July, 2008 issue) on "What Works? Modernizing the Knowledge-Base of Social Work." It highlights the need for empirical efficacy and effectiveness research in social work and appreciates empirical rigor…

  14. Simple and low cost method for metal-based micro-capillary channels for heat exchanger use

    Science.gov (United States)

    Ogbonnaya, E.; Champagne, C.; Weiss, L.

    2013-11-01

    In this work, we present an alternative, low cost method for the fabrication of a heat exchanger utilizing metal-based microchannels using the UV-LiGA technique. Lithography is used to pattern dry film negative photoresist (Ordyl P-50100) on the substrate. The resist is laminated over the substrate and exposed with a UV source. The use of dry film resist allows for simple and inexpensive microchannel patterns without requiring advanced cleanroom equipment. Following the lithography process, electrodeposition of metals is used to fill the recesses patterned in the resist. In this work, nickel has been electroplated into the bounding resist structure. After electroplating, the remaining resist is dissolved leaving free standing metal structures. The fabricated exchanger is then evaluated based on thermal absorption of simulated waste heat sources and capillary action of the metal channels themselves. Channels are fabricated to heights of 60, 70 and 90 μm respectively on copper substrate using these methods. Working fluid mass transfer rate from the heated microchannel heat exchanger (MHE) is utilized as a basic metric of operation. The mass transfer rate recorded from the nickel-based MHE is 2.19, 2.81 and 3.20 mg s-1 respectively for the different channel heights. This implies an effective thermal power consumption rate of 1.66, 2.13 and 2.42 kW m-2 respectively. By contrast, an MHE fabricated with 115 and 142 μm tall channels on silicon substrate is shown to evaporate up to 2.84 and 3.04 mg s-1 respectively, giving an effective thermal power consumption of 2.15 and 2.31 kW m-2 respectively. An investigation of working fluid contact angle with the electroplated nickel surface is also presented. The surface is found to be a porous structure stemming from the electroplating process.

  15. Simple and low cost method for metal-based micro-capillary channels for heat exchanger use

    International Nuclear Information System (INIS)

    In this work, we present an alternative, low cost method for the fabrication of a heat exchanger utilizing metal-based microchannels using the UV-LiGA technique. Lithography is used to pattern dry film negative photoresist (Ordyl P-50100) on the substrate. The resist is laminated over the substrate and exposed with a UV source. The use of dry film resist allows for simple and inexpensive microchannel patterns without requiring advanced cleanroom equipment. Following the lithography process, electrodeposition of metals is used to fill the recesses patterned in the resist. In this work, nickel has been electroplated into the bounding resist structure. After electroplating, the remaining resist is dissolved leaving free standing metal structures. The fabricated exchanger is then evaluated based on thermal absorption of simulated waste heat sources and capillary action of the metal channels themselves. Channels are fabricated to heights of 60, 70 and 90 μm respectively on copper substrate using these methods. Working fluid mass transfer rate from the heated microchannel heat exchanger (MHE) is utilized as a basic metric of operation. The mass transfer rate recorded from the nickel-based MHE is 2.19, 2.81 and 3.20 mg s−1 respectively for the different channel heights. This implies an effective thermal power consumption rate of 1.66, 2.13 and 2.42 kW m−2 respectively. By contrast, an MHE fabricated with 115 and 142 μm tall channels on silicon substrate is shown to evaporate up to 2.84 and 3.04 mg s−1 respectively, giving an effective thermal power consumption of 2.15 and 2.31 kW m−2 respectively. An investigation of working fluid contact angle with the electroplated nickel surface is also presented. The surface is found to be a porous structure stemming from the electroplating process. (paper)

  16. Evolutionary Prisoner's Dilemma Game Based on Division of Work

    Institute of Scientific and Technical Information of China (English)

    LI Zhi-Hua; WANG Bing-Hong; LIU Run-Ran; YANG Han-Xin

    2009-01-01

    We propose a new two-type-player prisoner's dilemma game based on the division of work on a square lattice, in which a fraction of the population μ are assigned type A and the rest B.In a one-shot two-player game, we let both of their original payoffs be scaled by a same multiplicative factor α > 1, if two neighboring players are of different types; however we leave the payoffs unchanged if they are of the same type.Then we show that combined with the two-type setup, the square lattice can assist to induce different social ranks according to players' abilities to collect payoffs.Simulation results show that the density of cooperation is significantly promoted for a wide range of the temptation to defection parameters and that there are optimal values for both α and μ leading to the maximal cooperation level.We reach these results by analyzing the distribution of the players in the social ranks and we also show some typical snapshots of the system.

  17. Long-term heat storage in calcium sulfoaluminate cement (CSA) based concrete

    Energy Technology Data Exchange (ETDEWEB)

    Kaufmann, Josef P.; Winnefeld, Frank [Empa Swiss Federal Laboratories for Materials Science and Technology, Duebendorf (Switzerland). Lab. for Concrete and Construction Chemistry

    2011-07-01

    In general, the selection of materials proposed for solar heat storage is based on one of two principal processes: sensible heat storage or latent heat storage. Sensible heat storage utilizes the specific heat capacity of a material, while latent heat storage is based on the change in enthalpy (heat content) associated with a phase change of the material. Long time sensible heat storage requires excellent thermal insulation whereas latent heat storage allows permanent (seasonal) storage without significant energy losses and any special insulation. Ettringite, one of the cement hydration products, exhibits a high dehydration enthalpy. Calcium sulfoaluminate cement based concrete containing a high amount of ettringite is henceproposed as an efficient latent heat storage material. Compared to conventional heat storage materials this innovative concrete mixture has a high loss-free storage energy density (> 100-150 kWh/m{sup 3}) which is much higher than the one of paraffin or the (loss-sensitive) sensible heat of water. Like common concrete the CSA-concrete is stable and even may carry loads. The dehydration of the CSA-concrete is achieved at temperatures below 100 C. The rehydration process occurs as soon as water (liquid or vapor) is added. In contrast to paraffin, the phase change temperature is not fixed and the latent heat may be recovered at any desired temperature. Furthermore the heat conductivity of this material is high, so that the energy transfer from/to an exchange medium is easy. Additionally CSA-concrete is not flammable and absolutely safe regarding any health aspects. The cost of such CSA-concrete isin the order of normal concrete. The main application is seen in house heating systems. Solar heat, mostly generated during the summer period by means of roof collectors, can be stored in CSA-concrete until the winter. A part or even the whole annual heatingenergy may be produced and saved locally by the householder himself. Additional applications may be

  18. Improved collaborative filtering algorithm based on heat conduction

    Institute of Scientific and Technical Information of China (English)

    Qiang GUO; Jianguo LIU; Binghong WANG

    2009-01-01

    In this paper, we present an improved collabo-rative filtering (ICF) algorithm by using the heat diffusion process to generate the user correlation. This algorithm has remarkably higher accuracy than the standard collaborative filtering (CF) using Pearson correlation. Furthermore, we introduce a free parameter β to regulate the contributions of objects to user correlation. The numerical simulation results indicate that decreasing the influence of popular objects can further improve the algorithmic accuracy and diversity.

  19. THERMODYNAMIC ANALYSIS OF DIFFERENT WORKING FLUIDS USED IN ORGANIC RANKINE CYCLE FOR RECOVERING WASTE HEAT FROM GT-MHR

    Directory of Open Access Journals (Sweden)

    AMIN HABIBZADEH

    2016-01-01

    Full Text Available In this paper, the performance of 13 working fluids in two Organic Rankine Cycles, which operate as the bottoming cycles for recovering waste heat from gas turbine modular helium reactor (GT-MHR, is investigated. Working fluids are classified in three dry, isentropic and wet fluids. The effect of varying pump temperature and evaporator pressure on the thermal efficiency, total exergy loss of the combined cycle is studied for each category, and the results are compared. The results are calculated for an optimum pressure ratio in which thermal efficiency is maximum. According to the results, dry fluids show a higher thermal efficiency while wet fluids have the lowest values. However, the highest value for thermal efficiency is for R141b, which is an isentropic fluid. Furthermore, the results indicate that pump temperature increase, reduces the total thermal efficiency and increases the total exergy loss of the combined cycle. Increasing evaporator pressure leads to an optimum pressure that maximizes total thermal efficiency. According to the optimized pressure ratio and evaporator pressure, R141b in isentropic fluids, R123 in dry fluids and R717 in wet fluids have the highest thermal efficiency values.

  20. Out of the Comfort Zone: Enhancing Work-Based Learning about Employability through Student Reflection on Work Placements

    Science.gov (United States)

    Eden, Sally

    2014-01-01

    This paper examines the work-based learning about employability reported by 26 undergraduate Geography and Environmental Management students on part-time, unpaid work placements. The students' "reflective essays" emphasized their learning more in terms of emotional challenges than in terms of skills, as being pushed out of their…

  1. Preparation and Recipe Optimization of Water-based Architectural Heat Insulation Coatings

    Institute of Scientific and Technical Information of China (English)

    CHEN Lijun; SHI Hongxin; XIANG Juping; WU Hongke

    2008-01-01

    Water-based architectural heat insulation coatings were studied to overcome the drawbacks of conventional inorganic silicate heat insulation coatings.The heat insulation coatings were prepared with the method of mechanical agitation when the mixed organic polymer emulsions were used as binder of the coatings and the mixed heat insulating aggregates were applied as powder,and some assistants were also added.Water temperature difference in the plastic container,which was coated with heat insulation coatings,represented the heat-insulating property of the coatings.The influences of components of mixed polymer emulsion,mass ratio of polymer emulsion to powder,particle size of heat insulating aggregates,added amount of air entraining admixture and the match of thickeners on the properties of the coatings were studied.The experimental results show that the heat insulation coatings with good finishing,heat-insulation property and artificial weathering can be prepared when the binder is composed of 66.92% styrene-acrylic emulsion,16.59% elastic emulsion and 16.49% silicone-acrylic emulsion,the mass ratio of polymer emulsion to powder is 0.45,the particle size of heat insulating aggregates is in the rang of 200 and 250 mesh size,the added amount of sericite is 15%,and the added amount of air entraining admixture is in the range of 1.0% and 1.5% and the thickeners are the mixtures of ASE-60 and RM-5000.

  2. Experimental study on rack cooling system based on a pulsating heat pipe

    Science.gov (United States)

    Lu, Qianyi; Jia, Li

    2016-02-01

    A rack cooling system based on a large scale flat plate pulsating heat pipe is proposed. The heat generated from IT equipment in a closed rack is transferred by the rear door pulsating heat pipe to the chilled air passage and is avoided to release into the room. The influence of the start-up performance of the heat pipe, the load of the rack and the load dissipation to the temperature and the velocity distribution in the rack are discussed. It is found that the temperature would be lower and the temperature distribution would be more uniform in the rack when the pulsating heat pipe is in operation. Also, the effect of rack electricity load on temperature distribution is analyzed. It is indicated that higher velocity of chilled air will improve heat transfer of the rack.

  3. Investigation of Martensite Formation in Fe Based Alloys During Heating From Boiling Nitrogen Temperature

    DEFF Research Database (Denmark)

    Villa, Matteo; Christiansen, Thomas L.; Hansen, Mikkel F.;

    2015-01-01

    he austenite-to-martensite transformation at temperatures below room temperature was investigated in situ by magnetometry in Fe-N, Fe-Cr-C and Fe-Cr-Ni based alloys. After quenching to room temperature, samples were immersed in boiling nitrogen and martensite formation was followed during...... heating was convincingly demonstrated for all investigated materials by showing heating rate dependent transformation kinetics. Moreover, magnetometry showed that the heating rate influences the fraction of martensite formed during the thermal treatment. The activation energy for thermally activated...... subsequent heating to room temperature. Different tests were performed with heating rates ranging from 0.5 K/min to 10 K/min. For comparison a sample was up-quenched in water to verify whether martensite formation can be suppressed at high heating rates. Thermally activated formation of martensite during...

  4. Numerical analysis of pulsating heat pipe based on separated flow model

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jong Soo; Im, Yong Bin; Bui, Ngoc Hung [Pukyong National Univ., Pusan (Korea, Republic of)

    2005-09-15

    The examination on the operating mechanism of a Pulsating Heat Pipe (PHP) using visualization revealed that the working fluid in the PHP oscillated to the axial direction by the contraction and expansion of vapor plugs. This contraction and expansion is due to the formation and extinction of bubbles in the evaporating and condensing section, respectively. In this paper, a theoretical model of PHP was presented. The theoretical model was based on the separated flow model with two liquid slugs and three vapor plugs. The results show that the diameter, surface tension and charge ratio of working fluid have significant effects on the performance of the PHP. The following conclusions were obtained. The periodic oscillations of liquid slugs and vapor plugs were obtained under specified parameters. When the hydraulic diameter of the PHP was increased to d=3 mm, the frequency of oscillation decreased. By increasing the charging ratio from 40 to 60 by volume ratio, the pressure difference between the evaporating section and condensing section increased, the amplitude of oscillation reduced, and the oscillation frequency decreased. The working fluid with higher surface tension resulted in an increase in the amplitude and frequency of oscillation. Also the average temperature of vapor plugs decreased.

  5. Comparative study of alternative ORC-based combined power systems to exploit high temperature waste heat

    International Nuclear Information System (INIS)

    Highlights: • Three ORC-based combined systems for ICE exhaust waste heat recovery are studied. • A parametric investigation is conducted under several typical engine conditions. • Performance is evaluated considering six thermodynamic, techno-economic indexes. • DORC distinguishes among other solutions for its highest energy recovery capacity. • TEG–ORC system becomes attractive when exhaust temperature is relatively low. - Abstract: In this paper, various combined power systems which regard organic Rankine cycle (ORC) as bottoming cycle to recover engine’s high temperature exhaust heat are proposed. The topping recovery cycle includes steam Rankine cycle (RC), Brayton cycle (BC) and thermoelectric generator (TEG). Comprehensive evaluations are conducted under five typical engine conditions, ranging from high load to low load, and system performance is assessed in terms of many thermodynamic indexes, such as net output power, thermal efficiency, recovery efficiency and exergy efficiency. Besides that, the irreversibility of each component is also discussed in detail. R123, R245fa and R600a for ORC system are considered to analyze the influence of working fluids. Considering the system techno-economy, the turbine size parameter (SP) and heat transfer capacity (UA) are chosen as key indicators. The results show that compared with the other two investigated approaches, dual-loop ORC (DORC) possesses the highest energy exploitation capacity under the whole operating region, with a 5.57% increase of fuel economy under the rated condition, but its values of SP and UA are large as well. TEG–ORC becomes appealing while under the relatively low load

  6. Experimental study of laminar forced convective heat transfer of deionized water based copper (I) oxide nanofluids in a tube with constant wall heat flux

    Science.gov (United States)

    Umer, Asim; Naveed, Shahid; Ramzan, Naveed

    2016-10-01

    Nanofluids, having 1-100 nm size particles in any base fluid are promising fluid for heat transfer intensification due to their enhanced thermal conductivity as compared with the base fluid. The forced convection of nanofluids is the major practical application in heat transfer equipments. In this study, heat transfer enhancements at constant wall heat flux under laminar flow conditions were investigated. Nanofluids of different volume fractions (1, 2 and 4 %) of copper (I) oxide nanoparticles in deionized water were prepared using two step technique under mechanical mixing and ultrasonication. The results were investigated by increasing the Reynolds number of the nanofluids at constant heat flux. The trends of Nusselt number variation with dimensionless length (X/D) and Reynolds numbers were studied. It was observed that heat transfer coefficient increases with increases particles volume concentration and Reynolds number. The maximum enhancement in heat transfer coefficient of 61 % was observed with 4 % particle volume concentration at Reynolds number (Re ~ 605).

  7. Study of mixtures based on hydrocarbons used in ORC (Organic Rankine Cycle) for engine waste heat recovery

    International Nuclear Information System (INIS)

    For high temperature ORC (Organic Rankine Cycle) used in engine waste heat recovery, it's very critical to select a high temperature working fluid. HCs (Hydrocarbons) usually have excellent cycle performance, but the flammability limits their practical application. Considering that some retardants can be used to suppress flammability, the paper presents an application of mixtures based on hydrocarbons blending with refrigerant retardants to engine waste heat ORC. Three pure hydrocarbons (cyclopentane, cyclohexane, benzene) and two retardants (R11, R123) are selected for combination. Thermal efficiency and exergy loss are selected as the main objective functions. Based on thermodynamic model, the effects of retardants mass fraction, evaporation temperature and IHE (internal heat exchanger) are investigated. Results show that zeotropic mixtures do have higher thermal efficiency and lower exergy loss than pure fluids, at a certain mixture ratio. There exists the OMR (optimal mixture ratio) for different mixtures, and it changes with the evaporation temperature. When adding IHE to system, cycle performance could be obviously improved, and for benzene/R11 (0.7/0.3), the efficiency growth is about 7.12%∼9.72%. Using it, the maximum thermal efficiency of the system can achieve 16.7%, and minimum exergy loss is only 30.76 kW. - Highlights: • A theoretical analysis of Organic Rankine Cycle for engine exhaust heat recovery is proposed. • Mixtures based on hydrocarbons as working fluids have been suggested. • Effects of the IHE (internal heat exchanger) on ORC system are investigated. • OMR (Optimal mixture ratio) changes with the evaporation temperature. • Using the system, maximum thermal efficiency can achieve 16.7%

  8. Evaluation of the operational cost savings potential from a D-CHP system based on a monthly power-to-heat ratio analysis

    OpenAIRE

    Alta Knizley; Pedro J. Mago; James Tobermann

    2015-01-01

    This paper focuses on the analysis of a combined heat and power (CHP) system utilizing two power generation units operating simultaneously under differing operational strategies (D-CHP) on the basis of operational cost savings. A cost optimization metric, based on the facility monthly power-to-heat ratio (PHR), is presented in this paper. The PHR is defined as the ratio between the facility electric load and thermal load. Previous work in this field has suggested that D-CHP system performance...

  9. Simulation and Optimization of the Heat Exchanger for Automotive Exhaust-Based Thermoelectric Generators

    Science.gov (United States)

    Su, C. Q.; Huang, C.; Deng, Y. D.; Wang, Y. P.; Chu, P. Q.; Zheng, S. J.

    2016-03-01

    In order to enhance the exhaust waste heat recovery efficiency of the automotive exhaust-based thermoelectric generator (TEG) system, a three-segment heat exchanger with folded-shaped internal structure for the TEG system is investigated in this study. As the major effect factors of the performance for the TEG system, surface temperature, and thermal uniformity of the heat exchanger are analyzed in this research, pressure drop along the heat exchanger is also considered. Based on computational fluid dynamics simulations and temperature distribution, the pressure drop along the heat exchanger is obtained. By considering variable length and thickness of folded plates in each segment of the heat exchanger, response surface methodology and optimization by a multi-objective genetic algorithm is applied for surface temperature, thermal uniformity, and pressure drop for the folded-shaped heat exchanger. An optimum design based on the optimization is proposed to improve the overall performance of the TEG system. The performance of the optimized heat exchanger in different engine conditions is discussed.

  10. Work Based Learning in Intercultural Settings: A Model in Practice

    Science.gov (United States)

    Leeming, David Elvis; Mora, Maria Dolores Iglesias

    2016-01-01

    The Intercultural Business Communication at the University of Central Lancashire offers a taught module with a work placement that exists within a multicultural context as part of an MA in Intercultural Business Communication. As part of this process, students must work towards completing two practical assessments, a project presented in a report…

  11. Space Launch System Base Heating Test: Environments and Base Flow Physics

    Science.gov (United States)

    Mehta, Manish; Knox, Kyle S.; Seaford, C. Mark; Dufrene, Aaron T.

    2016-01-01

    The NASA Space Launch System (SLS) vehicle is composed of four RS-25 liquid oxygen-hydrogen rocket engines in the core-stage and two 5-segment solid rocket boosters and as a result six hot supersonic plumes interact within the aft section of the vehicle during flight. Due to the complex nature of rocket plume-induced flows within the launch vehicle base during ascent and a new vehicle configuration, sub-scale wind tunnel testing is required to reduce SLS base convective environment uncertainty and design risk levels. This hot-fire test program was conducted at the CUBRC Large Energy National Shock (LENS) II short-duration test facility to simulate flight from altitudes of 50 kft to 210 kft. The test program is a challenging and innovative effort that has not been attempted in 40+ years for a NASA vehicle. This paper discusses the various trends of base convective heat flux and pressure as a function of altitude at various locations within the core-stage and booster base regions of the two-percent SLS wind tunnel model. In-depth understanding of the base flow physics is presented using the test data, infrared high-speed imaging and theory. The normalized test design environments are compared to various NASA semi-empirical numerical models to determine exceedance and conservatism of the flight scaled test-derived base design environments. Brief discussion of thermal impact to the launch vehicle base components is also presented.

  12. Heat-stop structure design with high cooling efficiency for large ground-based solar telescope.

    Science.gov (United States)

    Liu, Yangyi; Gu, Naiting; Rao, Changhui; Li, Cheng

    2015-07-20

    A heat-stop is one of the most important thermal control devices for a large ground-based solar telescope. For controlling the internal seeing effect, the temperature difference between the heat-stop and the ambient environment needs to be reduced, and a heat-stop with high cooling efficiency is required. In this paper, a novel design concept for the heat-stop, in which a multichannel loop cooling system is utilized to obtain higher cooling efficiency, is proposed. To validate the design, we analyze and compare the cooling efficiency for the multichannel and existing single-channel loop cooling system under the same conditions. Comparative results show that the new design obviously enhances the cooling efficiency of the heat-stop, and the novel design based on the multichannel loop cooling system is obviously better than the existing design by increasing the thermal transfer coefficient.

  13. Analysis of variable-base heating and cooling degree-days for Turkey

    Energy Technology Data Exchange (ETDEWEB)

    Buyukalaca, Orhan; Bulut, Husamettin; Yilmaz, Tuncay [Cukurova Univ., Dept. of Mechanical Engineering, Adana (Turkey)

    2001-08-01

    The degree-day method is one of the well-known and the simplest methods used in the Heating, Ventilating and Air-Conditioning industry to estimate heating and cooling energy requirements. In this study, the heating and cooling degree-days for Turkey are determined by using long-term recent measured data. Five different base temperatures ranging from 14 to 22 deg C are chosen in the calculation of heating degree-days. In the case of cooling degree-days, 6 different base temperatures in the range of 18 to 28 deg C are used. Yearly heating and cooling degree-days are given both in tabular form and as counter-maps for all the provinces of Turkey (78 weather stations). (Author)

  14. Heat-stop structure design with high cooling efficiency for large ground-based solar telescope.

    Science.gov (United States)

    Liu, Yangyi; Gu, Naiting; Rao, Changhui; Li, Cheng

    2015-07-20

    A heat-stop is one of the most important thermal control devices for a large ground-based solar telescope. For controlling the internal seeing effect, the temperature difference between the heat-stop and the ambient environment needs to be reduced, and a heat-stop with high cooling efficiency is required. In this paper, a novel design concept for the heat-stop, in which a multichannel loop cooling system is utilized to obtain higher cooling efficiency, is proposed. To validate the design, we analyze and compare the cooling efficiency for the multichannel and existing single-channel loop cooling system under the same conditions. Comparative results show that the new design obviously enhances the cooling efficiency of the heat-stop, and the novel design based on the multichannel loop cooling system is obviously better than the existing design by increasing the thermal transfer coefficient. PMID:26367826

  15. A model to predict the behaviour at part load operation of once-through heat recovery steam generators working with water at supercritical pressure

    OpenAIRE

    Rovira de Antonio, Antonio José; Valdes del Fresno, Manuel; Durán, María Dolores

    2010-01-01

    This paper describes a one-dimensional mathematical model that allows simulating the heat exchange in a steam generator working with water at supercritical pressure. The model has been developed in order to simulate the full and part load behaviour of heat recovery steam generators (HRSGs) of combined cycle gas turbine (CCGT) power plants. It takes into account the strong variation of some of the thermal and transport properties of fluids at supercritical pressure and discusses what parameter...

  16. Numerical prediction of micro-channel LD heat sink operated with antifreeze based on CFD method

    Science.gov (United States)

    Liu, Gang; Liu, Yang; Wang, Chao; Wang, Wentao; Wang, Gang; Tang, Xiaojun

    2014-12-01

    To theoretically study the feasibility of antifreeze coolants applied as cooling fluids for high power LD heat sink, detailed Computational Fluid Dynamics (CFD) analysis of liquid cooled micro-channels heat sinks is presented. The performance operated with antifreeze coolant (ethylene glycol aqueous solution) compared with pure water are numerical calculated for the heat sinks with the same micro-channels structures. The maximum thermal resistance, total pressure loss (flow resistance), thermal resistance vs. flow-rate, and pressure loss vs. flow-rate etc. characteristics are numerical calculated. The results indicate that the type and temperature of coolants plays an important role on the performance of heat sinks. The whole thermal resistance and pressure loss of heat sinks increase significantly with antifreeze coolants compared with pure water mainly due to its relatively lower thermal conductivity and higher fluid viscosity. The thermal resistance and pressure loss are functions of the flow rate and operation temperature. Increasing of the coolant flow rate can reduce the thermal resistance of heat sinks; meanwhile increase the pressure loss significantly. The thermal resistance tends to a limit with increasing flow rate, while the pressure loss tends to increase exponentially with increasing flow rate. Low operation temperature chiefly increases the pressure loss rather than thermal resistance due to the remarkable increasing of fluid viscosity. The actual working point of the cooling circulation system can be determined on the basis of the pressure drop vs. flow rate curve for the micro-channel heat sink and that for the circulation system. In the same system, if the type or/and temperature of the coolant is changed, the working point is accordingly influenced, that is, working flow rate and pressure is changed simultaneously, due to which the heat sink performance is influenced. According to the numerical simulation results, if ethylene glycol aqueous

  17. Model-based Optimizing Control of a Water-to-Water Heat Pump Unit

    OpenAIRE

    Morten C. Svensson

    1996-01-01

    This paper outlines the basic principles of on-line model-based steady-state optimizing control of continuous processes, and illustrates how this control approach can be used to optimize the operating conditions of heat pumps.

