J. M. Belman-Flores, Raul Roman, Julio Valle-Hernández, Juan Serrano
R404A refrigerant is one of the most widely used hydrofluorocarbons in the commercial refrigeration industry for low and medium temperatures. However, this refrigerant contributes negatively to the environment due to its high global warming potential (GWP = 3943), and for several years, it has been labeled as one of the refrigerants that should be phased out. The present study theoretically evaluates low-GWP refrigerants as a replacement alternative to R404A, including R407H, R442A, R449A, R454A, R454C, R455A, R459B, and R465A. The analysis focuses on the comparison between relative differences in the volumetric flow in the compressor suction and the coefficient of performance for four configurations of the vapor compression cycle, such as the basic cycle, the cycle with an internal heat exchanger, the cycle with direct injection, and the cycle with a sub-cooler. According to the proposed operating conditions of evaporation temperature (−10°C and −40°C) and condensation temperature (40°C and 55°C), R454A could be the best long-term replacement option for its low GWP, energy performance, and direct fit for any configuration. R459B could also be considered a viable option, but with certain design modifications. On the contrary, the refrigerants R465A, R455A, and R454C would be discarded because they present a greater non-adaptation to the compressor in each configuration analyzed.
{"title":"Theoretical investigation of low global warming potential blends replacing R404A: the simple refrigeration cycle and its modifications","authors":"J. M. Belman-Flores, Raul Roman, Julio Valle-Hernández, Juan Serrano","doi":"10.1115/1.4064425","DOIUrl":"https://doi.org/10.1115/1.4064425","url":null,"abstract":"\u0000 R404A refrigerant is one of the most widely used hydrofluorocarbons in the commercial refrigeration industry for low and medium temperatures. However, this refrigerant contributes negatively to the environment due to its high global warming potential (GWP = 3943), and for several years, it has been labeled as one of the refrigerants that should be phased out. The present study theoretically evaluates low-GWP refrigerants as a replacement alternative to R404A, including R407H, R442A, R449A, R454A, R454C, R455A, R459B, and R465A. The analysis focuses on the comparison between relative differences in the volumetric flow in the compressor suction and the coefficient of performance for four configurations of the vapor compression cycle, such as the basic cycle, the cycle with an internal heat exchanger, the cycle with direct injection, and the cycle with a sub-cooler. According to the proposed operating conditions of evaporation temperature (−10°C and −40°C) and condensation temperature (40°C and 55°C), R454A could be the best long-term replacement option for its low GWP, energy performance, and direct fit for any configuration. R459B could also be considered a viable option, but with certain design modifications. On the contrary, the refrigerants R465A, R455A, and R454C would be discarded because they present a greater non-adaptation to the compressor in each configuration analyzed.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"49 2","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139383583","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To enhance the cooling deficiency that occurs in a baseline endwall using axially-arranged cooling holes, this paper proposes a new locally-enhanced hole layout using curtain cooling and fan-shaped film holes being arranged on iso-Mach lines. The objective of cooling hole re-design is to minimize secondary flows and thus to provide better film coverage. In experiments, Infrared thermography techniques are applied to validate overall cooling effectiveness of the newly-designed endwall, and aero-thermal fields at the cascade exit are detected by five-hole and thermocouple probes. Additionally, computational fluid dynamic simulations are performed to provide complementary flow insights. A comparison with the baseline hole layout reveals that for a given total coolant flow rate, the newly-designed endwall significantly improves the cooling performance by up to 27% without a noticeable aerodynamic penalty, resulting in a lower and more uniform temperature field. Curtain coolant effectively suppresses the development of horseshoe vortex and provides adequate thermal protection for leading-edge junctures and pressure-side corner regions. The redistribution of fan-shaped film holes reinforces the cooling performance in the passage throat and trailing edge regions. At low and high total mass flow rates, the coolant split between various cooling sources has a substantial impact on cooling performance.
