Pub Date : 2025-01-27DOI: 10.1016/j.ijheatfluidflow.2025.109758
Andong Wu, Qing Cheng, Han Wang
Microchannel heat sinks play a vital role in the heat dissipation of miniaturized and highly integrated electronic devices. In this paper, a novel microchannel heat sinks consisting of fan-shaped cavities and circular ribs (MC-FCR) and the flow and heat transfer characteristics are both studied numerically. With comparation with the traditional smooth straight microchannel (MC), the microchannel with fan-shaped cavities (MC-FC), and the microchannel with circular ribs (MC-CR), the average friction coefficient (f), Nusselt number (Nu) and thermal enhancement efficiency (η) with Reynolds numbers (Re) ranging from 100 to 1000 were mainly studied. The results show that the circular rib structure can increase the degree of turbulence in the microchannel effectively, and the fan-shaped cavity can guide the fluid to form vortices, which bring the average temperature down at least 20 K. In addition, the combination of circular ribs and fan-shaped cavities can improve heat transfer performance while reducing pressure drop, and facilitate the formation of more uniform fluid flow in the channel. Then the relative radius of circular rib (α) and ellipticity (β) are proposed for optimizing the global characteristics of MC-FCR, which results in the thermal enhancement efficiency η for MC-FCR with α = 0.5 and β = 0.5 can achieve 1.431 at Re = 300.
{"title":"Research on flow and heat transfer characteristics of microchannel heat sinks with fan-shaped cavities and circular ribs","authors":"Andong Wu, Qing Cheng, Han Wang","doi":"10.1016/j.ijheatfluidflow.2025.109758","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109758","url":null,"abstract":"<div><div>Microchannel heat sinks play a vital role in the heat dissipation of miniaturized and highly integrated electronic devices. In this paper, a novel microchannel heat sinks consisting of fan-shaped cavities and circular ribs (MC-FCR) and the flow and heat transfer characteristics are both studied numerically. With comparation with the traditional smooth straight microchannel (MC), the microchannel with fan-shaped cavities (MC-FC), and the microchannel with circular ribs (MC-CR), the average friction coefficient (<em>f</em>), Nusselt number (<em>Nu</em>) and thermal enhancement efficiency (<em>η</em>) with Reynolds numbers (<em>Re</em>) ranging from 100 to 1000 were mainly studied. The results show that the circular rib structure can increase the degree of turbulence in the microchannel effectively, and the fan-shaped cavity can guide the fluid to form vortices, which bring the average temperature down at least 20 K. In addition, the combination of circular ribs and fan-shaped cavities can improve heat transfer performance while reducing pressure drop, and facilitate the formation of more uniform fluid flow in the channel. Then the relative radius of circular rib (<em>α</em>) and ellipticity (<em>β</em>) are proposed for optimizing the global characteristics of MC-FCR, which results in the thermal enhancement efficiency <em>η</em> for MC-FCR with <em>α</em> = 0.5 and <em>β</em> = 0.5 can achieve 1.431 at <em>Re</em> = 300.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109758"},"PeriodicalIF":2.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-27DOI: 10.1016/j.ijheatfluidflow.2025.109745
Rahim Aytug Ozer
One of the biggest challenges to technological advancements is the inability to efficiently dissipate waste heat from electronic components, which negatively effect performance and reliability. Immersion cooling systems provide an effective alternative for thermal management due to their high cooling capacity, uniform heat distribution and economic advantages. This study focuses on enhancing the thermal efficiency of single-phase immersion cooling systems by optimizing the geometric parameters of a heat sink, a passive cooling method. The innovation of this work lies in the systematic optimization of three key parameters: fin height, channel width and heat flux. These parameters were varied at three levels and an experimental design was developed using response surface methodology (RSM), which involved conducting 15 experiments. The optimal values for maximum thermal performance were determined to be 2.0 mm for channel width, 13.8889 mm for fin height and 45898.98 W/m2 for heat flux. The study reveals that the most influential parameters on thermal enhancement are channel width, fin height and heat flux respectively. The results demonstrate significant potential for improving thermal management in electronic cooling systems. Based on the findings, a reliable correlation for the enhancement rate is proposed, offering a practical tool for designing more efficient and sustainable cooling systems. This innovative approach contributes to the development of more effective thermal management solutions, with potential applications in industries such as electronics, power systems, and data centers.
