T. Anzawa, Qiang Yu, M. Yamagiwa, T. Shibutani, M. Shiratori
This paper presents a fundamental method to evaluate thermal fatigue life of power module. Coupled electrical-thermal analysis was performed to obtain the distribution of temperature due to electric current. Then, thermo-mechanical analysis was carried out to calculate inelastic strain range generated in a solder joint. Crack path simulation technique was used to evaluate total fatigue life and rise in temperature. Fatigue crack initiates under Al bonding wire for the IGBT module. Crack propagation induces the change in thermal properties of power devices. Total fatigue life changes with configuration of model.
{"title":"Reliability evaluation on deterioration of power device using coupled electrical-thermal-mechanical analysis","authors":"T. Anzawa, Qiang Yu, M. Yamagiwa, T. Shibutani, M. Shiratori","doi":"10.1115/1.4002451","DOIUrl":"https://doi.org/10.1115/1.4002451","url":null,"abstract":"This paper presents a fundamental method to evaluate thermal fatigue life of power module. Coupled electrical-thermal analysis was performed to obtain the distribution of temperature due to electric current. Then, thermo-mechanical analysis was carried out to calculate inelastic strain range generated in a solder joint. Crack path simulation technique was used to evaluate total fatigue life and rise in temperature. Fatigue crack initiates under Al bonding wire for the IGBT module. Crack propagation induces the change in thermal properties of power devices. Total fatigue life changes with configuration of model.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125378523","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167186
H. Khater, O. Abdelsalam, M. Hanafy, Y. Abdelraouf
A low temperature Proton Exchange Membrane Fuel Cell (PEMFC) system, fueled by natural gas is proposed and its performance is investigated by establishing a thermodynamic model of integral approach using energy and species mass conservation in addition to chemical and thermal equilibrium and electrochemical principals. Adiabatic cell reactions with temperature changes are assumed. Activation, ohmic and concentration potential losses are considered in cell voltage calculations. Estimate of the cost of electricity (COE) of the proposed system is also made using data fits of the available purchase costs. Computer programs using the Engineering Equation Solver (EES) supported with graphical user interface (GUI) are established for solution. Parametric studies are conducted to this system over ranges of: stack pressure, stack inlet temperature, reformer temperature, gas shift temperature and current density. Output power, electrical efficiency and the COE are calculated to investigate the economically optimum operating range of each input parameter.
{"title":"Analytical simulation of rich hydrogen gas - Air Proton Exchange Membrane Fuel Cell system fueled by natural gas","authors":"H. Khater, O. Abdelsalam, M. Hanafy, Y. Abdelraouf","doi":"10.1109/THETA.2008.5167186","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167186","url":null,"abstract":"A low temperature Proton Exchange Membrane Fuel Cell (PEMFC) system, fueled by natural gas is proposed and its performance is investigated by establishing a thermodynamic model of integral approach using energy and species mass conservation in addition to chemical and thermal equilibrium and electrochemical principals. Adiabatic cell reactions with temperature changes are assumed. Activation, ohmic and concentration potential losses are considered in cell voltage calculations. Estimate of the cost of electricity (COE) of the proposed system is also made using data fits of the available purchase costs. Computer programs using the Engineering Equation Solver (EES) supported with graphical user interface (GUI) are established for solution. Parametric studies are conducted to this system over ranges of: stack pressure, stack inlet temperature, reformer temperature, gas shift temperature and current density. Output power, electrical efficiency and the COE are calculated to investigate the economically optimum operating range of each input parameter.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115884373","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167176
A. Bontemps, J. Ribeiro, S. Ferrouillat, J. Gruss, O. Soriano, Biran Wang
This paper describes an experimental study on convective heat transfer and flow behaviour of SiO2/water nanofluids at different concentrations (5, 16 and 34 % in weight) inside a 1.3mm diameter tube heated at constant heat flux. The experimental test bench allowing us to measure local wall temperatures as well as fluid inlet/outlet temperatures is described. The flow regimes range from laminar to turbulent in the heated tube.
