Pub Date : 2024-04-01DOI: 10.1615/jenhheattransf.2024052195
Xiangyu Wang, Xiang-Hua XU, Xingang Liang
Optimizing structure parameters is pivotal in enhancing the convective heat. This study leverages machine learning methods to establish a relationship between input parameters and targets, providing a novel approach to structure parameter optimization in convective heat transfer of a unilateral-heated square channel with inclined ribs. Initially, dimensional analysis is employed to identify structure parameters that influence friction coefficient, Nusselt number, and comprehensive heat transfer characteristic (PEC). A substantial dataset is procured through batch modeling and CFD simulations. The Gaussian process regression is applied to train the data due to its continuity and smoothness. The influence of the rib structure parameters on the flow and heat transfer characteristics is analyzed by CFD simulations and the training results. Finally, the structure parameters corresponding to the optimal Nu and PEC are obtained via the well-trained machine learning model. The optimization results are validated through CFD simulations, yielding the best structure parameters that demonstrate a 7% and 3% increase in Nu and PEC, respectively, which is better than the best results from the numerical data used for training the machine learning model. The heat transfer mechanism and heat transfer effects of the unilateral-heated square channels with inclined ribs are analyzed. This study underscores the potential of machine learning in optimizing convective heat transfer channels, benefiting future research and applications in this field.
优化结构参数是提高对流热量的关键。本研究利用机器学习方法建立了输入参数与目标之间的关系，为带有倾斜肋片的单侧加热方形通道对流传热中的结构参数优化提供了一种新方法。首先，采用尺寸分析来确定影响摩擦系数、努塞尔特数和综合传热特性（PEC）的结构参数。通过批量建模和 CFD 模拟获得了大量数据集。由于数据具有连续性和平滑性，因此采用高斯过程回归来训练数据。通过 CFD 模拟和训练结果分析了肋骨结构参数对流动和传热特性的影响。最后，通过训练有素的机器学习模型获得了与最佳 Nu 和 PEC 相对应的结构参数。通过 CFD 模拟验证了优化结果，得出的最佳结构参数表明 Nu 和 PEC 分别增加了 7% 和 3%，优于用于训练机器学习模型的数值数据的最佳结果。研究分析了带有倾斜肋片的单侧加热方形通道的传热机制和传热效果。这项研究强调了机器学习在优化对流传热通道方面的潜力，有利于该领域未来的研究和应用。
{"title":"Heat Convection Enhancement of Unilateral-Heated Square Channels by Inclined Ribs Optimization with Machine Learning","authors":"Xiangyu Wang, Xiang-Hua XU, Xingang Liang","doi":"10.1615/jenhheattransf.2024052195","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024052195","url":null,"abstract":"Optimizing structure parameters is pivotal in enhancing the convective heat. This study leverages machine learning methods to establish a relationship between input parameters and targets, providing a novel approach to structure parameter optimization in convective heat transfer of a unilateral-heated square channel with inclined ribs. Initially, dimensional analysis is employed to identify structure parameters that influence friction coefficient, Nusselt number, and comprehensive heat transfer characteristic (PEC). A substantial dataset is procured through batch modeling and CFD simulations. The Gaussian process regression is applied to train the data due to its continuity and smoothness. The influence of the rib structure parameters on the flow and heat transfer characteristics is analyzed by CFD simulations and the training results. Finally, the structure parameters corresponding to the optimal Nu and PEC are obtained via the well-trained machine learning model. The optimization results are validated through CFD simulations, yielding the best structure parameters that demonstrate a 7% and 3% increase in Nu and PEC, respectively, which is better than the best results from the numerical data used for training the machine learning model. The heat transfer mechanism and heat transfer effects of the unilateral-heated square channels with inclined ribs are analyzed. This study underscores the potential of machine learning in optimizing convective heat transfer channels, benefiting future research and applications in this field.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"46 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140802341","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}
Pub Date : 2024-03-01DOI: 10.1615/jenhheattransf.2024052045
Kuan-Fu Sung, I-Chuan Chang, Chien-Yuh Yang
This study experimentally investigated the heat transfer and pressure drop performance of refrigerant HFC-245fa flow boiling in microchannel heat exchangers with and without micro porous coating. The flow boiling heat transfer performance at various mass fluxes, heating rate, exit vapor qualities and surface coating thickness was compared. The test results show that the 52 m coating thickness porous surface exhibited 65% to 148% higher heat transfer performance than the smooth surface. However, for the 98 m microporous coating surface, the heat transfer coefficients were only from 41% to 90% higher than those on smooth surface at various mass fluxes. This shows that the thicker coating layer thickness did not provide better heat transfer performance. The improvement on the maximum heat fluxes by applying micro porous coatings was only 3% to 10% in comparing to that on smooth surface. Partial dryout was observed at high and moderate mass fluxes on both smooth and porous coating channels. It happened at lower exit vapor qualities in micro porous coating channels than that in smooth channels. The partial dryout exit vapor qualities increased with decreasing mass fluxes. For the lowest mass flux, owing to the low heat flux and low nucleation suppression, no significant partial dryout was investigated. The pressure drops in micro porous coating channels were around 25 to 47% higher than those in smooth channels. There was not significant influence of micro porous coating layer thickness on flow boiling pressures drops.