{"title":"Improving turbine endwall overall cooling effectiveness using curtain cooling and redistributed film-hole layouts: an experimental and computational study","authors":"Hang Wu, Xing Yang, Qiang Zhao, Zhenping Feng","doi":"10.1115/1.4064429","DOIUrl":"https://doi.org/10.1115/1.4064429","url":null,"abstract":"\u0000 To enhance the cooling deficiency that occurs in a baseline endwall using axially-arranged cooling holes, this paper proposes a new locally-enhanced hole layout using curtain cooling and fan-shaped film holes being arranged on iso-Mach lines. The objective of cooling hole re-design is to minimize secondary flows and thus to provide better film coverage. In experiments, Infrared thermography techniques are applied to validate overall cooling effectiveness of the newly-designed endwall, and aero-thermal fields at the cascade exit are detected by five-hole and thermocouple probes. Additionally, computational fluid dynamic simulations are performed to provide complementary flow insights. A comparison with the baseline hole layout reveals that for a given total coolant flow rate, the newly-designed endwall significantly improves the cooling performance by up to 27% without a noticeable aerodynamic penalty, resulting in a lower and more uniform temperature field. Curtain coolant effectively suppresses the development of horseshoe vortex and provides adequate thermal protection for leading-edge junctures and pressure-side corner regions. The redistribution of fan-shaped film holes reinforces the cooling performance in the passage throat and trailing edge regions. At low and high total mass flow rates, the coolant split between various cooling sources has a substantial impact on cooling performance.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"68 24","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Faruk Yildiz, E. Alpman, L. Kavurmacioğlu, Cengiz Camci
This paper presents a time-efficient method to optimize the positions of film cooling holes on a gas turbine blade's squealer tip for cooling and aerodynamic performance. A computational approach is employed for the optimization, including validations against experiments. Five discrete film cooling holes are considered, and two different blowing ratios of 0.4 and 1.0 are studied. The positions of cooling holes on the tip along the tangential direction are varied as the input parameters of optimization. The multi-objective optimization uses an algorithm with an artificial neural network for fast fitness function predictions. The best cooling configuration found by the optimization achieves a 13.43% reduction in total heat flux and a 0.4% increase in aerodynamic loss when the blowing rate is 1.0. Including the casing relative motion in the computations results in a total pressure loss coefficient increase of about 8 % for both blowing ratios. For M=1.0, imposing the casing's motion results in a 10.2% reduction in total heat transfer to the tip compared to the stationary casing. For the lower blowing rate of 0.4, the total heat flux reduction to the tip is 12.0% because of imposed casing motion. Hence, the cooling effectiveness can be improved by employing the particular position optimization method presented in this study. The results suggest that experimental and computational heat transfer studies on cooled turbine blade tips, especially in cascade arrangements, need to consider the relative motion of the blade tip.
{"title":"Aerothermal Optimization of Film Cooling Hole Locations on the Squealer Tip of an HP Turbine Blade","authors":"Faruk Yildiz, E. Alpman, L. Kavurmacioğlu, Cengiz Camci","doi":"10.1115/1.4064431","DOIUrl":"https://doi.org/10.1115/1.4064431","url":null,"abstract":"\u0000 This paper presents a time-efficient method to optimize the positions of film cooling holes on a gas turbine blade's squealer tip for cooling and aerodynamic performance. A computational approach is employed for the optimization, including validations against experiments. Five discrete film cooling holes are considered, and two different blowing ratios of 0.4 and 1.0 are studied. The positions of cooling holes on the tip along the tangential direction are varied as the input parameters of optimization. The multi-objective optimization uses an algorithm with an artificial neural network for fast fitness function predictions. The best cooling configuration found by the optimization achieves a 13.43% reduction in total heat flux and a 0.4% increase in aerodynamic loss when the blowing rate is 1.0. Including the casing relative motion in the computations results in a total pressure loss coefficient increase of about 8 % for both blowing ratios. For M=1.0, imposing the casing's motion results in a 10.2% reduction in total heat transfer to the tip compared to the stationary casing. For the lower blowing rate of 0.4, the total heat flux reduction to the tip is 12.0% because of imposed casing motion. Hence, the cooling effectiveness can be improved by employing the particular position optimization method presented in this study. The results suggest that experimental and computational heat transfer studies on cooled turbine blade tips, especially in cascade arrangements, need to consider the relative motion of the blade tip.