{"title":"EXperimental study of convective heat transfer and pressure loss of SiO2/water nanofluids Part 2: Imposed uniform heat flux - Energetic performance criterion","authors":"A. Bontemps, J. Ribeiro, S. Ferrouillat, J. Gruss, O. Soriano, Biran Wang","doi":"10.1109/THETA.2008.5167176","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167176","url":null,"abstract":"This paper describes an experimental study on convective heat transfer and flow behaviour of SiO2/water nanofluids at different concentrations (5, 16 and 34 % in weight) inside a 1.3mm diameter tube heated at constant heat flux. The experimental test bench allowing us to measure local wall temperatures as well as fluid inlet/outlet temperatures is described. The flow regimes range from laminar to turbulent in the heated tube.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"15 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115592571","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167173
W. Chekirou, N. Boukheit, T. Kerbache
This paper presents a one-dimensional mathematical model which accounts for heat and mass transfer in a tubular adsorber as well as the effects of non-uniform temperature and uniform pressure distribution, using the pair activated carbon AC-35/ methanol as an adsorbent/adsorbate. The modelling and the analysing of the adsorber is the key point of such studies, because of the complex coupled heat and mass transfer phenomena that occur during the working cycle. This model consists of the energy equation in the adsorbent layers, the energy balance equation of the adsorber wall, and state equation of the bivariant solid- vapour equilibrium using the Dubinin-Astakhov model to describe the adsorption phenomena. The discretization of equations system is carried out using the finite differences method with a fully implicit scheme. The resolution of the discretized system is carried out using an iterative method. The validity of the model has been checked by using theoretical results of the thermodynamic cycle under the same numerical conditions. A good agreement between numerical simulation and theoretical results has been achieved. This comparison shows that the proposed model can describe the details of thermal behaviour in a tubular adsorber of the solar refrigerator. Several main factors affecting the solar performance and the cooling power system's are discussed according to the results of computer simulations, such as: equivalent conductivity of the solid adsorbent, heat transfer coefficient between the tube wall and the porous media and the emissivity of the metallic adsorber wall. The relationship between the performance system's and these factors is investigated.
{"title":"Effect of coupled heat and mass transfers on the performance of adsorptive solar refrigerator using the pair activated carbon / methanol","authors":"W. Chekirou, N. Boukheit, T. Kerbache","doi":"10.1109/THETA.2008.5167173","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167173","url":null,"abstract":"This paper presents a one-dimensional mathematical model which accounts for heat and mass transfer in a tubular adsorber as well as the effects of non-uniform temperature and uniform pressure distribution, using the pair activated carbon AC-35/ methanol as an adsorbent/adsorbate. The modelling and the analysing of the adsorber is the key point of such studies, because of the complex coupled heat and mass transfer phenomena that occur during the working cycle. This model consists of the energy equation in the adsorbent layers, the energy balance equation of the adsorber wall, and state equation of the bivariant solid- vapour equilibrium using the Dubinin-Astakhov model to describe the adsorption phenomena. The discretization of equations system is carried out using the finite differences method with a fully implicit scheme. The resolution of the discretized system is carried out using an iterative method. The validity of the model has been checked by using theoretical results of the thermodynamic cycle under the same numerical conditions. A good agreement between numerical simulation and theoretical results has been achieved. This comparison shows that the proposed model can describe the details of thermal behaviour in a tubular adsorber of the solar refrigerator. Several main factors affecting the solar performance and the cooling power system's are discussed according to the results of computer simulations, such as: equivalent conductivity of the solid adsorbent, heat transfer coefficient between the tube wall and the porous media and the emissivity of the metallic adsorber wall. The relationship between the performance system's and these factors is investigated.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"53 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128595269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167164
R. Moffat
This paper presents some observations and recommendations about thermal management based on my experience as a researcher, teacher, and consultant. These comments are focused mainly on air cooling, at the system and board level. It is important to integrate the testing and CFD approaches to problems and have their results interpreted by someone well-schooled in heat transfer. Data doesn't solve a problem, data simply makes the problem visible. It takes a trained person to solve a thermal problem-someone who can look at the data, recognizes the root cause of the problem, and who knows what to change to fix it. Every house needs one. CFD codes are mainly used to identify potential problems. They can do more. It is not difficult to instruct a CFD code to generate diagnostic data that will help reveal the nature of the problem-not just that a problem exists. It is increasingly important to have a working knowledge of heat exchanger theory and to keep that viewpoint in mind when looking at larger-scale problems, like heat sinks. Recent advances in micro-scale manufacture of heat transfer surfaces show promise of new ultra-compact heat exchangers that will fit in to the electronics environment. That field bears watching.
