Pub Date : 2025-01-11DOI: 10.1016/j.ijthermalsci.2025.109698
Tingting Wu , Lianjian Mo , Yibo Yan , Yanxin Hu , Kaizhao Liu , Da Chen
In order to promote the effective application of self-rewetting fluids in the field of evaporation and to develop novel working fluids, a visual experimental setup for droplet evaporation was designed to investigate the evaporation mechanism of n-pentanol solution droplets. The study focused on exploring the influence of different wettability surfaces and substrate temperatures on the geometric morphology, surface heat flow patterns and internal flow of droplets. The Marangoni number during the evaporation process was calculated, and the formation mechanism of surface heat flow patterns was analyzed. The results show that n-pentanol solution droplets on strongly wetted surfaces exhibit constant wetting diameter mode and mixed mode, while on weakly wetted surfaces, they mainly display the constant contact angle mode. The contact line slip motion of droplets on weakly wetted surfaces is more pronounced. The evaporation time of n-pentanol solution droplets on strongly and weakly wetted surfaces is 13.9 % and 12.4 % shorter than that of deionized water, respectively. Furthermore, during the evaporation process of n-pentanol solution droplets, flower-like thermal flow patterns, twin vortices thermal flow patterns, and stable thermocapillary flow are successively observed on the surface, with heat flow patterns becoming more pronounced at higher temperatures. As evaporation progresses, the Marangoni number gradually decreases, and the internal flow of droplets slows down, approaching stability. The use of strongly wetted surfaces and n-pentanol solution exhibits a strong Marangoni effect.
{"title":"Study on the evaporation characteristics of self-rewetting droplets on different wettability surfaces","authors":"Tingting Wu , Lianjian Mo , Yibo Yan , Yanxin Hu , Kaizhao Liu , Da Chen","doi":"10.1016/j.ijthermalsci.2025.109698","DOIUrl":"10.1016/j.ijthermalsci.2025.109698","url":null,"abstract":"<div><div>In order to promote the effective application of self-rewetting fluids in the field of evaporation and to develop novel working fluids, a visual experimental setup for droplet evaporation was designed to investigate the evaporation mechanism of n-pentanol solution droplets. The study focused on exploring the influence of different wettability surfaces and substrate temperatures on the geometric morphology, surface heat flow patterns and internal flow of droplets. The Marangoni number during the evaporation process was calculated, and the formation mechanism of surface heat flow patterns was analyzed. The results show that n-pentanol solution droplets on strongly wetted surfaces exhibit constant wetting diameter mode and mixed mode, while on weakly wetted surfaces, they mainly display the constant contact angle mode. The contact line slip motion of droplets on weakly wetted surfaces is more pronounced. The evaporation time of n-pentanol solution droplets on strongly and weakly wetted surfaces is 13.9 % and 12.4 % shorter than that of deionized water, respectively. Furthermore, during the evaporation process of n-pentanol solution droplets, flower-like thermal flow patterns, twin vortices thermal flow patterns, and stable thermocapillary flow are successively observed on the surface, with heat flow patterns becoming more pronounced at higher temperatures. As evaporation progresses, the Marangoni number gradually decreases, and the internal flow of droplets slows down, approaching stability. The use of strongly wetted surfaces and n-pentanol solution exhibits a strong Marangoni effect.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109698"},"PeriodicalIF":4.9,"publicationDate":"2025-01-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138011","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-01-10DOI: 10.1016/j.ijthermalsci.2025.109685
Lin Cheng , Yuheng Zhang , Zhaohan Wang , Yongkang Sun , Chunhui Ma , Zengguang Xu , Jiang Hu
The leakage of the buried water pipelines will not only cause waste of water resources, but also cause secondary disasters that will endanger the safety of life and property of residents along the pipeline. Therefore, leakage monitoring is crucial for buried water pipelines. In this study, based on the active heated fibre optic optical frequency domain reflectometry (AHFO-OFDR), the buried water pipelines leakage monitoring test considering the influence of leakage size, flow velocity and other factors was carried out, and the corresponding finite element numerical model was established to verify the reliability of the test results. The research results show that the AHFO-OFDR technology can realize the accurate positioning of the pipeline leakage point and the leakage quantity and leakage velocity can be roughly judged. The relevant conclusions are consistent with the numerical simulation results, so it is considered that the experimental results obtained by AHFO-OFDR have high accuracy.