{"title":"Heat sink optimization with response surface methodology for single phase immersion cooling","authors":"Rahim Aytug Ozer","doi":"10.1016/j.ijheatfluidflow.2025.109745","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109745","url":null,"abstract":"<div><div>One of the biggest challenges to technological advancements is the inability to efficiently dissipate waste heat from electronic components, which negatively effect performance and reliability. Immersion cooling systems provide an effective alternative for thermal management due to their high cooling capacity, uniform heat distribution and economic advantages. This study focuses on enhancing the thermal efficiency of single-phase immersion cooling systems by optimizing the geometric parameters of a heat sink, a passive cooling method. The innovation of this work lies in the systematic optimization of three key parameters: fin height, channel width and heat flux. These parameters were varied at three levels and an experimental design was developed using response surface methodology (RSM), which involved conducting 15 experiments. The optimal values for maximum thermal performance were determined to be 2.0 mm for channel width, 13.8889 mm for fin height and 45898.98 W/m<sup>2</sup> for heat flux. The study reveals that the most influential parameters on thermal enhancement are channel width, fin height and heat flux respectively. The results demonstrate significant potential for improving thermal management in electronic cooling systems. Based on the findings, a reliable correlation for the enhancement rate is proposed, offering a practical tool for designing more efficient and sustainable cooling systems. This innovative approach contributes to the development of more effective thermal management solutions, with potential applications in industries such as electronics, power systems, and data centers.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109745"},"PeriodicalIF":2.6,"publicationDate":"2025-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140607","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-25DOI: 10.1016/j.ijheatfluidflow.2025.109762
Yi Zhang , Ye Tian , Guangming Du
This paper focuses on investigating the impact of incident shocks on the atomization, evaporation, and diffusion characteristics of a liquid jet in supersonic flow. By adjusting the position of the shock wave generator, the interaction between the incident shock wave and the wall can be modified. The gas–liquid two-phase flow process is solved using the Euler-Lagrange method, allowing for the analysis of the atomization, evaporation, and mixing processes of kerosene. Through a thorough examination of the numerical simulation results, the underlying mechanisms by which shock waves affect the breakup and evaporation of kerosene are revealed. The findings indicate that the passage of the airflow through the incident shock wave leads to an increase in temperature and pressure. This, in turn, accelerates the evaporation process of kerosene droplets, resulting in a deeper penetration of kerosene vapor. The penetration depth can be increased by up to 39.7 %. Additionally, the decrease in airflow velocity after the shock and the formation of vortex structures in the flow field, caused by the incident shock, effectively enhance the diffusion and mixing of kerosene. These results provide valuable insights for improving the mixing characteristics of fuel atomization and evaporation, ultimately enhancing the subsequent combustion process.
