Our particle–image-velocimetry experiment on the turbulent flow of a viscoelastic fluid through a backward-facing step reveals three different flows in low-, middle-, and high-diffusivity states, which depend on the balance between Weissenberg and Reynolds numbers. Although the middle-diffusivity state is characterized by a high-speed flow with eddy diffusivity similar to the Newtonian counterpart, the low-diffusivity state exhibits a straight flow in the high-speed region without eddy diffusivity. The Reynolds shear stress observed in the high-diffusivity state was higher than that of the Newtonian fluid, indicating active momentum transport. This is caused by the temporal–spatial meandering motion of the streamwise wave number corresponding to one-third of the channel half-height only in the wall-normal direction. The three states are determined by the disequilibrium state of the production and dissipation rates in the turbulent kinetic energy. The meandering motion became prominent when the turbulent production rate surpassed the dissipation rate. Besides, heat transfer enhancement was observed in the high-diffusivity state.
{"title":"Inertia-viscoelastic meandering motion in a backward-facing step flow","authors":"Shumpei Hara , Ryusuke Ii , Shohei Onishi , Takahiro Tsukahara , Yasuo Kawaguchi","doi":"10.1016/j.ijheatmasstransfer.2025.126793","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126793","url":null,"abstract":"<div><div>Our particle–image-velocimetry experiment on the turbulent flow of a viscoelastic fluid through a backward-facing step reveals three different flows in low-, middle-, and high-diffusivity states, which depend on the balance between Weissenberg and Reynolds numbers. Although the middle-diffusivity state is characterized by a high-speed flow with eddy diffusivity similar to the Newtonian counterpart, the low-diffusivity state exhibits a straight flow in the high-speed region without eddy diffusivity. The Reynolds shear stress observed in the high-diffusivity state was higher than that of the Newtonian fluid, indicating active momentum transport. This is caused by the temporal–spatial meandering motion of the streamwise wave number corresponding to one-third of the channel half-height only in the wall-normal direction. The three states are determined by the disequilibrium state of the production and dissipation rates in the turbulent kinetic energy. The meandering motion became prominent when the turbulent production rate surpassed the dissipation rate. Besides, heat transfer enhancement was observed in the high-diffusivity state.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126793"},"PeriodicalIF":5.0,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464988","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 : 2025-02-22DOI: 10.1016/j.ijheatmasstransfer.2025.126804
Jithu J. , Kasavajhula Naga Vasista , Suraj Kumar , Balaji Srinivasan , C. Balaji
Electric vehicles (EVs) have emerged as a promising solution for addressing some of the crucial sustainable development goals like affordable and clean energy. However, they are susceptible to battery thermal runaway raising serious safety concerns. To mitigate these concerns, it is imperative to design an effective battery thermal management system (BTMS). A knowledge of the thermophysical properties of the battery is a prerequisite for designing an effective BTMS. It is challenging to measure these properties as the batteries exhibit anisotropic behavior. The current work employs the powerful Metropolis Hastings–Markov Chain Monte Carlo (MH-MCMC) coupled Bayesian-inference-based inverse methodology driven by an artificial neural network (ANN) to estimate the orthotropic thermal conductivities (kxx, kyy, and kzz) of an actual AMP20M1HD-A pouch-type Li-ion battery using experimentally measured surface temperatures at suitable locations for five different heat inputs. The obtained average mean estimates (kxx = (20.14 ± 1.44) W/mK, kyy = (2.90 ± 0.2) W/mK, and kzz = (21.47 ± 1.39) W/mK) were found to be in close agreement with the values reported in the literature. The impact of temperature on kxx, kyy, and kzz was studied, and the results show that the properties are temperature-independent. Based on the sensitivity analysis conducted, the most and the least sensitive thermocouples in the estimation of kxx, kyy, and kzz were identified. The outcomes of the current work show the superiority of the proposed inverse methodology in the thermal characterization of live batteries using minimal temperature measurements and temperature measuring devices having varied levels of uncertainty.