  18. Correlation study on physical properties of working fluids and heat transfer performance of pulsating heat pipes%振荡热管传热性能与工质物性关系分析

    Institute of Scientific and Technical Information of China (English)

    崔晓钰; 于洋; 朱悦; 李治华; 孙慎德; 韩华

    2013-01-01

    Deionized water,methanol,ethanol and acetone were chosen as working fluids to investigate operation and heat transfer characteristics of pulsating heat pipes (PHP). The experiment was designed to find out critical physical properties for the heat transfer of PHP under different conditions. The results showed that at small heating power,heat transfer depended on the speed of oscillation,and the key factor was kinetic viscosity. As the heating power increased,oscillatory flow accelerated accordingly,and the differences in frequency and amplitude of temperature oscillation gradually decreased,indicating the heat transfer of PHP was affected by kinetic viscosity,liquid specific heat and latent heat. As the heating power increased to a certain point,oscillatory flows of different WFs became faster and,at this stage,WFs of high latent heat and specific heat were preferable for heat transfer. The correlation study on the physical properties of WFs and the heat transfer performance of PHP may help to understand the heat transfer mechanism and operation characteristics of PHP at different situations and provide reference for the establishment of theoretical model.%选取去离子水、甲醇、乙醇和丙酮为工质,考察不同工质不同充液率的振荡热管运行特征,寻找影响振荡热管传热性能的物性因素。结果表明:在小功率时,传热性能受是否启动振荡及振荡流速支配,与动力黏度密切相关;随加热功率增大,振荡流速加快,不同工质振荡热管温度振荡频率和幅度差别渐小,动力黏度和液态比热容、汽化潜热共同影响振荡热管传热性能;在大功率时,振荡流速较快,充注汽化潜热、比热容大的工质振荡热管传热性能更具优势。振荡热管和物性的关联分析可为认识不同情况下振荡热管的传热机理和工作特性、建立振荡热管理论模型提供参考。

  19. Indirect and Mixed Direct-Indirect Heat Integration of Batch Processes Based on Pinch Analysis

    Directory of Open Access Journals (Sweden)

    Daniel Favrat

    2001-09-01

    Full Text Available

    This paper introduces a methodology for the heat integration of industrial batch processes. Based on Pinch Analysis principles, this methodology resorts to intermediate heat storage to prevent adverse effects on the operating flexibility, which are often associated with direct heat exchange only. A systematic procedure, backed with a graphical representation, allows the determination of the minimum number of heat storage units assuming vertical heat transfer and their range of feasible operation as a function of the amount of heat recovery. Understanding the cause and the bottleneck effect of the socalled storage pinch, heuristic rules are proposed to screen major options corresponding to minimum cost solutions. For a given number of heat storage units, these rules could be automated to a large extent, making the procedure suitable for targeting purposes. The operating temperature of the heat storage units can be optimized with ease, while other continuous degrees of freedom are more difficult to address using the proposed methodology. Preliminary guidelines are proposed to extend the methodology to mixed direct-indirect heat integration.

    •  This paper was presented at the ECOS’00 Conference in Enschede, July 5-7, 2000 and revised

  20. Community-based rehabilitation: working in partnership with eye care

    Directory of Open Access Journals (Sweden)

    Joerg Weber

    2013-05-01

    Full Text Available Any response to the needs of people with visual impairment and their families will be more effective if eye care workers and CBR programme staff can work together at the community level.

  1. A novel NGL (natural gas liquid) recovery process based on self-heat recuperation

    International Nuclear Information System (INIS)

    This study examined an innovative self-heat-recuperation technology that circulates latent and sensible heat in the thermal process and applied it to the NGL (natural gas liquid) recovery process. A CGCC (column grand composite curve) was used to assess the thermodynamic feasibility of implementing the heat pump system and self-heat-recuperation technology into a conventional distillation column. The proposed distillation based on self-heat recuperation reduced the energy consumption dramatically by compressing the effluent stream, whose temperature was increased to provide the minimum temperature difference for the heat exchanger, and circulating the stream heat in the process. According to a simulation of the proposed sequence, up to 73.43 and 83.48% of the condenser and reboiler energy, respectively, were saved compared to a conventional column. This study also proposes heat integration to improve the performance of self-heat recuperation. The results showed that the modified sequence saves up 64.35, 100.00 and 31.60% of the condenser energy requirements, reboiler energy requirements and OP (operating cost), respectively, compared to a classical heat pump system, and 90.24, 100.00, and 67.19%, respectively, compared to a conventional column. The use of these sequences to retrofit a distillation column to save energy was also considered. - Highlights: • Innovative self-heat-recuperation technology that circulates latent and sensible heat. • A CGCC (column grand composite curve) is used to assess the thermodynamic feasibility. • The proposed sequence saves up 67.19% of the OP (operating cost). • The proposed sequences can be used to retrofit a distillation column to save energy

  2. Thermal management of electronics using phase change material based pin fin heat sinks

    International Nuclear Information System (INIS)

    This paper reports the results of an experimental study carried out to explore the thermal characteristics of phase change material based heat sinks for electronic equipment cooling. The phase change material (PCM) used in this study is n – eicosane. All heat sinks used in the present study are made of aluminium with dimensions of 80 × 62 mm2 base with a height of 25 mm. Pin fins acts as the thermal conductivity enhancer (TCE) to improve the distribution of heat more uniformly as the thermal conductivity of the PCM is very low. A total of three different pin fin heat sink geometries with 33, 72 and 120 pin fins filled with phase change materials giving rise to 4%, 9% and 15% volume fractions of the TCE respectively were experimentally investigated. Baseline comparisons are done with a heat sink filled with PCM, without any fin. Studies are conducted for heat sinks on which a uniform heat load is applied at the bottom for the finned and unfinned cases. The effect of pin fins of different volume fractions with power levels ranging from 4 to 8 W corresponding to a heat flux range of 1. 59 to 3.17 kW/m2, was explored in this paper. The volume fraction of the PCM (PCM volume / (Total volume – fin volume)) is also varied as 0. 3, 0.6 and 1 to determine the effect of PCM volume on the overall performance of the electronic equipment.

  3. The Hybrid Sterling Engine: boosting photovoltaic efficiency and deriving mechanical work from fluid expansion and heat capture

    Science.gov (United States)

    Beets, Nathan; Wake Forest CenterNanotechnology; Molecular Materials Team; Fraunhofer Institute Collaboration

    2015-11-01

    Two major problems with many third generation photovoltaics is their complex structure and greater expense for increased efficiency. Spectral splitting devices have been used by many with varying degrees of success to collect more and more of the spectrum, but simple, efficient, and cost-effective setups that employ spectral splitting remain elusive. This study explores this problem, presenting a solar engine that employs stokes shifting via laser dyes to convert incident light to the wavelength bandgap of the solar cell and collects the resultant infrared radiation unused by the photovoltaic cell as heat in ethylene glycol or glycerin. When used in conjunction with micro turbines, fluid expansion creates mechanical work, and the temperature difference between the cell and the environment is made available for use. The effect of focusing is also observed as a means to boost efficiency via concentration. Experimental results from spectral scans, vibrational voltage analysis of the PV itself and temperature measurements from a thermocouple are all compared to theoretical results using a program in Mathematica written to model refraction and lensing in the devices used, a quantum efficiency test of the cells, the absorption and emission curves of the dues used to determine the spectrum shift, and the various equations for fill factor, efficiency, and current in different setups. An efficiency increase well over 50% from the control devices is observed, and a new solar engine proposed.

  4. Operationalizing Evidence-Based Practice: The Development of an Institute for Evidence-Based Social Work

    Science.gov (United States)

    Regehr, Cheryl; Stern, Susan; Shlonsky, Aron

    2007-01-01

    Although evidence-based practice (EBP) has received increasing attention in social work in the past few years, there has been limited success in moving from academic discussion to engaging social workers in the process of implementing EBP in practice. This article describes the challenges, successes, and future aims in the process of developing a…

  5. Detection of seal contamination in heat-sealed food packaging based on active infrared thermography

    Science.gov (United States)

    D'huys, Karlien; Saeys, Wouter; De Ketelaere, Bart

    2015-05-01

    In the food industry packaging is often applied to protect the product from the environment, assuring quality and safety throughout shelf life if properly performed. Packaging quality depends on the material used and the closure (seal). The material is selected based on the specific needs of the food product to be wrapped. However, proper closure of the package is often harder to achieve. One problem possibly jeopardizing seal quality is the presence of food particles between the seal. Seal contamination can cause a decreased seal strength and thus an increased packaging failure risk. It can also trigger the formation of microchannels through which air and microorganisms can enter and spoil the enclosed food. Therefore, early detection and removal of seal-contaminated packages from the production chain is essential. In this work, a pulsed-type active thermography method using the heat of the sealing bars as an excitation source was studied for detecting seal contamination. The cooling profile of contaminated seals was recorded. The detection performance of four processing methods (based on a single frame, a fit of the cooling profile, pulsed phase thermography and a matched filter) was compared. High resolution digital images served as a reference to quantify contamination. The lowest detection limit (equivalent diameter of 0.63 mm) and the lowest processing time (0.42 s per sample) were obtained for the method based on a single frame. Presumably, practical limitations in the recording stage prevented the added value of active thermography to be fully reflected in this application.

  6. Influence of heat treatment of rayon-based activated carbon fibers on the adsorption of formaldehyde.

    Science.gov (United States)

    Rong, Haiqin; Ryu, Zhenyu; Zheng, Jingtang; Zhang, Yuanli

    2003-05-15

    The influence of heat treatment of rayon-based activated carbon fibers on the adsorption behavior of formaldehyde was studied. Heat treatment in an inert atmosphere of nitrogen for rayon-based activated carbon fibers (ACFs) resulted in a significant increase in the adsorption capacities and prolongation of breakthrough time on removing of formaldehyde. The effect of different heat-treatment conditions on the adsorption characteristics was investigated. The porous structure parameters of the samples under study were investigated using nitrogen adsorption at the low temperature 77.4 K. The pore size distributions of the samples under study were calculated by density functional theory. With the aid of these analyses, the relationship between structure and adsorption properties of rayon-based ACFs for removing formaldehyde was revealed. Improvement of their performance in terms of adsorption selectivity and adsorption rate for formaldehyde were achieved by heat post-treatment in an inert atmosphere of nitrogen.

  7. Analysis of the Properties of Working Substances for the Organic Rankine Cycle based Database "REFPROP"

    Science.gov (United States)

    Galashov, Nikolay; Tsibulskiy, Svyatoslav; Serova, Tatiana

    2016-02-01

    The object of the study are substances that are used as a working fluid in systems operating on the basis of an organic Rankine cycle. The purpose of research is to find substances with the best thermodynamic, thermal and environmental properties. Research conducted on the basis of the analysis of thermodynamic and thermal properties of substances from the base "REFPROP" and with the help of numerical simulation of combined-cycle plant utilization triple cycle, where the lower cycle is an organic Rankine cycle. Base "REFPROP" describes and allows to calculate the thermodynamic and thermophysical parameters of most of the main substances used in production processes. On the basis of scientific publications on the use of working fluids in an organic Rankine cycle analysis were selected ozone-friendly low-boiling substances: ammonia, butane, pentane and Freon: R134a, R152a, R236fa and R245fa. For these substances have been identified and tabulated molecular weight, temperature of the triple point, boiling point, at atmospheric pressure, the parameters of the critical point, the value of the derivative of the temperature on the entropy of the saturated vapor line and the potential ozone depletion and global warming. It was also identified and tabulated thermodynamic and thermophysical parameters of the steam and liquid substances in a state of saturation at a temperature of 15 °C. This temperature is adopted as the minimum temperature of heat removal in the Rankine cycle when working on the water. Studies have shown that the best thermodynamic, thermal and environmental properties of the considered substances are pentane, butane and R245fa. For a more thorough analysis based on a gas turbine plant NK-36ST it has developed a mathematical model of combined cycle gas turbine (CCGT) triple cycle, where the lower cycle is an organic Rankine cycle, and is used as the air cooler condenser. Air condenser allows stating material at a temperature below 0 °C. Calculation of the

  8. Two-phase working fluids for the temperature range 100-350 C. [in heat pipes for solar applications

    Science.gov (United States)

    Saaski, E. W.; Tower, L.

    1977-01-01

    The decomposition and corrosion of two-phase heat transfer liquids and metal envelopes have been investigated on the basis of molecular, bond strengths and chemical thermodynamics. Potentially stable heat transfer fluids for the temperature range 100 to 350 C have been identified, and reflux heat pipe tests initiated with 10 fluids and carbon steel and aluminum envelopes to experimentally establish corrosion behavior and noncondensable gas generation rates.

  9. A MEMS-based heating holder for the direct imaging of simultaneous in-situ heating and biasing experiments in scanning/transmission electron microscopes.

    Science.gov (United States)

    Mele, Luigi; Konings, Stan; Dona, Pleun; Evertz, Francis; Mitterbauer, Christoph; Faber, Pybe; Schampers, Ruud; Jinschek, Joerg R

    2016-04-01

    The introduction of scanning/transmission electron microscopes (S/TEM) with sub-Angstrom resolution as well as fast and sensitive detection solutions support direct observation of dynamic phenomena in-situ at the atomic scale. Thereby, in-situ specimen holders play a crucial role: accurate control of the applied in-situ stimulus on the nanostructure combined with the overall system stability to assure atomic resolution are paramount for a successful in-situ S/TEM experiment. For those reasons, MEMS-based TEM sample holders are becoming one of the preferred choices, also enabling a high precision in measurements of the in-situ parameter for more reproducible data. A newly developed MEMS-based microheater is presented in combination with the new NanoEx™-i/v TEM sample holder. The concept is built on a four-point probe temperature measurement approach allowing active, accurate local temperature control as well as calorimetry. In this paper, it is shown that it provides high temperature stability up to 1,300°C with a peak temperature of 1,500°C (also working accurately in gaseous environments), high temperature measurement accuracy (<4%) and uniform temperature distribution over the heated specimen area (<1%), enabling not only in-situ S/TEM imaging experiments, but also elemental mapping at elevated temperatures using energy-dispersive X-ray spectroscopy (EDS). Moreover, it has the unique capability to enable simultaneous heating and biasing experiments.

  10. A MEMS-based heating holder for the direct imaging of simultaneous in-situ heating and biasing experiments in scanning/transmission electron microscopes.

    Science.gov (United States)

    Mele, Luigi; Konings, Stan; Dona, Pleun; Evertz, Francis; Mitterbauer, Christoph; Faber, Pybe; Schampers, Ruud; Jinschek, Joerg R

    2016-04-01

    The introduction of scanning/transmission electron microscopes (S/TEM) with sub-Angstrom resolution as well as fast and sensitive detection solutions support direct observation of dynamic phenomena in-situ at the atomic scale. Thereby, in-situ specimen holders play a crucial role: accurate control of the applied in-situ stimulus on the nanostructure combined with the overall system stability to assure atomic resolution are paramount for a successful in-situ S/TEM experiment. For those reasons, MEMS-based TEM sample holders are becoming one of the preferred choices, also enabling a high precision in measurements of the in-situ parameter for more reproducible data. A newly developed MEMS-based microheater is presented in combination with the new NanoEx™-i/v TEM sample holder. The concept is built on a four-point probe temperature measurement approach allowing active, accurate local temperature control as well as calorimetry. In this paper, it is shown that it provides high temperature stability up to 1,300°C with a peak temperature of 1,500°C (also working accurately in gaseous environments), high temperature measurement accuracy (<4%) and uniform temperature distribution over the heated specimen area (<1%), enabling not only in-situ S/TEM imaging experiments, but also elemental mapping at elevated temperatures using energy-dispersive X-ray spectroscopy (EDS). Moreover, it has the unique capability to enable simultaneous heating and biasing experiments. PMID:26818213

  11. Investigation of Creep Feed Grinding Parameters and Heat treatment Effects on the Nickel-base Superalloys

    Institute of Scientific and Technical Information of China (English)

    Hasan Jamshidi; Sayed Ali Sadough Vanini; Alireza Attari

    2004-01-01

    The Nickel base Superalloys are the most famous complicated and useable of Superalloys to make hot zone components of the gas turbines. The complicated dimensional tolerances, specially at the root of the blade show importance of grinding processes at the production of blades root. The prediction of the effect of machining parameters on the soundness of component surface strengthening for reaching to a suitable surface finishing and avoiding from crack formation at the work part during machining operation often is not easy and feasible so needs to more industrial investigation.This research is about frame 5 blade designed by GE and made from Superalloy IN738LC has been investigated. The formation of a plastically deformed and heat affected zone during grinding of Superalloy IN738LC with a high depth of cut but slow work speed (creep feed grinding) was investigated. Parameters such as work speed, depth of cut and radial dressing speed have been considered as variables and their effects have been studied. During experimental performed, the voltage and current of motor measured and power and special energy calculated.Some samples heat-treated (of the 1176℃ for 1 hr under neutral argon gas and cooling rate of 15℃/min up to 537℃ and then air cooling) to study grains recrystallization. Other samples have been created from the roots of blades and then coated by Nickel to measure boundary layer micro-hardness. The results show that increasing work speed leads to increasing the use power. Increasing the depth of cut, by increasing material removal rate, and the radial dressing speed, by decreasing power, lead to decreasing special energy. The temperature created by grinding lead to decreasing plastic deformation and boundary layer formation. When the radial dressing speed changes from 1 to 0.6 μm/rev and other parameters are kept unchanged the roughness of surface increases and the special energy decreases. Sufficient dressing is very essential in limiting the width

  12. Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

    Institute of Scientific and Technical Information of China (English)

    Bao-wei Li; Hong-xia Li; Xue-feng Zhang; Xiao-lin Jia; Zhi-chao Sun

    2015-01-01

    The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared from Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment meth-ods:conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a dif-ferential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier trans-form infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron micros-copy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the proc-essing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs from that of the conventional heating process.

  13. Nucleation and crystallization of tailing-based glass-ceramics by microwave heating

    Science.gov (United States)

    Li, Bao-wei; Li, Hong-xia; Zhang, Xue-feng; Jia, Xiao-lin; Sun, Zhi-chao

    2015-12-01

    The effect of microwave radiation on the nucleation and crystallization of tailing-based glass-ceramics was investigated using a 2.45 GHz multimode microwave cavity. Tailing-based glass samples were prepared from Shandong gold tailings and Guyang iron tailings utilizing a conventional glass melting technique. For comparison, the tailing-based glass samples were crystallized using two different heat-treatment methods: conventional heating and hybrid microwave heating. The nucleation and crystallization temperatures were determined by performing a differential thermal analysis of the quenched tailing-based glass. The prepared glass-ceramic samples were further characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, thermal expansion coefficient measurements, and scanning electron microscopy. The results demonstrated that hybrid microwave heating could be successfully used to crystallize the tailing-based glass, reduce the processing time, and decrease the crystallization temperature. Furthermore, the results indicated that the nucleation and crystallization mechanism of the hybrid microwave heating process slightly differs from that of the conventional heating process.

  14. Varying properties of in situ heat treatment of a tar sands formation based on assessed viscosities

    Energy Technology Data Exchange (ETDEWEB)

    Karanikas, John Michael; Vinegar, Harold J

    2014-03-04

    A method for treating a tar sands formation includes providing heat to at least part of a hydrocarbon layer in the formation from a plurality of heaters located in the formation. The heat is allowed to transfer from the heaters to at least a portion of the formation. A viscosity of one or more zones of the hydrocarbon layer is assessed. The heating rates in the zones are varied based on the assessed viscosities. The heating rate in a first zone of the formation is greater than the heating rate in a second zone of the formation if the viscosity in the first zone is greater than the viscosity in the second zone. Fluids are produced from the formation through the production wells.

  15. Low Bandgap InAs-Based Thermophotovoltaic Cells for Heat-Electricity Conversion

    Science.gov (United States)

    Krier, A.; Yin, M.; Marshall, A. R. J.; Krier, S. E.

    2016-06-01

    The practical realization of thermophotovoltaic (TPV) cells, which can directly convert heat into electric power, is of considerable technological interest. However, most existing TPV cells require heat sources at temperatures of ˜1800°C. Here we report a low bandgap mid-infrared cell based on InAs and demonstrate TPV operation with heat sources at temperatures in the range 500-950°C. The maximum open circuit voltage ( V oc) and short circuit current density ( J sc) were measured as 0.06 V and 0.89 A cm-2 for a blackbody temperature of 950°C and an incident power density of 720 mW cm-2 without antireflection coating or electrode optimisation. TPV operation was obtained with heat sources at temperatures as low as 500°C, which represents progress towards energy scavenging and waste heat recovery applications.

  16. Evaluation and Application of Satellite-Based Latent Heating Profile Estimation Methods

    Science.gov (United States)

    Olson, William S.; Grecu, Mircea; Yang, Song; Tao, Wei-Kuo

    2004-01-01

    In recent years, methods for estimating atmospheric latent heating vertical structure from both passive and active microwave remote sensing have matured to the point where quantitative evaluation of these methods is the next logical step. Two approaches for heating algorithm evaluation are proposed: First, application of heating algorithms to synthetic data, based upon cloud-resolving model simulations, can be used to test the internal consistency of heating estimates in the absence of systematic errors in physical assumptions. Second, comparisons of satellite-retrieved vertical heating structures to independent ground-based estimates, such as rawinsonde-derived analyses of heating, provide an additional test. The two approaches are complementary, since systematic errors in heating indicated by the second approach may be confirmed by the first. A passive microwave and combined passive/active microwave heating retrieval algorithm are evaluated using the described approaches. In general, the passive microwave algorithm heating profile estimates are subject to biases due to the limited vertical heating structure information contained in the passive microwave observations. These biases may be partly overcome by including more environment-specific a priori information into the algorithm s database of candidate solution profiles. The combined passive/active microwave algorithm utilizes the much higher-resolution vertical structure information provided by spaceborne radar data to produce less biased estimates; however, the global spatio-temporal sampling by spaceborne radar is limited. In the present study, the passive/active microwave algorithm is used to construct a more physically-consistent and environment-specific set of candidate solution profiles for the passive microwave algorithm and to help evaluate errors in the passive algorithm s heating estimates. Although satellite estimates of latent heating are based upon instantaneous, footprint- scale data, suppression

  17. On the preliminary design of hyperthermia treatments based on infusion and heating of magnetic nanofluids.

    Science.gov (United States)

    Di Michele, F; Pizzichelli, G; Mazzolai, B; Sinibaldi, E

    2015-04-01

    We study a magnetic-nanoparticle-mediated hyperthermia treatment by considering both the nanofluid infusion and the subsequent thermal activation of the infused nanoparticles. Our study aims at providing a quantitative framework, which is currently missing, for the design of hyperthermia treatments. In more detail, we consider a heterogeneous spherical tumor, and we obtain a simplified analytical expression for the nanoparticles concentration profile during the infusion. We then exploit such an expression in order to compute the steady-state temperature profile achieved through the heating step. Despite the simplifications introduced to enable the analytical derivations, we account for many physically relevant aspects including tissue heterogeneity, poroelasticity, blood perfusion, and nanoparticles absorption onto tissue. Moreover, our approach permits to elucidate the effects on the final temperature profile of the following control parameters: infusion duration and flow rate, nanoparticles concentration in the nanofluid, magnetic field intensity and frequency. We present illustrative numerical results, based on parameters values taken from experimental studies, which are consistent with previous numerical investigations and current hyperthermia approaches. In particular, we obtain optimal working curves which could be effectively used for planning real procedures. While not laying any claims of generality, this work takes a preliminary yet quantitative step toward the design of hyperthermia treatments. PMID:25640871

  18. A MEMS-based Benzene Gas Sensor with a Self-heating WO3 Sensing Layer

    Directory of Open Access Journals (Sweden)

    Lung-Ming Fu

    2009-04-01

    Full Text Available In the study, a MEMS-based benzene gas sensor is presented, consisting of a quartz substrate, a thin-film WO3 sensing layer, an integrated Pt micro-heater, and Pt interdigitated electrodes (IDEs. When benzene is present in the atmosphere, oxidation occurs on the heated WO3 sensing layer. This causes a change in the electrical conductivity of the WO3 film, and hence changes the resistance between the IDEs. The benzene concentration is then computed from the change in the measured resistance. A specific orientation of the WO3 layer is obtained by optimizing the sputtering process parameters. It is found that the sensitivity of the gas sensor is optimized at a working temperature of 300 °C. At the optimal working temperature, the experimental results show that the sensor has a high degree of sensitivity (1.0 KΩ ppm-1, a low detection limit (0.2 ppm and a rapid response time (35 s.

  19. Work based learning partnerships and structural capital: the case of Middlesex University.

    OpenAIRE

    Garnett, Jonathan

    2002-01-01

    The aim of the project is to enhance the value of work based learning to Middlesex University through the development of a critical understanding of the relationship between the Middlesex approach to work based learning and the concept of structural capital. The project considers the Middlesex approach to work based learning and identifies the salient features of the approach. Key to the distinctive nature of the Middlesex approach is the recognition by the University of Work Based Learnin...

  20. Cutting heat dissipation in high-speed machining of carbon steel based on the calorimetric method

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The cutting heat dissipation in chips,workpiece,tool and surroundings during the high-speed machining of carbon steel is quantitatively investigated based on the calorimetric method.Water is used as the medium to absorb the cutting heat;a self-designed container suitable for the high-speed lathe is used to collect the chips,and two other containers are adopted to absorb the cutting heat dissipated in the workpiece and tool,respectively.The temperature variations of the water,chips,workpiece,tool and surroundings during the closed high-speed machining are then measured.Thus,the cutting heat dissipated in each component of the cutting system,total cutting heat and heat flux are calculated.Moreover,the power resulting from the main cutting force is obtained according to the measured cutting force and predetermined cutting speed.The accuracy of cutting heat measurement by the calorimetric method is finally evaluated by comparing the total cutting heat flux with the power resulting from the main cutting force.