{"title":"Study on atomization and evaporation characteristics of liquid jets under shock wave action in supersonic flow","authors":"Yi Zhang , Ye Tian , Guangming Du","doi":"10.1016/j.ijheatfluidflow.2025.109762","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109762","url":null,"abstract":"<div><div>This paper focuses on investigating the impact of incident shocks on the atomization, evaporation, and diffusion characteristics of a liquid jet in supersonic flow. By adjusting the position of the shock wave generator, the interaction between the incident shock wave and the wall can be modified. The gas–liquid two-phase flow process is solved using the Euler-Lagrange method, allowing for the analysis of the atomization, evaporation, and mixing processes of kerosene. Through a thorough examination of the numerical simulation results, the underlying mechanisms by which shock waves affect the breakup and evaporation of kerosene are revealed. The findings indicate that the passage of the airflow through the incident shock wave leads to an increase in temperature and pressure. This, in turn, accelerates the evaporation process of kerosene droplets, resulting in a deeper penetration of kerosene vapor. The penetration depth can be increased by up to 39.7 %. Additionally, the decrease in airflow velocity after the shock and the formation of vortex structures in the flow field, caused by the incident shock, effectively enhance the diffusion and mixing of kerosene. These results provide valuable insights for improving the mixing characteristics of fuel atomization and evaporation, ultimately enhancing the subsequent combustion process.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109762"},"PeriodicalIF":2.6,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-25DOI: 10.1016/j.ijheatfluidflow.2025.109751
V.A. Kosyakov , R.V. Fursenko , V.M. Chudnovsky
In the present study a single act of laser-induced subcooled boiling at the end of a laser waveguide is studied numerically. This type of boiling is accompanied by the growth and rapid collapse of a single vapor bubble, which gives rise to a cumulative jet directed away from the waveguide endface. These jets have an elevated temperature which have a number of applications, particularly in medicine. This study offers a physical explanation for the elevated jet temperature observed during subcooled boiling. Dependencies of jet temperature, jet velocity and maximum vapor bubble size on the initial temperature distribution of the liquid are obtained. It is shown that the jet temperature is predominantly influenced by the volume of water heated at the initial stage but not evaporated in the course of the process due to insufficient temperature. On the contrary, the volume of evaporated liquid affects maximum bubble size and jet velocity but has almost no effect on the jet temperature.
{"title":"Numerical study of the temperature of cumulative jet formed as a result of laser-induced subcooled boiling at the end of the waveguide","authors":"V.A. Kosyakov , R.V. Fursenko , V.M. Chudnovsky","doi":"10.1016/j.ijheatfluidflow.2025.109751","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109751","url":null,"abstract":"<div><div>In the present study a single act of laser-induced subcooled boiling at the end of a laser waveguide is studied numerically. This type of boiling is accompanied by the growth and rapid collapse of a single vapor bubble, which gives rise to a cumulative jet directed away from the waveguide endface. These jets have an elevated temperature which have a number of applications, particularly in medicine. This study offers a physical explanation for the elevated jet temperature observed during subcooled boiling. Dependencies of jet temperature, jet velocity and maximum vapor bubble size on the initial temperature distribution of the liquid are obtained. It is shown that the jet temperature is predominantly influenced by the volume of water heated at the initial stage but not evaporated in the course of the process due to insufficient temperature. On the contrary, the volume of evaporated liquid affects maximum bubble size and jet velocity but has almost no effect on the jet temperature.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109751"},"PeriodicalIF":2.6,"publicationDate":"2025-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-23DOI: 10.1016/j.ijheatfluidflow.2025.109760
Kun Du , Jiaxin Li , Tingrui Liang , Cunliang Liu , Bengt Sunden
Film cooling is a promising cooling method for turbine vanes. Inspired by hydrogen gas turbines, this paper investigates the effect of different water vapor volume fraction produced by hydrogen combustion on the film cooling of turbine vanes. Initially, to validate the turbulence model, the PSP experimental method was employed to conduct experiments on single-hole flat plate and vane models without water vapor in the mainstream. Through numerical simulation, laid-back fan-shaped and cylindrical holes in single-hole flat plate models were studied. Compared with different cases with varying water vapor volume fractions in the mainstream, the results show that the film cooling effects for both hole types weakened as the water vapor volume fraction increased. This phenomenon primarily occurs because the constant-pressure specific heat of the mainstream flow increases with higher water vapor concentration. By comparing different definitions of the cooling effectiveness, further verification confirmed that the weakening of the film cooling effect when there was water vapor in the mainstream flow is caused by changes in the constant-pressure specific heat. Numerical simulations were also performed on a real engine turbine vane model. The comparison between cases with and without water vapor showed that, although the film cooling effect of the blade was reduced under higher water vapor concentration, the position and type of holes in the vane also influenced the degree to which the film cooling effect weakened due to water vapor concentration.