{"title":"Experimental study on leakage monitoring of buried water pipelines based on actively heated optical frequency domain reflection technology","authors":"Lin Cheng , Yuheng Zhang , Zhaohan Wang , Yongkang Sun , Chunhui Ma , Zengguang Xu , Jiang Hu","doi":"10.1016/j.ijthermalsci.2025.109685","DOIUrl":"10.1016/j.ijthermalsci.2025.109685","url":null,"abstract":"<div><div>The leakage of the buried water pipelines will not only cause waste of water resources, but also cause secondary disasters that will endanger the safety of life and property of residents along the pipeline. Therefore, leakage monitoring is crucial for buried water pipelines. In this study, based on the active heated fibre optic optical frequency domain reflectometry (AHFO-OFDR), the buried water pipelines leakage monitoring test considering the influence of leakage size, flow velocity and other factors was carried out, and the corresponding finite element numerical model was established to verify the reliability of the test results. The research results show that the AHFO-OFDR technology can realize the accurate positioning of the pipeline leakage point and the leakage quantity and leakage velocity can be roughly judged. The relevant conclusions are consistent with the numerical simulation results, so it is considered that the experimental results obtained by AHFO-OFDR have high accuracy.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109685"},"PeriodicalIF":4.9,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
<div><div>Previous studies concerning ceiling fires (fire source located on the ceiling) under normal atmospheric pressure. However, research exploring the behavior of ceiling fires under sub-atmospheric pressures, which may occur at high altitudes, remains absent. This study addresses this gap through experiments carried out in a variable atmospheric pressure chamber and numerical simulations. A horizontal mica plate was used as the ceiling, and numerical study was conducted to compare with the experimental data. Five atmospheric pressures (40, 55, 70, 85 and 100 kPa), various heat release rates, burner diameters and fuel types (methane and propane) were considered. Key parameters obtained included the flame radius, maximum flame thickness, temperature profile and total heat flux beneath the ceiling. Experimentally, the flame radius and maximum flame thickness were estimated based on 50 % flame appearance probability. Numerically, the flame radius was estimated by <span><math><mrow><mo>Δ</mo><mi>T</mi><mo>=</mo><mn>500</mn><mi>K</mi></mrow></math></span> (<span><math><mrow><mo>Δ</mo><mi>T</mi></mrow></math></span> is temperature rise above the ambient) in the isothermal-temperature profile. From the results, the flame radius (<span><math><mrow><msub><mi>R</mi><mi>f</mi></msub></mrow></math></span>) increases as atmospheric pressure decreases, with the maximum flame thickness being significantly smaller than the flame radius. Regarding the temperature profile, temperature rise remains nearly constant under various sub-atmospheric pressures in the near field of fire source, and it gradually increases as atmospheric pressure decreases in the far field. The heat flux in the near field of fire source decreases as atmospheric pressure decreases, and it increases as atmospheric pressure decreases in the far field. Then, the prediction models for the temperature rise and total heat flux profiles were obtained, both the non-dimensional temperature rise and heat flux under various sub-atmospheric pressures can be described well by using the flame radius as characteristic length. Additionally, the physical analysis of the air entrainment behavior of ceiling fires under sub-atmospheric pressures was conducted, and the rate of flame air entrainment decreases as atmospheric pressure decreases. Finally, a novel characteristic length <span><math><mrow><msub><mi>l</mi><mrow><mi>a</mi><mo>,</mo><mi>p</mi></mrow></msub><mo>=</mo><msup><mrow><mo>(</mo><mrow><mover><mi>Q</mi><mo>˙</mo></mover><mo>/</mo><mrow><mo>(</mo><mrow><mrow><mo>(</mo><mrow><mn>0.48</mn><msup><mi>P</mi><mo>∗</mo></msup><mo>+</mo><mn>0.52</mn></mrow><mo>)</mo></mrow><mrow><mo>(</mo><mrow><mo>Δ</mo><msub><mi>H</mi><mi>c</mi></msub><mo>/</mo><mi>s</mi></mrow><mo>)</mo></mrow></mrow><mo>)</mo></mrow></mrow><mo>)</mo></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow></math></span> (where <span><math><mrow><mover><mi>Q</mi><mo>˙</mo></mover></mrow></math></span> is the heat release rate