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"17 14","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382942","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aerodynamic experiments in high speed flow domain mainly rely on precise measurement transient surface temperatures and subsequent quantification of heat flux. These experiments are mainly simulated in high enthalpy short-duration facilities for which test flow duration are in the order of few milliseconds and the thermal loads resemble the nature of step/impulse. This study focuses on a specially designed fast-response coaxial surface junction thermal probe (CSTP) with capability of capturing transient temperature signals. The short-duration calibration experiments are realized to mimic the simulated flow conditions of high enthalpy test facilities. The classical one-dimensional heat conduction modelling has been used to deduce surface heat flux from the acquired temperature responses. It demonstrates a commendable accuracy of 2.5% when compared with known heat loads of calibration experiment. An advanced soft computing technique, the Adaptive Neuro-Fuzzy Inference System (ANFIS), is introduced for short-duration heat flux predictions. This methodology successfully recovers known (step or ramp) heat loads within a specific experimental time frame (0.2s). The results exhibit excellent agreement in prediction of trend and magnitude, carrying uncertainties of 3% for radiative and 5% for convective experiments. Consequently, the CSTP appears as a rapidly responsive transient heat flux sensor; for real-time short-duration experiments. The soft computing approach (ANFIS) offers an alternative means of heat flux estimation from temperature history irrespective of mode of heat transfer and nature of heat load, marked by its prediction accuracy, diminished mathematical intricacies, and reduced numerical requisites.
{"title":"Soft Computing Model for Inverse Prediction of Surface Heat Flux from Temperature Responses in Short-Duration Heat Transfer Experiments","authors":"Sima Nayak, Niranjan Sahoo, Masaharu Komiyama","doi":"10.1115/1.4064432","DOIUrl":"https://doi.org/10.1115/1.4064432","url":null,"abstract":"\u0000 Aerodynamic experiments in high speed flow domain mainly rely on precise measurement transient surface temperatures and subsequent quantification of heat flux. These experiments are mainly simulated in high enthalpy short-duration facilities for which test flow duration are in the order of few milliseconds and the thermal loads resemble the nature of step/impulse. This study focuses on a specially designed fast-response coaxial surface junction thermal probe (CSTP) with capability of capturing transient temperature signals. The short-duration calibration experiments are realized to mimic the simulated flow conditions of high enthalpy test facilities. The classical one-dimensional heat conduction modelling has been used to deduce surface heat flux from the acquired temperature responses. It demonstrates a commendable accuracy of 2.5% when compared with known heat loads of calibration experiment. An advanced soft computing technique, the Adaptive Neuro-Fuzzy Inference System (ANFIS), is introduced for short-duration heat flux predictions. This methodology successfully recovers known (step or ramp) heat loads within a specific experimental time frame (0.2s). The results exhibit excellent agreement in prediction of trend and magnitude, carrying uncertainties of 3% for radiative and 5% for convective experiments. Consequently, the CSTP appears as a rapidly responsive transient heat flux sensor; for real-time short-duration experiments. The soft computing approach (ANFIS) offers an alternative means of heat flux estimation from temperature history irrespective of mode of heat transfer and nature of heat load, marked by its prediction accuracy, diminished mathematical intricacies, and reduced numerical requisites.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"52 48","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139382292","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhenxing Zhang, Dan Wang, Yue Guo, Lei Shen, Xiaodan Wang
Due to the increase in heat load, the demand for heat dissipation of the cabin cooling module has increased. The fan arrangement and the design of the fan cowl can significantly affect the intake air parameters, thereby affecting the performance of the heat exchangers. In this paper, the whole vehicle model was set up and the effect of the fan installation distance, the fan cowl coverage ratio, and the radial extension of the fan cowl outlet was researched by numerical simulation. The results show that due to the relative position of the layout of the cooling module, the effect of the fan arrangement and the fan cowl design on the intake parameters of the radiator is greater than that of the intercooler. The improvement of the air velocity uniformity can reduce the intake air average temperature for better heat dissipation, a 2% improvement in air intake velocity uniformity can lead to a 6% reduction in air intake average temperature event at a low air mass flow. The greater installation distance of the fan or the higher closing degree of the fan cowl, the more favorable intake parameters to ensure the better cooling performance of the heat exchangers. Moreover, when the fan cowl coverage ratio reaches 0.9, the air intake average temperature increases by 5.6%, which means that the fan cowl coverage should not be too high. This study will provide useful reference information for the design of cooling modules in the cabin.