{"title":"Do's and don'ts in thermal management","authors":"R. Moffat","doi":"10.1109/THETA.2008.5167164","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167164","url":null,"abstract":"This paper presents some observations and recommendations about thermal management based on my experience as a researcher, teacher, and consultant. These comments are focused mainly on air cooling, at the system and board level. It is important to integrate the testing and CFD approaches to problems and have their results interpreted by someone well-schooled in heat transfer. Data doesn't solve a problem, data simply makes the problem visible. It takes a trained person to solve a thermal problem-someone who can look at the data, recognizes the root cause of the problem, and who knows what to change to fix it. Every house needs one. CFD codes are mainly used to identify potential problems. They can do more. It is not difficult to instruct a CFD code to generate diagnostic data that will help reveal the nature of the problem-not just that a problem exists. It is increasingly important to have a working knowledge of heat exchanger theory and to keep that viewpoint in mind when looking at larger-scale problems, like heat sinks. Recent advances in micro-scale manufacture of heat transfer surfaces show promise of new ultra-compact heat exchangers that will fit in to the electronics environment. That field bears watching.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133796542","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
K. Yamamoto, Masamichi Nakamura, Hiroshi Yamashita
Particulate matters (PM) including soot in diesel exhaust gas are severe environmental problems. It is expected that emission of soot particles can penetrate into the lung, causing human carcinogenic effects. To reduce these emissions especially from heavy-duty vehicles such as cargo trucks and buses, a diesel particulate filter (DPF) has been developed for the after-treatment of exhaust gas. In simple explanation of DPF, it traps PM when exhaust gas passes its porous wall. However, since the filter would be plugged with particles to cause an increase of filter back-pressure, filter regeneration process is needed. In this study, we simulate the flow in DPF by the lattice Boltzmann method (LBM). So far, the LBM has been widely used in fluid simulation, and has been an alternative and promising numerical scheme. It has been confirmed that, through the Chapman-Enskog procedure, the Navier-Stokes equations are derived from LB equations. In the LBM, the treatment of boundary conditions is simple and easy, and it is appropriate to simulate porous media flows such as DPF. In this paper, our approach for LB simulation of combustion is briefly explained. Here, the real filter is used in the simulation. The inner structure of the filter sample is scanned by a 3D X-ray CT technique. By conducting tomography-assisted simulation, we obtain local velocity and pressure distributions in the filter, which is hardly obtained by measurements. First, the flow and pressure profiles are visualized, compared with the empirical equation of the Ergun equation. Then, the soot combustion is simulated. Based on the temperature change and reaction inside the filter, the heat and mass transfer in the filter regeneration process is discussed.