{"title":"Flow Boiling Heat Transfer in Microchannel Heat Exchangers with Micro Porous Coating Surface","authors":"Kuan-Fu Sung, I-Chuan Chang, Chien-Yuh Yang","doi":"10.1615/jenhheattransf.2024052045","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024052045","url":null,"abstract":"This study experimentally investigated the heat transfer and pressure drop performance of refrigerant HFC-245fa flow boiling in microchannel heat exchangers with and without micro porous coating. The flow boiling heat transfer performance at various mass fluxes, heating rate, exit vapor qualities and surface coating thickness was compared. The test results show that the 52 m coating thickness porous surface exhibited 65% to 148% higher heat transfer performance than the smooth surface. However, for the 98 m microporous coating surface, the heat transfer coefficients were only from 41% to 90% higher than those on smooth surface at various mass fluxes. This shows that the thicker coating layer thickness did not provide better heat transfer performance. The improvement on the maximum heat fluxes by applying micro porous coatings was only 3% to 10% in comparing to that on smooth surface.\u0000Partial dryout was observed at high and moderate mass fluxes on both smooth and porous coating channels. It happened at lower exit vapor qualities in micro porous coating channels than that in smooth channels. The partial dryout exit vapor qualities increased with decreasing mass fluxes. For the lowest mass flux, owing to the low heat flux and low nucleation suppression, no significant partial dryout was investigated.\u0000The pressure drops in micro porous coating channels were around 25 to 47% higher than those in smooth channels. There was not significant influence of micro porous coating layer thickness on flow boiling pressures drops.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"35 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140299669","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}
Pub Date : 2024-03-01DOI: 10.1615/jenhheattransf.2024051600
Maharshi Shukla, Satish Kandlikar
Extensive research shows the necessity of efficient cooling systems to enable electronic components to operate at high-performance levels for a sustained period. While conventional methods have served the cooling needs so far, rising computational power, energy efficiency, and sustainability requirements call for improved techniques. The literature shows the effectiveness of two-phase systems in cooling electronic components like microprocessors. The literature further describes various enhancement mechanisms to elevate the Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) in these systems. While a high CHF is desired, having a high HTC is equally important to keep the operating temperatures below a permissible limit. The present article summarizes enhancement structures found in the literature that are suitable for electronic cooling to provide this dual enhancement in CHF and HTC. New enhancement evaluation criteria are introduced that also consider the surface temperature limit imposed by the electronic components. The CHF Enhancement Ratio (ERCHF) represents the ratio of CHF for enhancement structures to the CHF for a plain surface, and the Enhancement Index (EI) represents the ratio of wall superheat at CHF with the enhanced structures, to the wall superheat at its respective CHF condition for a plain surface.