{"title":"Effects of water vapor concentration on the film cooling effectiveness of hydrogen gas turbine vane","authors":"Kun Du , Jiaxin Li , Tingrui Liang , Cunliang Liu , Bengt Sunden","doi":"10.1016/j.ijheatfluidflow.2025.109760","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109760","url":null,"abstract":"<div><div>Film cooling is a promising cooling method for turbine vanes. Inspired by hydrogen gas turbines, this paper investigates the effect of different water vapor volume fraction produced by hydrogen combustion on the film cooling of turbine vanes. Initially, to validate the turbulence model, the PSP experimental method was employed to conduct experiments on single-hole flat plate and vane models without water vapor in the mainstream. Through numerical simulation, laid-back fan-shaped and cylindrical holes in single-hole flat plate models were studied. Compared with different cases with varying water vapor volume fractions in the mainstream, the results show that the film cooling effects for both hole types weakened as the water vapor volume fraction increased. This phenomenon primarily occurs because the constant-pressure specific heat of the mainstream flow increases with higher water vapor concentration. By comparing different definitions of the cooling effectiveness, further verification confirmed that the weakening of the film cooling effect when there was water vapor in the mainstream flow is caused by changes in the constant-pressure specific heat. Numerical simulations were also performed on a real engine turbine vane model. The comparison between cases with and without water vapor showed that, although the film cooling effect of the blade was reduced under higher water vapor concentration, the position and type of holes in the vane also influenced the degree to which the film cooling effect weakened due to water vapor concentration.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109760"},"PeriodicalIF":2.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140606","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-23DOI: 10.1016/j.ijheatfluidflow.2025.109757
Wei-Mon Yan , Yu-Fan Lin , Uzair Sajjad , Tien-Fu Yang , Saman Rashidi
Heat transfer and energy storage characteristics in double-layered enclosure packed with microencapsulated phase change material (MEPCM) are investigated numerically and experimentally in details. The rectangular enclosure is partitioned by an Al-plate to provide a double-layered enclosure. The top surface of enclosure is heated with varied heat flux with sine wave variation, the bottom surface is maintained at a low and constant temperature and the other vertical surfaces are thermally insulated. Two microencapsulated phase change materials made by paraffin with melting temperatures about 28 ℃ and 37℃, are selected. The high-temperature wall heat fluxes () of , and are considered. The low-temperature wall boundary conditions are set to ℃, ℃ , and ℃ The results show that better net thermal energy storage is found for a case with a higher wall heat flux at the top surface. In addition, better thermal energy storage is noted when the MEPCM with low melting temperature is packed at the upper enclosure near the heated wall. Also, more energy storage is experienced for a double-layered enclosure with a higher partitioned ratio λ. The melting point temperature of microcapsule phase change materials needs to be between high/low-temperature wall heating conditions to effectively store heat.