{"title":"Experimental and numerical studies on flame radius, temperature profile and heat flux of axi-symmetric ceiling fires under various sub-atmospheric pressures","authors":"Yunsong Li, Xiepeng Sun, Yuhang Chen, Longhua Hu, Xiaolei Zhang","doi":"10.1016/j.ijthermalsci.2025.109697","DOIUrl":"10.1016/j.ijthermalsci.2025.109697","url":null,"abstract":"<div><div>Previous studies concerning ceiling fires (fire source located on the ceiling) under normal atmospheric pressure. However, research exploring the behavior of ceiling fires under sub-atmospheric pressures, which may occur at high altitudes, remains absent. This study addresses this gap through experiments carried out in a variable atmospheric pressure chamber and numerical simulations. A horizontal mica plate was used as the ceiling, and numerical study was conducted to compare with the experimental data. Five atmospheric pressures (40, 55, 70, 85 and 100 kPa), various heat release rates, burner diameters and fuel types (methane and propane) were considered. Key parameters obtained included the flame radius, maximum flame thickness, temperature profile and total heat flux beneath the ceiling. Experimentally, the flame radius and maximum flame thickness were estimated based on 50 % flame appearance probability. Numerically, the flame radius was estimated by <span><math><mrow><mo>Δ</mo><mi>T</mi><mo>=</mo><mn>500</mn><mi>K</mi></mrow></math></span> (<span><math><mrow><mo>Δ</mo><mi>T</mi></mrow></math></span> is temperature rise above the ambient) in the isothermal-temperature profile. From the results, the flame radius (<span><math><mrow><msub><mi>R</mi><mi>f</mi></msub></mrow></math></span>) increases as atmospheric pressure decreases, with the maximum flame thickness being significantly smaller than the flame radius. Regarding the temperature profile, temperature rise remains nearly constant under various sub-atmospheric pressures in the near field of fire source, and it gradually increases as atmospheric pressure decreases in the far field. The heat flux in the near field of fire source decreases as atmospheric pressure decreases, and it increases as atmospheric pressure decreases in the far field. Then, the prediction models for the temperature rise and total heat flux profiles were obtained, both the non-dimensional temperature rise and heat flux under various sub-atmospheric pressures can be described well by using the flame radius as characteristic length. Additionally, the physical analysis of the air entrainment behavior of ceiling fires under sub-atmospheric pressures was conducted, and the rate of flame air entrainment decreases as atmospheric pressure decreases. Finally, a novel characteristic length <span><math><mrow><msub><mi>l</mi><mrow><mi>a</mi><mo>,</mo><mi>p</mi></mrow></msub><mo>=</mo><msup><mrow><mo>(</mo><mrow><mover><mi>Q</mi><mo>˙</mo></mover><mo>/</mo><mrow><mo>(</mo><mrow><mrow><mo>(</mo><mrow><mn>0.48</mn><msup><mi>P</mi><mo>∗</mo></msup><mo>+</mo><mn>0.52</mn></mrow><mo>)</mo></mrow><mrow><mo>(</mo><mrow><mo>Δ</mo><msub><mi>H</mi><mi>c</mi></msub><mo>/</mo><mi>s</mi></mrow><mo>)</mo></mrow></mrow><mo>)</mo></mrow></mrow><mo>)</mo></mrow><mrow><mn>1</mn><mo>/</mo><mn>2</mn></mrow></msup></mrow></math></span> (where <span><math><mrow><mover><mi>Q</mi><mo>˙</mo></mover></mrow></math></span> is the heat release rate","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109697"},"PeriodicalIF":4.9,"publicationDate":"2025-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138514","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-01-09DOI: 10.1016/j.ijthermalsci.2025.109688
MingKai Guo , GuoShuai Qin , Chunsheng Lu , MingHao Zhao , Lan Wu
Manipulating carrier redistribution in piezoelectric semiconductors via piezo- and thermo-photonic effects offering a promising approach for developing tunable optoelectronic devices. In this paper, we present a combined theoretical analysis and photoelectric bridge experiments to characterize and modulate electron transport in a single ZnO nanowire device with two identical electrodes by varying the intensity of ultraviolet light. Additionally, we have developed a comprehensive photo-thermal coupling model that integrates photoexcitation, photothermal and secondary pyroelectric (or thermal strain) effects. This model enables the extraction of carrier concentration and barrier height from the current-voltage curves through parameter inversion. Our findings provide deep insights into the electrical characteristics of nanodevices under bias control and open new avenues for the design of innovative electronic and optoelectronic nanodevices.