{"title":"Enhancement Evaluation Criteria for Pool Boiling Enhancement Structures in Electronics Cooling: CHF Enhancement Ratio (ER-CHF) and Enhancement Index (EI)","authors":"Maharshi Shukla, Satish Kandlikar","doi":"10.1615/jenhheattransf.2024051600","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024051600","url":null,"abstract":"Extensive research shows the necessity of efficient cooling systems to enable electronic components to operate at high-performance levels for a sustained period. While conventional methods have served the cooling needs so far, rising computational power, energy efficiency, and sustainability requirements call for improved techniques. The literature shows the effectiveness of two-phase systems in cooling electronic components like microprocessors. The literature further describes various enhancement mechanisms to elevate the Critical Heat Flux (CHF) and Heat Transfer Coefficient (HTC) in these systems. While a high CHF is desired, having a high HTC is equally important to keep the operating temperatures below a permissible limit. The present article summarizes enhancement structures found in the literature that are suitable for electronic cooling to provide this dual enhancement in CHF and HTC. New enhancement evaluation criteria are introduced that also consider the surface temperature limit imposed by the electronic components. The CHF Enhancement Ratio (ERCHF) represents the ratio of CHF for enhancement structures to the CHF for a plain surface, and the Enhancement Index (EI) represents the ratio of wall superheat at CHF with the enhanced structures, to the wall superheat at its respective CHF condition for a plain surface.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"19 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140019523","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}
Pub Date : 2024-02-01DOI: 10.1615/jenhheattransf.2024051508
Zhou Wang, Li Jia, Hongling Lu, Yutong Shen, Liaofei Yin
Due to the different application for portable electronic devices, there are instantaneous changes in the thermal load of the CPU and battery in the operation. The traditional uniform structure wick can not allow for evaporation and reflow of the working fluid under complex conditions, hence reducing the heat transfer performance of the vapor chamber (VC). This paper puts forward a novel style of VC to overcome the difficulty of heat export for electronic devices with dual heat sources. The wick with gradient structure in heat source zone and reflow zone was made by the method of zonal sintering, which could effectively promote the evaporation and reflow of working fluid with multi-heating sources and complex conditions. The influence of step heating condition and pulse heating condition on the heat transfer performance of the VC with various filling ratios was analyzed. The results showed that under the step heating condition, the best heat transfer performance of the VC was achieved at a filling ratio of approximately 90%, with a minimum thermal resistance of only 0.31 oC/W at 45 W. Under the pulse heating condition, in order to significantly reduce the temperature hysteretic effect of the VC, a gradient structure core was sintered in different regions, and the maximum hysteretic temperature was 2.7 oC when the filling ratio wass 80% and 100%. The temperature lag could be effectively eliminated when the filling ratio was 90%. The results of the research supplied a theoretical basis for the design and testing of VC under complex working conditions and the development of efficient heat transfer elements.
{"title":"Influence of transient heat pulse on heat transfer performance of vapor chamber with different filling ratios","authors":"Zhou Wang, Li Jia, Hongling Lu, Yutong Shen, Liaofei Yin","doi":"10.1615/jenhheattransf.2024051508","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024051508","url":null,"abstract":"Due to the different application for portable electronic devices, there are instantaneous changes in the thermal load of the CPU and battery in the operation. The traditional uniform structure wick can not allow for evaporation and reflow of the working fluid under complex conditions, hence reducing the heat transfer performance of the vapor chamber (VC). This paper puts forward a novel style of VC to overcome the difficulty of heat export for electronic devices with dual heat sources. The wick with gradient structure in heat source zone and reflow zone was made by the method of zonal sintering, which could effectively promote the evaporation and reflow of working fluid with multi-heating sources and complex conditions. The influence of step heating condition and pulse heating condition on the heat transfer performance of the VC with various filling ratios was analyzed. The results showed that under the step heating condition, the best heat transfer performance of the VC was achieved at a filling ratio of approximately 90%, with a minimum thermal resistance of only 0.31 oC/W at 45 W. Under the pulse heating condition, in order to significantly reduce the temperature hysteretic effect of the VC, a gradient structure core was sintered in different regions, and the maximum hysteretic temperature was 2.7 oC when the filling ratio wass 80% and 100%. The temperature lag could be effectively eliminated when the filling ratio was 90%. The results of the research supplied a theoretical basis for the design and testing of VC under complex working conditions and the development of efficient heat transfer elements.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"6 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140004491","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}
Pub Date : 2024-02-01DOI: 10.1615/jenhheattransf.2024051452
El Bachir Lahmer, Jaouad Benhamou, Youssef Admi, Mohammed Amine Moussaoui, Ahmed Mezrhab, Rakesh Kumar Phanden
The present work evaluates thermal exchange through a double-mini channel heat sink employed as a cooling system for electronic components. Different factors influencing heat exchange enhancement were investigated using Ansys-Fluent software, which enables the simulation of the fluid flow and heat transfer. The evaluation of thermal exchange between the cold fluid and heated solid with high thermal dissipation has been accurately analyzed under the effect of system geometry, fluid nature, and cooling system materials. The numerical outcomes demonstrated that the heat transfer quality significantly increases with the variation of the system shape. In addition, the nature of the fluid and cooling system materials enhances the heat transfer rate.