{"title":"Experimental and numerical study on heat transfer and energy storage characteristics in double-layered enclosure packed with microencapsulated phase change material","authors":"Wei-Mon Yan , Yu-Fan Lin , Uzair Sajjad , Tien-Fu Yang , Saman Rashidi","doi":"10.1016/j.ijheatfluidflow.2025.109757","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109757","url":null,"abstract":"<div><div>Heat transfer and energy storage characteristics in double-layered enclosure packed with microencapsulated phase change material (MEPCM) are investigated numerically and experimentally in details. The rectangular enclosure is partitioned by an Al-plate to provide a double-layered enclosure. The top surface of enclosure is heated with varied heat flux with sine wave variation, the bottom surface is maintained at a low and constant temperature and the other vertical surfaces are thermally insulated. Two microencapsulated phase change materials made by paraffin with melting temperatures about <span><math><mrow><msub><mtext>T</mtext><mtext>M</mtext></msub><mo>=</mo></mrow></math></span>28 ℃ and 37℃, are selected. The high-temperature wall heat fluxes (<span><math><msub><mtext>q</mtext><mtext>h</mtext></msub></math></span>) of <span><math><mrow><mtext>22.7sin(</mtext><mi>ω</mi><mtext>t)</mtext><mtext>W</mtext><mo>/</mo><msup><mrow><mtext>m</mtext></mrow><mtext>2</mtext></msup><mtext>, 39.0sin(</mtext><mi>ω</mi><mtext>t)</mtext><mtext>W</mtext><mo>/</mo><msup><mrow><mtext>m</mtext></mrow><mtext>2</mtext></msup></mrow></math></span>, and <span><math><mrow><mtext>61.3sin(</mtext><mi>ω</mi><mtext>t)</mtext><mtext>W</mtext><mo>/</mo><msup><mrow><mtext>m</mtext></mrow><mtext>2</mtext></msup></mrow></math></span> are considered. The low-temperature wall boundary conditions are set to <span><math><mtext>15</mtext></math></span> ℃, <span><math><mrow><mspace></mspace><mtext>20</mtext></mrow></math></span> ℃ , and <span><math><mtext>25</mtext></math></span> ℃<span><math><mo>.</mo></math></span> The results show that better net thermal energy storage is found for a case with a higher wall heat flux at the top surface. In addition, better thermal energy storage is noted when the MEPCM with low melting temperature is packed at the upper enclosure near the heated wall. Also, more energy storage is experienced for a double-layered enclosure with a higher partitioned ratio λ. The melting point temperature of microcapsule phase change materials needs to be between high/low-temperature wall heating conditions to effectively store heat.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109757"},"PeriodicalIF":2.6,"publicationDate":"2025-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140608","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-20DOI: 10.1016/j.ijheatfluidflow.2025.109752
Sherin Moustafa , Gaosheng Wei , M.Abd El-Hamid , Fei Sun , Xiaoze Du
Growing need for high-performance electronic devices has necessitate effective heat management solutions. This study conducts a three-dimensional numerical analysis of phase change material (PCM)-based heat sinks, examining single, double, and triple-layered structures with and without internal fins. The heat sinks are subjected to heat fluxes of 30,000 W/m2 and 100,000 W/m2 applied from both the bottom and side directions. The analysis evaluates the thermal performance of low-melting-point alloy (LMPA) PCM and paraffin-based PCM with comparable melting temperatures, while maintaining a constant PCM volume fraction (100 %) and under a set point temperature (SPT) of 100 °C. A cascading approach in the triple-layered module, where PCM layers are arranged in decreasing melting temperatures along the heat flux direction, is introduced. The results show that the cascaded PCM configuration in three layers are more effective to slow down the base temperature increase of the heat sink than the single and double ones. The presence of fins with triple layered LMPA PCM module shows a superior base temperature reduction, the complete melting time reach to about 1113 s under the temperature of 95.26 °C, remaining well below the SPT of 100 °C. This demonstrates the capability of LMPAs to sustain lower temperatures for extended periods, outperforming paraffin in terms of thermal shock resistance and faster melting under high heat flux. This work advances the design of PCM-based heat sinks by integrating cascaded configurations, metal PCM, and high-conductivity fins, offering an innovative holistic analysis of their combined effects on performance and providing a viable solution for cooling high-power electronic devices.