{"title":"An inverse methodology to estimate the orthotropic thermal conductivities of AMP20M1HD-A pouch-type Li-ion battery","authors":"Jithu J. , Kasavajhula Naga Vasista , Suraj Kumar , Balaji Srinivasan , C. Balaji","doi":"10.1016/j.ijheatmasstransfer.2025.126804","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126804","url":null,"abstract":"<div><div>Electric vehicles (EVs) have emerged as a promising solution for addressing some of the crucial sustainable development goals like affordable and clean energy. However, they are susceptible to battery thermal runaway raising serious safety concerns. To mitigate these concerns, it is imperative to design an effective battery thermal management system (BTMS). A knowledge of the thermophysical properties of the battery is a prerequisite for designing an effective BTMS. It is challenging to measure these properties as the batteries exhibit anisotropic behavior. The current work employs the powerful Metropolis Hastings–Markov Chain Monte Carlo (MH-MCMC) coupled Bayesian-inference-based inverse methodology driven by an artificial neural network (ANN) to estimate the orthotropic thermal conductivities (k<sub>xx</sub>, k<sub>yy</sub>, and k<sub>zz</sub>) of an actual AMP20M1HD-A pouch-type Li-ion battery using experimentally measured surface temperatures at suitable locations for five different heat inputs. The obtained average mean estimates (k<sub>xx</sub> = (20.14 ± 1.44) W/mK, k<sub>yy</sub> = (2.90 ± 0.2) W/mK, and k<sub>zz</sub> = (21.47 ± 1.39) W/mK) were found to be in close agreement with the values reported in the literature. The impact of temperature on k<sub>xx</sub>, k<sub>yy</sub>, and k<sub>zz</sub> was studied, and the results show that the properties are temperature-independent. Based on the sensitivity analysis conducted, the most and the least sensitive thermocouples in the estimation of k<sub>xx</sub>, k<sub>yy</sub>, and k<sub>zz</sub> were identified. The outcomes of the current work show the superiority of the proposed inverse methodology in the thermal characterization of live batteries using minimal temperature measurements and temperature measuring devices having varied levels of uncertainty.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126804"},"PeriodicalIF":5.0,"publicationDate":"2025-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143464989","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 : 2025-02-21DOI: 10.1016/j.ijheatmasstransfer.2025.126841
Lincai Li , Linhao Fan , Jiaqi Wang , Kui Jiao
This study investigates the proton transfer (PT) mechanisms at the triple phase boundary (TPB) within the catalyst layers (CLs) of proton exchange membrane fuel cells using ab initio molecular dynamics simulations. Despite extensive research into chemical reactions, the complete PT process at the TPB is still unclear, making it difficult to improve CLs by designing structures with higher PT conductivity and better stabilities. Therefore, this work focuses on three critical parameters affecting PT conductivity: the distance between Pt and ionomers (h), the distance between ionomer side chains (d), and the crystal surface. As the h increases, water condensation on the Pt surface intensifies, forming a one-way water channel that hinders proton detachment from SO3H groups while facilitating PT between groups. The diffusion coefficient of water and hydronium ions decreases with d, indicating that narrow water channels caused by excessive ionomers surrounding the Pt catalysts can reduce proton conductivity. In addition, the Pt(111) facet exhibits the highest PT frequency of 3.2 times per ps, owing to its superior water condensation and complete solvation structures. This is followed by Pt(110) and Pt(100),with PT frequencies of 1.85 and 1.1 times per ps, respectively. This study also proves that the PT at the TPB is primarily via water-mediated surface migration, with the H3O+ migration accounting for most of the contribution, particularly in water-deficient environments, which far exceeds the proton hopping.