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

    International Nuclear Information System (INIS)

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

  2. Visual Working Efficiency Analysis Method of Cockpit Based On ANN

    Directory of Open Access Journals (Sweden)

    Yingchun CHEN

    2012-09-01

    Full Text Available The Artificial Neural Networks method is applied on visual working efficiency of cockpit. A Self-Organizing Map (SOM network is demonstrated selecting material with near properties. Then a Back-Propagation (BP network automatically learns the relationship between input and output. After a set of training, the BP network is able to estimate material characteristics using knowledge and criteria learned before. Results indicate that trained network can give effective prediction for material.

  3. Heat transfer optimization of SCO2 porous flow based on Brinkman model

    Directory of Open Access Journals (Sweden)

    Lin David T.W.

    2016-01-01

    Full Text Available The purpose of this study is to obtain the optimal operating condition in order to find the maximum supercritical CO2 heat extraction in the enhanced geothermal system (EGS. In this study, the heat transfer model conjugated with the Brinkman model is used to evaluate the thermal behavior in the reservoir of the EGS. This numerical model is validated by experiment. Optimization is processed based on the Nelder-Mead approach. The optimal operating conditions are proposed with different pressure, porosity. This study will build the optimal platform of heat source of geothermal power plant.

  4. Alternative ethanol based cooling carriers with corrosion inhibitors in geothermal heat pump systems

    OpenAIRE

    Gustafsson, Isac

    2015-01-01

    Ground source heat pumps are very popular in the Nordic countries. The method of exchanging heat with the ground is based on the principle that a secondary fluid is circulating through a U-pipe borehole heat exchanger inserted into energy wells. Water is a very good secondary fluid, but aqueous solutions of ethanol are recommended in Sweden as a secondary fluid for such application. One reason is the fact that addition of ethanol decreases the freezing point of the fluid, which is preferred s...

  5. Lithuanian heat sector: Today based on imported fossil fuel, tomorrow - On local biofuel and wastes

    Energy Technology Data Exchange (ETDEWEB)

    Janukonis, Andrius

    2010-09-15

    District heating sector is one of the most important energy sectors in Lithuania, operation of which is closely related to other energy sectors such as electricity, natural gas, oil products, renewable energy sources. Main priorities of Lithuanian energy policy based on the experience of the neighboring countries and directives of the European Union's environmental protection, security and reliability of energy supply and availability of district heating services to all users. It is necessary to use widely the biofuel in the DHS sector for the heat production, unused amounts of which are very big.

  6. Development of a plastic rotary heat exchanger for room-based ventilation in existing apartments

    DEFF Research Database (Denmark)

    Smith, Kevin Michael; Svendsen, Svend

    2015-01-01

    The existing building stock will likely undergo widespread energy renovations to meet future emissions targets. Single-room ventilation may enable the process due to its simple installation, low fan power, and potential for local heat recovery. A short plastic rotary heat exchanger is developed...... for single-room ventilation based on thermal design theory. Performance is predicted from correlations of dimensionless groups for regenerative heat exchangers, and this guides the selection of a polycarbonate honeycomb with small circular channels. Experiments quantify flows and determine temperature...

  7. Ventilation model experiments of longwall working face with E or W type ventilation. With fracture fall and heat source in goaf

    Energy Technology Data Exchange (ETDEWEB)

    Shikada, Norimitsu; Kinoshita, Michiaki; Senju, Hiromichi; Isei, Takehiro

    1987-01-25

    By using 1/10 scale model of the longwall working face, ventilation flow around the working face is examined with fracture fall and heat source in goaf area. Parameters, combined for the test with fracture fall, include ventilation methods in goaf, flowing rate in each roadway, position of roadway, presence or absence of heat source and fracture fall in goaf, etc. It is confirmed that, with fracture fall, air flow rate in the self-advancing frame, outflow rate into goaf and inflow rate into the self-advancing frame are increased. Heat sources, located in the goaf, do not greatly influence the direction and velocity of air flow. The range of maximum temperature depends on the method of ventilation and the velocity of air in each roadway, as typically represented by 3 - 4 sections. (16 figs, 5 refs)

  8. Segmented heat exchanger

    Science.gov (United States)

    Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann

    2010-12-14

    A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.

  9. Thermo-Economic and Heat Transfer Optimization of Working-Fluid Mixtures in a Low-Temperature Organic Rankine Cycle System

    OpenAIRE

    Oyeniyi A. Oyewunmi; Markides, Christos N.

    2016-01-01

    In the present paper, we consider the employment of working-fluid mixtures in organic Rankine cycle (ORC) systems with respect to thermodynamic and heat-transfer performance, component sizing and capital costs. The selected working-fluid mixtures promise reduced exergy losses due to their non-isothermal phase-change behaviour, and thus improved cycle efficiencies and power outputs over their respective pure-fluid components. A multi-objective cost-power optimization of a specific low-temperat...

  10. Heat pipe based thermal management systems for energy-efficient data centres

    OpenAIRE

    Jouhara, H; Meskimmon, R

    2014-01-01

    This paper investigates the potential applications for heat-pipe based heat exchangers in enhancing the efficiency of data centres’ cooling. The paper starts by assessing current industry practise and highlighting the challenges facing the data-storage industry; illustrating the legislative, technical and commercial constraints that are now, or will be prevalent in the industry as the sector continues to grow to cater for the ever increasing appetite for public sector, commercial and consumer...

  11. Helping the Working Poor: Employer- vs. Employee-Based Subsidies

    OpenAIRE

    Stacy Dickert-Conlin; Douglas Holtz-Eakin

    1999-01-01

    In the United States and Europe there has been renewed interest in subsidizing firms that employ disadvantaged workers as a means of addressing poverty and other social problems. In contrast, the prevailing practice is largely to provide social welfare benefits directly to individuals. Which approach is better? We re-examine the relative merits of employee- versus employer-based labor market subsidies and conclude there are good reasons to continue to rely on the direct, employee-based approa...

  12. 29 CFR 1917.152 - Welding, cutting and heating (hot work) 12 (See also § 1917.2, definition of Hazardous cargo...

    Science.gov (United States)

    2010-07-01

    ... electric shock. (f) Ventilation and employee protection in welding, cutting and heating—(1) Mechanical..., fumes and smoke below a hazardous level. (ii) Local exhaust ventilation shall consist of movable hoods... 29 Labor 7 2010-07-01 2010-07-01 false Welding, cutting and heating (hot work) 12 (See also...

  13. Effect of Evaporator Section Lengths and Working Fluids on Operational Limit of Closed Loop Oscillating Heat Pipes with Check Valves (CLOHP/CV

    Directory of Open Access Journals (Sweden)

    P. Meena

    2009-01-01

    Full Text Available This research aims to the effect of evaporator section lengths and working fluids on operational limit of closed loop oscillating heat pipes with check valves (CLOHP/CV with R123 Ethanol and Water were used as the working fluids. A set of CLOHP/CV was made of copper tubes in combination of following dimension: 1.77 mm inside diameter: 10 turns: 5, 10 and 15 cm equal lengths for evaporator, adiabatic and condenser sections. The working fluid was filled in the tube at the filling ratio of 50%. The evaporator section was given heat by heater while the condenser section was cooled by volume water in a cold bath. The adiabatic section was properly insulated. In the test operation. Which the temperature at the adiabatic section was controlled at 60°C in steady-state condition. From The obtained results obtained, it could be concluded as follows. When the evaporator lengths increased from 5 cm to 10 and 15 cm the critical heat transfer flux decreased. There was working fluids change from R123 to Ethanol and water the critical heat flux decreased.

  14. Making a Virtue out of a Necessity: Part Time Work as a Site for Undergraduate Work-Based Learning

    Science.gov (United States)

    Shaw, Sue; Ogilvie, Chrissy

    2010-01-01

    Purpose: This paper seeks to challenge the view that student part time employment detracts from academic attainment and presents evidence that when linked to formal undergraduate study provides rich learning experiences. It also explores the extent to which formerly accepted pre-requisites for work based learning (WBL) apply in this model and how…

  15. "Working." A Teacher's Guide to a Vocational Reading Program Based on Selected Interviews Contained in "Working" by Studs Terkel.

    Science.gov (United States)

    Eakin, David; And Others

    This teacher's guide is intended to help vocational English teachers implement a program based on Studs Terkel's book "Working," a collection of more than 100 interviews with people about their jobs. The 30 interviews selected for inclusion in the curriculum either illustrate occupations taught in the schools or deal with occupations related to…

  16. Problem based Learning versus Design Thinking in Team based Project work

    DEFF Research Database (Denmark)

    Denise J. Stokholm, Marianne

    2014-01-01

    project based learning issues, which has caused a need to describe and compare the two models; in specific the understandings, approaches and organization of learning in project work. The PBL model viewing the process as 3 separate project stages including; problem analysis, problem solving and project...... report, with focus on problem solving through analysis. Design Based Learning viewing the process as series of integrated design spaces including; alignment, research, mission, vision, concept, product and process report, with focus on innovative ideation though integration. There is a need of renewing......All educations at Aalborg University has since 1974 been rooted in Problem Based Learning (PBL). In 1999 a new education in Industrial design was set up, introducing Design Based Learning (DBL). Even though the two approaches have a lot in common they also hold different understandings of core...

  17. Heat-transfer-method-based cell culture quality assay through cell detection by surface imprinted polymers.

    Science.gov (United States)

    Eersels, Kasper; van Grinsven, Bart; Khorshid, Mehran; Somers, Veerle; Püttmann, Christiane; Stein, Christoph; Barth, Stefan; Diliën, Hanne; Bos, Gerard M J; Germeraad, Wilfred T V; Cleij, Thomas J; Thoelen, Ronald; De Ceuninck, Ward; Wagner, Patrick

    2015-02-17

    Previous work has indicated that surface imprinted polymers (SIPs) allow for highly specific cell detection through macromolecular cell imprints. The combination of SIPs with a heat-transfer-based read-out technique has led to the development of a selective, label-free, low-cost, and user-friendly cell detection assay. In this study, the breast cancer cell line ZR-75-1 is used to assess the potential of the platform for monitoring the quality of a cell culture in time. For this purpose, we show that the proposed methodology is able to discriminate between the original cell line (adherent growth, ZR-75-1a) and a descendant cell line (suspension growth, ZR-75-1s). Moreover, ZR-75-1a cells were cultured for a prolonged period of time and analyzed using the heat-transfer method (HTM) at regular time intervals. The results of these experiments demonstrate that the thermal resistance (Rth) signal decays after a certain number of cell culture passages. This can likely be attributed to a compromised quality of the cell culture due to cross-contamination with the ZR-75-1s cell line, a finding that was confirmed by classical STR DNA profiling. The cells do not express the same functional groups on their membrane, resulting in a weaker bond between cell and imprint, enabling cell removal by mechanical friction, provided by flushing the measuring chamber with buffer solution. These findings were further confirmed by HTM and illustrate that the biomimetic sensor platform can be used as an assay for monitoring the quality of cell cultures in time.

  18. Development of a working fluid for high temperature heat pumps; Entwicklung eines Arbeits-Fluids fuer Hochtemperatur-Waermepumpen

    Energy Technology Data Exchange (ETDEWEB)

    Kabelac, S. [Helmut-Schmidt-Univ./Uni der Bundeswehr Hamburg (Germany); Flohr, F. [Solvay Fluor GmbH, Hannover (Germany); Stadtlaender, C. [FKW-Forschungszentrum fuer Kaeltetechnik und Waermepumpen GmbH, Hannover (Germany)

    2006-06-15

    In industrial processes, heat is required at high temperatures to above 120 C. Heat pumps will be used for this purpose and in the past with R114. In a public research project the zeotropic refrigerant mixture R365mfc/R227ea was proved to be a long term solution. After thermo-physical and chemical-thermal investigations a field test system was constructed as a high temperature heat pump for industrial use which was then installed, commissioned and measured. (orig.)

  19. Artificial Neural Networks-Based Software for Measuring Heat Collection Rate and Heat Loss Coefficient of Water-in-Glass Evacuated Tube Solar Water Heaters.

    Science.gov (United States)

    Liu, Zhijian; Liu, Kejun; Li, Hao; Zhang, Xinyu; Jin, Guangya; Cheng, Kewei

    2015-01-01

    Measurements of heat collection rate and heat loss coefficient are crucial for the evaluation of in service water-in-glass evacuated tube solar water heaters. However, conventional measurement requires expensive detection devices and undergoes a series of complicated procedures. To simplify the measurement and reduce the cost, software based on artificial neural networks for measuring heat collection rate and heat loss coefficient of water-in-glass evacuated tube solar water heaters was developed. Using multilayer feed-forward neural networks with back-propagation algorithm, we developed and tested our program on the basis of 915 measured samples of water-in-glass evacuated tube solar water heaters. This artificial neural networks-based software program automatically obtained accurate heat collection rate and heat loss coefficient using simply "portable test instruments" acquired parameters, including tube length, number of tubes, tube center distance, heat water mass in tank, collector area, angle between tubes and ground and final temperature. Our results show that this software (on both personal computer and Android platforms) is efficient and convenient to predict the heat collection rate and heat loss coefficient due to it slow root mean square errors in prediction. The software now can be downloaded from http://t.cn/RLPKF08.

  20. Entransy dissipation-based constraint for optimization of heat exchanger networks in thermal systems

    International Nuclear Information System (INIS)

    The Lagrange multiplier method is introduced for the global optimization of HENs (heat exchanger networks) with fixed layouts to give the optimal configuration of thermal systems that cannot be determined by other methods, such as HEN synthesis or linear programming method. A four-loop HEN with five heat exchangers and heat exchangers in thermodynamic systems are optimized as two examples from different perspectives. The first perspective is based on energy conservation where the energy and heat transfer equations act as the constraints in the Lagrange function. The second perspective is the heat transfer irreversibility where the entransy dissipation-based equation acts as the constraint. The entransy dissipation-based constraint eliminates the number of unknown intermediate fluid temperatures in the HENs and the corresponding number of constraints for HENs in thermal systems, which greatly simplifies the solution of optimization equations. Although the entropy generation-based equation can also act as a constraint, the intermediate fluid temperatures in the HENs cannot be eliminated because the entropy generation is a function of the absolute fluid temperature. As a result, the number of constraints is the same as when using energy conservation, so the optimization procedure for multi-component thermal systems cannot be simplified. - Highlights: • Lagrange multiplier method is a good option in thermal system optimization. • Entransy balance equation acts as a constraint without intermediate temperatures. • Entransy dissipation-based method greatly simplifies the optimization. • Entransy method is superior to traditional and entropy methods in some cases

  1. Strategic development of the Greek centre for work based learning partnerships (GCWBLP)

    OpenAIRE

    Thomas, Panagiotis

    2003-01-01

    Work based learning (WBL) is the term being used to describe a class of university programmes that bring together universities and work organisations to create new learning opportunities in workplaces. Middlesex University was a pioneer in the institutional development of work based learning through its National Centre of Work Based Learning Partnerships (NCWBLP) established in 1993. The Greek Centre (GCWBLP) was established in Athens and began operations in 1997 to promote WBL programm...

  2. Power optimization of chemically driven heat engine based on first and second order reaction kinetic theory and probability theory

    Science.gov (United States)

    Zhang, Lei; Chen, Lingen; Sun, Fengrui

    2016-03-01

    The finite-time thermodynamic method based on probability analysis can more accurately describe various performance parameters of thermodynamic systems. Based on the relation between optimal efficiency and power output of a generalized Carnot heat engine with a finite high-temperature heat reservoir (heat source) and an infinite low-temperature heat reservoir (heat sink) and with the only irreversibility of heat transfer, this paper studies the problem of power optimization of chemically driven heat engine based on first and second order reaction kinetic theory, puts forward a model of the coupling heat engine which can be run periodically and obtains the effects of the finite-time thermodynamic characteristics of the coupling relation between chemical reaction and heat engine on the power optimization. The results show that the first order reaction kinetics model can use fuel more effectively, and can provide heat engine with higher temperature heat source to increase the power output of the heat engine. Moreover, the power fluctuation bounds of the chemically driven heat engine are obtained by using the probability analysis method. The results may provide some guidelines for the character analysis and power optimization of the chemically driven heat engines.

  3. [Urban heat island effect based on urban heat island source and sink indices in Shenyang, Northeast China].

    Science.gov (United States)

    Li, Li-Guang; Xu, Shen-Lai; Wang, Hong-Bo; Zhao, Zi-Qi; Cai, Fu; Wu, Jin-Wen; Chen, Peng-Shi; Zhang, Yu-Shu

    2013-12-01

    Based on the remote images in 2001 and 2010, the source and sink areas of urban heat island (UHI) in Shenyang City, Northeast China were determined by GIS technique. The effect of urban regional landscape pattern on UHI effect was assessed with land surface temperature (LST), area rate index (CI) of the source and sink areas and intensity index (LI) of heat island. The results indicated that the land use type changed significantly from 2001 to 2010, which significantly changed the source and sink areas of UHI, especially in the second and third circle regions. The source and sink areas were 94.3% and 5.7% in the first circle region, 64.0% and 36.0% in the third circle region in 2001, while they were 93.4% and 6.6%, 70.2% and 29.8% in 2010, respectively. It suggested that the land use pattern extended by a round shape in Shenyang led to the corresponding UHI pattern. The LST in the study area tended to decrease from the first circle region to the third. The UHI intensity was characterized with a single center in 2001 and with several centers in 2010, and the grade of UHI intensity was in a decreasing trend from 2001 to 2010. The absolute value of CI increased from the first circle region to the third, and the L1 was close to 1, suggesting the change in land use pattern had no significant influence on UHI in Shenyang.

  4. Making Digital Game-Based Learning Work: Domain Knowledge Transparency

    Science.gov (United States)

    Wang, Feihong; Burton, John K.

    2010-01-01

    During the past two decades, the popularity of computer and video games has prompted games to be a source of study for educational applications (Dickey, 2007). The most distinguishing characteristic of games is their capability to engage and motivate their players (Kiili, 2005). Educators started to explore game-based learning by testing…

  5. Why Problem-Based Learning Works: Theoretical Foundations

    Science.gov (United States)

    Marra, Rose M.; Jonassen, David H.; Palmer, Betsy; Luft, Steve

    2014-01-01

    Problem-based learning (PBL) is an instructional method where student learning occurs in the context of solving an authentic problem. PBL was initially developed out of an instructional need to help medical school students learn their basic sciences knowledge in a way that would be more lasting while helping to develop clinical skills…

  6. Brain-Based Learning and Educational Neuroscience: Boundary Work

    Science.gov (United States)

    Edelenbosch, Rosanne; Kupper, Frank; Krabbendam, Lydia; Broerse, Jacqueline E. W.

    2015-01-01

    Much attention has been given to "bridging the gap" between neuroscience and educational practice. In order to gain better understanding of the nature of this gap and of possibilities to enable the linking process, we have taken a boundary perspective on these two fields and the brain-based learning approach, focusing on…

  7. Threshold Studies of Heated HMX-Based Energetic Material Targets Using the Steven Impact Test

    Energy Technology Data Exchange (ETDEWEB)

    Switzer, L L; Vandersall, K S; Chidester, S K; Greenwood, D W; Tarver, C M

    2003-07-01

    Impact tests performed at low velocity on heated energetic material samples are of interest when considering the situation of energetic materials involved in a fire. To determine heated reaction thresholds, Steven Test targets containing PBX 9404 or LX-04 samples heated to the range of 150-170 C were impacted at velocities up to 150 m/s by two different projectile head geometries. Comparing these measured thresholds to ambient temperature thresholds revealed that the heated LX-04 thresholds were considerably higher than ambient, whereas the heated PBX 9404 thresholds were only slightly higher than the ambient temperature thresholds. The violence of reaction level of the PBX 9404 was considerably higher than that of the LX-04 as measured with four overpressure gauges. The varying results in these samples with different HMX/binder configurations indicate that friction plays a dominant role in reaction ignition during impact. This work outlines the experimental details, compares the thresholds and violence levels of the heated and ambient temperature experiments, and discusses the dominant mechanisms of the measured thresholds.

  8. Renewable-based low-temperature district heating for existing buildings in various stages of refurbishment

    DEFF Research Database (Denmark)

    Brand, Marek; Svendsen, Svend

    2013-01-01

    and, for 98% of the year, to below 60 °C. However for the temperatures below 60 °C a low-temperature DH substation is required for DHW (domestic hot water) heating. This research shows that renewable sources of heat can be integrated into the DH system without problems and contribute to the fossil...... temperature should be as low as possible. We used IDA–ICE software to simulate a typical Danish single-family house from the 1970s connected to DH at three different stages of envelope and space heating system refurbishment. We wanted to investigate how low the DH supply temperature can be without reducing......Denmark is aiming for a fossil-free heating sector for buildings by 2035. Judging by the national heating plan, this will be achieved mainly by a further spread of DH (district heating) based on the renewable heat sources. To make the most cost-effective use of these sources, the DH supply...

  9. Champagne Heat Pump

    Science.gov (United States)

    Jones, Jack A.

    2004-01-01

    The term champagne heat pump denotes a developmental heat pump that exploits a cycle of absorption and desorption of carbon dioxide in an alcohol or other organic liquid. Whereas most heat pumps in common use in the United States are energized by mechanical compression, the champagne heat pump is energized by heating. The concept of heat pumps based on other absorption cycles energized by heat has been understood for years, but some of these heat pumps are outlawed in many areas because of the potential hazards posed by leakage of working fluids. For example, in the case of the water/ammonia cycle, there are potential hazards of toxicity and flammability. The organic-liquid/carbon dioxide absorption/desorption cycle of the champagne heat pump is similar to the water/ammonia cycle, but carbon dioxide is nontoxic and environmentally benign, and one can choose an alcohol or other organic liquid that is also relatively nontoxic and environmentally benign. Two candidate nonalcohol organic liquids are isobutyl acetate and amyl acetate. Although alcohols and many other organic liquids are flammable, they present little or no flammability hazard in the champagne heat pump because only the nonflammable carbon dioxide component of the refrigerant mixture is circulated to the evaporator and condenser heat exchangers, which are the only components of the heat pump in direct contact with air in habitable spaces.

  10. A control method for agricultural greenhouses heating based on computational fluid dynamics and energy prediction model

    International Nuclear Information System (INIS)

    Highlights: • A novel control method for the heating greenhouse with SWSHPS is proposed. • CFD is employed to predict the priorities of FCU loops for thermal performance. • EPM is act as an on-line tool to predict the total energy demand of greenhouse. • The CFD–EPM-based method can save energy and improve control accuracy. • The energy savings potential is between 8.7% and 15.1%. - Abstract: As energy heating is one of the main production costs, many efforts have been made to reduce the energy consumption of agricultural greenhouses. Herein, a novel control method of greenhouse heating using computational fluid dynamics (CFD) and energy prediction model (EPM) is proposed for energy savings and system performance. Based on the low-Reynolds number k–ε turbulence principle, a CFD model of heating greenhouse is developed, applying the discrete ordinates model for the radiative heat transfers and porous medium approach for plants considering plants sensible and latent heat exchanges. The CFD simulations have been validated, and used to analyze the greenhouse thermal performance and the priority of fan coil units (FCU) loops under the various heating conditions. According to the heating efficiency and temperature uniformity, the priorities of each FCU loop can be predicted to generate a database with priorities for control system. EPM is built up based on the thermal balance, and used to predict and optimize the energy demand of the greenhouse online. Combined with the priorities of FCU loops from CFD simulations offline, we have developed the CFD–EPM-based heating control system of greenhouse with surface water source heat pumps system (SWSHPS). Compared with conventional multi-zone independent control (CMIC) method, the energy savings potential is between 8.7% and 15.1%, and the control temperature deviation is decreased to between 0.1 °C and 0.6 °C in the investigated greenhouse. These results show the CFD–EPM-based method can improve system

  11. The Optimal Evaporation Temperature of Subcritical ORC Based on Second Law Efficiency for Waste Heat Recovery

    Directory of Open Access Journals (Sweden)

    Xiaoxiao Xu

    2012-03-01

    Full Text Available The subcritical Organic Rankine Cycle (ORC with 28 working fluids for waste heat recovery is discussed in this paper. The effects of the temperature of the waste heat, the critical temperature of working fluids and the pinch temperature difference in the evaporator on the optimal evaporation temperature (OET of the ORC have been investigated. The second law efficiency of the system is regarded as the objective function and the evaporation temperature is optimized by using the quadratic approximations method. The results show that the OET will appear for the temperature ranges investigated when the critical temperatures of working fluids are lower than the waste heat temperatures by 18 ± 5 K under the pinch temperature difference of 5 K in the evaporator. Additionally, the ORC always exhibits the OET when the pinch temperature difference in the evaporator is raised under the fixed waste heat temperature. The maximum second law efficiency will decrease with the increase of pinch temperature difference in the evaporator.

  12. Interfacial design of Cu-based composites prepared by powder metallurgy for heat sink applications

    OpenAIRE

    Schubert, Th; Trindade, B.; Weißgärber, T.; Kieback, B.

    2008-01-01

    Thermal aspects are becoming increasingly important for the reliability of the electronic components due to the continuous progress of the electronic industries. Therefore, the effective thermal management is a key issue for packaging of high performance semiconductors. The ideal material working as heat sink and heat spreader should have a CTE of (4-8) × 10-6 K-1 and a high thermal conductivity. Metal matrix composites offer the possibility to tailor the properties of a metal by adding an ap...

  13. Experimental studies on seasonal heat storage based on stable supercooling of a sodium acetate water mixture

    DEFF Research Database (Denmark)

    Furbo, Simon; Dragsted, Janne; Fan, Jianhua;

    2011-01-01

    to transfer heat to and from the module have been tested. Further, a solidification start method, based on a strong cooling of a small part of the salt water mixture in the module by boiling CO2 in a small brass tank in good thermal contact to the outer side of the module wall, has been tested. Tests......Laboratory tests of a 230 l seasonal heat storage module with a sodium acetate water mixture have been carried out. The aim of the tests is to elucidate how best to design a seasonal heat storage based on the salt water mixture, which supercools in a stable way. The module can be a part...... of a seasonal heat storage, that will be suitable for solar heating systems which can fully cover the yearly heat demand of Danish low energy buildings. The tested module has approximately the dimensions 2020 mm x 1285 mm x 80 mm. The module material is steel and the wall thickness is 2 mm. Different methods...