{"title":"Simulation of flow and heat transfer in diesel particulate filter","authors":"K. Yamamoto, Masamichi Nakamura, Hiroshi Yamashita","doi":"10.1115/1.4003448","DOIUrl":"https://doi.org/10.1115/1.4003448","url":null,"abstract":"Particulate matters (PM) including soot in diesel exhaust gas are severe environmental problems. It is expected that emission of soot particles can penetrate into the lung, causing human carcinogenic effects. To reduce these emissions especially from heavy-duty vehicles such as cargo trucks and buses, a diesel particulate filter (DPF) has been developed for the after-treatment of exhaust gas. In simple explanation of DPF, it traps PM when exhaust gas passes its porous wall. However, since the filter would be plugged with particles to cause an increase of filter back-pressure, filter regeneration process is needed. In this study, we simulate the flow in DPF by the lattice Boltzmann method (LBM). So far, the LBM has been widely used in fluid simulation, and has been an alternative and promising numerical scheme. It has been confirmed that, through the Chapman-Enskog procedure, the Navier-Stokes equations are derived from LB equations. In the LBM, the treatment of boundary conditions is simple and easy, and it is appropriate to simulate porous media flows such as DPF. In this paper, our approach for LB simulation of combustion is briefly explained. Here, the real filter is used in the simulation. The inner structure of the filter sample is scanned by a 3D X-ray CT technique. By conducting tomography-assisted simulation, we obtain local velocity and pressure distributions in the filter, which is hardly obtained by measurements. First, the flow and pressure profiles are visualized, compared with the empirical equation of the Ergun equation. Then, the soot combustion is simulated. Based on the temperature change and reaction inside the filter, the heat and mass transfer in the filter regeneration process is discussed.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134124899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Thermal design requirements are mostly driven by the peak temperatures. Reducing or eliminating hot spots could alleviate the design requirement for the whole package. Combination of solid-state and liquid cooling will allow removal of both hot spots and background heating. In this paper, we analyze the performance of thin film Bi2Te3 microcooler and the 3D SiGe based microrefrigerator and optimize the maximum cooling and cooling power density in the presence of flow. Liquid flow and heat transfer coefficient will change the background temperature of the chip but they also affect the performance of the solid-state coolers used to remove hot spots. Both Peltier cooling at interfaces and Joule heating inside the device could be affected by the fluid flow. We analyze conventional Peltier coolers as well as 3D coolers. We study the impact of various parameters such as thermoelectric leg thickness, thermal interface resistances, and geometry factor on the overall system performance. We find that the cooling of conventional Peltier cooler is significantly reduced in the presence of fluid flow. On the other hand, 3D SiGe can be effective to remove high power density hot spots up to 500 W/cm2. 3D microrefrigerators can have a significant impact if the thermoelectric figure-of-Thermal design requirements are mostly driven by the peak temperatures. Reducing or eliminating hot spots could alleviate the design requirement for the whole package. Combination of solid-state and liquid cooling will allow removal of both hot spots and background heating. In this paper, we analyze the performance of thin film Bi2Te3 microcooler and the 3D SiGe based microrefrigerator and optimize the maximum cooling and cooling power density in the presence of flow. Liquid flow and heat transfer coefficient will change the background temperature of the chip but they also affect the performance of the solid-state coolers used to remove hot spots. Both Peltier cooling at interfaces and Joule heating inside the device could be affected by the fluid flow. We analyze conventional Peltier coolers as well as 3D coolers. We study the impact of various parameters such as thermoelectric leg thickness, thermal interface resistances, and geometry factor on the overall system performance. We find that the cooling of conventional Peltier cooler is significantly reduced in the presence of fluid flow. On the other hand, 3D SiGe can be effective to remove high power density hot spots up to 500 W/cm2. 3D microrefrigerators can have a significant impact if the thermoelectric figure-of-merit, ZT, could reach 0.5 for a material grown on silicon substrate. It is interesting to note that there is an optimum microrefrigerator active region thickness that gives the maximum localized cooling. For liquid heat transfer coefficient between 5000 and 20000 W/m2/K, the optimum is found to be between 10 and 20 mum.merit, ZT, could reach 0.5 for a material grown on silicon substrate. It is interesting to note that
{"title":"Solid-state microrefrigeration in conjonction with liquid cooling","authors":"Y. Ezzahri, A. Shakouri","doi":"10.1115/1.4001853","DOIUrl":"https://doi.org/10.1115/1.4001853","url":null,"abstract":"Thermal design requirements are mostly driven by the peak temperatures. Reducing or eliminating hot spots could alleviate the design requirement for the whole package. Combination of solid-state and liquid cooling will allow removal of both hot spots and background heating. In this paper, we analyze the performance of thin film Bi2Te3 microcooler and the 3D SiGe based microrefrigerator and optimize the maximum cooling and cooling power density in the presence of flow. Liquid flow and heat transfer coefficient will change the background temperature of the chip but they also affect the performance of the solid-state coolers used to remove hot spots. Both Peltier cooling at interfaces and Joule heating inside the device could be affected by the fluid flow. We analyze conventional Peltier coolers as well as 3D coolers. We study the impact of various parameters such as thermoelectric leg thickness, thermal interface resistances, and geometry factor on the overall system performance. We find that the cooling of conventional Peltier cooler is significantly reduced in the presence of fluid flow. On the other hand, 3D SiGe can be effective to remove high power density hot spots up to 500 W/cm2. 