{"title":"Unveiling proton transfer dynamics at the triple phase boundary of fuel cells via Ab Initio molecular dynamics","authors":"Lincai Li , Linhao Fan , Jiaqi Wang , Kui Jiao","doi":"10.1016/j.ijheatmasstransfer.2025.126841","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126841","url":null,"abstract":"<div><div>This study investigates the proton transfer (PT) mechanisms at the triple phase boundary (TPB) within the catalyst layers (CLs) of proton exchange membrane fuel cells using ab initio molecular dynamics simulations. Despite extensive research into chemical reactions, the complete PT process at the TPB is still unclear, making it difficult to improve CLs by designing structures with higher PT conductivity and better stabilities. Therefore, this work focuses on three critical parameters affecting PT conductivity: the distance between Pt and ionomers (<em>h</em>), the distance between ionomer side chains (<em>d</em>), and the crystal surface. As the <em>h</em> increases, water condensation on the Pt surface intensifies, forming a one-way water channel that hinders proton detachment from SO<sub>3</sub>H groups while facilitating PT between <span><math><msubsup><mtext>SO</mtext><mn>3</mn><mo>−</mo></msubsup></math></span> groups. The diffusion coefficient of water and hydronium ions decreases with <em>d</em>, indicating that narrow water channels caused by excessive ionomers surrounding the Pt catalysts can reduce proton conductivity. In addition, the Pt(111) facet exhibits the highest PT frequency of 3.2 times per ps, owing to its superior water condensation and complete solvation structures. This is followed by Pt(110) and Pt(100),with PT frequencies of 1.85 and 1.1 times per ps, respectively. This study also proves that the PT at the TPB is primarily via water-mediated surface migration, with the H<sub>3</sub>O<sup>+</sup> migration accounting for most of the contribution, particularly in water-deficient environments, which far exceeds the proton hopping.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126841"},"PeriodicalIF":5.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454456","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 : 2025-02-21DOI: 10.1016/j.ijheatmasstransfer.2025.126855
Longfei Wang , Xinzi Liu , Mingdong Zhao , Junkui Mao , Chengliang Lv , Dewei Zhang , Yiming Liu
Fractal structures exhibit remarkable integrated performance due to their extremely high surface-to-volume ratio and adaptability. However, the exceedingly high degree of freedom in fractal designs introduces numerous geometric control variables, thereby complicating topological optimization. This study proposes a novel construction method for fractal structures and conducts flow and heat transfer analyses on various topological configurations of fractal units. Furthermore, intelligent algorithms are employed to perform topological optimization on typical fractal units. The results indicate that the performance of fractal units is predominantly influenced by bifurcation parameters and flow channel numbers. The heat transfer efficiency and pressure drop of fractal units increase with higher bifurcation numbers and angles. Meanwhile, the convergence of multiple fluid streams within the channels leads to significant pressure losses. An increase in flow channel numbers can enhance heat transfer while reducing pressure loss. Although increasing the complexity of the fractal topology improves heat transfer performance, this enhancement is insufficient to offset the adverse effects of increased pressure loss. Optimization using genetic algorithms yielded representative optimal structures which, under identical heat transfer performance, exhibited only 58 % of the original pressure drop. This finding indicates that employing intelligent algorithms is effective for achieving efficient topological optimization of fractal structures.
{"title":"Investigation in cooling performance and structural optimization for typical fractal units in turbine blades","authors":"Longfei Wang , Xinzi Liu , Mingdong Zhao , Junkui Mao , Chengliang Lv , Dewei Zhang , Yiming Liu","doi":"10.1016/j.ijheatmasstransfer.2025.126855","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126855","url":null,"abstract":"<div><div>Fractal structures exhibit remarkable integrated performance due to their extremely high surface-to-volume ratio and adaptability. However, the exceedingly high degree of freedom in fractal designs introduces numerous geometric control variables, thereby complicating topological optimization. This study proposes a novel construction method for fractal structures and conducts flow and heat transfer analyses on various topological configurations of fractal units. Furthermore, intelligent algorithms are employed to perform topological optimization on typical fractal units. The results indicate that the performance of fractal units is predominantly influenced by bifurcation parameters and flow channel numbers. The heat transfer efficiency and pressure drop of fractal units increase with higher bifurcation numbers and angles. Meanwhile, the convergence of multiple fluid streams within the channels leads to significant pressure losses. An increase in flow channel numbers can enhance heat transfer while reducing pressure loss. Although increasing the complexity of the fractal topology improves heat transfer performance, this enhancement is insufficient to offset the adverse effects of increased pressure loss. Optimization using genetic algorithms yielded representative optimal structures which, under identical heat transfer performance, exhibited only 58 % of the original pressure drop. This finding indicates that employing intelligent algorithms is effective for achieving efficient topological optimization of fractal structures.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126855"},"PeriodicalIF":5.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454457","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 : 2025-02-21DOI: 10.1016/j.ijheatmasstransfer.2025.126794