{"title":"Photo-thermal coupling effects on carrier transfer and barrier height in ZnO nanowires","authors":"MingKai Guo , GuoShuai Qin , Chunsheng Lu , MingHao Zhao , Lan Wu","doi":"10.1016/j.ijthermalsci.2025.109688","DOIUrl":"10.1016/j.ijthermalsci.2025.109688","url":null,"abstract":"<div><div>Manipulating carrier redistribution in piezoelectric semiconductors via piezo- and thermo-photonic effects offering a promising approach for developing tunable optoelectronic devices. In this paper, we present a combined theoretical analysis and photoelectric bridge experiments to characterize and modulate electron transport in a single ZnO nanowire device with two identical electrodes by varying the intensity of ultraviolet light. Additionally, we have developed a comprehensive photo-thermal coupling model that integrates photoexcitation, photothermal and secondary pyroelectric (or thermal strain) effects. This model enables the extraction of carrier concentration and barrier height from the current-voltage curves through parameter inversion. Our findings provide deep insights into the electrical characteristics of nanodevices under bias control and open new avenues for the design of innovative electronic and optoelectronic nanodevices.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109688"},"PeriodicalIF":4.9,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-01-09DOI: 10.1016/j.ijthermalsci.2024.109667
Sławomira Janiak , Daria Mazurek-Rudnicka , Dariusz Heim , Igor Klementowski
The article presents a method of estimating the uncertainty for measurement of thermal conductivity (λ) using hot-wire technique. An originally designed and developed measuring system for determining thermal conductivity of solid bodies using hot-wire technique (HWT) was applied. Thanks to low costs, high accuracy, and short measurement time, it is a common dynamic technique, effectively used in a transitional states. The experiments were conducted for PCM-gypsum composites in different temperatures of samples, to estimate the uncertainty in solid, liquid and transitional states of PCM. The experimental value of the thermal conductivity of the tested composite and values of relative components of standard uncertainties of this parameter were determined. A satisfactory, low value of complex relative extended uncertainty (below 4 %) of thermal conductivity U(λ)/λ was obtained. It was confirmed that the uncertainty does not depend on the sample temperature and physical state of PCM.