  14. A combined thermodynamic cycle based on methanol dissociation for IC (internal combustion) engine exhaust heat recovery

    International Nuclear Information System (INIS)

    In this paper, a novel approach for exhaust heat recovery was proposed to improve IC (internal combustion) engine fuel efficiency and also to achieve the goal for direct usage of methanol as IC engine fuel. An open organic Rankine cycle system using methanol as working medium is coupled to IC engine exhaust pipe for exhaust heat recovery. In the bottom cycle, the working medium first undergoes dissociation and expansion processes, and is then directed back to IC engine as fuel. As the external bottom cycle and the IC engine main cycle are combined together, this scheme forms a combined thermodynamic cycle. Then, this concept was applied to a turbocharged engine, and the corresponding simulation models were built for both of the external bottom cycle and the IC engine main cycle. On this basis, the energy saving potential of this combined cycle was estimated by parametric analyses. Compared to the methanol vapor engine, IC engine in-cylinder efficiency has an increase of 1.4–2.1 percentage points under full load conditions, while the external bottom cycle can increase the fuel efficiency by 3.9–5.2 percentage points at the working pressure of 30 bar. The maximum improvement to the IC engine global fuel efficiency reaches 6.8 percentage points. - Highlights: • A combined thermodynamic cycle using methanol as working medium for IC engine exhaust heat recovery is proposed. • The external bottom cycle of exhaust heat recovery and IC engine working cycle are combined together. • IC engine fuel efficiency could be improved from both in-cylinder working cycle and external bottom cycle. • The maximum improvement to the IC engine global fuel efficiency reaches 6.8 percentage points at full load

  15. Back propagation neural network based control for the heating system of a polysilicon reduction furnace

    Science.gov (United States)

    Cheng, Yuhua; Chen, Kai; Bai, Libing; Dai, Meizhi

    2013-12-01

    In this paper, the Back Propagation (BP) neural network based control strategy is proposed for the heating system of a polysilicon reduction furnace. It is applied to obtain the control signal Id, which is used to adjust the heating power through operations of the silicon core temperature, furnace temperature, silicon core voltage, and resistance of the current control cycle. With the control signal Id the polycrystalline silicon can be heated from room temperature to the required temperature smoothly and steadily. The proposed BP network applied in this paper can obtain the accurate control signal Id and achieve the precise control purpose. This paper presents the principle of the BP network and demonstrates the effectiveness of the BP network in the heating system of a polysilicon reduction furnace by combining the simulation analysis with experimental results.

  16. Experimental performance evaluation of heat pump-based steam supply system

    Science.gov (United States)

    Kaida, T.; Sakuraba, I.; Hashimoto, K.; Hasegawa, H.

    2015-08-01

    Heat pumps have become increasingly important as a technology to reduce primary energy consumption and greenhouse effect gas emission. They are presently used mainly on residential air-conditioning and domestic hot water and are expected to spread to industrial heating processes. In 2011, Kobe Steel, Ltd. developed and commercialized two heat pump- based steam supply systems; the high efficiency steam supply system with a steam temperature of 120°C (SGH120) and the system which enables a steam temperature of 165°C (sGh165). For promoting the spread of these industrial heat pumps and enhancing the reliability of them, we investigate experimentally steam generation rate, energy efficiency and controlled performance of the SGH165 under various operating conditions on the assumption of actual different industrial processes, and evaluate technical possibilities for better performance.

  17. Effect of working-fluid filling ratio and cooling-water flow rate on the performance of solar collector with closed-loop oscillating heat pipe

    International Nuclear Information System (INIS)

    This study experimentally investigated the effect of the working-fluid filling ratio (FR) and the cooling-water flow rate (CWFR) on the top heat loss and the performance of a solar collector equipped with a closed-loop oscillating heat pipe (CLOHP). The CLOHP was composed of a heating section, a cooling section, and an adiabatic section; it had a 0.002-m internal diameter and eight turns. The heating section was attached to a copper plate coated with black chrome, which absorbed energy from a solar simulator that had 12 halogen lamps and was controlled by a voltage regulator. The cooling section was inserted into the collector's cooling box, which was made of a transparent acrylic plate. The FR of the working fluid ranged from 30% to 80% with a 10% interval, and the CWFRs were 0.15 l/min, 0.30 l/min, and 0.45 l/min. The experimental results show that the solar collector equipped with the CLOHP has good performance at working-fluid FRs of 60% and 70% with low flow rates of 0.15 l/min and 0.30 l/min

  18. Remote Sensing-Based Characterization of Settlement Structures for Assessing Local Potential of District Heat

    Directory of Open Access Journals (Sweden)

    Michael Nast

    2011-07-01

    Full Text Available In Europe, heating of houses and commercial areas is one of the major contributors to greenhouse gas emissions. When considering the drastic impact of an increasing emission of greenhouse gases as well as the finiteness of fossil resources, the usage of efficient and renewable energy generation technologies has to be increased. In this context, small-scale heating networks are an important technical component, which enable the efficient and sustainable usage of various heat generation technologies. This paper investigates how the potential of district heating for different settlement structures can be assessed. In particular, we analyze in which way remote sensing and GIS data can assist the planning of optimized heat allocation systems. In order to identify the best suited locations, a spatial model is defined to assess the potential for small district heating networks. Within the spatial model, the local heat demand and the economic costs of the necessary heat allocation infrastructure are compared. Therefore, a first and major step is the detailed characterization of the settlement structure by means of remote sensing data. The method is developed on the basis of a test area in the town of Oberhaching in the South of Germany. The results are validated through detailed in situ data sets and demonstrate that the model facilitates both the calculation of the required input parameters and an accurate assessment of the district heating potential. The described method can be transferred to other investigation areas with a larger spatial extent. The study underlines the range of applications for remote sensing-based analyses with respect to energy-related planning issues.

  19. Relationship of heat treatment-mechanical properties of nickel base superalloys

    International Nuclear Information System (INIS)

    The nickel-base superalloys have high strength, excellent corrosion resistant, and good creep and fatigue resistance. These alloy improved properties at high temperature derive their mechanical and creep behavior on γ precipitate morphology, and the evolution of such morphology during different heat treatment conditions. The main microstructural variable of Nickel-based superalloys, responsible for the mechanical properties are: a) amount and morphology of precipitates; b) size and shape of grains; and c) carbide distribution. In this work, a Nickel-base superalloy Nimonic 80A, modified little with Zr prepared by melting and casting practices of materials electrolytic in vacuum-induction melting (VIM) type Balzers, to obtain five alloys different and ingots of 2 Kg and 1 Kg, with composition in weight % of Nimonic 80-A is: Ni = bal (76.66), C = 0.01, Cr = 19.83, Fe = 2.4, Mn = 0.17, Si 0.47, Al = 0.19, Zr = 0.4. The solidification process is made in a steel mold. After having realized four thermal treatments, the most representative microstructures there were obtained. The results from tensile tests performed on Instron Servohydraulic testing systems at uniaxial dynamic testing, at constant speeds to ,0.2 cm/min, were: the yield strength, the ultimate strength value, percentage elongation and area reduction. Creep tests were performed at in stress of 90 and 129 MPa, at a temperature of 600 and 680 Centigrades at different times and width of specimen of 1 mm. The alloys were analyzed by MEB(JEOL 35CF) at different magnifications. The nucleation and growth of intergranular cavities during creep of alloy Nimonic M3, were investigated. One sample was deformed in creep at 129 MPa and 680 Centigrades during 110 hs. Creep samples were annealing heat treated at 800 Centigrades, during 7 days. After a careful sample preparation procedure, 3100 of cavities were measured in the sample . The cavity size distributions in the sample were obtained. The cavity growth rate, was

  20. Construction and realization of the knowledge base and inference engine of an IDSS model for air-conditioning cooling/heating sources selection

    Institute of Scientific and Technical Information of China (English)

    LiuYing; WangRuzhu; LiYunfei; ZhangXiaosong

    2003-01-01

    The knowledge representation mode and inference control strategy were analyzed according to the specialties of air-conditioning cooling/heating sources selection. The constructing idea and working procedure for knowledge base and inference engine were proposed while the realization technique of the C language was discussed. An intelligent decision support system (IDSS) model based on such knowledge representation and inference mechanism was developed by domain engineers. The model was verified to have a small kernel and powerful capability in list processing and data driving, which was successfully used in the design of a cooling/heating sources system for a large-sized office building.

  1. Experimental Study on Machining Shape Hole of Ni-based Super-heat-resistant Alloy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Inconel 718 and Waspaloy, Nickel-based super-heat-resistant alloy, are high-strength, thermal-resistant and corrosion-resistant alloy that are widely used in parts of gas turbines and airplane engines. Due to their extremely tough and thermal-resistant nature, they are well known as materials that are difficult to cut. Shape holes on a disc of an aircraft engine, made of Ni-based super-heat-resistant alloy, are required with good surface integrity and geometric accuracy. This kind of shape hole is produced ...

  2. Modeling and Optimization for Heat Exchanger Networks Synthesis Based on Expert System and Genetic Algorithm

    Institute of Scientific and Technical Information of China (English)

    LIZhihong

    2002-01-01

    A new superstructure from of heat exchanger networks(HEN) is proposed based on expert system (ES). The new superstructure from is combined with the practical engineering.The different investment cost formula for different heat exchanger is also presented based on ES.The mathematical model for the simultaneous optimization of network configuration is established and solved by a genetic algorithm.This method can deal with larger scale HEN synthesis and the optimal HEN configuration is obtained automatically.Finally,a case study is presented to demonstrate the effectiveness of the method.

  3. Working Toward a Competency-Based Preceptor Development Program.

    Science.gov (United States)

    Gueorguieva, Vera; Chang, Ann; Fleming-Carroll, Bonnie; Breen-Reid, Karen M; Douglas, Mary; Parekh, Sandhaya

    2016-09-01

    Preceptorship programs are widely used in nursing education and transition to practice. This article describes a variety of improvements implemented in an academic health sciences center on the basis of findings from a study previously conducted with preceptors in the same institution. A long-standing preceptor preparation program was redesigned and expanded into two levels-an introductory workshop directed toward meeting the needs of new preceptors, and an advanced workshop for experienced preceptors. Organization-specific preceptor competencies were developed as a foundation for preceptor practice. The competencies also informed the revised preceptor development program that included selection, ongoing development, and evaluation. A more structured support system, a standardized performance feedback process, and additional recognition strategies were incorporated in the new competency-based preceptor program. J Contin Educ Nurs. 2016;47(9):427-432. PMID:27580510

  4. A finite element method based microwave heat transfer modeling of frozen multi-component foods

    Science.gov (United States)

    Pitchai, Krishnamoorthy

    Microwave heating is fast and convenient, but is highly non-uniform. Non-uniform heating in microwave cooking affects not only food quality but also food safety. Most food industries develop microwavable food products based on "cook-and-look" approach. This approach is time-consuming, labor intensive and expensive and may not result in optimal food product design that assures food safety and quality. Design of microwavable food can be realized through a simulation model which describes the physical mechanisms of microwave heating in mathematical expressions. The objective of this study was to develop a microwave heat transfer model to predict spatial and temporal profiles of various heterogeneous foods such as multi-component meal (chicken nuggets and mashed potato), multi-component and multi-layered meal (lasagna), and multi-layered food with active packages (pizza) during microwave heating. A microwave heat transfer model was developed by solving electromagnetic and heat transfer equations using finite element method in commercially available COMSOL Multiphysics v4.4 software. The microwave heat transfer model included detailed geometry of the cavity, phase change, and rotation of the food on the turntable. The predicted spatial surface temperature patterns and temporal profiles were validated against the experimental temperature profiles obtained using a thermal imaging camera and fiber-optic sensors. The predicted spatial surface temperature profile of different multi-component foods was in good agreement with the corresponding experimental profiles in terms of hot and cold spot patterns. The root mean square error values of temporal profiles ranged from 5.8 °C to 26.2 °C in chicken nuggets as compared 4.3 °C to 4.7 °C in mashed potatoes. In frozen lasagna, root mean square error values at six locations ranged from 6.6 °C to 20.0 °C for 6 min of heating. A microwave heat transfer model was developed to include susceptor assisted microwave heating of a

  5. Feasibility of computed tomography based thermometry during interstitial laser heating in bovine liver

    International Nuclear Information System (INIS)

    To assess the feasibility of computed tomography (CT) based thermometry during interstitial laser heating in the bovine liver. Four freshly exercised cylindrical blocks of bovine tissue were heated using a continuous laser of Nd:YAG (wavelength: 1064 nm, active length: 30 mm, power: 10-30 W). All tissues were imaged at least once before and 7 times during laser heating using CT and temperatures were simultaneously measured with 5 calibrated thermal sensors. The dependency of the average CT numbers as a function of temperature was analysed with regression analysis and a CT thermal sensitivity was derived. During laser heating, the growing hypodense area was observed around the laser source and that area showed an increase as a function of time. The formation of hypodense area was caused by declining in CT numbers at increasing temperatures. The regression analysis showed an inverse linear dependency between temperature and average CT number with -0.65 ± 0.048 HU/ C (R2 = 0.75) for the range of 18-85 C in bovine liver. The non-invasive CT based thermometry during interstitial laser heating is feasible in the bovine liver. CT based thermometry could be further developed and may be of potential use during clinical LITT of the liver. (orig.)

  6. Feasibility of computed tomography based thermometry during interstitial laser heating in bovine liver

    Energy Technology Data Exchange (ETDEWEB)

    Pandeya, G.D. [University of Groningen, Department of Radiology, UMC Groningen, Hanzeplein 1, PO Box 30001, Groningen (Netherlands); Siemens AG, H IM CT PLM-E PA, Forchheim (Germany); Klaessens, J.H.G.M. [UMC Utrecht, Department of Medical Technology and Clinical Physics, Utrecht (Netherlands); Greuter, M.J.W.; Oudkerk, M. [University of Groningen, Department of Radiology, UMC Groningen, Hanzeplein 1, PO Box 30001, Groningen (Netherlands); Schmidt, B.; Flohr, T. [Siemens AG, H IM CT PLM-E PA, Forchheim (Germany); Hillegersberg, R. van [UMC Utrecht, Department of Surgical Oncology, Utrecht (Netherlands)

    2011-08-15

    To assess the feasibility of computed tomography (CT) based thermometry during interstitial laser heating in the bovine liver. Four freshly exercised cylindrical blocks of bovine tissue were heated using a continuous laser of Nd:YAG (wavelength: 1064 nm, active length: 30 mm, power: 10-30 W). All tissues were imaged at least once before and 7 times during laser heating using CT and temperatures were simultaneously measured with 5 calibrated thermal sensors. The dependency of the average CT numbers as a function of temperature was analysed with regression analysis and a CT thermal sensitivity was derived. During laser heating, the growing hypodense area was observed around the laser source and that area showed an increase as a function of time. The formation of hypodense area was caused by declining in CT numbers at increasing temperatures. The regression analysis showed an inverse linear dependency between temperature and average CT number with -0.65 {+-} 0.048 HU/ C (R{sup 2} = 0.75) for the range of 18-85 C in bovine liver. The non-invasive CT based thermometry during interstitial laser heating is feasible in the bovine liver. CT based thermometry could be further developed and may be of potential use during clinical LITT of the liver. (orig.)

  7. Metamorphoses of cogeneration-based district heating in Romania: A case study

    International Nuclear Information System (INIS)

    The paper presents the birth and evolution of the cogeneration-based district heating (DH) system in a medium size city in Romania (Targoviste). The evolution of the industrialization degree was the main factor which controlled the population growth and led to a continuous reconfiguration of the DH system. The DH system assisted by cogeneration emerged as a solution in a certain phase of the demographic development of the city. The political and social changes occurring in Romania after 1990 have had important negative consequences on the DH systems in small towns. In Targoviste the DH system survived but in 2001 the solution based on cogeneration became economically inefficient, due to the low technical quality of the existing equipment and the low gas prices, to the procedure of setting the DH tariffs and the service cost at consumer's level and to some bureaucratic problems. Energy policy measures taken at national and local levels in 2003 and 2005 led to the re-establishment of the cogeneration-based district heating in 2005. However, a different technical solution has been adopted. Details about the present (2009) cogeneration-based DH system in Targoviste are presented together with several technical and economical indicators. The main conclusion is that by a proper amendment of the technical solutions, cogeneration could be a viable solution for DH even in case of abrupt social and demographic changes, such as those occurring in Romania after 1990. - Research Highlights: →Birth and evolution of the cogeneration-based district heating system in a medium size city. →The industrialization degree is the main factor which controlled the reconfiguration of the district heating system. →Each stage of the evolution of district heating system has been a technological leap. →Cogeneration is a solution for district heating even in case of abrupt social changes.

  8. Thermodynamic analysis of a low-temperature waste heat recovery system based on the concept of solar chimney

    International Nuclear Information System (INIS)

    Highlights: • A low grade waste heat recovery system based on the concept of solar chimney is proposed. • The effects of three key factors on the system performance are examined. • Thermodynamics analysis is to find a better way to utilize low grade heat source efficiently. - Abstract: The utilization of low-temperature waste heat draws more and more attention due to serious energy crisis nowadays. This paper proposes a low-temperature waste heat recovery system based on the concept of solar chimney. In the system, low-temperature waste heat is used to heat air to produce an air updraft in the chimney tower. The air updraft propels a turbine fixed at the base of the chimney tower to convert waste heat into electricity. The mathematical model of the system is established based on first law and second law of thermodynamics. Hot water is selected as the representative of low-temperature waste heat sources for researching. The heat source temperature, ambient air temperature and area of heat transfer are examined to evaluate their effects on the system performance such as velocity of updraft, mass flow rate of air, power output, conversion efficiency, and exergy efficiency. The velocity of air demonstrates a better stability than the mass flow rate of air and the pressure difference when temperature of heat source, ambient air temperature or area of heat transfer changes

  9. Research of water-base nano-PU paint for heat insulation

    Science.gov (United States)

    Jwo, Ching-Song; Jeng, Lung-Yue; Cheng, Ho; Chen, Sih-Li

    2008-12-01

    The purpose of this study is to research and produce water-base nano-PU paint with energy conservation, environmental consciousness and high efficiency of heat insulation, which can be enhance the traditional PU paint for performance improvement of heat insulation and range of application. In this study, research will be held on the two-stage synthesis method. The SiO2 nanoparticles are added into the water-base PU paint to improve the properties of traditional PU paint. Next, the fundamental properties of this paint, including water resistance, weather rsistance, weak acid solvent resistance, and heat insulation rate, will be measured and analyzed, and the performance of heat insulation will be evaluated in order to confirm the performance and practicability of the heat insulation of water-base nano-PU paint in this study. The experimental results show that for the SiO2/W-PU composite nanopaint prepared by two-stage synthesis method, the dispersion of SiO2 powder in the water-base PU (W-PU) paint is even. For the SiO2/W-PU nanocomposite paint prepared by adding SiO2 powder at 8% wt. to the marketed water-base PU, the water absorption of its experimental sample is enhanced by around 10.1 times, whereas its weak acid dissolve erosion rate is increased by 3.3 times. However, the average heat insulation rate in the thermal properties is also increased, increasing around 24.22% for the W-PU paint without SiO2 powder. Through the multilayered coating construction, the water-base nano-PU paint added with SiO2 powder can be used on any facility of heat insulation, including vehicle, safety helmet, umbrella, drapes, and outer wall of building. The newly developed water-base nano-PU paint with high thermal resistance is especially suitable for application to the shell coating of air conditioner and cooling tower,. Due to the better thermal resistance of this nanopaint, the problems of poor heat transfer and temperature rise of cooling water caused by direct sunlight can be

  10. Thermal treatment system of hazardous residuals in three heating zones based on a microprocessor

    International Nuclear Information System (INIS)

    Thermal treatment system consists of a high power electric oven of three heating zones where each zone works up to 1200 Centigrades; it has the capacity of rising the central zone temperature up to 1000 Centigrades in 58 minutes approximately. This configuration of three zones could be programmed to different temperatures and they will be digitally controlled by a control microprocessor, which has been controlled by its own assembler language, in function of the PID control. There are also other important controls based on this microprocessor, as a signal amplification, starting and shutdown of high power step relays, activation and deactivation of both analogic/digital and digital/analogic convertors, port activation and basic data storage of the system. Two main characteristics were looked for this oven design; the first was the possibility of controlling the three zone temperature and the second was to reduce the rising and stabilization operation time and its digitized control. The principal function of the three zone oven is to accelerate the degradation of hazardous residuals by an oxidation instead combustion, through relatively high temperatures (minimum 800 Centigrades and maximum 1200 Centigrades); this process reduces the ash and volatile particulate production. The hazardous residuals will be pumped into the degradation system and after atomized through a packaged column; this step will avoid the direct contact of the residuals with the oven cores. These features make this system as closed process, which means that the residuals can not leak to the working area, reducing the exposure risk to the personnel. This three step oven system is the first stage of the complete hazardous residuals degradation system; after this, the flow will go into a cold plasma region where the process is completed, making a closed system. (Author)

  11. Method for calculating thermal properties of lightweight floor heating panels based on an experimental setup

    DEFF Research Database (Denmark)

    Weitzmann, Peter; Svendsen, Svend

    2005-01-01

    , radiation and conduction of the heat transfer between pipe and surrounding materials. The European Standard for floor heating, EN1264, does not cover lightweight systems, while the supplemental Nordtest Method VVS127 is aimed at lightweight systems. The thermal properties can be found using tabulated values...... or experiments. Neither includes dynamic properties. This article describes a method to find steady-state and dynamical thermal properties in an experimental setup based on finding a characteristic thermal resistance between pipe and heat transfer plate, which can be directly implemented in a numerical...... presented here. Consequently, the test setup can also be used to for tests based on Nordtest VVS 127. The advantage of using the method developed here is that it can be used directly for building energy simulations, while the drawback is the need to build a test setup to find the contact resistance. However...

  12. Experimental investigation of Cu-based, double-layered, microchannel heat exchangers

    International Nuclear Information System (INIS)

    Cu-based, single- and double-layered, microchannel heat exchangers (MHEs) were fabricated and assembled. Comparative measurements on liquid flow characteristics and heat transfer performance were conducted on these devices. Results were compared at the individual microchannel level as well as at the device level. The present results demonstrate that double-layered MHEs exhibit similar heat transfer performance while suffering a much lower pressure drop penalty compared to single-layered MHEs. Another Cu-based, double-layered, liquid–liquid counter-flow MHE was fabricated, assembled and tested. Results show that a low-volume, multilayered, high-performance, liquid-to-liquid MHE is achievable following the manufacturing protocols of the present double-layered, liquid–liquid counter-flow MHE. (paper)

  13. Independent air dehumidification with membrane-based total heat recovery: Modeling and experimental validation

    Energy Technology Data Exchange (ETDEWEB)

    Liang, C.H.; Zhang, L.Z.; Pei, L.X. [Key Laboratory of Enhanced Heat Transfer and Energy Conservation of Education Ministry, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640 (China)

    2010-03-15

    Fresh air ventilation is helpful for the control of epidemic respiratory disease like Swine flu (H1N1). Fresh air dehumidification systems with energy recovery measures are the key equipments to realize this goal. As a solution, an independent air dehumidification system with membrane-based total heat recovery is proposed. A prototype is built in laboratory. A detailed model is proposed and a cell-by-cell simulation technique is used in simulation to evaluate performances. The results indicate that the model can predict the system accurately. The effects of varying operating conditions like air-flow rates, temperature, and air relative humidity on the air dehumidification rates, cooling powers, electric power consumption, and thermal coefficient of performance are evaluated. The prototype has a COP of 6.8 under nominal operating conditions with total heat recovery. The performance is rather robust to outside weather conditions with a membrane-based total heat exchanger. (author)

  14. Performance analysis of exhaust waste heat recovery system for stationary CNG engine based on organic Rankine cycle

    International Nuclear Information System (INIS)

    In order to improve the electric efficiency of a stationary compressed natural gas (CNG) engine, a set of organic Rankine cycle (ORC) system with internal heat exchanger (IHE) is designed to recover exhaust energy that is used to generate electricity. R416A is selected as the working fluid for the waste heat recovery system. According to the first and second laws of thermodynamics, the performances of the ORC system for waste heat recovery are discussed based on the analysis of engine exhaust waste heat characteristics. Subsequently, the stationary CNG engine-ORC with IHE combined system is presented. The electric efficiency and the brake specific fuel consumption (BSFC) are introduced to evaluate the operating performances of the combined system. The results show that, when the evaporation pressure is 3.5 MPa and the engine is operating at the rated condition, the net power output and the thermal efficiency of the ORC system with IHE can reach up to 62.7 kW and 12.5%, respectively. Compared with the stationary CNG engine, the electric efficiency of the combined system can be increased by a maximum 6.0%, while the BSFC can be reduced by a maximum 5.0%. - Highlights: • The characteristics of exhaust energy for the stationary CNG engine are investigated. • The ORC system with IHE is designed to recover the exhaust energy from engine. • Zeotropic mixture R416A is used as the working fluid of the ORC system. • The electric efficiency of combined system is defined and investigated. • BSFC of combined system is studied under various operating conditions of engine

  15. Heat Exchangers Networks Synthesis and Optimisation Performed by an Exergy-Based Expert Assistant

    Directory of Open Access Journals (Sweden)

    Enrico Sciubba

    2000-03-01

    Full Text Available This paper presents a novel method for the design of “optimal” (or quasi-optimal Heat Exchanger Network (HEN. The method consists of an Expert System (ES based on a small number of powerful and strongly selective heuristic rules. The important contribution of this study lies in the formulation of the rules (that have been adapted from the existing literature as logical propositions, and in their subsequent implementation in a prototype ES that performs interactively with the user. There is a high demand for an “automatic” (in some sense methodology that may conveniently be adapted to design-and-optimisation problems. Pinch Technology (PT, at present the most widely adopted design procedure, is very successful in most types of applications (except in cases where mechanical and thermal power must be optimised concurrently, but it constitutes an operative tool, and assumes that the user is already familiar with the design of HEN. The approach presented in this paper is entirely different: we do not "mask" the thermodynamic and thermo-economic principles that guide the engineer in the path towards the “optimal” HEN configuration, and do not allow concerns about "user friendliness" to impair the necessary participation of the user to the HEN synthesis procedure. In fact, though ES of this work (which we prefer to call "Expert Assistant", to underline its peculiarity of constantly interacting with the user is still lacking many of the capabilities that a good designer possesses, the underlying procedure is, unlike any of the other existing Design-and-Optimisation Procedures, entirely inspectable by the user about its decision-making rules. It can be interrogated about its decision making, so that the logical path followed from the design data to the final solution can be inspected at will, and it can be used to directly compare different alternatives in a logically systematic fashion. The paper begins with a brief review of the HEN design

  16. Support schemes and ownership structures - The policy context for fuel cell based micro-combined heat and power

    Energy Technology Data Exchange (ETDEWEB)

    Ropenus, S.; Thorsten Schroeder, S.; Costa, A.; Obe, E.