Benjamin Sponagle , Simon Maranda , William Delgado-Diaz , Remo Waser , Dominic Groulx , Jörg Worlitschek
This work presents a novel modeling technique for non-spherical capsule-shaped latent heat packed bed storage (PBS) systems aiming for resource efficiency in iterative optimization and design. The current simulation methods for such systems are resource-intensive and not suitable for iterative design. To address this, it is proposed to combine an efficient approach of detailed simulations of a single capsule during the phase change process with a one-dimensional (1D) model. Finite element simulations are used to capture local phenomena and characterize heat transfer rates from the capsules. The resulting heat flux dataset is integrated into a finite volume model to simulate the entire PCM-PBS system effectively. By combining these approaches, the computational resources needed are significantly reduced while maintaining accuracy. Experimental validation was conducted using a PCM-PBS setup with steel cans containing stearic acid and water as the heat transfer fluid. The results were able to reproduce the temperature history measured at four locations within the packed bed as well as the outlet temperature and total energy remove from the system during discharge for six separate experiments. These confirm the effectiveness of this simulation technique and provide validation. It addresses a knowledge gap in both experimental and numerical aspects, offering potential improvements in charge/discharge rate, energy density, and cost-effectiveness of PCM-PBS systems.
{"title":"Experimental validation of a novel modelling technique for packed bed thermal storage systems containing non-spherical phase change material capsules","authors":"Benjamin Sponagle , Simon Maranda , William Delgado-Diaz , Remo Waser , Dominic Groulx , Jörg Worlitschek","doi":"10.1016/j.ijheatmasstransfer.2025.126794","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126794","url":null,"abstract":"<div><div>This work presents a novel modeling technique for non-spherical capsule-shaped latent heat packed bed storage (PBS) systems aiming for resource efficiency in iterative optimization and design. The current simulation methods for such systems are resource-intensive and not suitable for iterative design. To address this, it is proposed to combine an efficient approach of detailed simulations of a single capsule during the phase change process with a one-dimensional (1D) model. Finite element simulations are used to capture local phenomena and characterize heat transfer rates from the capsules. The resulting heat flux dataset is integrated into a finite volume model to simulate the entire PCM-PBS system effectively. By combining these approaches, the computational resources needed are significantly reduced while maintaining accuracy. Experimental validation was conducted using a PCM-PBS setup with steel cans containing stearic acid and water as the heat transfer fluid. The results were able to reproduce the temperature history measured at four locations within the packed bed as well as the outlet temperature and total energy remove from the system during discharge for six separate experiments. These confirm the effectiveness of this simulation technique and provide validation. It addresses a knowledge gap in both experimental and numerical aspects, offering potential improvements in charge/discharge rate, energy density, and cost-effectiveness of PCM-PBS systems.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126794"},"PeriodicalIF":5.0,"publicationDate":"2025-02-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454455","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 : 2025-02-20DOI: 10.1016/j.ijheatmasstransfer.2025.126830
Ali H. Al-Zaidi , Mohamed M. Mahmoud , Atanas Ivanov , Tassos G. Karayiannis
Bubble nucleation and dynamics can play a significant role in the nucleate boiling mechanism during flow boiling. Understanding the behaviour of nucleating bubbles at different operating conditions can help identify the control parameters that should be included in proposed heat transfer models and correlations. This paper presents an experimental work on measurements of active nucleation site density, bubble generation frequency and departure diameter during flow boiling of refrigerant HFE-7100 in a microgap heat exchanger. The microgap heat exchanger had a heated flat surface of 20 mm width, 25 mm length and an adiabatic transparent cover located 1 mm above the heated surface. This allowed direct flow visualisation using a high-speed, high-resolution camera of a relatively large observation area. The effect of heat flux, mass flux and system pressure on the active nucleation site density and bubble dynamics (frequency and departure diameter) was examined. All experiments were carried out at inlet sub-cooling of 5 K, inlet pressure of 1 and 2 bar, mass flux of 100−200 kg/m2 s and wall heat flux up to 84 kW/m2. The experimental results were then compared with existing models and correlations predicting nucleation site density, bubble generation frequency and departure diameter with limited success. The dominant parameters were also identified, and new correlations were proposed based on the experimental results. The results of the current work can help develop accurate prediction heat transfer models and encourage and enable researchers working in numerical modelling to consider nucleation from multiple sites, rather than simulating one single nucleation site.