3D microrefrigerators can have a significant impact if the thermoelectric figure-of-Thermal design requirements are mostly driven by the peak temperatures. Reducing or eliminating hot spots could alleviate the design requirement for the whole package. Combination of solid-state and liquid cooling will allow removal of both hot spots and background heating. In this paper, we analyze the performance of thin film Bi2Te3 microcooler and the 3D SiGe based microrefrigerator and optimize the maximum cooling and cooling power density in the presence of flow. Liquid flow and heat transfer coefficient will change the background temperature of the chip but they also affect the performance of the solid-state coolers used to remove hot spots. Both Peltier cooling at interfaces and Joule heating inside the device could be affected by the fluid flow. We analyze conventional Peltier coolers as well as 3D coolers. We study the impact of various parameters such as thermoelectric leg thickness, thermal interface resistances, and geometry factor on the overall system performance. We find that the cooling of conventional Peltier cooler is significantly reduced in the presence of fluid flow. On the other hand, 3D SiGe can be effective to remove high power density hot spots up to 500 W/cm2. 3D microrefrigerators can have a significant impact if the thermoelectric figure-of-merit, ZT, could reach 0.5 for a material grown on silicon substrate. It is interesting to note that there is an optimum microrefrigerator active region thickness that gives the maximum localized cooling. For liquid heat transfer coefficient between 5000 and 20000 W/m2/K, the optimum is found to be between 10 and 20 mum.merit, ZT, could reach 0.5 for a material grown on silicon substrate. It is interesting to note that","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131305639","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167188
E. Faghani, B. Farhanieh, R. Maddahian, P. Faghani
In this research the fluid and thermal characteristics of a rectangular turbulent jet flow is studied numerically. The results of three dimensional jet issued from a rectangular nozzle are presented. A numerical method employing control volume approach with collocated grid arrangement was employed. Velocity and pressure fields are coupled with SIMPLEC algorithm. The turbulent stresses are approximated using k-epsiv model with two different inlet conditions. The velocity and temperature fields are presented and the rates of their decay at jet centerline are noted. The velocity vectors of a main flow and secondary flow are illustrated. Also effect of aspect ratio (AR) on mixing in rectangular cross section jets is considered. Investigated AR was among 1:1 to 1:4. The results showed that the jet entrains more with smaller AR. Special attention has been drawn on the influence of the Reynolds number (based on hydraulic diameter) as well as the inflow conditions on the evolution of the rectangular jet. An influence on the jet evolution is found for smaller Re, but the jet is close to a converged state for higher Reynolds numbers. The influence of the inflow conditions on the jet characteristics is so strong.
{"title":"Numerical investigation of effect of aspect ratio of rectangular nozzles","authors":"E. Faghani, B. Farhanieh, R. Maddahian, P. Faghani","doi":"10.1109/THETA.2008.5167188","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167188","url":null,"abstract":"In this research the fluid and thermal characteristics of a rectangular turbulent jet flow is studied numerically. The results of three dimensional jet issued from a rectangular nozzle are presented. A numerical method employing control volume approach with collocated grid arrangement was employed. Velocity and pressure fields are coupled with SIMPLEC algorithm. The turbulent stresses are approximated using k-epsiv model with two different inlet conditions. The velocity and temperature fields are presented and the rates of their decay at jet centerline are noted. The velocity vectors of a main flow and secondary flow are illustrated. Also effect of aspect ratio (AR) on mixing in rectangular cross section jets is considered. Investigated AR was among 1:1 to 1:4. The results showed that the jet entrains more with smaller AR. Special attention has been drawn on the influence of the Reynolds number (based on hydraulic diameter) as well as the inflow conditions on the evolution of the rectangular jet. An influence on the jet evolution is found for smaller Re, but the jet is close to a converged state for higher Reynolds numbers. The influence of the inflow conditions on the jet characteristics is so strong.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116729631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other common liquids, self-rewetting fluids have the property that the surface tension increases with temperature. The increasing surface tension at a higher temperature can cause the liquid to be drawn towards a heated surface if a dry spot appears, and thus to improve boiling heat transfer. In experiments, 1-butanol and 1-pentanol were added to water at a concentration of less than 1 wt% to make self-rewetting fluid. A pulsating heat pipe made from an extruded multi-port tube was partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of four when the maximum heater temperature was limited to 110degC. Thus, the use of a self-rewetting fluid in a PHP was shown to be highly effective in improving the heat transport capability of pulsating heat pipes.