{"title":"Evaluation of Heat Transfer Rate of Double-Layered Heat Sink Cooling System with High Energy Dissipation","authors":"El Bachir Lahmer, Jaouad Benhamou, Youssef Admi, Mohammed Amine Moussaoui, Ahmed Mezrhab, Rakesh Kumar Phanden","doi":"10.1615/jenhheattransf.2024051452","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024051452","url":null,"abstract":"The present work evaluates thermal exchange through a double-mini channel heat sink employed as a cooling system for electronic components. Different factors influencing heat exchange enhancement were investigated using Ansys-Fluent software, which enables the simulation of the fluid flow and heat transfer. The evaluation of thermal exchange between the cold fluid and heated solid with high thermal dissipation has been accurately analyzed under the effect of system geometry, fluid nature, and cooling system materials. The numerical outcomes demonstrated that the heat transfer quality significantly increases with the variation of the system shape. In addition, the nature of the fluid and cooling system materials enhances the heat transfer rate.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"2021 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769401","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}
Pub Date : 2024-02-01DOI: 10.1615/jenhheattransf.2024051487
Xin Liu, Yiqing Guo, Jingchun Min, Xuan ZHANG, Xiaomin Wu
The collision and freezing of supercooled water droplets exist in many fields and are usually unconducive. The superhydrophobic surfaces used for anti-icing generally have microstructures or local protrusions which could be simplified as small spherical targets comparable to the droplet in size. The supercooled water droplets' collision and freezing on small low-temperature superhydrophobic spherical targets with the sphere-to-droplet diameter ratio D* ≤ 1 are studied numerically in this work. Coupling the solidification-melting model, the Volume of Fluid (VOF) method is used to implement numerical simulations. The supercooling degree, Weber number, and sphere-to-droplet diameter ratio effects on the collision and freezing behaviors and the area coverage ratio of the droplet on the low-temperature small sphere are investigated. Six typical morphologies are identified: full dripping, partial dripping, lower adhesion, wrapping adhesion, upper adhesion, and rebound. The water droplet is found to be more likely to drip down with the increasing Weber number, and the decreasing supercooling degree and the decreasing diameter ratio. A comprehensive morphology map is eventually established to illustrate the combined influence of the Weber number and diameter ratio on the occurrences of the rebound, adhesion, and dripping for different supercooling degrees. This work provides theoretical guidance for the engineering design and structural optimization of anti-icing surfaces.