{"title":"Comparative study of different multilayered PCM finned heat sinks using low melting point alloys and paraffin: A numerical analysis","authors":"Sherin Moustafa , Gaosheng Wei , M.Abd El-Hamid , Fei Sun , Xiaoze Du","doi":"10.1016/j.ijheatfluidflow.2025.109752","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109752","url":null,"abstract":"<div><div>Growing need<!--> <!-->for high-performance electronic devices has necessitate<!--> <!-->effective heat management solutions. This study conducts a three-dimensional numerical analysis of phase change material (PCM)-based heat sinks, examining single, double, and triple-layered structures with and without internal fins. The heat sinks are subjected to heat fluxes of 30,000 W/m<sup>2</sup> and 100,000 W/m<sup>2</sup> applied from both the bottom and side directions. The analysis evaluates the thermal performance of low-melting-point alloy (LMPA) PCM and paraffin-based PCM with comparable melting temperatures, while maintaining a constant PCM volume fraction (100 %) and under a set point temperature (SPT) of 100 °C. A cascading approach in the triple-layered module, where PCM layers are arranged in decreasing melting temperatures along the heat flux direction, is introduced. The results show that the cascaded PCM configuration in three layers are more effective to slow down the base temperature increase of the heat sink than the single and double ones. The presence of fins with triple layered LMPA PCM module shows a superior base temperature reduction, the complete melting time reach to about 1113 s under the temperature of 95.26 °C, remaining well below the SPT of 100 °C. This demonstrates the capability of LMPAs to sustain lower temperatures for extended periods, outperforming paraffin in terms of thermal shock resistance and faster melting under high heat flux. This work advances the design of PCM-based heat sinks by integrating cascaded configurations, metal PCM, and high-conductivity fins, offering an innovative holistic analysis of their combined effects on performance and providing a viable solution for cooling high-power electronic devices.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109752"},"PeriodicalIF":2.6,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-17DOI: 10.1016/j.ijheatfluidflow.2025.109748
Chuang Wang, Shouguang Yao, Xiya Chen, Xuan Yan, Xiaoyv Zhan
Aiming at the generally low thermal conductivity of PCM in the LHTES (latent heat thermal energy storage) system, this study proposes a new kind of fin structure by adding arc-shaped fractal fins on the longitudinal straight fins for the improvement of the melting efficiency within the horizontal double-tube LHTES system. Numerical simulations were performed to analyze the effects of the curvature direction of arc-shaped fins, curvature size, and distance between fractal fins on the thermal characteristics. The results indicate that negative curvature fins have better melting performance. With the influence of natural convection, the temperature response speed of the PCM near the outer pipe wall at the higher half of the system is faster than that in the central region; versus conventional straight fins, a 90° fractal fin has the best melting characteristics versus a traditional straight fin, and reducing the PCM complete melting time by 34.27 %. The fractal fin spacing change affects the internal PCM’s phase transition process. The PCM melts the fastest when the fractal fin spacing decreases uniformly from lateral to medial. This results in a 2.5 % reduction in total melt time and a 2.57 % improvement in energy storage rate over a system with uniformly distributed fins. Finally, the minimum complete melting time, together with the fastest energy storage rate of the PCM, are taken as the optimization objectives. Response surface methodology is used to optimize fin radian angle and spacing. The results indicate that the system has optimal melting characteristics when the fin radian angle θ = 98.81°, the fin spacing tolerance d = 0.20 mm, and the total melting rate of the PCM are enhanced by 35.297 %. The energy storage rate is improved by 52.16 %.
{"title":"Thermal performance analysis of arc-shaped fins of horizontal latent heat thermal energy storage system","authors":"Chuang Wang, Shouguang Yao, Xiya Chen, Xuan Yan, Xiaoyv Zhan","doi":"10.1016/j.ijheatfluidflow.2025.109748","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109748","url":null,"abstract":"<div><div>Aiming at the generally low thermal conductivity of PCM in the LHTES (latent heat thermal energy storage) system, this study proposes a new kind of fin structure by adding arc-shaped fractal fins on the longitudinal straight fins for the improvement of the melting efficiency within the horizontal double-tube LHTES system. Numerical simulations were performed to analyze the effects of the curvature direction of arc-shaped fins, curvature size, and distance between fractal fins on the thermal characteristics. The results indicate that negative curvature fins have better melting performance. With the influence of natural convection, the temperature response speed of the PCM near the outer pipe wall at the higher half of the system is faster than