{"title":"An experimental study on a pulsating heat pipe with self-rewetting fluid","authors":"K. Fumoto, M. Kawaji, T. Kawanami","doi":"10.1115/1.4001855","DOIUrl":"https://doi.org/10.1115/1.4001855","url":null,"abstract":"This paper discusses a pulsating heat pipe (PHP) using a self-rewetting fluid. Unlike other common liquids, self-rewetting fluids have the property that the surface tension increases with temperature. The increasing surface tension at a higher temperature can cause the liquid to be drawn towards a heated surface if a dry spot appears, and thus to improve boiling heat transfer. In experiments, 1-butanol and 1-pentanol were added to water at a concentration of less than 1 wt% to make self-rewetting fluid. A pulsating heat pipe made from an extruded multi-port tube was partially filled with the self-rewetting fluid water mixture and tested for its heat transport capability at different input power levels. The experiments showed that the maximum heat transport capability was enhanced by a factor of four when the maximum heater temperature was limited to 110degC. Thus, the use of a self-rewetting fluid in a PHP was shown to be highly effective in improving the heat transport capability of pulsating heat pipes.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"119 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116819199","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2008-12-01DOI: 10.1109/THETA.2008.5167177
E. Elshafei, M. Awad, E. El-Negiry, A. Ali
The convective heat transfer and pressure drop characteristics in corrugated channels were experimentally investigated. Experiments were performed on channels of uniform wall temperature and of fixed corrugation ratio, gamma (2A/L=0.2) over a range of Reynolds number, 3220 lesReles9420. Corrugated channels of 0deg, 90deg and 180deg phase shift and with different spacing are considered. The effects of these geometrical parameters on the heat transfer and pressure drop are discussed. The obtained results showed a significant heat transfer enhancement and pressure drop penalty associated with corrugated channels. The average heat transfer coefficients and pressure drops exceeded by about 2.6 to 3.2 and 1.9 to 2.6 times those for parallel plate channel, respectively, depending upon both the spacing and phase shift. The effect of spacing variations on heat transfer and pressure drop was more pronounced than that of phase shift variation, especially at high Reynolds number. Comparing results of the tested channels by considering the flow area goodness factor (j/f), it was better for corrugated flow channel with geometrical parameters of 2 les epsiv les 3, and Phi les 90deg.
{"title":"Heat transfer and pressure loss in narrow channels with corrugated walls","authors":"E. Elshafei, M. Awad, E. El-Negiry, A. Ali","doi":"10.1109/THETA.2008.5167177","DOIUrl":"https://doi.org/10.1109/THETA.2008.5167177","url":null,"abstract":"The convective heat transfer and pressure drop characteristics in corrugated channels were experimentally investigated. Experiments were performed on channels of uniform wall temperature and of fixed corrugation ratio, gamma (2A/L=0.2) over a range of Reynolds number, 3220 lesReles9420. Corrugated channels of 0deg, 90deg and 180deg phase shift and with different spacing are considered. The effects of these geometrical parameters on the heat transfer and pressure drop are discussed. The obtained results showed a significant heat transfer enhancement and pressure drop penalty associated with corrugated channels. The average heat transfer coefficients and pressure drops exceeded by about 2.6 to 3.2 and 1.9 to 2.6 times those for parallel plate channel, respectively, depending upon both the spacing and phase shift. The effect of spacing variations on heat transfer and pressure drop was more pronounced than that of phase shift variation, especially at high Reynolds number. Comparing results of the tested channels by considering the flow area goodness factor (j/f), it was better for corrugated flow channel with geometrical parameters of 2 les epsiv les 3, and Phi les 90deg.","PeriodicalId":414963,"journal":{"name":"2008 Second International Conference on Thermal Issues in Emerging Technologies","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125453472","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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