{"title":"Determining the uncertainty in measurements of thermal conductivity (λ) of gypsum composites modified by PCM using the hot-wire technique","authors":"Sławomira Janiak , Daria Mazurek-Rudnicka , Dariusz Heim , Igor Klementowski","doi":"10.1016/j.ijthermalsci.2024.109667","DOIUrl":"10.1016/j.ijthermalsci.2024.109667","url":null,"abstract":"<div><div>The article presents a method of estimating the uncertainty for measurement of thermal conductivity (λ) using hot-wire technique. An originally designed and developed measuring system for determining thermal conductivity of solid bodies using hot-wire technique (HWT) was applied. Thanks to low costs, high accuracy, and short measurement time, it is a common dynamic technique, effectively used in a transitional states. The experiments were conducted for PCM-gypsum composites in different temperatures of samples, to estimate the uncertainty in solid, liquid and transitional states of PCM. The experimental value of the thermal conductivity of the tested composite and values of relative components of standard uncertainties of this parameter were determined. A satisfactory, low value of complex relative extended uncertainty (below 4 %) of thermal conductivity U(λ)/λ was obtained. It was confirmed that the uncertainty does not depend on the sample temperature and physical state of PCM.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109667"},"PeriodicalIF":4.9,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137858","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-09DOI: 10.1016/j.ijthermalsci.2024.109496
Prasad Sonavane , Roop L. Mahajan
In this paper, we report the findings from an experimental investigation aimed at assessing the potential for reducing pumping power penalty in channels partially filled with metal foams while maintaining thermal performance. The thermal–hydraulic performance parameter , where is the Colburn-J factor and is the friction factor was used to compare the relative performance of foams at various values of blockage fractions (), where is defined as the ratio of the height of the foam to the height of the channel. The metal foam samples considered were 10 PPI 6101-T6 Aluminum, with porosity of 94%–96%, and B of 1/6, 1/3, 2/3, 5/6, and 1. The Reynolds number (based on the channel hydraulic diameter and inlet velocity) was varied from 1000 to 15,000. A modification was made to all configurations with by attaching an aluminum plate on top, thereby creating a clear separation between the foam-free and the foam-filled flows. The results of our investigation indicate that the plated configurations outperformed their non-plated counterparts in almost all flow scenarios, with B 1/3 configuration yielding the most optimal performance. We also explored the impact of Pores Per Inch (PPI) for this specific case and found that lower PPI values are preferable. The experimental setup led to significant improvements: thermal–hydraulic efficiency was boosted by 14.5%, pressure drop was reduced by up to 40%, and minimal temperature rise was observed for the case of . These outcomes highlight the impact of partial foam blockage on enhancing heat transfer and reducing pressure drop, making it a valuable approach for applications requiring efficient thermal management. The insights presented in this study should be of interest to the heat transfer community.
{"title":"Partially filled metal foam channels for improved thermal–hydraulic performance in forced convection: An experimental investigation","authors":"Prasad Sonavane , Roop L. Mahajan","doi":"10.1016/j.ijthermalsci.2024.109496","DOIUrl":"10.1016/j.ijthermalsci.2024.109496","url":null,"abstract":"<div><div>In this paper, we report the findings from an experimental investigation aimed at assessing the potential for reducing pumping power penalty in channels partially filled with metal foams while maintaining thermal performance. The thermal–hydraulic performance parameter <span><math><mrow><mi>J</mi><mo>/</mo><msup><mrow><mi>F</mi></mrow><mrow><mn>1</mn><mo>/</mo><mn>3</mn></mrow></msup></mrow></math></span>, where <span><math><mi>J</mi></math></span> is the Colburn-J factor and <span><math><mi>F</mi></math></span> is the friction factor was used to compare the relative performance of foams at various values of blockage fractions (<span><math><mi>B</mi></math></span>), where <span><math><mi>B</mi></math></span> is defined as the ratio of the height of the foam to the height of the channel. The metal foam samples considered were 10 PPI 6101-T6 Aluminum, with porosity of <span><math><mo>∼</mo></math></span> 94%–96%, and B of 1/6, 1/3, 2/3, 5/6, and 1. The Reynolds number (based on the channel hydraulic diameter and inlet velocity) was varied from 1000 to 15,000. A modification was made to all configurations with <span><math><mrow><mi>B</mi><mo><</mo><mn>1</mn></mrow></math></span> by attaching an aluminum plate on top, thereby creating a clear separation between the foam-free and the foam-filled flows. The results of our investigation indicate that the plated configurations outperformed their non-plated counterparts in almost all flow scenarios, with B <span><math><mo>=</mo></math></span> 1/3 configuration yielding the most optimal performance. We also explored the impact of Pores Per Inch (PPI) for this specific case and found that lower PPI values are preferable. The experimental setup led to significant improvements: thermal–hydraulic efficiency was boosted by 14.5%, pressure drop was reduced by up to 40%, and minimal temperature rise was observed for the case of <span><math><mrow><mi>B</mi><mo>=</mo><mn>5</mn><mo>/</mo><mn>6</mn></mrow></math></span>. These outcomes highlight the impact of partial foam blockage on enhancing heat transfer and reducing pressure drop, making it a valuable approach for applications requiring efficient thermal management. The insights presented in this study should be of interest to the heat transfer community.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109496"},"PeriodicalIF":4.9,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138013","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-01-09DOI: 10.1016/j.ijthermalsci.2025.109679
Congcong Ren , Jingwei Han , Wei Chang , Chen Li , Wenming Li
Microchannel flow boiling with excellent heat dissipation capability is widely applied to thermal management of various high-power density thermal systems. Previously, microchannel flow boiling has been thoroughly studied under constant heat loads. However, in practical applications, the thermal components usually suffer from dynamic input power, resulting in significant fluctuation of working temperature. Hence, the research of transient behaviors of flow boiling is very important, particularly for dynamic heat loads. In this study, systematic experiments were carried out to understand transient thermal responses of microchannel configuration with auxiliary channels and multiple micronozzles, which was previously investigated under steady state condition and significant enhancements were reported. Here, transient wall temperature and overall heat transfer coefficient (HTC) were presented under pulse heating. The impact of heating pulse on flow boiling and two-phase flow regimes was investigated. Additionally, visualizations were synchronized with flow boiling heat transfer characteristics. Comprehensive comparisons were presented to elucidate the effect of this configuration in enhancement of flow boiling performance. Noticeably, the transient HTC was significantly increased by ∼225 % in contrary to plain wall microchannel at 380 kg/m2s.