{"title":"COLLISION MORPHOLOGIES OF SUPERCOOLED WATER DROPLETS ON SMALL LOW-TEMPERATURE SUPERHYDROPHOBIC SPHERICAL TARGETS","authors":"Xin Liu, Yiqing Guo, Jingchun Min, Xuan ZHANG, Xiaomin Wu","doi":"10.1615/jenhheattransf.2024051487","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024051487","url":null,"abstract":"The collision and freezing of supercooled water droplets exist in many fields and are usually unconducive. The superhydrophobic surfaces used for anti-icing generally have microstructures or local protrusions which could be simplified as small spherical targets comparable to the droplet in size. The supercooled water droplets' collision and freezing on small low-temperature superhydrophobic spherical targets with the sphere-to-droplet diameter ratio D* ≤ 1 are studied numerically in this work. Coupling the solidification-melting model, the Volume of Fluid (VOF) method is used to implement numerical simulations. The supercooling degree, Weber number, and sphere-to-droplet diameter ratio effects on the collision and freezing behaviors and the area coverage ratio of the droplet on the low-temperature small sphere are investigated. Six typical morphologies are identified: full dripping, partial dripping, lower adhesion, wrapping adhesion, upper adhesion, and rebound. The water droplet is found to be more likely to drip down with the increasing Weber number, and the decreasing supercooling degree and the decreasing diameter ratio. A comprehensive morphology map is eventually established to illustrate the combined influence of the Weber number and diameter ratio on the occurrences of the rebound, adhesion, and dripping for different supercooling degrees. This work provides theoretical guidance for the engineering design and structural optimization of anti-icing surfaces.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"14 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769522","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}
Pub Date : 2024-02-01DOI: 10.1615/jenhheattransf.2024051522
AMAN SINGH RAJPOOT, TUSHAR Choudhary, ANOOP SHUKLA, H. CHELLADURAI, UPENDRA RAJAK, ABHINAV ANAND SINHA
The performance and emissions characteristics of a diesel engine running on several fuel combinations, including diesel, biodiesel, and fuel mixed with TiO2 nanoparticles, are assessed in this research on a diesel engine. The study investigates how performance and emissions are impacted when diesel and biodiesel are treated with 50 and 100 ppm of TiO2 nanoparticles under varied engine loads ranging from 25 to 100%. The BTE values for the mixed biodiesel fuels with TiO2 nanoparticles (B0Ti50, B0Ti100, B5Ti50, and B5Ti100) show an improvement over normal diesel (B0) and biodiesel (B5) fuels. The addition of TiO2 nanoparticles leads to reductions in brake specific fuel consumption (BSFC) of up to 8% with B0 and up to 14.29% with B5, and improvements in brake thermal efficiency (BTE) of up to 2% with B0 and up to 4.02% with B5. With regard to carbon dioxide (CO2) and hydrocarbon (HC) emissions, the use of TiO2 nanoparticles decreased emissions by up to 18.4% at the cost of nitric oxide (NO) emissions, which increased by up to 5.87%. The exergy performance coefficient (Exp) and sustainability index (SI) increased by up to 18.99% and 5.63%, respectively. The percentage changes showed enhanced engine performance, lower emissions, and improved energy conversion efficiency with the inclusion of nanoparticles. The results suggest fuel blends' advantages in terms of energy and the environment; however, it is also important to look at the economic feasibility and stability of TiO2 nanoparticles.
{"title":"Experimental Investigation on Behavior of a Diesel Engine with Energy, Exergy, and Sustainability Analysis Using Titanium Oxide (Tio2) Blended Diesel and Biodiesel","authors":"AMAN SINGH RAJPOOT, TUSHAR Choudhary, ANOOP SHUKLA, H. CHELLADURAI, UPENDRA RAJAK, ABHINAV ANAND SINHA","doi":"10.1615/jenhheattransf.2024051522","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024051522","url":null,"abstract":"The performance and emissions characteristics of a diesel engine running on several fuel combinations, including diesel, biodiesel, and fuel mixed with TiO2 nanoparticles, are assessed in this research on a diesel engine. The study investigates how performance and emissions are impacted when diesel and biodiesel are treated with 50 and 100 ppm of TiO2 nanoparticles under varied engine loads ranging from 25 to 100%. The BTE values for the mixed biodiesel fuels with TiO2 nanoparticles (B0Ti50, B0Ti100, B5Ti50, and B5Ti100) show an improvement over normal diesel (B0) and biodiesel (B5) fuels. The addition of TiO2 nanoparticles leads to reductions in brake specific fuel consumption (BSFC) of up to 8% with B0 and up to 14.29% with B5, and improvements in brake thermal efficiency (BTE) of up to 2% with B0 and up to 4.02% with B5. With regard to carbon dioxide (CO2) and hydrocarbon (HC) emissions, the use of TiO2 nanoparticles decreased emissions by up to 18.4% at the cost of nitric oxide (NO) emissions, which increased by up to 5.87%. The exergy performance coefficient (Exp) and sustainability index (SI) increased by up to 18.99% and 5.63%, respectively. The percentage changes showed enhanced engine performance, lower emissions, and improved energy conversion efficiency with the inclusion of nanoparticles. The results suggest fuel blends' advantages in terms of energy and the environment; however, it is also important to look at the economic feasibility and stability of TiO2 nanoparticles.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"126 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769655","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}