    2010-05-15

    In recent years, fuel cell based micro-combined heat and power has received increasing attention due to its potential contribution to energy savings, efficiency gains, customer proximity and flexibility in operation and capacity size. The FC4Home project assesses technical and economic aspects of the ongoing fuel cell based micro-combined heat and power (mCHP) demonstration projects by addressing the socio-economic and systems analyses perspectives of a large-scale promotion scheme of fuel cells. This document constitutes the deliverable of Work Package 1 of the FC4Home project and provides an introduction to the policy context for mCHP. Section 1 describes the rationale for the promotion of mCHP by explaining its potential contribution to European energy policy goals. Section 2 addresses the policy context at the supranational European level by outlining relevant EU Directives on support schemes for promoting combined heat and power and energy from renewable sources. These Directives are to be implemented at the national level by the Member States. Section 3 conceptually presents the spectrum of national support schemes, ranging from investment support to market-based operational support. The choice of support scheme simultaneously affects risk and technological development, which is the focus of Section 4. Subsequent to this conceptual overview, Section 5 takes a glance at the national application of support schemes for mCHP in practice, notably in the three country cases of the FC4Home project, Denmark, France and Portugal. Another crucial aspect for the diffusion of the mCHP technology is possible ownership structures. These may range from full consumer ownership to ownership by utilities and energy service companies, which is discussed in Section 6. Finally, a conclusion (Section 7) wraps up previous findings and provides a short 'preview' of the quantitative analyses in subsequent Work Packages by giving some food for thought on the way. (author)

  17. Experimental performance investigation of a shell and tube heat exchanger by exergy based sensitivity analysis

    Science.gov (United States)

    Mert, Suha Orçun; Reis, Alper

    2016-06-01

    Heat exchangers are used extensively in many industrial branches, primarily so in chemical and energy sectors. They also have important household usage as they are used in central and local heating systems. Any betterment on heat exchangers will serve greatly in preserving our already dwindling and costly energy resources. Strong approach of exergy analysis -which helps find out where the first steps should be taken in determining sources of inefficiencies and how to remedy them- will be used as a means to this end. The maximum useful work that can be harnessed from systems relationships with its environment is defined as exergy. In this study, the inlet and outlet flow rate values of fluids and temperature of hot stream both on shell and tube parts of a shell-tube heat exchange system have been inspected and their effects on the exergy efficiency of this thermal system have been analyzed. It is seen that the combination of high tube side inlet temperature, low shell side flow rate and high tube side flow rate are found to be the optimum for this experimental system with reaching 75, 65, and 32 % efficiencies respectively. Selecting operating conditions suitable to this behavior will help to increase the overall efficiency of shell-tube heat exchange systems and cause an increment in energy conservation.

  18. Thermal dispersivity based calibration of a numerical borehole heat exchanger model

    Science.gov (United States)

    Wagner, Valentin; Bayer, Peter; Bisch, Gerhard; Klaas, Norbert; Braun, Jürgen; Blum, Philipp

    2013-04-01

    Shallow geothermal energy is used worldwide as a heat and/or cooling source for buildings. The most often used technique to exploit energy from the subsurface is ground source heat pump systems in combination with a borehole heat exchanger (BHE). The BHE consists either of one U-pipe, two U-pipes or a coaxial pipe, which are inserted in a borehole. The remaining void space is filled with a grouting material to improve the thermal connection between the pipes and the subsurface and to protect the subsurface if there is a leakage in the pipes. In the pipes, a heat carrier fluid is circulated to establish a thermal gradient around the BHE and thus promote conductive heat transfer. This causes a temperature anomaly in the subsurface. Extension and magnitude of such temperature anomalies do not only depend on the amount of exchanged energy, but also on the characteristics of the ground and the installed ground source heat pump system itself. In this study, we developed a high-resolution finite element BHE model to simulate the heat propagation from a BHE to the subsurface or vice versa. First, the resulting heat propagation predicted by the numerical model is compared to the analogous analytical solutions. Then the numerical model is calibrated based on a large-scale geothermal tank experiment. The tank has a size of 9m × 6m × 4.5m (length × width × depth), and it hosts a layered artificial aquifer with four BHEs, which are surrounded by a dense temperature sensor network (> 150 PT-100 temperature sensors). In the tank, a hydraulic gradient can be established and thus groundwater flow can be imitated. By calibrating the numerical model, the sensitivity of longitudinal and transversal dispersivity values is evaluated. Our analysis cannot prove that the commonly assumed ratio of 1:10 between transversal and longitudinal dispersivity is correct. Rather, it is shown that there exists a wide range of possible parameter value combinations.

  19. A numerical method for PCM-based pin fin heat sinks optimization

    International Nuclear Information System (INIS)

    Highlights: • Optimization of PCM-based heat sink by using the Taguchi method. • Derivation of optimal PCM percentage to reach the maximum critical time. • Optimization is performed for four different critical temperatures. • Effective design factors are fins’ height and fins’ number. • The optimum configuration depends on geometric properties and the critical temperature. - Abstract: This paper presents a numerical investigation on geometric optimization of PCM-based pin fin heat sinks. Paraffin RT44HC is used as PCM while the fins and heat sink base is made of aluminum. The fins act as thermal conductivity enhancers (TCEs). The main goal of the study is to obtain the configurations that maximize the heat sink operational time. An approach witch couples Taguchi method with numerical simulations is utilized for this purpose. Number of fins, fins height, fins thickness and the base thickness are parameters which are studied for optimization. In this study natural convection and PCM volume variation during melting process are considered in the simulations. Optimization is performed for different critical temperatures of 50 °C, 60 °C, 70 °C and 80 °C. Results show that a complex relation exists between PCM and TCE volume percentages. The optimal case strongly depends on the fins’ number, fins’ height and thickness and also the critical temperature. The optimum PCM percentages are found to be 60.61% (corresponds to 100 pin fin heat sink with 4 mm thick fins) for critical temperature of 50 °C and 82.65% (corresponds to 100 pin fin heat sink with 2 mm thick fins) for other critical temperatures

  20. Experimental analysis of the performance of an air-water heat pump designed for R22 working with propane

    International Nuclear Information System (INIS)

    After describing the technical characteristics of a heat pump designed for R22, the changes necessary to fit the use of propane and the experimental set-up, in this article the research program on propane as refrigerant is presented, together with the experimental results of the chiller performance with R22 and R290 in cooling mode

  1. Aircraft Sheet Metal Practices, Blueprint Reading, Sheet Metal Forming and Heat Treating; Sheet Metal Work 2: 9855.04.

    Science.gov (United States)

    Dade County Public Schools, Miami, FL.

    This course is designed to familiarize vocational students with construction in sheet metal layout. The document outlines goals, specific block objectives, layout practices, blueprint reading, sheet metal forming (by hand and by machine), and heat treatment of metals, and includes posttest samples. Layout techniques and air foil developing are…

  2. Fluid Analysis and Improved Structure of an ATEG Heat Exchanger Based on Computational Fluid Dynamics

    Science.gov (United States)

    Tang, Z. B.; Deng, Y. D.; Su, C. Q.; Yuan, X. H.

    2015-06-01

    In this study, a numerical model has been employed to analyze the internal flow field distribution in a heat exchanger applied for an automotive thermoelectric generator based on computational fluid dynamics. The model simulates the influence of factors relevant to the heat exchanger, including the automotive waste heat mass flow velocity, temperature, internal fins, and back pressure. The result is in good agreement with experimental test data. Sensitivity analysis of the inlet parameters shows that increase of the exhaust velocity, compared with the inlet temperature, makes little contribution (0.1 versus 0.19) to the heat transfer but results in a detrimental back pressure increase (0.69 versus 0.21). A configuration equipped with internal fins is proved to offer better thermal performance compared with that without fins. Finally, based on an attempt to improve the internal flow field, a more rational structure is obtained, offering a more homogeneous temperature distribution, higher average heat transfer coefficient, and lower back pressure.

  3. Design of an additional heat sink based on natural circulation in pressurized water reactors

    International Nuclear Information System (INIS)

    Residual heat removal through the steam generators in Nuclear Power Plant with pressurized water reactors (PWR) or pressurized heavy water reactors (PHWR in pressured vessel or pressured tube types) requires the maintenance of the steam generator inventory and the availability of and appropriate heat sink, which are based on the operability of the steam generators feedwater system. This paper describes the conceptual design of an assured heat removal system which includes only passive elements and is based on natural circulation. The system can supplement the original systems of the plant. The new system includes a condenser/boiler heat exchanger to condense the steam produced in the steam generator, transferring the heat to the water of an open pool at atmospheric pressure. The condensed steam flows back to the steam generators by natural circulation effects. The performance of an Atucha type PHWR nuclear power station with and without the proposed system is calculated in an emergency power case for the first 5000 seconds after the incident. The analysis shows that the proposed system offers the possibility to cool-down the plant to a low energy state during several hours and avoids the repeated actuation of the primary and secondary system safety valves. (Author)

  4. LWR decay heat calculations using a GRS improved ENDF/B-6 based ORIGEN data library

    Energy Technology Data Exchange (ETDEWEB)

    Hesse, U.; Hummelsheim, K.I.; Kilger, R.; Moser, F.E.; Langenbuch, S. [Gesellschaft fur Anlagen- und Reaktorsicherheit (GRS) mbH, Forschungsinstitute, Garching (Germany)

    2008-07-01

    The known ORNL ORIGEN code is widely spread over the world for inventory, activity and decay heat tasks and is used stand-alone or implemented in activation, shielding or burn-up systems. More than 1000 isotopes with more than six coupled neutron capture and radioactive decay channels are handled simultaneously by the code. The characteristics of the calculated inventories, e.g., masses, activities, neutron and photon source terms or the decay heat during short or long decay time steps are achieved by summing over all isotopes, characterized in the ORIGEN libraries. An extended nuclear GRS-ORIGENX data library is now developed for practical appliance. The library was checked for activation tasks of structure material isotopes and for actinide and fission product burn-up calculations compared with experiments and standard methods. The paper is directed to the LWR decay heat calculation features of the new library and shows the differences of dynamical and time integrated results of Endf/B-6 based and older Endf/B-5 based libraries for decay heat tasks compared to fission burst experiments, ANS curves and some other published data. A multi-group time exponential evaluation is given for the fission burst power of {sup 235}U, {sup 238}U, {sup 239}Pu and {sup 241}Pu, to be used in quick LWR reactor accident decay heat calculation tools. (authors)

  5. Research on the Specific Heat Capacity of PBX Formulations Based on RDX

    Directory of Open Access Journals (Sweden)

    Flávio Rodrigues Chaves

    2016-07-01

    Full Text Available The experimental results of specific heat capacity of 2 plastic bonded explosives formulations based on 1,3,5-trinitroperhydro-1,3,5-triazine, using differential scanning calorimetry thermal analysis, and the theoretical ones calculated with the specific heat capacity and mass fraction of individual compounds are compared for a temperature range between 340 and 410 K. Apart the filler, the plastic bonded explosives composition includes the binder based on hydroxyl-terminated polybutadiene, the plasticizer bis (2-ethylhexyl sebacate and the curing agent isophorone diisocyanate. The experimental and theoretical results showed a better approach when no curing agent is added. Without curing agent, the specific heat capacity of plastic bonded explosives increases linearly with temperature. When plastic bonded explosive is cured, the specific heat capacity is nearly constant until 380 K and decreases linearly for higher temperature values. These results suggest that phase change requires adjusting parameters to different heating rates in order to describe adequately the experimental data.

  6. A numerical study of EGS heat extraction process based on a thermal non-equilibrium model for heat transfer in subsurface porous heat reservoir

    Science.gov (United States)

    Chen, Jiliang; Jiang, Fangming

    2016-02-01

    With a previously developed numerical model, we perform a detailed study of the heat extraction process in enhanced or engineered geothermal system (EGS). This model takes the EGS subsurface heat reservoir as an equivalent porous medium while it considers local thermal non-equilibrium between the rock matrix and the fluid flowing in the fractured rock mass. The application of local thermal non-equilibrium model highlights the temperature-difference heat exchange process occurring in EGS reservoirs, enabling a better understanding of the involved heat extraction process. The simulation results unravel the mechanism of preferential flow or short-circuit flow forming in homogeneously fractured reservoirs of different permeability values. EGS performance, e.g. production temperature and lifetime, is found to be tightly related to the flow pattern in the reservoir. Thermal compensation from rocks surrounding the reservoir contributes little heat to the heat transmission fluid if the operation time of an EGS is shorter than 15 years. We find as well the local thermal equilibrium model generally overestimates EGS performance and for an EGS with better heat exchange conditions in the heat reservoir, the heat extraction process acts more like the local thermal equilibrium process.

  7. Modeling of Artificial Neural Network for Predicting Specific Heat capacity of working fluid LiBr-H2O used in Vapor Absorption Refrigeration System

    Directory of Open Access Journals (Sweden)

    Dheerendra Vikram Singh

    2011-05-01

    Full Text Available The objective of this work is to model an artificial neural network (ANN to predict the value of specific heat capacity of working fluid LiBr-H2O used in vapour absorption refrigeration systems. A feed forward back propagation algorithm is used for the network, which is most popular for ANN. The consistence between experimental and ANN’s approach result was achieved by a mean relative error -0.00573, sum of the squares due to error0.00321, coefficient of multiple determination R-square 0.99961and root mean square error 0.01573 for test data. These results had been achieved in Matlab environment and the use of derived equations in any programmable language for deriving the specific heat capacity of LiBr-H2O solution.

  8. A Computer-Based Simulation for Teaching Heat Transfer across a Woody Stem

    Science.gov (United States)

    Maixner, Michael R.; Noyd, Robert K.; Krueger, Jerome A.

    2010-01-01

    To assist student understanding of heat transfer through woody stems, we developed an instructional package that included an Excel-based, one-dimensional simulation model and a companion instructional worksheet. Guiding undergraduate botany students to applying principles of thermodynamics to plants in nature is fraught with two main obstacles:…

  9. Heat pumps

    CERN Document Server

    Brodowicz, Kazimierz; Wyszynski, M L; Wyszynski

    2013-01-01

    Heat pumps and related technology are in widespread use in industrial processes and installations. This book presents a unified, comprehensive and systematic treatment of the design and operation of both compression and sorption heat pumps. Heat pump thermodynamics, the choice of working fluid and the characteristics of low temperature heat sources and their application to heat pumps are covered in detail.Economic aspects are discussed and the extensive use of the exergy concept in evaluating performance of heat pumps is a unique feature of the book. The thermodynamic and chemical properties o

  10. Critical Temperature Differences of a Standing Wave Thermoacoustic Prime Mover with Various Helium-Based Binary Mixture Working Gases

    Science.gov (United States)

    Setiawan, Ikhsan; Nohtomi, Makoto; Katsuta, Masafumi

    2015-06-01

    Thermoacoustic prime movers are energy conversion devices which convert thermal energy into acoustic work. The devices are environmentally friendly because they do not produce any exhaust gases. In addition, they can utilize clean energy such as solar-thermal energy or waste heat from internal combustion engines as the heat sources. The output mechanical work of thermoacoustic prime movers are usually used to drive a thermoacoustic refrigerator or to generate electricity. A thermoacoustic prime mover with low critical temperature difference is desired when we intend to utilize low quality of heat sources such as waste heat and sun light. The critical temperature difference can be significantly influenced by the kinds of working gases inside the resonator and stack's channels of the device. Generally, helium gas is preferred as the working gas due to its high sound speed which together with high mean pressure will yield high acoustic power per unit volume of the device. Moreover, adding a small amount of a heavy gas to helium gas may improve the efficiency of thermoacoustic devices. This paper presents numerical study and estimation of the critical temperature differences of a standing wave thermoacoustic prime mover with various helium-based binary-mixture working gases. It is found that mixing helium (He) gas with other common gases, namely argon (Ar), nitrogen (N2), oxygen (O2), and carbon dioxide (CO2), at appropriate pressures and molar compositions, reduce the critical temperature differences to lower than those of the individual components of the gas mixtures. In addition, the optimum mole fractions of Hegas which give the minimum critical temperature differences are shifted to larger values as the pressure increases, and tends to be constant at around 0.7 when the pressure increases more than 2 MPa. However, the minimum critical temperature differences slightly increase as the pressure increases to higher than 1.5 MPa. Furthermore, we found that the lowest

  11. Performance analysis of absorption heat transformer cycles using ionic liquids based on imidazolium cation as absorbents with 2,2,2-trifluoroethanol as refrigerant

    International Nuclear Information System (INIS)

    Highlights: • TFE + [emim][BF4] (or [bmim][BF4]) absorption heat transformer cycles are studied. • Influence of various operating conditions on cycle’s performance is investigated. • Performance comparisons with H2O + LiBr and TFE + TEGDME cycles are done. • Enthalpy data for TFE + [emim][BF4] (or [bmim][BF4]) liquid mixtures are calculated. • TFE + [emim][BF4] (or [bmim][BF4]) cycles have higher gross temperature lift (GTL). - Abstract: A detailed thermodynamic performance analysis of a single-stage absorption heat transformer and double absorption heat transformer cycles using new working pairs composed of ionic liquids (1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4])) as absorbent and 2,2,2-trifluoroethanol (TFE) as refrigerant has been studied. Several performance indicators were used to evaluate and compare the performance of the cycles using the TFE + [emim][BF4] and TFE + [bmim][BF4] working pairs with the conventional H2O + LiBr and organic TFE + TEGDME working pairs. The obtained results show that the ionic liquid based working pairs are suitable candidates to replace the conventional H2O + LiBr working pairs in order to avoid the disadvantages associated with it mainly crystallization and corrosion and also they perform better (higher gross temperature lift) than TFE + TEGDME working pair at several operating conditions considered in this work

  12. Development of materials database system for cae system of heat treatment based on data mining technology

    Institute of Scientific and Technical Information of China (English)

    GU Qiang; ZHONG Rui; JU Dong-ying

    2006-01-01

    Computer simulation for materials processing needs a huge database containing a great deal of various physical properties of materials. In order to employ the accumulated large data on materials heat treatment in the past years,it is significant to develop an intelligent database system. Based on the data mining technology for data analysis,an intelligent database web tool system of computer simulation for heat treatment process named as IndBASEweb-HT was built up. The architecture and the arithmetic of this system as well as its application were introduced.

  13. Measuring the heat-transfer coefficient of nanofluid based on copper oxide in a cylindrical channel

    Science.gov (United States)

    Guzei, D. V.; Minakov, A. V.; Rudyak, V. Ya.; Dekterev, A. A.

    2014-03-01

    The heat-transfer coefficient of nanofluid during its flow in a cylindrical channel is studied experimentally. The studied nanofluid was prepared based on distilled water and CuO nanoparticles. Nanoparticle concentration varied in the range from 0.25 to 2% in the volume. The nanofluid was stabilized using a xanthane gum biopolymer the mass concentration of which did not exceed 0.03%. Considerable intensification of heat transfer was found. The nanofluid appeared to be Newtonian when particle concentrations exceeded 0.25%. Estimates for rheological parameters of the nanofluid and thermal conductivity coefficient have been obtained.

  14. Design and development of a shape memory alloy activated heat pipe-based thermal switch

    Science.gov (United States)

    Benafan, O.; Notardonato, W. U.; Meneghelli, B. J.; Vaidyanathan, R.

    2013-10-01

    This work reports on the design, fabrication and testing of a thermal switch wherein the open and closed states were actuated by shape memory alloy (SMA) elements while heat was transferred by a two-phase heat pipe. The motivation for such a switch comes from NASA’s need for thermal management in advanced spaceport applications associated with future lunar and Mars missions. As the temperature can approximately vary between -233 and 127 ° C during lunar day/night cycles, the switch was designed to reject heat from a cryogen tank into space during the night cycle while providing thermal isolation during the day cycle. A Ni47.1Ti49.6Fe3.3 (at.%) alloy that exhibited a reversible phase transformation between a trigonal R-phase and a cubic austenite phase was used as the sensing and actuating elements. Thermomechanical actuation, accomplished through an antagonistic spring system, resulted in strokes up to 7 mm against bias forces of up to 45 N. The actuation system was tested for more than thirty cycles, equivalent to one year of operation. The thermal performance, accomplished via a variable length, closed two-phase heat pipe, was evaluated, resulting in heat transfer rates of 13 W using pentane and 10 W using R-134a as working fluids. Experimental data were also compared to theoretical predictions where possible. Direct comparisons between different design approaches of SMA helical actuators, highlighting the effects of the helix angle, were carried out to give a layout of more accurate design methodologies.

  15. Examining Inclusion of Evidence-Based Practice on Social Work Training Program Websites

    Science.gov (United States)

    Wike, Traci L.; Bledsoe, Sarah E.; Bellamy, Jennifer L.; Grady, Melissa D.

    2013-01-01

    Websites represent a visible medium for social work programs to communicate information about social work research, academics, and professional training priorities, including evidence-based practice (EBP). However, few studies have examined the content of social work program websites. This exploratory study aimed to answer the question: Are EBP…

  16. Integrating Social Neuroscience and Social Work: Innovations for Advancing Practice-Based Research

    Science.gov (United States)

    Matto, Holly C.; Strolin-Goltzman, Jessica

    2010-01-01

    Throughout the social work profession, there is ongoing interest in building a social science agenda that can address the complex practice-based questions faced by social work professionals today. Methodological innovations and unique funding opportunities have already significantly advanced research on social work practice. Still, there is…

  17. Heat transfer and parametric studies of an encapsulated phase change material based cool thermal energy storage system

    Institute of Scientific and Technical Information of China (English)

    CHERALATHAN M.; VELRAJ R.; RENGANARAYANAN S.

    2006-01-01

    This work investigates the transient behaviour of a phase change material based cool thermal energy storage (CTES)system comprised of a cylindrical storage tank filled with encapsulated phase change materials (PCMs) in spherical container integrated with an ethylene glycol chiller plant. A simulation program was developed to evaluate the temperature histories of the heat transfer fluid (HTF) and the phase change material at any axial location during the charging period. The results of the model were validated by comparison with experimental results of temperature profiles of HTF and PCM. The model was also used to investigate the effect of porosity, Stanton number, Stefan number and Peclet number on CTES system performance. The results showed that increase in porosity contributes to a higher rate of energy storage. However, for a given geometry and heat transfer coefficient, the mass of PCM charged in the unit decreases as the increase in porosity. The St number as well as the Ste number is also influential in the performance of the unit. The model is a convenient and more suitable method to determine the heat transfer characteristics of CTES system. The results reported are much useful for designing CTES system.

  18. Three-zonal engineering method of heat calculation for fluidized bed furnaces based on data on commercial investigations of heat generation distribution during biomass combustion

    Science.gov (United States)

    Litun, D. S.; Ryabov, G. A.

    2016-02-01

    A three-zonal method of heat calculation of furnaces for combustion of biomass and low-caloric fuel in the fluidized bed is described. The method is based on equations of thermal and material balances that account for heat generation by fuel in the zone, heat-and-mass transfer heat exchange between the furnace media and surfaces that bound the zone, and heat-and-mass transfer between furnace zones. The calculation procedure for heat generation by fuel in the fluidized bed (FB) using the heat generation portion by the fuel is proposed. Based on commercial investigations, the main factors that affect the average temperature in the FB and the portion of fuel heat that is released in the FB are determined. Results of commercial investigations showed that the airflow coefficient in the FB should be recognized as the main operation parameter that affects the average temperature in the FB and, consequently, heat generation in the FB. The gas flow rate in the FB can be marked out as the second factor that affects the consumption degree of oxidizer supplied in the FB. Commercial investigations revealed that mixing is affected by the gas flow rate in the FB and the bed material particle size, which may be changed during the boiler operation because of the agglomeration of particles of sand and ash. The calculation processing of commercial investigations on a KM-75-40M boiler of a CHP-3 of an Arkhangelsk Pulp and Paper Mill (APPM), which was carried out using the inverse problem procedure by means of a developed computer program, determined the range of the fuel heat release share in the FB, which was 0.26-0.45 at an excess air factor of 0.59-0.93 in the bed, and the heat release share in the maximum temperature zone in the total heat release in the superbed space. The heat release share in the bed is determined as an approximating function of the excess air factor in the bed and the fluidization number. The research results can be used during designing boilers with the

  19. Total Heat Exchange Factor Based on Non-Gray Radiation Properties of Gas in Reheating Furnace

    Institute of Scientific and Technical Information of China (English)

    CUI Miao; CHEN Hai-geng; XU Li; WU Bin

    2009-01-01

    Modified mathematical models based on imaginary plane zone method in reheating furnace were developed in which non-gray radiation properties of gas were considered,and the Newton's method and the finite difference method were adopted.Effects of productivity,fuel consumption,fuel-air ratio,calorific value of fuel and inserting depth of thermocouple on total heat exchange factor along the length of reheating furnace were investigated.The resuits show that total heat exchange factor increases with productivity or inserting depth of thermocouple,and it decreases when fuel consumption,fuel-air ratio or calorific value of fuel increases.The results are valuable for dynamical compensation of total heat exchange factor for online control mathematical models in reheating furnace.