{"title":"Transient thermal characteristics of silicon microchannel flow boiling","authors":"Congcong Ren , Jingwei Han , Wei Chang , Chen Li , Wenming Li","doi":"10.1016/j.ijthermalsci.2025.109679","DOIUrl":"10.1016/j.ijthermalsci.2025.109679","url":null,"abstract":"<div><div>Microchannel flow boiling with excellent heat dissipation capability is widely applied to thermal management of various high-power density thermal systems. Previously, microchannel flow boiling has been thoroughly studied under constant heat loads. However, in practical applications, the thermal components usually suffer from dynamic input power, resulting in significant fluctuation of working temperature. Hence, the research of transient behaviors of flow boiling is very important, particularly for dynamic heat loads. In this study, systematic experiments were carried out to understand transient thermal responses of microchannel configuration with auxiliary channels and multiple micronozzles, which was previously investigated under steady state condition and significant enhancements were reported. Here, transient wall temperature and overall heat transfer coefficient (HTC) were presented under pulse heating. The impact of heating pulse on flow boiling and two-phase flow regimes was investigated. Additionally, visualizations were synchronized with flow boiling heat transfer characteristics. Comprehensive comparisons were presented to elucidate the effect of this configuration in enhancement of flow boiling performance. Noticeably, the transient HTC was significantly increased by ∼225 % in contrary to plain wall microchannel at 380 kg/m<sup>2</sup>s.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109679"},"PeriodicalIF":4.9,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-01-09DOI: 10.1016/j.ijthermalsci.2025.109695
Xinlei Li, Huiren Zhu, Cunliang Liu, Lin Ye, Zhipeng Xu, Guodong Li, Weijiang Xu
Impingement structure, renowned for its compact design and exceptional heat transfer capabilities, finds widespread application in diverse cooling systems. The presence of ribs and the prevailing crossflow conditions exert a significant influence on the flow and heat transfer characteristics of the impingement. This study employs the turbulence model to numerically investigate the performance of a single-nozzle impingement with a ribbed target. Experimental validation, conducted using the steady-state copper block method, ensures the accuracy of the numerical simulations. By delving into the secondary impact phenomenon induced by the ribs, a step rib configuration is proposed to enhance heat transfer. The optimal rib arrangement under varying crossflow conditions is also explored. The findings reveal that step ribs can effectively elevate the and the by 7.67 % and 25.47 %, compared to a smooth target. This improvement underscores that the enhancement in heat transfer performance is not solely attributed to an increased heat transfer area but also benefits from favorable aerodynamic effects. The optimal rib placement varies with different crossflow conditions. Under low crossflow conditions, the most advantageous rib positioning coincides with the region influenced by the crossflow stagnation point. Conversely, at high crossflow conditions, the optimal rib placement is upstream of the impingement jet.