Pub Date : 2024-02-01DOI: 10.1615/jenhheattransf.2024051809
Wentao Ji, Yi Du, Guo-Hui Ou, Pu-Hang Jin, Chuang-Yao Zhao, Ding-Cai Zhang, Wen-Quan Tao
The flow and heat transfer experiments are conducted in this paper for eleven internally grooved tubes. Refrigerants are boiling or condensing outside the tube. The experimental tubes have the internal helical rib heights of 0.25-0.36 mm, helix angles of 40-60°, rib base thicknesses of 0.40-0.79 mm, rib tip thicknesses of 0.078-0.283 mm, and Ns (Number of circumferential micro-fins per circle) of 40-50.It shows that the heat transfer enhanced ratios is usually ranging from 2.3-3.64. The friction factor relative to the smooth tube are about 1.8 to 3.3 times higher. Analyzing the effect of rib geometry on flow and heat transfer, it was found that the higher the height of the internal rib, the better the enhancement of convective heat transfer in the tube. The greater the thickness of the rib tip and base, the more detrimental to the friction factor in the tube. It had not noticeable influence on the heat transfer performance as the helix angle increases from 45° to 50°. For the increase of Ns, it appears that 45 ribs per circle is the best value in the present study when considering the increase in pressure loss. The thermal-hydraulic performance of eleven tubes were also evaluated. It shows that Tube-1 had the best performance in the condensing tubes and Tube-7 had the best performance in the boiling tubes.
{"title":"Effect of Geometrical Parameters on the Thermal-Hydraulic Performance of Internal Helically Ribbed Tubes","authors":"Wentao Ji, Yi Du, Guo-Hui Ou, Pu-Hang Jin, Chuang-Yao Zhao, Ding-Cai Zhang, Wen-Quan Tao","doi":"10.1615/jenhheattransf.2024051809","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024051809","url":null,"abstract":"The flow and heat transfer experiments are conducted in this paper for eleven internally grooved tubes. Refrigerants are boiling or condensing outside the tube. The experimental tubes have the internal helical rib heights of 0.25-0.36 mm, helix angles of 40-60°, rib base thicknesses of 0.40-0.79 mm, rib tip thicknesses of 0.078-0.283 mm, and Ns (Number of circumferential micro-fins per circle) of 40-50.It shows that the heat transfer enhanced ratios is usually ranging from 2.3-3.64. The friction factor relative to the smooth tube are about 1.8 to 3.3 times higher. Analyzing the effect of rib geometry on flow and heat transfer, it was found that the higher the height of the internal rib, the better the enhancement of convective heat transfer in the tube. The greater the thickness of the rib tip and base, the more detrimental to the friction factor in the tube. It had not noticeable influence on the heat transfer performance as the helix angle increases from 45° to 50°. For the increase of Ns, it appears that 45 ribs per circle is the best value in the present study when considering the increase in pressure loss. The thermal-hydraulic performance of eleven tubes were also evaluated. It shows that Tube-1 had the best performance in the condensing tubes and Tube-7 had the best performance in the boiling tubes.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"53 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139978428","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}
Pub Date : 2024-02-01DOI: 10.1615/jenhheattransf.2024050485
Wei Li
The heat transfer and pressure drop of R410A and R32 within a smooth and an enhanced dimpled tube were measured for mass fluxes from 100 kg m−2 s−1 to 400 kg m−2 s−1, average vapor qualities between 0.2 and 0.8, and saturation temperatures between 35℃ and 45℃.dimpled. The test section length was 2 meters, and the outer and inner diameters of the tubes were 9.52 and 8.32 mm, respectively. The inner surface of the enhanced tube was dimpled. Three dimpled tubes and three smooth tubes, differing by material (copper, aluminum, and stainless steel) were tested to examine the material effect. The measured condensation heat transfer coefficient (HTC) for the copper smooth tube was between 1.10 to 1.16 times higher than that of the aluminum, and likewise, between 1.19 to 1.31 times higher than that of the stainless-steel tube. Similarly, the condensation HTC for the copper dimpled tube was between 1.06 to 1.15 times higher than that of the aluminum dimpled tube, and between 1.26 to 1.38 times higher than that of stainless-steel tube dimpled tube. In general, and the condensation HTC for R32 was greater than that for R410A owed mainly to the greater liquid thermal conductivity of R32. Flow patterns were observed for different vapor qualities and use to establish corresponding heat transfer mechanisms. Finally, a new correlation for dimpled tubes was proposed based a modified smooth tube correlation, which predicted the measurements to within 20 %.