{"title":"Bubble nucleation site density, generation frequency and departure diameter in flow boiling of HFE-7100","authors":"Ali H. Al-Zaidi , Mohamed M. Mahmoud , Atanas Ivanov , Tassos G. Karayiannis","doi":"10.1016/j.ijheatmasstransfer.2025.126830","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126830","url":null,"abstract":"<div><div>Bubble nucleation and dynamics can play a significant role in the nucleate boiling mechanism during flow boiling. Understanding the behaviour of nucleating bubbles at different operating conditions can help identify the control parameters that should be included in proposed heat transfer models and correlations. This paper presents an experimental work on measurements of active nucleation site density, bubble generation frequency and departure diameter during flow boiling of refrigerant HFE-7100 in a microgap heat exchanger. The microgap heat exchanger had a heated flat surface of 20 mm width, 25 mm length and an adiabatic transparent cover located 1 mm above the heated surface. This allowed direct flow visualisation using a high-speed, high-resolution camera of a relatively large observation area. The effect of heat flux, mass flux and system pressure on the active nucleation site density and bubble dynamics (frequency and departure diameter) was examined. All experiments were carried out at inlet sub-cooling of 5 K, inlet pressure of 1 and 2 bar, mass flux of 100−200 kg/m<sup>2</sup> s and wall heat flux up to 84 kW/m<sup>2</sup>. The experimental results were then compared with existing models and correlations predicting nucleation site density, bubble generation frequency and departure diameter with limited success. The dominant parameters were also identified, and new correlations were proposed based on the experimental results. The results of the current work can help develop accurate prediction heat transfer models and encourage and enable researchers working in numerical modelling to consider nucleation from multiple sites, rather than simulating one single nucleation site.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126830"},"PeriodicalIF":5.0,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143445388","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 : 2025-02-20DOI: 10.1016/j.ijheatmasstransfer.2025.126805
Fatih Selimefendigil , Hakan F. Öztop
New cooling methods and alternate thermal management techniques are needed to improve performance of battery integrated systems, photovoltaic panels and electronic cooling. The miniaturization of electronic devices and higher processing demands result large amount of dissipated heat in a small volume which should be removed as effective as possible. This study proposes a new cooling system by using double elastic inclined fins and nano-enhanced magnetic field for cooling of two hot block which are installed in a T-shaped branching channel. FEM is used to investigate the effects of magnetic field strength (Hartmann number-Ha between 0 and 40), inclination of magnetic field ( between 0 and 90), inclination of first elastic fin ( between 0 and 135), and inclination of second elastic fin ( between −45 and 30) on the field of flow, thermal field, and cooling performance features. Using rigid fins improves cooling performance by 50% and 29% for walls W1 (first block front wall) and W2 (first block top wall) for the strongest magnetic field. When different magnetic field strength cases are compared, cooling rate degradation for hot surface W3 (first block rear wall) is 67% and 19% when elastic and rigid fins are used. The cooling performance of block in vertical channel improves with the use of a rigid fin. Higher magnetic field inclination generally results in cooling performance deterioration for walls of the block in the horizontal channel while trend is opposite for walls of the block in the vertical channel. Reduction of heat transfer up to 47% is obtained for hot wall W1 of horizontal block and it is reduced by about 67% for W4 (second block front wall) with varying inclination. Additionally, fin tilt of double elastic fins affects the cooling effectiveness of the heated blocks in both channels. The optimized scenario improves cooling performance by 254% for elastic fins and 195% for rigid fins when compared to reference configuration of using no-fin with pure fluid.