{"title":"Research on enhancing impingement structure heat transfer capability based on secondary impingement","authors":"Xinlei Li, Huiren Zhu, Cunliang Liu, Lin Ye, Zhipeng Xu, Guodong Li, Weijiang Xu","doi":"10.1016/j.ijthermalsci.2025.109695","DOIUrl":"10.1016/j.ijthermalsci.2025.109695","url":null,"abstract":"<div><div>Impingement structure, renowned for its compact design and exceptional heat transfer capabilities, finds widespread application in diverse cooling systems. The presence of ribs and the prevailing crossflow conditions exert a significant influence on the flow and heat transfer characteristics of the impingement. This study employs the <span><math><mrow><mi>k</mi><mo>−</mo><mi>w</mi><mspace></mspace><mtext>SST</mtext></mrow></math></span> turbulence model to numerically investigate the performance of a single-nozzle impingement with a ribbed target. Experimental validation, conducted using the steady-state copper block method, ensures the accuracy of the numerical simulations. By delving into the secondary impact phenomenon induced by the ribs, a step rib configuration is proposed to enhance heat transfer. The optimal rib arrangement under varying crossflow conditions is also explored. The findings reveal that step ribs can effectively elevate the <span><math><mrow><mi>N</mi><msub><mi>u</mi><mrow><mi>w</mi><mi>a</mi><mi>v</mi><mi>e</mi></mrow></msub></mrow></math></span> and the <span><math><mrow><mi>N</mi><msub><mi>u</mi><mrow><mi>p</mi><mi>a</mi><mi>v</mi><mi>e</mi></mrow></msub></mrow></math></span> by 7.67 % and 25.47 %, compared to a smooth target. This improvement underscores that the enhancement in heat transfer performance is not solely attributed to an increased heat transfer area but also benefits from favorable aerodynamic effects. The optimal rib placement varies with different crossflow conditions. Under low crossflow conditions, the most advantageous rib positioning coincides with the region influenced by the crossflow stagnation point. Conversely, at high crossflow conditions, the optimal rib placement is upstream of the impingement jet.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109695"},"PeriodicalIF":4.9,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143138513","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-01-08DOI: 10.1016/j.ijthermalsci.2025.109683
Wang Haitao, Lei Keke, Zhai Jianfeng
Safety in production has always been a basic national policy in China, but there are still many high-temperature work scenarios in China, which seriously endangers the physical and mental health of workers. In this paper, the equivalent temperature (EQT) was selected as the evaluation index of human thermal comfort, and the equivalent temperature of each segment of the human body was calculated by selecting appropriate measurement points and placing a human body model, and the skin temperature on the human surface was accurately set according to the biothermal equation. The calculated equivalent temperature was compared with the temperature range that the human body felt comfortable with, and the relationship between the local temperature of the human body and the comfortable temperature was quantitatively judged. FLUENT is used to obtain physical quantities such as air velocity, air temperature, and indoor average radiation temperature around each segment of the human body, and then substitute the formula to solve the EQT of each segment of the human body. By comparing the equivalent temperature of each part of the human body with the equivalent temperature range value that the human body feels comfortable with, it is found that when the air inlet wind speed is 3 m/s without thermal insulation measures and 0.5 m/s when there are thermal insulation measures, all parts of the human body are within the comfortable range. This paper provides ideas for the cooling improvement of the thermal environment of high-temperature plants.