  20. Mixed Convective Peristaltic Flow of Water Based Nanofluids with Joule Heating and Convective Boundary Conditions.

    Science.gov (United States)

    Hayat, Tasawar; Nawaz, Sadaf; Alsaedi, Ahmed; Rafiq, Maimona

    2016-01-01

    Main objective of present study is to analyze the mixed convective peristaltic transport of water based nanofluids using five different nanoparticles i.e. (Al2O3, CuO, Cu, Ag and TiO2). Two thermal conductivity models namely the Maxwell's and Hamilton-Crosser's are used in this study. Hall and Joule heating effects are also given consideration. Convection boundary conditions are employed. Furthermore, viscous dissipation and heat generation/absorption are used to model the energy equation. Problem is simplified by employing lubrication approach. System of equations are solved numerically. Influence of pertinent parameters on the velocity and temperature are discussed. Also the heat transfer rate at the wall is observed for considered five nanofluids using the two phase models via graphs. PMID:27104596

  1. Parallel-cascade-based mechanisms for heating solar coronal loops: test against observations

    CERN Document Server

    Li, Bo; Li, Xing; Xia, Li-Dong

    2014-01-01

    The heating of solar coronal loops is at the center of the problem of coronal heating. Given that the origin of the fast solar wind has been tracked down to atmospheric layers with transition region or even chromospheric temperatures, it is worthy attempting to address whether the mechanisms proposed to provide the basal heating of the solar wind apply to coronal loops as well. We extend the loop studies based on a classical parallel-cascade scenario originally proposed in the solar wind context by considering the effects of loop expansion, and perform a parametric study to directly contrast the computed loop densities and electron temperatures with those measured by TRACE and YOHKOH/SXT. This comparison yields that with the wave amplitudes observationally constrained by SUMER measurements, while the computed loops may account for a significant fraction of SXT loops, they seem too hot when compared with TRACE loops. Lowering the wave amplitudes does not solve this discrepancy, introducing magnetic twist will ...

  2. Microstructural evolution of a forged TiAl based alloy during heat treatment at subtransus temperature

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Microstmctural evolution of a forged TiA1 based alloy during heat treatment from 1180 ℃ to 1300 ℃ was investigated. The grain sizes of the alpha phases as wel1 as the sizes and the volume fractions of the gamma phases were eval-uated as a function of heat treatment temperature and time. When the alloys are isothermally heat treated at subtransustemperatures, the sizes of gamma phases(Dγ) increase slightly with heat treatment temperature and time and those of al-pha phases(Da) and the volume fractions of gamma phases(γ) vary significantly with holding time in the early stages ofheat treatments, but after heat treatments for 2 h, γ reveal little variations with holding times and Da approach limits,which can be described by Da0 = 0. 65Dγ/γ. Besides, it has been found that the alpha phases in the specimens heattreated at 1 260 ℃ and 1 300 ℃ contain lamellar structures, at low temperatures, however, appear featureless

  3. The Development of Time-Based Prospective Memory in Childhood: The Role of Working Memory Updating

    Science.gov (United States)

    Voigt, Babett; Mahy, Caitlin E. V.; Ellis, Judi; Schnitzspahn, Katharina; Krause, Ivonne; Altgassen, Mareike; Kliegel, Matthias

    2014-01-01

    This large-scale study examined the development of time-based prospective memory (PM) across childhood and the roles that working memory updating and time monitoring play in driving age effects in PM performance. One hundred and ninety-seven children aged 5 to 14 years completed a time-based PM task where working memory updating load was…

  4. Implementing Evidence-Based Practice Education in Social Work: A Transdisciplinary Approach

    Science.gov (United States)

    Bellamy, Jennifer L.; Mullen, Edward J.; Satterfield, Jason M.; Newhouse, Robin P.; Ferguson, Molly; Brownson, Ross C.; Spring, Bonnie

    2013-01-01

    Evidence based practice (EBP) is reflected in social work publications, accreditation standards, research, and funding opportunities. However, implementing EBP in social work practice and education has proven challenging, highlighting the need for additional resources. This paper describes the Transdisciplinary Model of EBP, a model based on…

  5. A Professional Development Weblog: Supporting Work-Based Learning in a TAFE Library

    Science.gov (United States)

    Costa, Cathy

    2007-01-01

    This paper explores whether a professional development weblog could support work-based learning in a TAFE Library. The paper includes both a literature review of material dealing with work-based learning in the VET sector, weblogs and their possible use as a professional development tool and an evaluation of a weblog project devised to support…

  6. Energy Analysis and Multi-Objective Optimization of an Internal Combustion Engine-Based CHP System for Heat Recovery

    Directory of Open Access Journals (Sweden)

    Abdolsaeid Ganjehkaviri

    2014-10-01

    Full Text Available A comprehensive thermodynamic study is conducted of a diesel based Combined Heat and Power (CHP system, based on a diesel engine and an Organic Rankine Cycle (ORC. Present research covers both energy and exergy analyses along with a multi-objective optimization. In order to determine the irreversibilities in each component of the CHP system and assess the system performance, a complete parametric study is performed to investigate the effects of major design parameters and operating conditions on the system’s performance. The main contribution of the current research study is to conduct both exergy and multi-objective optimization of a system using different working fluid for low-grade heat recovery. In order to conduct the evolutionary based optimization, two objective functions are considered in the optimization; namely the system exergy efficiency, and the total cost rate of the system, which is a combination of the cost associated with environmental impact and the purchase cost of each component. Therefore, in the optimization approach, the overall cycle exergy efficiency is maximized satisfying several constraints while the total cost rate of the system is minimized. To provide a better understanding of the system under study, the Pareto frontier is shown for multi-objective optimization and also an equation is derived to fit the optimized point. In addition, a closed form relationship between exergy efficiency and total cost rate is derived.

  7. Possible unconventional superconductivity in iron-based layered compound LaFePO: Study of heat capacity

    OpenAIRE

    Kohama, Yoshimitsu; Kamihara, Yoichi; Kawaji, Hitoshi; Atake, Tooru; Hirano, Masahiro; Hosono, Hideo

    2008-01-01

    Heat capacity measurements were performed on recently discovered iron based layered superconductors, non doped LaFePO and fluorine doped LaFePO. A relatively large electronic heat capacity coefficient and a small normalized heat capacity jump at Tc = 3.3 K were observed in LaFePO. LaFePO0.94F0.06 had a smaller electronic heat capacity coefficient and a larger normalized heat capacity jump at Tc = 5.8 K. These values indicate that these compounds have strong electron electron correlation and m...

  8. Note: Design and development of improved indirectly heated cathode based strip electron gun

    Energy Technology Data Exchange (ETDEWEB)

    Maiti, Namita; Patil, D. S.; Dasgupta, K. [Laser and Plasma Technology Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Bade, Abhijeet; Tembhare, G. U. [Department of Mechanical Engineering, Veermata Jijabai Technological Institute, Matunga, Mumbai 400 019 (India)

    2015-02-15

    An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor the non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length.

  9. Note: Design and development of improved indirectly heated cathode based strip electron gun

    International Nuclear Information System (INIS)

    An improved design of indirectly heated solid cathode based electron gun (200 kW, 45 kV, 270° bent strip type electron gun) has been presented. The solid cathode is made of thoriated tungsten, which acts as an improved source of electron at lower temperature. So, high power operation is possible without affecting structural integrity of the electron gun. The design issues are addressed based on the uniformity of temperature on the solid cathode and the single long filament based design. The design approach consists of simulation followed by extensive experimentation. In the design, the effort has been put to tailor the non-uniformity of the heat flux from the filament to the solid cathode to obtain better uniformity of temperature on the solid cathode. Trial beam experiments have been carried out and it is seen that the modified design achieves one to one correspondence of the solid cathode length and the electron beam length

  10. Multiobjective optimization of GMAW process of the AA 6063-t5 alloy based on penetration and heat affected zone

    International Nuclear Information System (INIS)

    The selection of technological parameters in a welding process must be led to the optimized results of the operation. Penetration is one of the most decisive factors for the success of the joint. Another important factor is the Heat Affected Zone (HAZ), when the mechanical properties of this one are modified respecting to the base material. The way in which the technological variables of the process affects to both them, penetration and HAZ, are inverse in each case. This work presents an optimization methodology based on the Design of Experiments (DOE) and the Response Surface Method (RSM) of the GMAW process applied to the aluminum alloy AA 6063-T5. This research is focused to obtain penetration rates that make HAZ values to be suitable in current applications. Welding rate has been found to be the most significant technological parameter for controlling the process. (Author)

  11. Characterization and Simulation of the Heat Transfer Behaviour of Water-Based ZnO Nanofluids.

    Science.gov (United States)

    Colla, Laura; Marinelli, Lorenzo; Fedele, Laura; Bobbo, Sergio; Manca, Oronzio

    2015-05-01

    This paper deals with the characterization and modelling of water-based nanofluids containing zinc oxide (ZnO) nanoparticles in concentrations ranging between 1 and 10 wt%. Low concentrations were chosen to reduce fouling and excessive pressure drops. First of all, the stability was verified by means of an instrument, based on the dynamic light scattering (DLS) technique, measuring mean nanoparticle diameters and Zeta potential. Moreover, nanofluids pH was measured. Then, thermal conductivities and dynamic viscosities were measured, analysing their dependence on temperature and nanoparticle concentration. Thermal conductivity was measured by means of a hot disk apparatus in the temperature range between 10 and 70 degrees C, while viscosity was measured by a magnetic suspension rheometer in the same range of temperatures. Finally, the heat transfer capability of these fluids was studied measuring their heat transfer coefficients in a dedicated apparatus between 18 and 40 degrees C. Heat transfer coefficient was evaluated at different Reynolds number, in turbulent flow regime. Reynolds and Nusselt numbers were deduced by using previously measured thermal conductivity and viscosity values. Moreover, numerical simulations in two-dimensional turbulent and steady state flow were carried out. No increase in heat transfer coefficient in the temperature range between 18 and 40 degrees C was found. Comparison between experimental and numerical simulation data, in terms of wall temperature profiles, showed a good agreement.

  12. Development of an energy efficient and environmentally friendly drum dryer using a heat pump with CO2 as working fluid

    OpenAIRE

    Knoph, Øyvind Lomeland

    2014-01-01

    The drum dryer is a common appliance for drying clothes in households today. It is constantly developed in order to reduce its environmental impact and energy consumption. An industrial partner has initiated a research project with the aim to substitute R134a with CO2 as refrigerant. R134a has a global warming potential (GWP) 1300 times the GWP of CO2, thus CO2 is a much more environmental friendly refrigerant. A drum dryer driven by a heat pump was previously modified to use CO2 as refrigera...

  13. Overview of improvements in work practices and instrumentation for CANDU primary heat transport feeders in-service inspections

    International Nuclear Information System (INIS)

    The Canadian nuclear industry has developed many advanced non-destructive inspection techniques to be applied safely in hazardous environments in recent years. Automated systems, manual tooling and specialized software modules have been designed since early 2000s to provide complete and very efficient fitness for service inspection of primary heat transport system carbon steel feeder pipes. These techniques deal with complex geometries, difficult access and, radioactive environment. Complementary NDE techniques, namely Ultrasounds, eddy current, phased-array UT and automated scanners are used. This presentation describes the improvements in inspection practices and the advanced data analysis features. (author)

  14. Reflectance-Based Estimation of Soil Heat Fluxes in the Texas High Plains

    Science.gov (United States)

    Gowda, P. H.; Colaizzi, P. D.; O'Shaughnessy, S.; Ha, W.; Howell, T. A.

    2010-12-01

    Soil heat flux (G) is one of the terms required for estimating evapotranspiration rates using an energy balance. Numerous reflectance-based models are available in the literature for estimating G fluxes. However, these models have shown wide variation in their performance. Therefore, operational ET remote sensing programs may require locally developed/calibrated models for accurately estimating G. The objective of this study was to develop and evaluate reflectance-based empirical G models for the semi-arid Texas High Plains. Soil heat flux was measured at 0.15 hz interval and averaged every 15 minutes at five different locations within a 4.7 ha lysimeter field with Pullman clay loam soil during the 2010 summer growing season. The field was planted to soybean and managed under dryland conditions. In each location, G was measured at 8 cm depth with two Campbell Scientific HFT3 soil heat flux plates. Soil temperature was measured at 2 and 6 cm above the soil heat flux plates. Soil moisture was measured in the 2-8 cm layer using Acclima SDI-12 sensors. Hourly G fluxes at the surface were calculated by adding the measured G fluxes at 8 cm to the energy stored above the heat flux plates. A multispectral radiometer (MSR, CROPSCAN, Inc.) and hand-held thermometer (EVEREST Interscience Inc.) measured surface reflectance in red and near infrared bandwidths and surface temperature (ST), respectively, daily at 11:30 AM CST to be consistent with the Landsat 5 overpass time. Fraction crop cover (FC) was measured by digital photographs taken twice a week. A set of G models was developed for estimating hourly fluxes based on measured reflectance, net radiation, ST, NDVI, and FC,. Resulting models were compared for performance with existing models available in the literature. In this presentation, we will discuss our G models for the Texas High Plains and the statistical results.

  15. Mapping Heat-related Risks for Community-based Adaptation Planning under Uncertainty

    Science.gov (United States)

    Bai, Yingjiu; Kaneko, Ikuyo; Kobayashi, Hikaru; Kurihara, Kazuo; Sasaki, Hidetaka; Murata, Akihiko; Takayabu, Izuru

    2016-04-01

    Climate change is leading to more frequent and intense heat waves. Recently, epidemiologic findings on heat-related health impacts have reinforced our understanding of the mortality impacts of extreme heat. This research has several aims: 1) to promote climate prediction services with spatial and temporal information on heat-related risks, using GIS (Geographical Information System), and digital mapping techniques; 2) to propose a visualization approach to articulating the evolution of local heat-health responses over time and the evaluation of new interventions for the implementation of valid community-based adaptation strategies and reliable actionable planning; and 3) to provide an appropriate and simple method of adjusting bias and quantifying the uncertainty in future outcomes, so that regional climate projections may be transcribed into useful forms for a wide variety of different users. Following the 2003 European heat wave, climatologists, medical specialists, and social scientists expedited efforts to revise and integrate risk governance frameworks for communities to take appropriate and effective actions themselves. Recently, the Coupled Model Intercomparison Project (CMIP) methodology has made projections possible for anyone wanting to openly access state-of-the-art climate model outputs and climate data to provide the backbone for decisions. Furthermore, the latest high-solution regional climate model (RCM) has been a huge increase in the volumes of data available. In this study, we used high-quality hourly projections (5-km resolution) from the Non-Hydrostatic Regional Climate Model (NHRCM-5km), following the SRES-A1B scenario developed by the Meteorological Research Institute (MRI) and observational data from the Automated Meteorological Data Acquisition System, Japan Meteorological Agency (JMA). The NHRCM-5km is a dynamic downscaling of results from the MRI-AGCM3.2S (20-km resolution), an atmospheric general circulation model (AGCM) driven by the

  16. Analysis of X-33 Linear Aerospike Plume Induced Base-Heating Environment During Power-Pack Out

    Science.gov (United States)

    Wang, Ten-See; Williams, Robert; Droege, Alan; Dagnostino, Mark; Lee, Young-Ching; Douglas, Stan; Turner, James E. (Technical Monitor)

    2001-01-01

    The objectives of this viewgraph presentation are to predict the following: (1) dual-engine base-heating at 57% PL at sea level, and (2) dual-engine base-heating during PPO at three ascent abort trajectories. A systematically anchored computational fluid dynamics and heat transfer three-dimensional transfer simulation is being used to study the effect of reduced power levels on base-heating environments during sea level testing and during PPO. Preliminary results show the following: (1) convective heating is higher for the 57% PL than for 100% PL on most of the pillows and flex seals during sea level testing; and (2) convective heating on pillows and flex seals on the 'off' engine side is higher than that on the 'on' engine side.

  17. Numerical thermal analysis of water's boiling heat transfer based on a turbulent jet impingement on heated surface

    Science.gov (United States)

    Toghraie, D.

    2016-10-01

    In this study, a numerical method for simulation of flow boiling through subcooled jet on a hot surface with 800 °C has been presented. Volume fraction (VOF) has been used to simulate boiling heat transfer and investigation of the quench phenomena through fluid jet on a hot horizontal surface. Simulation has been done in a fixed Tsub=55 °C, Re=5000 to Re=50,000 and also in different Tsub =Tsat -Tf between 10 °C and 95 °C. The effect of fluid jet velocity and subcooled temperature on the rewetting temperature, wet zone propagation, cooling rate and maximum heat flux has been investigated. The results of this study show that by increasing the velocity of fluid jet of water, convective heat transfer coefficient at stagnation point increases. More ever, by decreasing the temperature of the fluid jet, convective heat transfer coefficient increases.

  18. The moderating effects of work-based and non-work based support on the relation between job insecurity and subsequent strain

    Directory of Open Access Journals (Sweden)

    K Näswall

    2005-10-01

    Full Text Available Job insecurity is a stressor empirically linked to various negative outcomes, such as impaired work attitudes and adverse health symptoms. Less is known about how these negative consequences can be buffered. The present study investigates whether work-based and non-work based social support moderate the relation between job insecurity and subsequent strain. The results, based on Swedish longitudinal questionnaire data, show that job insecurity predicted strain, even after controlling for demographic variables and baseline levels. Non-work based support moderated the negative effect of job insecurity on mental health complaints and somatic complaints after controlling for baseline levels. The results suggest that employees can benefit from their support network during times of turbulence. Opsomming Werksonsekerheid is ’n stressor wat emperies verband hou met verskeie negatiewe uitkomste soos verlaagde werksgesindhede en nadelige gesondheidssimptome. Minder is bekend oor hoe hierdie negatiewe gevolge gebuffer kan word. Die huidige studie ondersoek of werks gebaseerde en nie-werks gebaseerde sosiale ondersteuning die verhouding tussen werksonsekerheid en daaropvolgende spanning modereer. Die resultate, gebaseer op Sweedse longitudinale vraelysdata, toon dat werksonsekerheid spanning voorpsel het, selfs na die kontrolering vir demografiese veranderlikes en basislyn veranderlikes. Nie-werks gebaseerde ondersteuning het die negatiewe effek van werksonsekerheid op psigiese ongesteldhede en somatiese simptome gemodereer nadat gekontroleer vir basislyn veranderlikes is. Die resultate stel voor dat werknemers voordeel kan trek uit hulle ondersteunings netwerk gedurende tye van turbulensie.

  19. Heat Transfer Analysis of an Engine Exhaust-Based Thermoelectric Evaporation System

    Science.gov (United States)

    Chen, Ming; Tan, Gangfeng; Guo, Xuexun; Deng, Yadong; Zhang, Hongguang; Yang, Kai

    2016-03-01

    Engine exhaust can be used by thermoelectric generators for improving thermal efficiency of internal combustion engines. In his paper, the performance of a thermoelectric evaporation system is investigated. First, the thermal characteristics of diesel engines are obtained according to the experiment data. Then, mathematical models are created based on the specified conditions of the coolant cycle and the evaporator geometric parameters. Finally, the heat transfer characteristics and power performance of the thermoelectric evaporation system are estimated, and a comparison with the system in which the heat exchanger operates with all-liquid coolant is investigated. The results show that the overall heat transfer rate of the thermoelectric evaporator system increases with engine power. At the rated condition, the two-phase zone with an area of 0.8689 m2 dominates the evaporator's heat transfer area compared with the preheated zone area of 0.0055 m2, and for the thermoelectric module, the cold-side temperature is stable at 74°C while the hot-side temperature drops from 341.8°C to 304.9°C along the exhaust direction. For certain thermoelectric cells, the temperature difference between the cold side and hot side rises with the engine load, and the temperature difference drops from 266.9°C to 230.6°C along the exhaust direction. For two cold-side systems with the same heat transfer, coolant mass flow rate in the evaporator with two-phase state is much less, and the temperature difference along with equivalent heat transfer length L is significantly larger than in the all-liquid one. At rated power point, power generated by thermoelectric cells in the two-phase evaporation system is 508.4 W, while the other is only 328.8 W.

  20. Hydrodynamics and heat transfer in reactor components cooled by liquid metal coolants in single/two phase. 11. meeting of the International Association for Hydraulic Research (IAHR) Working Group. Working material

    International Nuclear Information System (INIS)

    This Working Material includes the papers presented at the International Meeting 'Hydrodynamics and heat transfer in reactor components cooled by liquid metal coolants in single/two-phase', which was held 5-9 July 2004 at the State Scientific Center of Russian Federation - Institute for Physics and Power Engineering named after A.I. Leypunsky, in Obninsk near Moscow. The objectives of the meeting were to discuss new results obtained in the field of liquid metal coolant and to recommend the lines of further general physics and applied investigations, with the purpose of validating existing and codes under development for liquid metal cooled advanced and new generation nuclear reactors. Most of the contributions present results of experimental and numerical investigations into velocity, temperature and heat transfer in fuel subassemblies of fast reactors cooled by sodium or lead. In the frame of the meeting a benchmark problem devoted to heat transfer in the model subassembly of the fast reactor BREST-OD-300 was proposed. Experts from 5 countries (Japan, Netherlands, Spain, Republic of Korea, and Russia) took part in this benchmark exercise. The results of the benchmark calculations are summarized in the Working Material. The results of hydrodynamic studies of pressure head chambers and collector systems of liquid metal cooled reactors are presented in a number of papers. Also attention was given to the generalization of experimental data on hydraulic losses in the pipelines in case of mutual influence of local pressure drops, and to the modeling of natural convection in the fuel subassemblies and circuits with liquid metal cooling. Special emphasis at the meeting was placed on thermal hydraulics issues related to the development and design of target systems, such as heat removal in the target unit of the cascade subcritical reactor cooled by liquid salt; the target complex MK-1 for accelerator driven systems cooled by eutectic lead-bismuth alloy; and the test

  1. Quantitative Assessment of the Condensed Phase Heats of Reaction in a Double Base Propellant

    Directory of Open Access Journals (Sweden)

    K. Kishore

    1985-01-01

    Full Text Available Heat of decomposition of the double base propellant has been calculated from the knowledge of the composition and decomposition enthalpy of the ingredients. This was compared with the experimentally observed value of the propellant decomposition which suggested that condensed phase contribution is very marginal (one twentieth of the total calorimetric value in double base propellants unlike composite solid propellants where condensed phase contribution is as high as one third. The condensed-phase in double base propellant was attributed to the nitration of the 2n-diphenylamine stabilizer in the propellant matrix.

  2. The Self-Heating Effect of Quantum Cascade Lasers Based on a Spectroscopic Method

    Institute of Scientific and Technical Information of China (English)

    WEI Lin; LI Ai-Zhen; ZHANG Yong-Gang; LI Yao-Yao

    2009-01-01

    We investigate the self-heating effect of mid-infrared quantum cascade lasers by using a direct-based pulse injecting current and spectroscopy method.Based on the characterization system,the thermal characteristics of gas source MBE grown 8.4μm InP-based GaInAs/AlInAs DFB-QCLs are evaluated.The method and characterization system are also useful in evaluating the therma/characteristics of other types of mid-infrared diode lasers.

  3. Will domestic consumers take up the renewable heat incentive? An analysis of the barriers to heat pump adoption using agent-based modelling

    International Nuclear Information System (INIS)

    The UK Government introduced the tariff-based domestic Renewable Heat Incentive (RHI) in April 2014 to encourage installation of renewable heat technologies as a key component of its carbon reduction policy. Of these, heat pumps are considered to be the most promising for widespread adoption and as such are the subject of this paper. Pilot studies prior to introduction of the policy identified non-financial barriers to uptake, such as the “hassle factor” involved, and initial figures indeed indicate that uptake is lower than expected. We analyse these non-financial barriers using an agent-based model and conclude that there is a tipping point beyond which adoption is likely to fall very sharply. We suggest that the RHI’s complex and stringent compliance requirements for home inspections and heat emitter performance may well have driven adoption past this point and that further intervention may be required if the key aims of the RHI are to be achieved. -- Highlights: •We examine the uptake of the UK Renewable Heat Incentive (RHI). •We use Agent-based modelling to simulate uptake in a heterogeneous population. •Simulation modelling suggests that uptake is sensitive to non-financial barriers. •Non-financial barriers were introduced after RHI policy impact assessment. •New barriers combined with sensitivity could explain observed lower than expected uptake

  4. Thermodynamical analysis of a quantum heat engine based on harmonic oscillators.

    Science.gov (United States)

    Insinga, Andrea; Andresen, Bjarne; Salamon, Peter

    2016-07-01

    Many models of heat engines have been studied with the tools of finite-time thermodynamics and an ensemble of independent quantum systems as the working fluid. Because of their convenient analytical properties, harmonic oscillators are the most frequently used example of a quantum system. We analyze different thermodynamical aspects with the final aim of the optimization of the performance of the engine in terms of the mechanical power provided during a finite-time Otto cycle. The heat exchange mechanism between the working fluid and the thermal reservoirs is provided by the Lindblad formalism. We describe an analytical method to find the limit cycle and give conditions for a stable limit cycle to exist. We explore the power production landscape as the duration of the four branches of the cycle are varied for short times, intermediate times, and special frictionless times. For short times we find a periodic structure with atolls of purely dissipative operation surrounding islands of divergent behavior where, rather than tending to a limit cycle, the working fluid accumulates more and more energy. For frictionless times the periodic structure is gone and we come very close to the global optimal operation. The global optimum is found and interestingly comes with a particular value of the cycle time. PMID:27575089

  5. Thermodynamical analysis of a quantum heat engine based on harmonic oscillators

    Science.gov (United States)

    Insinga, Andrea; Andresen, Bjarne; Salamon, Peter

    2016-07-01

    Many models of heat engines have been studied with the tools of finite-time thermodynamics and an ensemble of independent quantum systems as the working fluid. Because of their convenient analytical properties, harmonic oscillators are the most frequently used example of a quantum system. We analyze different thermodynamical aspects with the final aim of the optimization of the performance of the engine in terms of the mechanical power provided during a finite-time Otto cycle. The heat exchange mechanism between the working fluid and the thermal reservoirs is provided by the Lindblad formalism. We describe an analytical method to find the limit cycle and give conditions for a stable limit cycle to exist. We explore the power production landscape as the duration of the four branches of the cycle are varied for short times, intermediate times, and special frictionless times. For short times we find a periodic structure with atolls of purely dissipative operation surrounding islands of divergent behavior where, rather than tending to a limit cycle, the working fluid accumulates more and more energy. For frictionless times the periodic structure is gone and we come very close to the global optimal operation. The global optimum is found and interestingly comes with a particular value of the cycle time.