{"title":"Study on the Influence of Fan and Fan Cowl on Intake Air Parameters of Cooling Module","authors":"Zhenxing Zhang, Dan Wang, Yue Guo, Lei Shen, Xiaodan Wang","doi":"10.1115/1.4064423","DOIUrl":"https://doi.org/10.1115/1.4064423","url":null,"abstract":"\u0000 Due to the increase in heat load, the demand for heat dissipation of the cabin cooling module has increased. The fan arrangement and the design of the fan cowl can significantly affect the intake air parameters, thereby affecting the performance of the heat exchangers. In this paper, the whole vehicle model was set up and the effect of the fan installation distance, the fan cowl coverage ratio, and the radial extension of the fan cowl outlet was researched by numerical simulation. The results show that due to the relative position of the layout of the cooling module, the effect of the fan arrangement and the fan cowl design on the intake parameters of the radiator is greater than that of the intercooler. The improvement of the air velocity uniformity can reduce the intake air average temperature for better heat dissipation, a 2% improvement in air intake velocity uniformity can lead to a 6% reduction in air intake average temperature event at a low air mass flow. The greater installation distance of the fan or the higher closing degree of the fan cowl, the more favorable intake parameters to ensure the better cooling performance of the heat exchangers. Moreover, when the fan cowl coverage ratio reaches 0.9, the air intake average temperature increases by 5.6%, which means that the fan cowl coverage should not be too high. This study will provide useful reference information for the design of cooling modules in the cabin.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"13 3","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139385232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yurii Nikolaenko, Andrii Solomakha, R. Melnyk, L. Lipnitskyi, Volodymyr Kravets, Dmitrii Kozak, Demyd Pekur
In this paper a novel design of pulsating heat pipe (PHP) with one evaporator and two condensers located on both sides of the evaporator at an angle to the horizon was proposed, manufactured and experimentally investigated for the purpose of use in cooling systems for electronic devices operating in a tilted position. The PHP body is made of a copper capillary tube with an inner diameter of 1.5 mm. The working fluid is methanol. The number of turns is 4. The heating zone dimensions are 60 mm × 36 mm, the cooling zone is 200 mm × 35 mm. The dependences of the temperature in the heating and cooling zones and the PHP thermal resistance both on the power input (from 30 W to 200 W), and on the orientation in space (at tilt angles of 0°, 15°, 30°, 60°, 90°) were obtained. In the power range from 120 W to 200 W the tilt angle practically does not affect the thermal resistance. A comparison of the thermal resistance of the developed PHP with known PHPs filled with methanol, showed the high efficiency of the developed PHP: at power input from 120 W to 200 W, the thermal resistance was from 0.2 °C W−1 to 0.18°C W−1. The developed PHP design is promising for use in air cooling systems, for instance, of radar transmit/receive modules and high-power LED lighting systems.