{"title":"Effects of using double elastic inclined fins on cooling of protruding heated electronic equipment mounted in a bifurcating channel under nano-enhanced magneto forced convection: Computational analysis and optimized configurations","authors":"Fatih Selimefendigil , Hakan F. Öztop","doi":"10.1016/j.ijheatmasstransfer.2025.126805","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126805","url":null,"abstract":"<div><div>New cooling methods and alternate thermal management techniques are needed to improve performance of battery integrated systems, photovoltaic panels and electronic cooling. The miniaturization of electronic devices and higher processing demands result large amount of dissipated heat in a small volume which should be removed as effective as possible. This study proposes a new cooling system by using double elastic inclined fins and nano-enhanced magnetic field for cooling of two hot block which are installed in a T-shaped branching channel. FEM is used to investigate the effects of magnetic field strength (Hartmann number-Ha between 0 and 40), inclination of magnetic field (<span><math><mi>γ</mi></math></span> between 0 and 90), inclination of first elastic fin (<span><math><msub><mrow><mi>θ</mi></mrow><mrow><mn>1</mn></mrow></msub></math></span> between 0 and 135), and inclination of second elastic fin (<span><math><msub><mrow><mi>θ</mi></mrow><mrow><mn>2</mn></mrow></msub></math></span> between −45 and 30) on the field of flow, thermal field, and cooling performance features. Using rigid fins improves cooling performance by 50% and 29% for walls W1 (first block front wall) and W2 (first block top wall) for the strongest magnetic field. When different magnetic field strength cases are compared, cooling rate degradation for hot surface W3 (first block rear wall) is 67% and 19% when elastic and rigid fins are used. The cooling performance of block in vertical channel improves with the use of a rigid fin. Higher magnetic field inclination generally results in cooling performance deterioration for walls of the block in the horizontal channel while trend is opposite for walls of the block in the vertical channel. Reduction of heat transfer up to 47% is obtained for hot wall W1 of horizontal block and it is reduced by about 67% for W4 (second block front wall) with varying inclination. Additionally, fin tilt of double elastic fins affects the cooling effectiveness of the heated blocks in both channels. The optimized scenario improves cooling performance by 254% for elastic fins and 195% for rigid fins when compared to reference configuration of using no-fin with pure fluid.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126805"},"PeriodicalIF":5.0,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454451","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 : 2025-02-20DOI: 10.1016/j.ijheatmasstransfer.2025.126844
Chen Sun , Ren Dai , Leren Tao , Lihao Huang , Shengjie Gu , Yuxin Zhang , Zhipan Gu
This study investigated the evolution of flow patterns and heat transfer characteristics of flow boiling within vertical upward rectangular narrow channels. The channel, visualized and heated to simulate compact heat exchangers and the fuel channels of small modular reactors (SMRs), has geometric dimensions of 720 mm × 240 mm × 2.75 mm (l × w × s) and employs deionized water as the working fluid. Experimental conditions include inlet temperature in the range of 50 - 90 °C, mass flux between 4.04–24.24 kg/(m²·s), and heat flux between 3.32–64.12 kW/m². Images acquired via high-speed camera are presented to elucidate the flow regime physics. Different types of flow pattern maps were drawn and compared with other researchers’ data under adiabatic and steam heating conditions. A new type of dimensionless correlative flow pattern transition criterion for vertical rectangular narrow channels was obtained and showed good accuracy in predicting the critical vapor quality of flow pattern transition. The results indicated that thermo-hydraulic parameters influence the positions and length of flow patterns, and the overall trend of the local heat transfer coefficient (HTC) remains consistent during flow pattern transition. Peak HTC values occurred during the later processes of restricted bubbly flow and annular flow. Critical heat flux (CHF) exhibited a positive correlation with mass flux but showed minimal sensitivity to inlet temperature. Specially, due to the intermittent wetting behavior of the tidal flow, heat transfer deterioration demonstrated a delayed response, and the heat flux of optimal average HTC was higher than the CHF.