  6. Solar supported air heating of existing factory buildings; Solar unterstuetzte Luftheizung von Industriehallen im Bestand

    Energy Technology Data Exchange (ETDEWEB)

    Lomachenko, Olga; Urbaneck, Thorsten; Platzer, Bernd [Technische Univ. Chemnitz (Germany). Fakultaet fuer Maschinenbau

    2011-01-15

    The use of solar heating systems for heating of factory buildings is not widely spread today. However, by using solar heating systems large quantities of energy could be saved. The studies on solar systems are primarily focused on design of solar heating systems for apartment heating. Air heating in combination with solar heating system was until today barely analyzed and optimized. Up to now there are almost no studies on combination of air heating with solar heating conducted. In this work a study of decentralized air heating of an existing factory building in combination with solar heating device is conducted. The study is based on numerical simulation with TRNSYS simulation program. (orig.)

  7. Linear Fresnel Reflector based Solar Radiation Concentrator for Combined Heating and Power

    Science.gov (United States)

    Chatterjee, Aveek; Bernal, Eva; Seshadri, Satya; Mayer, Oliver; Greaves, Mikal

    2011-12-01

    We have designed and realized a test rig to characterize concentrated solar-based CHP (combined heat and power) generator. Cost benefit analysis has been used to compare alternate technologies, which can cogenerate electrical and thermal power. We have summarized the experimental setup and methods to characterize a concentrated solar thermal (CST) unit. In this paper, we demonstrate the performance data of a concentrated solar thermal system.

  8. A GIS extension model to calculate urban heat island intensity based on urban geometry

    OpenAIRE

    Nakata, C. M.; Souza, Léa Cristina Lucas; Rodrigues, Daniel Souto

    2015-01-01

    This paper presents a simulation model, which was incorporated into a Geographic Information System (GIS), in order to calculate the maximum intensity of urban heat islands based on urban geometry data. The method-ology of this study stands on a theoretical-numerical basis (Okeâ s model), followed by the study and selection of existing GIS tools, the design of the calculation model, the incorporation of the resulting algorithm into the GIS platform and the application of the tool, developed ...

  9. HCCI Heat Release Data for Combustion Simulation, based on Results from a Turbocharged Multi Cylinder Engine

    OpenAIRE

    Johansson, Thomas; Borgqvist, Patrick; Johansson, Bengt; Tunestål, Per; Aulin, Hans

    2010-01-01

    When simulating homogenous charge compression ignition or HCCI using one-dimensional models it is important to have the right combustion parameters. When operating in HCCI the heat release parameters will have a high influence on the simulation result due to the rapid combustion rate, especially if the engine is turbocharged. In this paper an extensive testing data base is used for showing the combustion data from a turbocharged engine operating in HCCI mode. The experimental data cover a wid...

  10. Heat-power working regimes of a high-frequency (0.44 MHz) 1000-kW induction plasmatron

    Science.gov (United States)

    Gorbanenko, V. M.; Farnasov, G. A.; Lisafin, A. B.

    2015-12-01

    The energy working regimes of a superpower high-frequency induction (HFI) plasmatron with a high-frequency (HF) generator are studied. The HFI plasmatron with a power of 1000 kVA and a working frequency of 440 kHz, in which air is used as a plasma-forming gas, can be used for treatment of various oxide powder materials. The energy regimes substantially influence finish products and their costs. Various working regimes of the HFI plasma unit and the following characteristics are studied: the dependence of the vibration power on the anode power, the dependence of the power losses on the anode power at various of plasma-forming gas flow rates, and the coefficients of efficiency of the plasmatron and the HFI-plasma unit at various powers. The effect of the plasma-forming gas flow rate on the bulk temperature is determined.

  11. Thermo-Economic and Heat Transfer Optimization of Working-Fluid Mixtures in a Low-Temperature Organic Rankine Cycle System

    Directory of Open Access Journals (Sweden)

    Oyeniyi A. Oyewunmi

    2016-06-01

    Full Text Available In the present paper, we consider the employment of working-fluid mixtures in organic Rankine cycle (ORC systems with respect to thermodynamic and heat-transfer performance, component sizing and capital costs. The selected working-fluid mixtures promise reduced exergy losses due to their non-isothermal phase-change behaviour, and thus improved cycle efficiencies and power outputs over their respective pure-fluid components. A multi-objective cost-power optimization of a specific low-temperature ORC system (operating with geothermal water at 98 °C reveals that the use of working-fluid-mixtures does indeed show a thermodynamic improvement over the pure-fluids. At the same time, heat transfer and cost analyses, however, suggest that it also requires larger evaporators, condensers and expanders; thus, the resulting ORC systems are also associated with higher costs. In particular, 50% n-pentane + 50% n-hexane and 60% R-245fa + 40% R-227ea mixtures lead to the thermodynamically optimal cycles, whereas pure n-pentane and pure R-245fa have lower plant costs, both estimated as having ∼14% lower costs per unit power output compared to the thermodynamically optimal mixtures. These conclusions highlight the importance of using system cost minimization as a design objective for ORC plants.

  12. Silicon Heat Pipe Array

    Science.gov (United States)

    Yee, Karl Y.; Ganapathi, Gani B.; Sunada, Eric T.; Bae, Youngsam; Miller, Jennifer R.; Beinsford, Daniel F.

    2013-01-01

    Improved methods of heat dissipation are required for modern, high-power density electronic systems. As increased functionality is progressively compacted into decreasing volumes, this need will be exacerbated. High-performance chip power is predicted to increase monotonically and rapidly with time. Systems utilizing these chips are currently reliant upon decades of old cooling technology. Heat pipes offer a solution to this problem. Heat pipes are passive, self-contained, two-phase heat dissipation devices. Heat conducted into the device through a wick structure converts the working fluid into a vapor, which then releases the heat via condensation after being transported away from the heat source. Heat pipes have high thermal conductivities, are inexpensive, and have been utilized in previous space missions. However, the cylindrical geometry of commercial heat pipes is a poor fit to the planar geometries of microelectronic assemblies, the copper that commercial heat pipes are typically constructed of is a poor CTE (coefficient of thermal expansion) match to the semiconductor die utilized in these assemblies, and the functionality and reliability of heat pipes in general is strongly dependent on the orientation of the assembly with respect to the gravity vector. What is needed is a planar, semiconductor-based heat pipe array that can be used for cooling of generic MCM (multichip module) assemblies that can also function in all orientations. Such a structure would not only have applications in the cooling of space electronics, but would have commercial applications as well (e.g. cooling of microprocessors and high-power laser diodes). This technology is an improvement over existing heat pipe designs due to the finer porosity of the wick, which enhances capillary pumping pressure, resulting in greater effective thermal conductivity and performance in any orientation with respect to the gravity vector. In addition, it is constructed of silicon, and thus is better

  13. Balancing incident heat and ion flow for process optimization in plasma based ion implantation

    International Nuclear Information System (INIS)

    Plasma based ion implantation at elevated temperatures is a technology often used to obtain thick surface layers of several μm by thermally activated diffusion, e.g. nitrogen in steel, titanium or aluminium. By lowering the pulse voltage at constant temperature, the current density can be increased at a constant heat flow. However, an upper limit is given by the ratio of the diffusion rate transporting the implanted ions from the surface towards the bulk and the sputter yield. This sputtering of the surface dominates for very high current densities and limits the maximum achievable layer thickness. Different maximum current densities were found for the four investigated systems - nitrogen in different steel grades, aluminium and titanium, as well as oxygen in titanium - reflecting the varying diffusivities. Additional requirements, besides the maximum current density, as a conformal treatment for complex objects containing small holes or trenches, as well as short heating times, can be solved most effectively by pulsed voltages in the range of 2-5 kV and an additional heating of the sample. The problem of a sample cooling time of several hours after the treatment is recognized. A partial solution would be to increase the gas pressure during the cooling phase for a more effective heat dissipation. (author)

  14. The Bermuda Triangle mysteries: an explanation based on the diffraction of heat waves

    Energy Technology Data Exchange (ETDEWEB)

    Njau, E.C. [Dar es Salaam Univ. (Tanzania, United Republic of). Dept. of Physics

    1995-12-31

    Studies based on actual meteorological records [E.C. Njau, Nuovo Cimento 15C, 17-23 (1992)] as well as analytical methods [E.C. Njau, Proc. Ind. Natn. Sci. Acad., 61A (4) (1995); Renewable Energy 4, 261-263 (1994)] have established the continuous existence of a series of large-scale, Eastward-moving heat waves along the Earth`s surface, whose individual crests and troughs are stretched approximately along the geographical North-South direction. In moving across the American continent, these waves encounter a line of physical barriers formed by the lofty Rocky and Andes ranges of mountains, which is continuous except for a significant gap or opening between Colombia and Mexico. This line of physical barriers consistently maintains a maximum height of 3000-4000 m between latitudes 40{sup o}S and 55{sup o}N except for a significant opening or slit located between Mexico and Colombia where the maximum height hardly exceeds 600 m. The Eastward-moving heat waves are thus incident obliquely on an approximately single-slit barrier when crossing the American continent and those parts of the waves which filter through this single slit essentially form some kind of single-slit diffraction (heat) patterns in, around and past the Bermuda Triangle. These diffraction heat patterns give rise to corresponding weather and ocean patterns which, to a large extent, account for the mysteries already noted in the Bermuda region. (Author)

  15. Surface chemistry of polyacrylonitrile- and rayon-based activated carbon fibers after post-heat treatment

    Energy Technology Data Exchange (ETDEWEB)

    Chiang Yuchun [Department of Mechanical Engineering, Yuan Ze University, 135 Yuan-Tung Road, Chung-Li, Taoyuan 320, Taiwan (China)]. E-mail: ycchiang@saturn.yzu.edu.tw; Lee, C.-Y. [Department of Mechanical Engineering, Yuan Ze University, 135 Yuan-Tung Road, Chung-Li, Taoyuan 320, Taiwan (China); Lee, H.-C. [Department of Mechanical Engineering, Yuan Ze University, 135 Yuan-Tung Road, Chung-Li, Taoyuan 320, Taiwan (China)

    2007-01-15

    Polyacrylonitrile- and rayon-based activated carbon fibers (ACFs) subject to heat treatment were investigated by means of elemental analyzer, and X-ray photoelectron spectroscopy (XPS). The total ash content of all ACFs was also analyzed. The adsorption of benzene, carbon tetrachloride and water vapor on ACFs was determined to shed light on the role of surface chemistry on gas adsorption. Results show that different precursors resulted in various elemental compositions and imposed diverse influence upon surface functionalities after heat treatment. The surface of heat-treated ACFs became more graphitic and hydrophobic. Three distinct peaks due to C, N, and O atoms were identified by XPS, and the high-resolution revealed the existence of several surface functionalities. The presence of nitride-like species, aromatic N-imines, or chemisorbed nitrogen oxides was found to be of great advantage to adsorption of water vapor or benzene, but the pyridine-N was not. Unstable complexes on the surface would hinder the fibers from adsorption of carbon tetrachloride. The rise in total ash content or hydrogen composition was of benefit to the access of water vapor. Modifications of ACFs by heat treatment have effectively improved adsorption performance.

  16. Combined mass and heat exchange network synthesis based on stage-wise superstructure model☆

    Institute of Scientific and Technical Information of China (English)

    Linlin Liu; Jian Du; Fenglin Yang

    2015-01-01

    Integrating multiple systems into one has become an important trend in Process Systems Engineering research field since there is strong demand from the modern industries. In this study, a stage-wise superstructure-based method is proposed to synthesize a combined mass and heat exchange network (CM&HEN) which has two parts as the mass exchange network (MEN) and heat exchange network (HEN) involved. To express the pos-sible heat exchange requirements resulted from mass exchange operations, a so cal ed“indistinct HEN super-structure (IHS)”, which can contain the all potential matches between streams, is constructed at first. Then, a non-linear programming (NLP) mathematical model is established for the simultaneous synthesis and optimiza-tion of networks. Therein, the interaction between mass exchange and heat exchange is modeling formulated. The NLP model has later been examined using an example from literature, and the effectiveness of the proposed method has been demonstrated with the results.

  17. Characterization of Metarhizium species and varieties based on molecular analysis, heat tolerance and cold activity

    Science.gov (United States)

    Fernandes, E.K.K.; Keyser, C.A.; Chong, J.P.; Rangel, D.E.N.; Miller, M.P.; Roberts, D.W.

    2010-01-01

    Aims: The genetic relationships and conidial tolerances to high and low temperatures were determined for isolates of several Metarhizium species and varieties. Methods and Results: Molecular-based techniques [AFLP and rDNA (ITS1, ITS2 and 5??8S) gene sequencing] were used to characterize morphologically identified Metarhizium spp. isolates from a wide range of sources. Conidial suspensions of isolates were exposed to wet heat (45 ?? 0??2??C) and plated on potato dextrose agar plus yeast extract (PDAY) medium. After 8-h exposure, the isolates divided clearly into two groups: (i) all isolates of Metarhizium anisopliae var. anisopliae (Ma-an) and Metarhizium from the flavoviride complex (Mf) had virtually zero conidial relative germination (RG), (ii) Metarhizium anisopliae var. acridum (Ma-ac) isolates demonstrated high heat tolerance (c. 70-100% RG). Conidial suspensions also were plated on PDAY and incubated at 5??C for 15 days, during which time RGs for Ma-an and Ma-ac isolates were virtually zero, whereas the two Mf were highly cold active (100% RG). Conclusions: Heat and cold exposures can be used as rapid tools to tentatively identify some important Metarhizium species and varieties. Significance and Impact of the Study: Identification of Metarhizium spp. currently relies primarily on DNA-based methods; we suggest a simple temperature-based screen to quickly obtain tentative identification of isolates as to species or species complexes. ?? 2009 The Society for Applied Microbiology.

  18. Irreversible three-heat-source refrigerator with heat transfer law of Q{alpha}{delta}(T{sup -1}) and its performance optimization based on ECOP criterion

    Energy Technology Data Exchange (ETDEWEB)

    Ngouateu Wouagfack, Paiguy Armand [University of Dschang, L2MSP, Department of Physics, PO Box 67, Dschang (Cameroon); Tchinda, Rene [University of Dschang, LISIE, University Institute of Technology Fotso Victor, PO Box 134, Bandjoun (Cameroon)

    2011-11-15

    The new thermo-ecological optimization of an absorption system for cooling applications operating between three temperature levels with the linear phenomenological heat transfer law of Q{alpha}{delta}(T{sup -} {sup 1}) has been performed by taking account the losses of heat resistance, internal irreversibility and leakage. The considered objective function is the ecological coefficient of performance (ECOP) and is defined as the cooling load per unit loss rate of availability. The comparative analysis with the ecological optimization criterion (E) defined in the literature and also with the cooling load optimization criterion (R) has been carried out to prove the utility of the new thermo-ecological optimization criterion (ECOP) for three-heat-source refrigerators with linear phenomenological heat transfer law. The results show that the three-heat-source refrigeration cycle working at maximum ECOP conditions has a significant advantage in terms of entropy production rate and coefficient of performance over the maximum E and maximum R conditions. The obtained results may provide a general theoretical tool for the thermo-ecological design of absorption refrigerator. (orig.)

  19. Consideration on the analytical method for heat anomalies based on distribution of heat discharge by hot springs

    International Nuclear Information System (INIS)

    Distribution of heat discharge by hot spring is a valuable feature for evaluating geologic repository site because it reflects both underground temperature and underground hydrologic conditions. Considering preparatory procedure of updating the manner of heat discharge calculation, several points have been noted. The following two points are particularly significant. For the time being naturally discharging hot springs occupy about 30 percent of the total amount of hot spring water in Japan. Therefore (1) we must evaluate natural discharge and pumped hot water separately. Recently developed hot springs, especially those by deep wells, are likely to be suffered from changes in their condition such as decrease in water temperature and/or production rate in a shot period after development. Therefore (2) hot spring data should be carefully treated for evaluating heat discharge by them. (author)

  20. Selection and optimization of pure and mixed working fluids for low grade heat utilization using organic Rankine cycles

    DEFF Research Database (Denmark)

    Andreasen, Jesper Graa; Larsen, Ulrik; Knudsen, Thomas;

    2014-01-01

    We present a generic methodology for organic Rankine cycle optimization, where the working fluid is included as an optimization parameter, in order to maximize the net power output of the cycle. The method is applied on two optimization cases with hot fluid inlet temperatures at 120°C and 90°C. P...

  1. Membrane-Based Osmotic Heat Engine with Organic Solvent for Enhanced Power Generation from Low-Grade Heat

    Energy Technology Data Exchange (ETDEWEB)

    Shaulsky, E; Boo, C; Lin, SH; Elimelech, M

    2015-05-05

    We present a hybrid osmotic heat engine (OHE) system that uses draw solutions with an organic solvent for enhanced thermal separation efficiency. The hybrid OHE system produces sustainable energy by combining pressure-retarded osmosis (PRO) as a power generation stage and membrane distillation (MD) utilizing low-grade heat as a separation stage. While previous OHE systems employed aqueous electrolyte draw solutions, using methanol as a solvent is advantageous because methanol is highly volatile and has a lower heat capacity and enthalpy of vaporization than water. Hence, the thermal separation efficiency of a draw solution with methanol would be higher than that of an aqueous draw solution. In this study, we evaluated the performance of LiCl-methanol as a potential draw solution for a PRO-MD hybrid OHE system. The membrane transport properties as well as performance with LiCl methanol draw solution were evaluated using thin-film composite (TFC) PRO membranes and compared to the results obtained with a LiCl water draw solution. Experimental PRO methanol flux and maximum projected power density of 47.1 L m(-2) h(-1) and 72.1 W m(-2), respectively, were achieved with a 3 M LiCl-methanol draw solution. The overall efficiency of the hybrid OHE system was modeled by coupling the mass and energy flows between the thermal separation (MD) and power generation (PRO) stages under conditions with and without heat recovery. The modeling results demonstrate higher ORE energy efficiency with the LiCl methanol draw solution compared to that with the LiCl water draw solution under practical operating conditions (i.e., heat recovery <90%). We discuss the implications of the results for converting low-grade heat to power.

  2. School based working memory training: Preliminary finding of improvement in children’s mathematical performance

    OpenAIRE

    Witt, Marcus

    2011-01-01

    Working memory is a complex cognitive system responsible for the concurrent storage and processing of information. Ggiven that a complex cognitive task like mental arithmetic clearly places demands on working memory (e.g., in remembering partial results, monitoring progress through a multi-step calculation), there is surprisingly little research exploring the possibility of increasing young children’s working memory capacity through systematic school-based training. Tthis study reports the pr...

  3. Simulation Based Assessment of Heat Pumping Potential in Non-Residential Buildings – Part 1: Modeling

    OpenAIRE

    Bertagnolio, Stéphane; Stabat, Pascal; Soccal, Benjamin; Gendebien, Samuel; Andre, Philippe

    2010-01-01

    1 Introduction A solution to reduce the energy consumption in office and health care buildings consist in better exploiting the potential of the heat pump technology. This can be done by recovering heat at the condenser when the chiller is used to produce cold (simultaneous heating and cooling demands) or by using the chiller in heat pump mode (non-simultaneous heating and cooling demands). Both strategies appear particularly feasible when cooling and heating needs and the heat pump techno...

  4. Micro-cogeneration units based on Stirling engine for heating and their real operation

    Science.gov (United States)

    Čierny, Jaroslav; Patsch, Marek

    2014-08-01

    This article was deal with micro-cogeneration units based on Stirling engine. We watched problematic of real working Stirling engine. The article also contain hookup of unit constructed at University of Zilina.

  5. Competitivity of biofuels in heating

    International Nuclear Information System (INIS)

    The competitivity of indigenous fuels in heating of residential houses in comparison with imported fuels, and both electricity and district heating, has been studied in this research, ordered by the Finnish Ministry of Trade and Industry. Heating plants of residential house scale (20-1000 kW) have been investigated in the research. Only the new heating plants are included in the investigation. The heat generation calculations concerning the residential heating plants have been made for following indigenous fuels: sod peat, fuel-chips, peat and wood pellets, firewood and straw. In addition to these, the calculations have been made for light fuel-oil, electric heating, district heating and natural gas. The local energy tariffs have to be taken into account in electric heating, district heating and natural gas heating. A calculation model, based on flowsheet calculation, forms the main result of the project. By using the model it is possible to update the competitivity data rapidly. Of all the indigenous fuels, sod peat and fuel-chips appeared to be competitive with electric and district heating costs in nearly all scales investigated. The construction of the heat generation costs of solid indigenous fuels differs remarkably from those of electric and district heating. The main part of the heating costs of wood chips and sod peat is formed of fixed costs; i.e. of investment costs and of the costs of heating and control work. The energy costs are the highest costs items in electric an district heating, as well as in the oil heating. It is possible to improve the competitivity of biofuels by developing cheaper boilers and fuel processing and storage devices

  6. Angle-dependent quantum Otto heat engine based on coherent dipole-dipole coupling

    Science.gov (United States)

    Su, Shan-He; Luo, Xiao-Qing; Chen, Jin-Can; Sun, Chang-Pu

    2016-08-01

    Electromagnetic interactions between molecules or within a molecule have been widely observed in biological systems and exhibit broad application for molecular structural studies. Quantum delocalization of molecular dipole moments has inspired researchers to explore new avenues to utilize this physical effect for energy harvesting devices. Herein, we propose a simple model of the angle-dependent quantum Otto heat engine which seeks to facilitate the conversion of heat to work. Unlike previous studies, the adiabatic processes are accomplished by varying only the directions of the magnetic field. We show that the heat engine continues to generate power when the angle relative to the vector r joining the centres of coupled dipoles departs from the magic angle θm where the static coupling vanishes. A significant improvement in the device performance has to be attributed to the presence of the quantum delocalized levels associated with the coherent dipole-dipole coupling. These results obtained may provide a promising model for the biomimetic design and fabrication of quantum energy generators.

  7. Low-power microwave-mediated heating for microchip-based PCR.

    Science.gov (United States)

    Marchiarullo, Daniel J; Sklavounos, Angelique H; Oh, Kyudam; Poe, Brian L; Barker, N Scott; Landers, James P

    2013-09-01

    Microwave energy has been used to rapidly heat food and drinks for decades, in addition to assisting other chemical reactions. However, only recently has microwave energy been applied in microfluidic systems to heat solution in reaction chambers, in particular, the polymerase chain reaction (PCR). One of the difficulties in developing microwave-mediated heating on a microchip is the construction of the appropriate architecture for delivery of the energy to specific micro-areas on the microchip. This work employs commercially-available microwave components commonly used in the wireless communications industry to generate a microwave signal, and a microstrip transmission line to deliver the energy to a 1 μL reaction chamber fabricated in plastic microdevices. A model was developed to create transmission lines that would optimally transmit energy to the reaction chamber at a given frequency, minimizing energy usage while focusing microwave delivery to the target chamber. Two different temperature control methods were demonstrated, varying microwave power or frequency. This system was used to amplify a fragment of the lambda-phage genome, thereby demonstrating its potential for integration into a portable PCR system. PMID:23843031

  8. Reflection in Work-Based Learning: Self-Regulation or Self-Liberation?

    Science.gov (United States)

    Siebert, Sabina; Walsh, Anita

    2013-01-01

    This article considers the role of reflective practice in work-based learning in higher education. The benefits of using reflection for learning at work have been widely recognised and the pedagogy to support reflection is now established. However, the use of reflective practice has been subjected to considerable critique, and many of the…

  9. Assessment of Work-based Learning: Some Lessons from the Teaching Profession.

    Science.gov (United States)

    Coll, Richard K.; Taylor, Neil; Grainger, Sheila

    2002-01-01

    Examination of methods of assessing teaching practica resulted in the following recommendations for other work-based learning programs: (1) identify whether the purpose is technical competence, professional artistry, or both; (2) determine the objectives for work placements; (3) identify the roles of academic and industry staff; and (4) determine…

  10. Web-Based Social Work Courses: Guidelines for Developing and Implementing an Online Environment

    Science.gov (United States)

    Dawson, Beverly Araujo; Fenster, Judy

    2015-01-01

    Although web-based courses in schools of social work have proliferated over the past decade, the literature contains few guidelines on steps that schools can take to develop such courses. Using Knowles's framework, which delineates tasks and themes involved in implementing e-learning in social work education, this article describes the cultivation…

  11. Service Learning and Community-Based Partnerships: A Model for Teaching Macro Practice Social Work

    Science.gov (United States)

    Nandan, Monica; Scott, Patricia

    2011-01-01

    This article describes an innovative project that combined service learning and community-based partnerships to teach macro practice skills to social work students and citizenship skills to primary school students. The partners, a small social work program, several primary schools, and an internationally recognized civic engagement program,…

  12. Critical elements in defining work-based identity in a post-apartheid South Africa

    Directory of Open Access Journals (Sweden)

    Sandra Lloyd

    2011-03-01

    Full Text Available Orientation: The main focus of the study was to answer the question: ‘Who am I at work?’ in a post-apartheid South African organisation.Research purpose: The aim of the specific research questions was to determine which life sphere and life role elements, and which work-based identity facets were significant in forming work-based identity.Motivation for the study: The findings of the study will enable the formulation of an integrative definition of work-based identity applicable to the South African context.Research design, approach and method: Qualitative data was collected by means of unstructured interviews with 29 employees representing a range of job titles, levels and demographics in a large South African manufacturing company. A grounded theory approach (open and axial coding was used to analyse the data.Main findings: Distinctive individual self-definitions and a number of common themes integrating social and personal identity perspectives emerged from the data. These themes provided a sound basis for the proposed integrative model to define work-based identity.Practical/managerial implications: The findings of this research will assist human resource practitioners to develop training interventions and management strategies for the potential enhancement of work-based identities. This will result in a more engaged and harmonised workforce.Contribution/value-add: This was the first study of its kind to identify and delineate significant work-based identity elements for the formation of a work-based identity within a South African work context.