{"title":"Experimental Investigation on the Thermal Performances of a New Design of Pulsating Heat Pipe with Two Condensers","authors":"Yurii Nikolaenko, Andrii Solomakha, R. Melnyk, L. Lipnitskyi, Volodymyr Kravets, Dmitrii Kozak, Demyd Pekur","doi":"10.1115/1.4064426","DOIUrl":"https://doi.org/10.1115/1.4064426","url":null,"abstract":"\u0000 In this paper a novel design of pulsating heat pipe (PHP) with one evaporator and two condensers located on both sides of the evaporator at an angle to the horizon was proposed, manufactured and experimentally investigated for the purpose of use in cooling systems for electronic devices operating in a tilted position. The PHP body is made of a copper capillary tube with an inner diameter of 1.5 mm. The working fluid is methanol. The number of turns is 4. The heating zone dimensions are 60 mm × 36 mm, the cooling zone is 200 mm × 35 mm. The dependences of the temperature in the heating and cooling zones and the PHP thermal resistance both on the power input (from 30 W to 200 W), and on the orientation in space (at tilt angles of 0°, 15°, 30°, 60°, 90°) were obtained. In the power range from 120 W to 200 W the tilt angle practically does not affect the thermal resistance. A comparison of the thermal resistance of the developed PHP with known PHPs filled with methanol, showed the high efficiency of the developed PHP: at power input from 120 W to 200 W, the thermal resistance was from 0.2 °C W−1 to 0.18°C W−1. The developed PHP design is promising for use in air cooling systems, for instance, of radar transmit/receive modules and high-power LED lighting systems.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"54 23","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139386915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The cobweb-like microchannel heat sink is acknowledged for its exceptional heat transfer capabilities in comparison to other biomimetic microchannel heat sinks. The objective of this paper is to improve the performance of the cobweb-like microchannel heat sink by optimizing its geometric structure parameters through a multi-objective approach. The Box-Behnken design method was utilized to conduct response surface analysis on the design variables, and the Pareto solution set was obtained by applying the multi-objective particle swarm optimization algorithm to the fitted functions of pressure and temperature. The TOPSIS method was used to select the most appropriate solution from the Pareto solution set. The performance of a microchannel heat sink was evaluated using the computational fluid dynamics (CFD) analysis. The optimized structure of the cobweb-like microchannel heat sink led to a decrease in the average temperature by 3K and a reduction in pressure drop by 1514Pa, as compared to the original design. This significant improvement in the overall performance highlights the importance of a well-designed channel structure in further enhancing the comprehensive performance of the microchannel heat sink.
{"title":"Multi-objective optimization design of a cobweb-like–channel heat sink using particle swarm algorithm","authors":"Hongmei Wei, Ruien Yu","doi":"10.1115/1.4064417","DOIUrl":"https://doi.org/10.1115/1.4064417","url":null,"abstract":"\u0000 The cobweb-like microchannel heat sink is acknowledged for its exceptional heat transfer capabilities in comparison to other biomimetic microchannel heat sinks. The objective of this paper is to improve the performance of the cobweb-like microchannel heat sink by optimizing its geometric structure parameters through a multi-objective approach. The Box-Behnken design method was utilized to conduct response surface analysis on the design variables, and the Pareto solution set was obtained by applying the multi-objective particle swarm optimization algorithm to the fitted functions of pressure and temperature. The TOPSIS method was used to select the most appropriate solution from the Pareto solution set. The performance of a microchannel heat sink was evaluated using the computational fluid dynamics (CFD) analysis. The optimized structure of the cobweb-like microchannel heat sink led to a decrease in the average temperature by 3K and a reduction in pressure drop by 1514Pa, as compared to the original design. This significant improvement in the overall performance highlights the importance of a well-designed channel structure in further enhancing the comprehensive performance of the microchannel heat sink.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"37 16","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zaria Robins, Nicholas Asbury, John Nuszkowski, Stephen Stagon, Rafael Padilla, Karl Hawes
Demands for more powerful and smaller electronic devices have increased the energy dissipation requirements. Accurate determination of the thermal performance of small sized heat sinks is necessary for innovation within the heat dissipation sector. This study designed, developed, and tested an apparatus for determining the thermal performance of mini heat sinks (MHS). The test apparatus consisted of a wind tunnel, fan, heater, heater block, five temperature sensors, air velocity sensor, and a data acquisition system. A robust dataset was created by testing the heater without a MHS and testing two different MHS materials of polycarbonate (PC) and aluminum (AL) and having 16 to 21 repeat tests. Linear and polynomial approximations for the temperature profile were explored. For the steady state tests, the mean and 90% confidence interval were calculated to determine statistically significant differences. The temperature gradient at the interface, rate of heat transfer, and the thermal resistances from the polynomial fit had higher variation than the linear fit. The experimentally determined heater surface temperature had a 90% confidence interval of ±0.3 to ±0.7°C. The 90% confidence intervals for the thermal resistances were 1.0 to 1.5 K/W for linear and 2.3 to 6.0 K/W for polynomial. Statistically significant differences for the temperature gradient at the interface, rate of heat transfer, and thermal resistances between the bare, PC, and AL were found. Due to heat losses, the linear fit had greater precision, but the polynomial fit had greater accuracy.