{"title":"Condensation heat transfer in smooth and three-dimensional dimpled tubes of various materials","authors":"Wei Li","doi":"10.1615/jenhheattransf.2024050485","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024050485","url":null,"abstract":"The heat transfer and pressure drop of R410A and R32 within a smooth and an enhanced dimpled tube were measured for mass fluxes from 100 kg m−2 s−1 to 400 kg m−2 s−1, average vapor qualities between 0.2 and 0.8, and saturation temperatures between 35℃ and 45℃.dimpled. The test section length was 2 meters, and the outer and inner diameters of the tubes were 9.52 and 8.32 mm, respectively. The inner surface of the enhanced tube was dimpled. Three dimpled tubes and three smooth tubes, differing by material (copper, aluminum, and stainless steel) were tested to examine the material effect. The measured condensation heat transfer coefficient (HTC) for the copper smooth tube was between 1.10 to 1.16 times higher than that of the aluminum, and likewise, between 1.19 to 1.31 times higher than that of the stainless-steel tube. Similarly, the condensation HTC for the copper dimpled tube was between 1.06 to 1.15 times higher than that of the aluminum dimpled tube, and between 1.26 to 1.38 times higher than that of stainless-steel tube dimpled tube. In general, and the condensation HTC for R32 was greater than that for R410A owed mainly to the greater liquid thermal conductivity of R32. Flow patterns were observed for different vapor qualities and use to establish corresponding heat transfer mechanisms. Finally, a new correlation for dimpled tubes was proposed based a modified smooth tube correlation, which predicted the measurements to within 20 %.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"72 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139919000","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}
Pub Date : 2024-02-01DOI: 10.1615/jenhheattransf.2024051290
Wentao Li, Kun Sun, Guoyan ZHOU, Xing Luo, Shan-Tung Tu, Stephan Kabelac, Ke Wang
For measuring the efficiency of non-metallic heat exchangers, a mathematical model was established based on the principle of the single-blow testing technique, in which the conductive thermal resistance across non-metallic plates of the exchangers was taken into account. The analytical solution was obtained by means of the Laplace transformation and numerical invers transform method. The accuracy of the model was verified by comparing it with the literature. The effect of the plate Bi number on the evaluated NTU was analyzed. Based on the single-blow transient testing technique and the present model, the heat transfer performance and frictional pressure drop of four types of non-metallic plates with different structural parameters were experimentally studied. The correlations for heat transfer and frictional pressure drop of non-metallic heat exchange structures are established.
{"title":"Analysis of the Single-Blow Transient Testing Technique for Non-metallic Heat Exchangers","authors":"Wentao Li, Kun Sun, Guoyan ZHOU, Xing Luo, Shan-Tung Tu, Stephan Kabelac, Ke Wang","doi":"10.1615/jenhheattransf.2024051290","DOIUrl":"https://doi.org/10.1615/jenhheattransf.2024051290","url":null,"abstract":"For measuring the efficiency of non-metallic heat exchangers, a mathematical model was established based on the principle of the single-blow testing technique, in which the conductive thermal resistance across non-metallic plates of the exchangers was taken into account. The analytical solution was obtained by means of the Laplace transformation and numerical invers transform method. The accuracy of the model was verified by comparing it with the literature. The effect of the plate Bi number on the evaluated NTU was analyzed. Based on the single-blow transient testing technique and the present model, the heat transfer performance and frictional pressure drop of four types of non-metallic plates with different structural parameters were experimentally studied. The correlations for heat transfer and frictional pressure drop of non-metallic heat exchange structures are established.","PeriodicalId":50208,"journal":{"name":"Journal of Enhanced Heat Transfer","volume":"39 1","pages":""},"PeriodicalIF":2.3,"publicationDate":"2024-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139769504","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：