{"title":"Human thermal comfort in the high-temperature radiant heat workshop","authors":"Wang Haitao, Lei Keke, Zhai Jianfeng","doi":"10.1016/j.ijthermalsci.2025.109683","DOIUrl":"10.1016/j.ijthermalsci.2025.109683","url":null,"abstract":"<div><div>Safety in production has always been a basic national policy in China, but there are still many high-temperature work scenarios in China, which seriously endangers the physical and mental health of workers. In this paper, the equivalent temperature (EQT) was selected as the evaluation index of human thermal comfort, and the equivalent temperature of each segment of the human body was calculated by selecting appropriate measurement points and placing a human body model, and the skin temperature on the human surface was accurately set according to the biothermal equation. The calculated equivalent temperature was compared with the temperature range that the human body felt comfortable with, and the relationship between the local temperature of the human body and the comfortable temperature was quantitatively judged. FLUENT is used to obtain physical quantities such as air velocity, air temperature, and indoor average radiation temperature around each segment of the human body, and then substitute the formula to solve the EQT of each segment of the human body. By comparing the equivalent temperature of each part of the human body with the equivalent temperature range value that the human body feels comfortable with, it is found that when the air inlet wind speed is 3 m/s without thermal insulation measures and 0.5 m/s when there are thermal insulation measures, all parts of the human body are within the comfortable range. This paper provides ideas for the cooling improvement of the thermal environment of high-temperature plants.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109683"},"PeriodicalIF":4.9,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137870","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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 : 2025-01-08DOI: 10.1016/j.ijthermalsci.2025.109680
Alhussein M. Abdel-Hafeez, Mohammed B. Effat, O. Hassan, N.Y. Abdel-Shafi
Optimizing lithium-ion battery (LIB) packs for electric vehicles requires balancing the need to increase volumetric energy density with the necessity of effective thermal management to ensure performance and safety. Recently, the prismatic cell form-factor has enabled the cell-to-pack approach which increases the battery pack energy density. Additionally, dielectric fluid immersion cooling (DFIC) has emerged as a promising battery thermal management (BTM) technology. This article investigates the effectiveness of DFIC's in managing the thermal performance of modules composed of prismatic lithium-ion cells. Specifically, the influence of intercell spacing on cells' temperature, pressure drop across a module, and the volumetric energy density of the module was investigated. The electrochemical-thermal performance of cells at different mass flow rates of the coolant, coolant types, rates of discharge, and the resting time between a charge and a discharge was assessed. The single-particle electrochemical-thermal model has been used to model the performance of the batteries. The model results show that DFIC can maintain the maximum temperature and maximum temperature difference of a cell within 25–40 °C and 0–5 °C, respectively, even when the distance between cells is < 1.0 mm and at <10 g/min. By reducing the intercell spacing, the volumetric energy density increases by 8.33 %. At 0.25 mm with mineral oil coolant, the pumping energy accounts for only 0.00185 % of the module's total energy per cycle. Among the coolants studied, deionized water gave better overall performance. This study shows that DFIC is viable BTM technology for high-energy and high-power battery packs.
{"title":"Effect of intercell spacing and operating conditions on the performance of prismatic lithium-ion batteries cooled by dielectric immersion Fluids:A numerical study","authors":"Alhussein M. Abdel-Hafeez, Mohammed B. Effat, O. Hassan, N.Y. Abdel-Shafi","doi":"10.1016/j.ijthermalsci.2025.109680","DOIUrl":"10.1016/j.ijthermalsci.2025.109680","url":null,"abstract":"<div><div>Optimizing lithium-ion battery (LIB) packs for electric vehicles requires balancing the need to increase volumetric energy density with the necessity of effective thermal management to ensure performance and safety. Recently, the prismatic cell form-factor has enabled the cell-to-pack approach which increases the battery pack energy density. Additionally, dielectric fluid immersion cooling (DFIC) has emerged as a promising battery thermal management (BTM) technology. This article investigates the effectiveness of DFIC's in managing the thermal performance of modules composed of prismatic lithium-ion cells. Specifically, the influence of intercell spacing on cells' temperature, pressure drop across a module, and the volumetric energy density of the module was investigated. The electrochemical-thermal performance of cells at different mass flow rates of the coolant, coolant types, rates of discharge, and the resting time between a charge and a discharge was assessed. The single-particle electrochemical-thermal model has been used to model the performance of the batteries. The model results show that DFIC can maintain the maximum temperature and maximum temperature difference of a cell within 25–40 °C and 0–5 °C, respectively, even when the distance between cells is < 1.0 mm and at <10 g/min. By reducing the intercell spacing, the volumetric energy density increases by 8.33 %. At 0.25 mm with mineral oil coolant, the pumping energy accounts for only 0.00185 % of the module's total energy per cycle. Among the coolants studied, deionized water gave better overall performance. This study shows that DFIC is viable BTM technology for high-energy and high-power battery packs.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"211 ","pages":"Article 109680"},"PeriodicalIF":4.9,"publicationDate":"2025-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143137857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"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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