{"title":"Thermal Test Apparatus for Mini Heat Sinks","authors":"Zaria Robins, Nicholas Asbury, John Nuszkowski, Stephen Stagon, Rafael Padilla, Karl Hawes","doi":"10.1115/1.4064428","DOIUrl":"https://doi.org/10.1115/1.4064428","url":null,"abstract":"\u0000 Demands for more powerful and smaller electronic devices have increased the energy dissipation requirements. Accurate determination of the thermal performance of small sized heat sinks is necessary for innovation within the heat dissipation sector. This study designed, developed, and tested an apparatus for determining the thermal performance of mini heat sinks (MHS). The test apparatus consisted of a wind tunnel, fan, heater, heater block, five temperature sensors, air velocity sensor, and a data acquisition system. A robust dataset was created by testing the heater without a MHS and testing two different MHS materials of polycarbonate (PC) and aluminum (AL) and having 16 to 21 repeat tests. Linear and polynomial approximations for the temperature profile were explored. For the steady state tests, the mean and 90% confidence interval were calculated to determine statistically significant differences. The temperature gradient at the interface, rate of heat transfer, and the thermal resistances from the polynomial fit had higher variation than the linear fit. The experimentally determined heater surface temperature had a 90% confidence interval of ±0.3 to ±0.7°C. The 90% confidence intervals for the thermal resistances were 1.0 to 1.5 K/W for linear and 2.3 to 6.0 K/W for polynomial. Statistically significant differences for the temperature gradient at the interface, rate of heat transfer, and thermal resistances between the bare, PC, and AL were found. Due to heat losses, the linear fit had greater precision, but the polynomial fit had greater accuracy.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"42 2","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139387087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Hong-Wei Chen, Shanshan Zhang, Yang Li, Chi Xu, Shu-Xing Qin
Electromagnetic (EM) heating effectively reduces oil viscosity and improves oil recovery rate by heating oil layers with EM radiation. However, the selection of well configurations for EM heating oil recovery has yet to be thoroughly studied. This article uses numerical simulation methods to study the effect of different well configurations on the oil recovery efficiency of EM heating heavy oil reservoirs. A complex EM heating model coupled with an EM temperature seepage field was established to simulate two different well configurations: vertical and horizontal wells. The results indicate that the horizontal well configuration is more efficient in heating heavy oil reservoirs in the same area than the vertical well configuration. Vertical heating wells facilitate the swift creation of a flow channel around the wellbore due to the direction of heavy oil flow coinciding with that of the well. However, the horizontal configuration takes longer for a flow channel to form. Despite this, the temperature distribution in the reservoir under the horizontal configuration is more uniform, and high temperatures do not accumulate around the heating wells. On the other hand, with a vertical configuration, the heat accumulates at the bottom of the well along with the flow of heavy oil. Increasing EM power and frequency can lead to a rise in reservoir temperature and facilitate the flow of heavy oil. However, it is important to note that beyond a certain point, the benefits of increased power and frequency become limited and may result in an excessively high temperature of heavy oil.