that in the central region; versus conventional straight fins, a 90° fractal fin has the best melting characteristics versus a traditional straight fin, and reducing the PCM complete melting time by 34.27 %. The fractal fin spacing change affects the internal PCM’s phase transition process. The PCM melts the fastest when the fractal fin spacing decreases uniformly from lateral to medial. This results in a 2.5 % reduction in total melt time and a 2.57 % improvement in energy storage rate over a system with uniformly distributed fins. Finally, the minimum complete melting time, together with the fastest energy storage rate of the PCM, are taken as the optimization objectives. Response surface methodology is used to optimize fin radian angle and spacing. The results indicate that the system has optimal melting characteristics when the fin radian angle <em>θ</em> = 98.81°, the fin spacing tolerance <em>d</em> = 0.20 mm, and the total melting rate of the PCM are enhanced by 35.297 %. The energy storage rate is improved by 52.16 %.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109748"},"PeriodicalIF":2.6,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140162","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-16DOI: 10.1016/j.ijheatfluidflow.2025.109753
Burak Kıyak , Hakan F. Öztop , Nirmalendu Biswas , Hakan Coşanay , Fatih Selimefendigil
Phase-change materials (PCMs) offer an effective way to store and release thermal energy to balance the supply and demand for energy. Both the melting and solidification processes have a major impact on how effectively energy storage works and also it is affected by the thermal conditions of the heating or cooling source. Thermal energy storage systems using (PCMs are often limited by slow melting and solidification rates. The current work explores a novel strategy of cyclic heating and cooling for improving the PCM melting and solidification process combined with variations in fin shapes and orientations, to address these inefficiencies. The fins are heated and cooled following cyclic heating and cooling pattern for three different cycle periods (CP) with same amplitude. As a result, PCM is subjected to cyclic heating and cooling. The finite volume method is employed to analyze the impact of cyclic heating–cooling cycles on PCM performance. An analysis is also conducted on the impact of the relative shape of fins—that is, flat, concave, and convex, positions—vertical and horizontal—on the melting and solidification process under three different cycle periods. By applying a finite volume-based computational approach, the numerical model is solved. It is observed that the overall thermal performance of PCM-based energy storage is modulated by the cyclic heating–cooling arrangements. With this, melting time is reduced by 47.1 % compared to horizontal fin arrangement. When the fin pair is arranged vertically (θ = 0°), with the increase in the cycle period to CP3, the amount of stored energy (during the heating cycle) is about 24.7 %. Similarly, the amount of stored energy recovery (during the cooling cycle) is about 43.6 %. When the fin pair is arranged horizontally (θ = 90°), the amount of energy stored is up to 10 % due to the increase in the cycle periods. Similarly, the amount of stored energy recovery (during the cooling cycle) is about 38.5 %. An improved fin designs, combined with cyclic heating–cooling strategies, present an effective solution to enhance PCM-based thermal energy storage systems.
{"title":"Effects of fin shapes and orientations with cyclic heating and cooling on melting and solidification of PCM-filled closed space","authors":"Burak Kıyak , Hakan F. Öztop , Nirmalendu Biswas , Hakan Coşanay , Fatih Selimefendigil","doi":"10.1016/j.ijheatfluidflow.2025.109753","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109753","url":null,"abstract":"<div><div>Phase-change materials (PCMs) offer an effective way to store and release thermal energy to balance the supply and demand for energy. Both the melting and solidification processes have a major impact on how effectively energy storage works and also it is affected by the thermal conditions of the heating or cooling source. Thermal energy storage systems using (PCMs are often limited by slow melting and solidification rates. The current work explores a novel strategy of cyclic heating and cooling for improving the PCM melting and solidification process combined with variations in fin shapes and orientations, to address these inefficiencies. The fins are heated and cooled following cyclic heating and cooling pattern for three different cycle periods (CP) with same amplitude. As a result, PCM is subjected to cyclic heating and cooling. The finite volume method is employed to analyze the impact of cyclic heating–cooling cycles on PCM performance. An analysis is also conducted on the impact of the relative shape of fins—that is, flat, concave, and convex, positions—vertical and horizontal—on the melting and solidification process under three different cycle periods. By applying a finite volume-based computational approach, the numerical model is solved. It is observed that the overall thermal performance of PCM-based energy storage is