  13. Higher Education Quality and Work-Based Learning: Two Concepts Not yet Fully Integrated

    Science.gov (United States)

    Gibbs, Paul; Armsby, Pauline

    2010-01-01

    This short paper recognises the growth in emphasis in work-based learning as Europe moves forward on economically driven life-long learning. We support such a move and point to issues which still need to be resolved.

  14. Scanned Hardcopy Maps, legato data base; public works, Published in 2006, Washoe County.

    Data.gov (United States)

    NSGIC GIS Inventory (aka Ramona) — This Scanned Hardcopy Maps dataset, was produced all or in part from Hardcopy Maps information as of 2006. It is described as 'legato data base; public works'. Data...

  15. HEAT PUMP USING SUBSOIL WATERS AS LOW TEMPERATURE HEAT SOURCE

    Directory of Open Access Journals (Sweden)

    Denysova Alla

    2015-08-01

    Full Text Available One of the basic directions of perfection of heat supply systems is the tendency of transition to the low-temperature heating systems based on application of heat pump installations. We consider heat supply system with heat pump installations using subsoil waters. Numerical simulation of thermal processes in the elements of a single-stage and double-stage heat pump systems has been worked out. Values of depths of wells and their quantity, necessary for effective operation of the offered installations, and values of capacity of electric water pumps for subsoil waters unit are calculated. Capacity of compressor electric drive and coefficient of performance of heat pump for the conditions of the city of Odessa are presented.

  16. Effect Of Cuo-Distilled Water Based Nanofluids On Heat Transfer Characteristics And Pressure Drop Characteristics.

    Directory of Open Access Journals (Sweden)

    SANDEEP KUMAR

    2014-09-01

    Full Text Available In this paper, the heat transfer and pressure drop characteristics of the distilled water and the copper oxide-distilled water based nanofluid flowing in a horizontal circular pipe under constant heat flux condition are studied. Copper oxide nanoparticles of 40nm size are dispersed in distilled water using sodium dodecyl sulphate as surfactant and sonicated the nanofluid for three hour. Both surfactant and sonication increases the stability of the nanofluid. The nanofluids are made in three different concentration i.e. 0.1 Vol. %, 0.25 Vol. % and 0.50 Vol. %. The thermal conductivity is measured by KD2 PRO, density with pycnometer, viscosity with Brookfield LVDV-III rheometer. The results show that the thermal conductivity increases with both temperature and concentration. The viscosity and density increases with concentration but decreases with temperature. The specific heat is calculated by model and it decreases with concentration. The experimental local Nusselt number of distilled water is compared with local Nusselt number obtained by the well known shah equation for laminar flow under constant heat flux condition for validation of the experimental set up. The relative error is 4.48 % for the Reynolds number 750.9. The heat transfer coefficient increases with increase in both flow rate and concentration. It increases from 14.33 % to 46.1 % when the concentration is increased from 0.1 Vol. % to 0.5 Vol. % at 20 LPH flow rate. Friction factor decreases with increase in flow rate. It decreases 66.54 % when the flow rate increases from 10 LPH to 30 LPH for 0.1 Vol. %.

  17. Regularized Fractional Power Parameters for Image Denoising Based on Convex Solution of Fractional Heat Equation

    Directory of Open Access Journals (Sweden)

    Hamid A. Jalab

    2014-01-01

    Full Text Available The interest in using fractional mask operators based on fractional calculus operators has grown for image denoising. Denoising is one of the most fundamental image restoration problems in computer vision and image processing. This paper proposes an image denoising algorithm based on convex solution of fractional heat equation with regularized fractional power parameters. The performances of the proposed algorithms were evaluated by computing the PSNR, using different types of images. Experiments according to visual perception and the peak signal to noise ratio values show that the improvements in the denoising process are competent with the standard Gaussian filter and Wiener filter.

  18. A review of solar energy based heat and power generation systems

    DEFF Research Database (Denmark)

    Modi, Anish; Bühler, Fabian; Andreasen, Jesper Graa;

    2017-01-01

    The utilization of solar energy based technologies has attracted increased interest in recent times in order to satisfy the various energy demands of our society. This paper presents a thorough review of the open literature on solar energy based heat and power plants. In order to limit the scope......) a biomass burner, and (5) an organic Rankine cycle. The various cases are compared on the basis of economic profitability and environmental performance. The results from the case studies indicate that it is economically and environmentally beneficial to invest in both small and large capacity solar...

  19. Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters

    OpenAIRE

    İnan, Umran Savaş; Graf, K. L.; Spasojevic, M.; Marshall, R. A.; Lehtinen, N. G.; Foust, F. R.

    2013-01-01

    JOURNAL OF GEOPHYSICAL RESEARCH: SPACE PHYSICS, VOL. 118, 7783–7797, doi:10.1002/2013JA019337, 2013 Extended lateral heating of the nighttime ionosphere by ground-based VLF transmitters K. L. Graf,1 M. Spasojevic,1 R. A. Marshall,2 N. G. Lehtinen,1 F. R. Foust,1 and U. S. Inan1,3 Received 16 August 2013; revised 9 October 2013; accepted 11 November 2013; published 3 December 2013. [1] The effects of ground-based very low frequency (VLF) transmitters on the lower ionospher...

  20. Effect of Heat Treatment Temperature on Properties of Chinese Calcined Flint Clay Based Plastic Refractories

    Institute of Scientific and Technical Information of China (English)

    ZHANG Wei; DAI Wenyong; YU Xinfeng; LI Liang

    2009-01-01

    Effects of different heat treatment temperatures on properties of Chinese calcined flint clay based plastic refractories were investigated using Chinese calcined flint clay as starting material,aluminum sulfate and fireclay as binding system.The results showed that with temperature rising,Chinese calcined flint clay based plastic refractories shrinked firstly and then expanded.The modulus of rupture (MOR) and the cold crushing strength (CCS) increased firstly and then decreased from 110 ℃ to 600 ℃,then increased obviously.Thermal expansion coefficient increased from 110 ℃ to 760 ℃,decreased from 760 ℃ to 1 300 ℃,and increased from 1 300 ℃ to 1 500 ℃.

  1. Optimization of wire-wrapped fuel assembly of LMR based on three-dimensional analysis of heat transfer

    International Nuclear Information System (INIS)

    In this work, performance evaluation of surrogate models in a wire-wrapped fuel assembly shape optimization is carried out. In addition to three basic models, i.e., Response Surface Approximation (RSA), Kriging (KRG) and Radial Basis Neural Network (RBNN), the multiple surrogate model Press Based Averaging (PBA) is also tested. Two design variables are selected to enhance the performance of wire wrapped fuel assembly and design points are selected using Latin Hypercube Sampling (LHS). Optimization problem has been stated as maximization of the objective function, defined as a linear combination of heat transfer and friction loss related terms with a weighing factor. Among the three basic models Kriging performs better while among the all models multiple surrogate model, PBA performs the best. Use of multiple surrogate PBA gives more robust approximation than individual surrogate. (author)

  2. Performance Analysis of Centrifugal Compressor under Multiple Working Conditions Based on Time-weighted Average

    OpenAIRE

    Zhao, Yuanyang; Xiao, Jun; Li, Liansheng; Yang, Qichao; Liu, Guangbin; Wang, Le; Tang, Bin

    2014-01-01

    A method of compressor performance analysis under multiple working conditions is present based on the Time-weighted average (TWA). The main operation parameters can be obtained based the estimate of the working conditions and times of compressors. Then the comprehensive analysis method can be used to get the overall performance of compressor. The performance of a basic centrifugal compressor was simulation by CFD method in this paper. The overall performance of the centrifugal compressor is c...

  3. Case-based model of emotional expression influence on work group socialization and performance

    OpenAIRE

    Yang, L.; Gilbert, N.

    2006-01-01

    An agent-based computational model, based on longitudinal ethnographic data about the dynamics of intra-group behaviour and work group performance, has been developed from observing an organizational group in the service sector. The model, in which the agents represent workers and tasks, is used to assess the effect of emotional expressions on the dynamics of interpersonal behaviour in work groups, particularly for groups that have recent newcomers. The model simulates the gradual socializati...

  4. Student perspectives on foundation degrees: employment skills and work-based learning

    OpenAIRE

    Huntington, James

    2009-01-01

    This thesis examines students' perspectives of Foundation Degrees, employment skills and work-based learning. It questions whether the primary remit of higher education should be the development of vocational skills for the workplace. It investigates: firstly, the perceived benefits to individuals undertaking a Foundation Degree in terms of developing appropriate employment related skills; secondly, whether the compulsory work based/related learning element, seen as the cornerstone of Foundat...

  5. Absorption refrigeration cycle driven by waste heat using R124-DMAC as working fluids%基于R124-DMAC为工质对的余热吸收式制冷

    Institute of Scientific and Technical Information of China (English)

    李星; 徐士鸣; 李见波

    2015-01-01

    Energy saving and emission reduction technologies for vehicles have been paid more attention in recent years, and it is necessary to investigate how to efficiently recover and utilize the waste heat from vehicle engines to drive automotive air conditioning system. Based on that, a full air-cooled bubble absorption refrigeration test system with 3 kW cooling capacity driven by waste heat, using R124-DMAC as working fluids was designed and built. In the system, engine exhaust gas was simulated by heated air. Operating parameters were tested through changing heat source temperature, chilled water temperature and pump flow rate. The maximum COP of the system could reach 0.54 under the condition of generator temperature 100℃ and evaporating temperature−4℃. Heat source and chilled water temperatures had an important effect on cooling capacity and COP, and this system had good stability. However when evaporating temperature was below 5℃, a rectification unit should be considered in order to improve cooling effects. Additionally, this experiment proved that the air-cooled bubble absorber worked well, providing theoretical support for the refrigeration system driven by waste heat in vehicle air conditioning.%设计并搭建了制冷量为3 kW、以R124-DMAC为工质、采用电热高温空气模拟发动机排气废热的空冷鼓泡吸收制冷实验系统,通过改变热空气进口温度、冷冻水温度和浓溶泵流率测试系统工作参数的变化趋势。实验结果表明,当发生器稀溶液出口温度约为100℃时,蒸发温度为−4℃,系统COP值最大可达到约0.54,而且实验系统稳定性较好;影响系统制冷量和COP值的主要参数是热空气进口温度和冷冻水温度;当蒸发温度低于5℃时,为了提高制冷效果需考虑设置精馏装置。

  6. Technoeconomic analysis of a biomass based district heating system. Paper no. IGEC-1-ID01

    International Nuclear Information System (INIS)

    District energy systems (DES) that produce steam, hot water or chilled water at a central plant and then distribute that energy to buildings in the district for space heating, domestic hot water heating and air conditioning provide opportunities for increasing energy efficiency and reducing greenhouse gas (GHG) emissions. Use of biomass, such as wood, wood byproducts and wastes, fast-growing trees, agricultural crops and waste, in place of conventional fossil fuels to produce the thermal energy needed by a DES, presents further opportunities for reducing green house gas emissions as well as providing rural employment, and local solutions to rural and remote energy needs. In this paper, a technoeconomic analysis of a biomass based DES for a community center in Nova Scotia, Canada is presented. The methodology used to size and design the heating and ventilating system, as well as the biomass based DES is discussed. Annual energy requirement and biomass fuel consumption predictions are presented along with cost estimates. A comparative assessment of the economic feasibility of the system vis-a-vis a conventional oil fired system is conducted. While the results are specific to the particular application, the design and analysis methodology that is presented in the paper can be used for any similar application. (author)

  7. Modelling mass and heat transfer in nano-based cancer hyperthermia.

    Science.gov (United States)

    Nabil, M; Decuzzi, P; Zunino, P

    2015-10-01

    We derive a sophisticated mathematical model for coupled heat and mass transport in the tumour microenvironment and we apply it to study nanoparticle delivery and hyperthermic treatment of cancer. The model has the unique ability of combining the following features: (i) realistic vasculature; (ii) coupled capillary and interstitial flow; (iii) coupled capillary and interstitial mass transfer applied to nanoparticles; and (iv) coupled capillary and interstitial heat transfer, which are the fundamental mechanisms governing nano-based hyperthermic treatment. This is an improvement with respect to previous modelling approaches, where the effect of blood perfusion on heat transfer is modelled in a spatially averaged form. We analyse the time evolution and the spatial distribution of particles and temperature in a tumour mass treated with superparamagnetic nanoparticles excited by an alternating magnetic field. By means of numerical experiments, we synthesize scaling laws that illustrate how nano-based hyperthermia depends on tumour size and vascularity. In particular, we identify two distinct mechanisms that regulate the distribution of particle and temperature, which are characterized by perfusion and diffusion, respectively. PMID:26587251

  8. Effect of Heat Treatment Process on Microstructure and Fatigue Behavior of a Nickel-Base Superalloy

    Directory of Open Access Journals (Sweden)

    Peng Zhang

    2015-09-01

    Full Text Available The study of fatigue behaviors for nickel-base superalloys is very significant because fatigue damage results in serious consequences. In this paper, two kinds of heat treatment procedures (Pro.I and Pro.II were taken to investigate the effect of heat treatment on microstructures and fatigue behaviors of a nickel-base superalloy. Fatigue behaviors were studied through total strain controlled mode at 650 °C. Manson-Coffin relationship and three-parameter power function were used to predict fatigue life. A good link between the cyclic/fatigue behavior and microscopic studies was established. The cyclic deformation mechanism and fatigue mechanism were discussed. The results show that the fatigue resistance significantly drops with the increase of total strain amplitudes. Manson-Coffin relationship can well predict the fatigue life for total strain amplitude from 0.5% to 0.8%. The fatigue resistance is related with heat treatment procedures. The fatigue resistance performance of Pro.I is better than that of Pro.II. The cyclic stress response behaviors are closely related to the changes of the strain amplitudes. The peak stress of the alloy gradually increases with the increase of total strain amplitudes. The main fracture mechanism is inhomogeneous deformation and the different interactions between dislocations and γ′ precipitates.

  9. Energy and Exergy Performances of Air-Based vs. Water-Based Heating and Cooling Systems: A Case Study of a Single-Family House

    DEFF Research Database (Denmark)

    Kazanci, Ongun Berk; Shukuya, Masanori; Olesen, Bjarne W.

    2016-01-01

    energy and exergy inputs to the system, energy and exergy inputs to the auxiliary components were also studied. Both heating and cooling cases were considered and three climatic zones were studied; Copenhagen (Denmark), Yokohama (Japan), and Ankara (Turkey). The analysis showed that the water......-based radiant heating and cooling system performed better than the air-based system both in terms of energy and exergy input to the heating/cooling plant. The relative benefits of the water-based system over the air-based system vary depending on the climatic zone. The air-based system also requires higher...

  10. Analysis of cooling effectiveness for heat flux based on reference enthalpy

    Institute of Scientific and Technical Information of China (English)

    CAI De-zhang; QIN Jiang; FAN Yi; WANG Yao-wu

    2008-01-01

    In order to quickly and accurately compute the wall temperature distribution along the combustor axi-al line, a method to compute the temperature field of combustion chamber with active regeneratively cooling waspresented. On the condition of nonstationary wall temperature, the one-dimensional cooling model based on ref-erence enthalpy was established, and the distribution of the wall heat flux and the wall temperature along the combustor axial line were obtained at different mach numbers by using the heat transfer empirical equation. For the existing two types of cooling system structure, the cooling effectiveness of which was investigated through the presented method. And the satisfactory results obtained show the validity of the method.

  11. Spin-dependent Otto quantum heat engine based on a molecular substance

    Science.gov (United States)

    Hübner, Wolfgang; Lefkidis, Georgios; Dong, Chuanding; Chaudhuri, Debapriya; Chotorlishvili, Levan; Berakdar, Jamal

    2015-03-01

    We explore the potential of single molecules for thermodynamic cycles. To this end we propose two molecular heat engines based on the realistic Ni2 dimer: a quantum Otto engine and a modified quantum Otto engine for which laser-induced optical excitations substitute for one of the heat-exchange points. For reliable predictions and to inspect the role of spin and electronic correlations we perform fully correlated ab initio calculations of the electronic structure and the excited states. We analyze the efficiency and the word output of the derived engines and find an enhancement when the spin degree of freedom is included. We also use the von Neumann entropy to describe correlations and entanglement of the engines during the cycles. Furthermore, we link our results to previous results regarding an isobaric stroke and a magnetic quantum Diesel engine on the same substance.

  12. PRECISE INTEGRAL ALGORITHM BASED SOLUTION FOR TRANSIENT INVERSE HEAT CONDUCTION PROBLEMS WITH MULTI-VARIABLES

    Institute of Scientific and Technical Information of China (English)

    WANG Yi-bo; YANG Hai-tian; WU Rui-feng

    2005-01-01

    By modeling direct transient heat conduction problems via finite element method (FEM) and precise integral algorithm, a new approach is presented to solve transient inverse heat conduction problems with multi-variables. Firstly, the spatial space and temporal domain are discretized by FEM and precise integral algorithm respectively. Then, the high accuracy semi-analytical solution of direct problem can be got. Finally, based on the solution, the computing model of inverse problem and expression of sensitivity analysis are established. Single variable and variables combined identifications including thermal parameters, boundary conditions and source-related terms etc. are given to validate the approach proposed in 1-D and 2-D cases. The effects of noise data and initial guess on the results are investigated. The numerical examples show the effectiveness of this approach.

  13. Heat-induced multimode interference variable optical attenuator based on novel organic-inorganic hybrid materials

    International Nuclear Information System (INIS)

    A heat-induced multimode interference (MMI) variable optical attenuator at 1310 nm wavelength, based on novel organic–inorganic hybrid materials is successfully designed and fabricated. The thermal stability and optical properties of the sol–gel materials are analyzed. The thermo-optic (TO) coefficient of the organic–inorganic hybrid material is obtained as −1.85 × 10−4 °C−1. The characteristic parameters of the waveguides and heat-induced electrodes are carefully designed and simulated. The propagation loss of a 4 μm-wide straight waveguide is 0.56 dB cm−1. The attenuation of the device is about −25 dB, and the applied electric power is 36.2 mW. The new material system and low-cost fabrication technique could be suitable for realizing large-scale photonic integrated circuits. (paper)

  14. Calculation and analysis of heat source of PWR assemblies based on Monte Carlo method

    International Nuclear Information System (INIS)

    When fission occurs in nuclear fuel in reactor core, it releases numerous neutron and γ radiation, which takes energy deposition in fuel components and yields many factors such as thermal stressing and radiation damage influencing the safe operation of a reactor. Using the three-dimensional Monte Carlo transport calculation program MCNP and continuous cross-section database based on ENDF/B series to calculate the heat rate of the heat source on reference assemblies of a PWR when loading with 18-month short refueling cycle mode, and get the precise values of the control rod, thimble plug and new burnable poison rod within Gd, so as to provide basis for reactor design and safety verification. (authors)

  15. Development of a thermal storage system based on the heat of adsorption of water in hygroscopic materials

    NARCIS (Netherlands)

    Wijsman, A.J.T.M.; Oosterhaven, R.; Ouden, C. den

    1979-01-01

    A thermal storage system based on the heat of adsorption of water in hygroscopic materials has been studied as a component of a solar space heating system. The aim of this project is to decrease the storage volume in comparison with a rock-bed storage system by increasing the stored energy density.

  16. Development and evaluation of materials for thermochemical heat storage based on the CaO/CaCO3 reaction couple

    Science.gov (United States)

    Sakellariou, Kyriaki G.; Tsongidis, Nikolaos I.; Karagiannakis, George; Konstandopoulos, Athanasios G.; Baciu, Diana; Charalambopoulou, Georgia; Steriotis, Theodore; Stubos, Athanasios; Arlt, Wolfgang

    2016-05-01

    The current work relates to the development of synthetic calcium oxide (CaO) based compositions as candidate materials for energy storage under a cyclic carbonation/decarbonation reaction scheme. Although under such a cyclic scheme the energy density of natural lime based CaO is high (˜ 3MJ/kg), the particular materials suffer from notable cycle-to-cycle deactivation. To this direction, pure CaO and CaO/Al2O3 composites have been prepared and preliminarily evaluated under the suggested cyclic carbonation/decarbonation scheme in the temperature range of 600-800°C. For the composite materials, Ca/Al molar ratios were in the range between 95/5 and 52/48 and upon calcination the formation of mixed Ca/Al phases was verified. The preliminary evaluation of materials studied was conducted under 3 carbonation/decarbonation cycles and the loss of activity for the case of natural CaO was obvious. Synthetic materials with superior stability/capture c.f. natural CaO were further subjected to multi-cyclic carbonation/decarbonation, via which the positive effect of alumina addition was made evident. Selected compositions exhibited adequately high CO2 capture capacity and stable performance during multi-cyclic operation. Moreover, this study contains preliminary experiments referring to proof-of-principle validation of a concept based on the utilization of a CaO-based honeycomb reactor/heat exchanger preliminary design. In particular, cordierite monolithic structures were coated with natural CaO and in total 11 cycles were conducted. Upon operation, clear signs of heat dissipation by the imposed flow in the duration of the exothermic reaction step were identified.

  17. Enhancement of natural convection heat transfer from a fin by triangular perforation of bases parallel and toward its tip

    Institute of Scientific and Technical Information of China (English)

    Abdullah H. AlEssa; Mohamad I. Al-Widyan

    2008-01-01

    This study examines the heat transfer enhancement from a horizontal rect- angular fin embedded with triangular perforations (their bases parallel and toward the fin tip) under natural convection. The fin's heat dissipation rate is compared to that of an equivalent solid one. The parameters considered axe geometrical dimensions and thermal properties of the fin and the perforations. The gain in the heat transfer enhancement and the fin weight reduction due to the perforations are considered. The study shows that the heat dissipation from the perforated fin for a certain range of triangular perforation di- mensions and spaces between perforations result in improvement in the heat transfer over the equivalent solid fin. The heat transfer enhancement of the perforated fin increases as the fin thermal conductivity and its thickness are increased.

  18. Proposition of updating the method used in calculating the heat demand based on a new concept of design outdoor temperature and of building – soil boundary heat transfer

    Directory of Open Access Journals (Sweden)

    Dan CONSTANTINESCU

    2010-01-01

    Full Text Available The dimensioning of the heating systems equipping new and existing buildings, in the case of their energy-related upgrading is an extremely important activity in the context of reaching the targets of the European Directive 31 /2010 / UE concerning the Buildings Energy Performance (PEC. The accurate determination, phenomenological based, of the buildings thermal response leads to determining the climatic parameters representative for the climatic zones and for the buildings structure.Unlike the EN 12831: 2003 European Regulation, the design outdoor temperature in the conditions of Romania’s various zones was determined by the identification of the thermal response specific to the transient conditions of the heat transfer through the composite structures of the opaque and glazing closing components with the thermal response in idealized, steadystate conditions; thus, the design outdoor temperature was determined, which is conditioned by an acceptable discomfort during the coldest pentads of a 48 years climatic statistics (1961-2008. The climatic parameter which generates the modeling similitude is the virtual outdoor temperature which allows the use of the steady-state conditions mathematical formalism in issues of heat transfer in transient conditions. A dependency relation between the design indoor temperature, identical to the resulting indoor temperature (different from the operational temperature and the air volume average temperature is emphasized.Special attention is given to the heat transfer at the building-soil boundary, in the form of various practical solutions (buildings the basement of which is not directly heated, equipped or not with heating systems, directly heated and occupied, as well as buildings on plinths; in all the cases, the solutions approached are specific to the envelope which is or not thermally insulated.

  19. A comparison of THI indices leads to a sensible heat-based heat stress index for shaded cattle that aligns temperature and humidity stress

    Science.gov (United States)

    Berman, A.; Horovitz, Talia; Kaim, M.; Gacitua, H.

    2016-01-01

    The combined temperature-humidity heat stress is estimated in farm animals by indices derived of an index based on human thermal comfort sensation. The latter index consists of temperature and humidity measures that sum to form the temperature-humidity index (THI). The hitherto unknown relative contribution of temperature and humidity to the THI was examined. A temperature-humidity data set (temperature 20-42 °C and relative humidity 10-70 %) was used to assess by regression procedures the relative weights of temperature and humidity in the variance of THI values produced by six commonly used heat stress indices. The temperature (Ta) effect was predominant (0.82-0.95 of variance) and humidity accounted for only 0.05 to 0.12 of THI variance, half of the variance encountered in animal responses to variable humidity heat stress. Significant difference in THI values was found between indices in the relative weights of temperature and humidity. As in THI indices, temperature and humidity are expressed in different physical units, their sum has no physical attributes, and empirical evaluations assess THI relation to animal responses. A sensible heat THI was created, in which at higher temperatures humidity reaches 0.25 of sensible heat, similarly to evaporative heat loss span in heat stressed animals. It relates to ambient temperature-humidity similarly to present THI; its values are similar to other THI but greater at higher humidity. In warm conditions, mean animal responses are similar in both indices. The higher sensitivity to humidity makes this index preferable for warm-humid conditions.

  20. Company welfare and social work ethics: a space for social work? : A discussion based on cases from Norway and Tanzania.

    OpenAIRE

    Anne Ryen; Eulalia Temba; Edmund Matotay

    2015-01-01

    This article deals with company welfare and social work ethics. If social work is concerned with welfare and distributional issues, we would assume company welfare to be an issue of great relevance to social workers, so why do we not come across any social workers in our fieldwork? This calls for the simple question “where do social workers work?” or rather “how come social workers do not work in private companies?” We explore into the combination of social work and private companies with spe...