{"title":"Multi-physical Field Numerical Simulation of Electromagnetic Heating in Heavy Oil Reservoirs with Different Well Configurations","authors":"Hong-Wei Chen, Shanshan Zhang, Yang Li, Chi Xu, Shu-Xing Qin","doi":"10.1115/1.4064424","DOIUrl":"https://doi.org/10.1115/1.4064424","url":null,"abstract":"\u0000 Electromagnetic (EM) heating effectively reduces oil viscosity and improves oil recovery rate by heating oil layers with EM radiation. However, the selection of well configurations for EM heating oil recovery has yet to be thoroughly studied. This article uses numerical simulation methods to study the effect of different well configurations on the oil recovery efficiency of EM heating heavy oil reservoirs. A complex EM heating model coupled with an EM temperature seepage field was established to simulate two different well configurations: vertical and horizontal wells. The results indicate that the horizontal well configuration is more efficient in heating heavy oil reservoirs in the same area than the vertical well configuration. Vertical heating wells facilitate the swift creation of a flow channel around the wellbore due to the direction of heavy oil flow coinciding with that of the well. However, the horizontal configuration takes longer for a flow channel to form. Despite this, the temperature distribution in the reservoir under the horizontal configuration is more uniform, and high temperatures do not accumulate around the heating wells. On the other hand, with a vertical configuration, the heat accumulates at the bottom of the well along with the flow of heavy oil. Increasing EM power and frequency can lead to a rise in reservoir temperature and facilitate the flow of heavy oil. However, it is important to note that beyond a certain point, the benefits of increased power and frequency become limited and may result in an excessively high temperature of heavy oil.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"53 1","pages":""},"PeriodicalIF":2.1,"publicationDate":"2024-01-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139386052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Guangfeng Wan, Qiang Guo, Yang Li, Gui-Yang Ma, Chi Xu, Ya-Ya Li
Moving bed part-fluidized boiler is a new type of furnace. The new combustion method in the furnace has attracted a lot of attention and shown attractive prospects. Two-dimensional computational fluid dynamic (CFD) simulations were performed for a 116 MW moving bed part-fluidized boiler to investigate the different combustion patterns of coal particles of different particle sizes inside the furnace chamber. A low-NOX combustion method based on the combination of laminar combustion and fluidized combustion is proposed. By comparing the effects of different air distributions on the fluidization state of coal particles, the air distribution values required for optimal fluidized combustion were obtained. The temperature field and pollutant distribution in the furnace chamber for the conventional combustion method and the new combustion method were also simulated. The results show that the combustion technology combining laminar combustion and fluidization of a moving bed part-fluidized boiler can significantly improve the combustion rate and reduce the NOX concentration at the furnace exit. When the secondary air speed is up to 15m/s, the coal particles smaller than 5mm are fully fluidized and burned in the whole furnace chamber. The coal particles larger than 5mm are burned on the bed. The pollutant emission of the boiler can reach the best condition. The new type of boiler can reach a super clean emission in which the NOX emission value is below 47mg/m3, and the SO2 emission value is reduced to 0.15mg/m3.
{"title":"Simulation of Heat and Mass Transfer in a Moving Bed Part-fluidized Boiler","authors":"Guangfeng Wan, Qiang Guo, Yang Li, Gui-Yang Ma, Chi Xu, Ya-Ya Li","doi":"10.1115/1.4064338","DOIUrl":"https://doi.org/10.1115/1.4064338","url":null,"abstract":"\u0000 Moving bed part-fluidized boiler is a new type of furnace. The new combustion method in the furnace has attracted a lot of attention and shown attractive prospects. Two-dimensional computational fluid dynamic (CFD) simulations were performed for a 116 MW moving bed part-fluidized boiler to investigate the different combustion patterns of coal particles of different particle sizes inside the furnace chamber. A low-NOX combustion method based on the combination of laminar combustion and fluidized combustion is proposed. By comparing the effects of different air distributions on the fluidization state of coal particles, the air distribution values required for optimal fluidized combustion were obtained. The temperature field and pollutant distribution in the furnace chamber for the conventional combustion method and the new combustion method were also simulated. The results show that the combustion technology combining laminar combustion and fluidization of a moving bed part-fluidized boiler can significantly improve the combustion rate and reduce the NOX concentration at the furnace exit. When the secondary air speed is up to 15m/s, the coal particles smaller than 5mm are fully fluidized and burned in the whole furnace chamber. The coal particles larger than 5mm are burned on the bed. The pollutant emission of the boiler can reach the best condition. The new type of boiler can reach a super clean emission in which the NOX emission value is below 47mg/m3, and the SO2 emission value is reduced to 0.15mg/m3.","PeriodicalId":17404,"journal":{"name":"Journal of Thermal Science and Engineering Applications","volume":"101 24","pages":""},"PeriodicalIF":2.1,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138958794","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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