{"title":"Experimental study on the relationship between the flow pattern and heat transfer characteristics of flow boiling in a vertical upward rectangular narrow channel","authors":"Chen Sun , Ren Dai , Leren Tao , Lihao Huang , Shengjie Gu , Yuxin Zhang , Zhipan Gu","doi":"10.1016/j.ijheatmasstransfer.2025.126844","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126844","url":null,"abstract":"<div><div>This study investigated the evolution of flow patterns and heat transfer characteristics of flow boiling within vertical upward rectangular narrow channels. The channel, visualized and heated to simulate compact heat exchangers and the fuel channels of small modular reactors (SMRs), has geometric dimensions of 720 mm × 240 mm × 2.75 mm (<em>l</em> × w × s) and employs deionized water as the working fluid. Experimental conditions include inlet temperature in the range of 50 - 90 °C, mass flux between 4.04–24.24 kg/(m²·s), and heat flux between 3.32–64.12 kW/m². Images acquired via high-speed camera are presented to elucidate the flow regime physics. Different types of flow pattern maps were drawn and compared with other researchers’ data under adiabatic and steam heating conditions. A new type of dimensionless correlative flow pattern transition criterion for vertical rectangular narrow channels was obtained and showed good accuracy in predicting the critical vapor quality of flow pattern transition. The results indicated that thermo-hydraulic parameters influence the positions and length of flow patterns, and the overall trend of the local heat transfer coefficient (HTC) remains consistent during flow pattern transition. Peak HTC values occurred during the later processes of restricted bubbly flow and annular flow. Critical heat flux (CHF) exhibited a positive correlation with mass flux but showed minimal sensitivity to inlet temperature. Specially, due to the intermittent wetting behavior of the tidal flow, heat transfer deterioration demonstrated a delayed response, and the heat flux of optimal average HTC was higher than the CHF.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126844"},"PeriodicalIF":5.0,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454452","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 : 2025-02-20DOI: 10.1016/j.ijheatmasstransfer.2025.126854
Junjie He , Xingang Wang , Xiangyang Xu , Xin Zhou , Wenxiao Chu , Qiuwang Wang
To ensure the stable operation of high-power transmitter and receiver (T/R) module in the complex aerospace environment, this study presents an integrated thermal buffer combing a vapor chamber (VC) with trapezoidal microgroove wick structure and heat storage container filled by phase change materials (PCMs). A common surface between the two components is manufactured by 3D printer without thermal contact resistance. The effects of gravity and vibration conditions on the thermal management performance are considered. Results show that the sustained operation significantly depends on the heat dissipation efficiency at the VC condensing surface while the tested integrated thermal buffer is capable to guarantee the continuous operation of the simulated T/R module for at least 5 cycles. However, when operating under a higher thermal power, the safely operating cycle drops to three dues to the not fully exploited PCM during fast charging process. Meanwhile, it is found that the high-frequency vibration can maintain the thermal resistance of vapor chamber below 0.15 K/W and suppress the temperature rise rate of simulated T/R module by 1.65 °C/min. Based on the standardized multiple linear regression, the deviation of the PCM's temperature from its melting point might lead to adverse effect on heat transfer performance. Provided that the heat dissipation performance at the condensing surface is maintained, increasing the heat flux or vibration frequency can reduce the average thermal resistance of VC. Among these, the variation in heat flux yields the most significant amelioration.