modulated by the cyclic heating–cooling arrangements. With this, melting time is reduced by 47.1 % compared to horizontal fin arrangement. When the fin pair is arranged vertically (<em>θ</em> = 0°), with the increase in the cycle period to CP3, the amount of stored energy (during the heating cycle) is about 24.7 %. Similarly, the amount of stored energy recovery (during the cooling cycle) is about 43.6 %. When the fin pair is arranged horizontally (<em>θ</em> = 90°), the amount of energy stored is up to 10 % due to the increase in the cycle periods. Similarly, the amount of stored energy recovery (during the cooling cycle) is about 38.5 %. An improved fin designs, combined with cyclic heating–cooling strategies, present an effective solution to enhance PCM-based thermal energy storage systems.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109753"},"PeriodicalIF":2.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140605","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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 : 2025-01-16DOI: 10.1016/j.ijheatfluidflow.2025.109747
Shuoshuo Wang, Shinan Chang, Weidong Yu, Ke Wu
The deformation and movement of droplets are a fundamental phenomenon in nature and industry. The droplet under shear airflow is involved in many aspects, and research on the droplet under different experimental conditions, such as airflow temperature, is still lacking. A series of experiments on droplet motion under different conditions were carried out. The speed and temperature of airflow ranged from 17.0 m/s to 35.0 m/s and −17.0 °C to 20.0 °C, respectively. The droplet volume varied from 5.0 to 40.0 μL. The droplet properties did not change under the cold airflow in the test time, which indicated that it did not freeze and remained liquid for a period of time. During the whole droplet motion in the view, no solidification is observed. The characteristic parameters including the position of the droplet centre, the wetting length, the droplet height and the difference between the cosines of the front contact angle and the rear contact angle (cah) of droplet were obtained by image post-processing. The maximum length ratio and the maximum height ratio of droplet deformation were discussed. The morphology of a droplet during its motion was classified into three regimes according to the droplet Reynolds number, S (sliding slightly), SS (sliding and moving), and SRS (sliding and rivulet formation, and separation). A map of the regimes of droplet motion under different conditions was obtained. It is found that when the Red is in a range from 0 to 25, the droplet motion is Regime I (S). With the Red increasing, the different regimes appeared. The order in which they appear is S, SS, and SRS. This study provides experimental reference data for the study of the droplet motion in different temperatures and shear of airflow.
{"title":"Experimental investigation of droplet moving on a horizontal metal plate driven by cold airflow","authors":"Shuoshuo Wang, Shinan Chang, Weidong Yu, Ke Wu","doi":"10.1016/j.ijheatfluidflow.2025.109747","DOIUrl":"10.1016/j.ijheatfluidflow.2025.109747","url":null,"abstract":"<div><div>The deformation and movement of droplets are a fundamental phenomenon in nature and industry. The droplet under shear airflow is involved in many aspects, and research on the droplet under different experimental conditions, such as airflow temperature, is still lacking. A series of experiments on droplet motion under different conditions were carried out. The speed and temperature of airflow ranged from 17.0 m/s to 35.0 m/s and −17.0 °C to 20.0 °C, respectively. The droplet volume varied from 5.0 to 40.0 μL. The droplet properties did not change under the cold airflow in the test time, which indicated that it did not freeze and remained liquid for a period of time. During the whole droplet motion in the view, no solidification is observed. The characteristic parameters including the position of the droplet centre, the wetting length, the droplet height and the difference between the cosines of the front contact angle and the rear contact angle (<em>cah</em>) of droplet were obtained by image post-processing. The maximum length ratio and the maximum height ratio of droplet deformation were discussed. The morphology of a droplet during its motion was classified into three regimes according to the droplet Reynolds number, S (sliding slightly), SS (sliding and moving), and SRS (sliding and rivulet formation, and separation). A map of the regimes of droplet motion under different conditions was obtained. It is found that when the Re<sub>d</sub> is in a range from 0 to 25, the droplet motion is Regime I (S). With the Re<sub>d</sub> increasing, the different regimes appeared. The order in which they appear is S, SS, and SRS. This study provides experimental reference data for the study of the droplet motion in different temperatures and shear of airflow.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"112 ","pages":"Article 109747"},"PeriodicalIF":2.6,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143140899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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