{"title":"Enhanced thermal management of cyclically operating T/R module in spatial environment","authors":"Junjie He , Xingang Wang , Xiangyang Xu , Xin Zhou , Wenxiao Chu , Qiuwang Wang","doi":"10.1016/j.ijheatmasstransfer.2025.126854","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126854","url":null,"abstract":"<div><div>To ensure the stable operation of high-power transmitter and receiver (T/R) module in the complex aerospace environment, this study presents an integrated thermal buffer combing a vapor chamber (VC) with trapezoidal microgroove wick structure and heat storage container filled by phase change materials (PCMs). A common surface between the two components is manufactured by 3D printer without thermal contact resistance. The effects of gravity and vibration conditions on the thermal management performance are considered. Results show that the sustained operation significantly depends on the heat dissipation efficiency at the VC condensing surface while the tested integrated thermal buffer is capable to guarantee the continuous operation of the simulated T/R module for at least 5 cycles. However, when operating under a higher thermal power, the safely operating cycle drops to three dues to the not fully exploited PCM during fast charging process. Meanwhile, it is found that the high-frequency vibration can maintain the thermal resistance of vapor chamber below 0.15 K/W and suppress the temperature rise rate of simulated T/R module by 1.65 °C/min. Based on the standardized multiple linear regression, the deviation of the PCM's temperature from its melting point might lead to adverse effect on heat transfer performance. Provided that the heat dissipation performance at the condensing surface is maintained, increasing the heat flux or vibration frequency can reduce the average thermal resistance of VC. Among these, the variation in heat flux yields the most significant amelioration.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126854"},"PeriodicalIF":5.0,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454453","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 : 2025-02-20DOI: 10.1016/j.ijheatmasstransfer.2025.126824
Han Wang , Zengpeng Wang, Dong Huang, Rijing Zhao
Immersion cooling is expected to be an effective cooling method for power batteries at high charge/discharge rates. However, dynamic behaviors such as sloshing will occur inside the immersion cooling battery module under actual driving conditions. This article aims to explore the effect of sloshing excitations on the dynamic characteristics of immersion cooling. For this purpose, the experimental system and numerical model of sloshing excitation coupled immersion cooling are established. The results show that sloshing excitations can enhance both single-phase and two-phase immersion cooling. In single-phase immersion cooling, the liquid sloshing increases the wettability of the battery surface and weakens the temperature stratification of the liquid pool. At a lateral acceleration of 3 m·s-2, the maximum battery temperature is 2.8°C lower than without sloshing excitations, the temperature standard deviation of a single battery is reduced by 35.7%, and the local heat flux is up to 20 kW·m-2. In two-phase immersion cooling, the sloshing excitation not only increases the surface wettability of the battery, but also promotes the release of bubbles on the battery surface, and the condensate on the cold plate slides into the liquid pool, which enhances the boiling and condensation process. After 1.0 s of sloshing excitation, the wetting ratio of condensate on the cold plate decreases by about 70.9%. The maximum heat flux is about twice that without sloshing excitation.
{"title":"Analysis of dynamic characteristics of single-phase/two-phase immersion cooling battery module under sloshing excitations","authors":"Han Wang , Zengpeng Wang, Dong Huang, Rijing Zhao","doi":"10.1016/j.ijheatmasstransfer.2025.126824","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126824","url":null,"abstract":"<div><div>Immersion cooling is expected to be an effective cooling method for power batteries at high charge/discharge rates. However, dynamic behaviors such as sloshing will occur inside the immersion cooling battery module under actual driving conditions. This article aims to explore the effect of sloshing excitations on the dynamic characteristics of immersion cooling. For this purpose, the experimental system and numerical model of sloshing excitation coupled immersion cooling are established. The results show that sloshing excitations can enhance both single-phase and two-phase immersion cooling. In single-phase immersion cooling, the liquid sloshing increases the wettability of the battery surface and weakens the temperature stratification of the liquid pool. At a lateral acceleration of 3 m·s<sup>-2</sup>, the maximum battery temperature is 2.8<sup>°</sup>C lower than without sloshing excitations, the temperature standard deviation of a single battery is reduced by 35.7%, and the local heat flux is up to 20 kW·m<sup>-2</sup>. In two-phase immersion cooling, the sloshing excitation not only increases the surface wettability of the battery, but also promotes the release of bubbles on the battery surface, and the condensate on the cold plate slides into the liquid pool, which enhances the boiling and condensation process. After 1.0 s of sloshing excitation, the wetting ratio of condensate on the cold plate decreases by about 70.9%. The maximum heat flux is about twice that without sloshing excitation.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126824"},"PeriodicalIF":5.0,"publicationDate":"2025-02-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143454454","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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