Pub Date : 2026-05-01Epub Date: 2025-12-18DOI: 10.1016/j.ijthermalsci.2025.110600
Qianru Wu , Maoqi Xu , Chengchun Zhang , Kuilin Huang , Jiachen Wang , Jiquan Yang , Changmeng Liu
In directed energy deposition-arc (DED-arc), the melt pool's thermodynamic behavior significantly impacts component morphology. Most existing studies focus on the influence of individual process parameters, with limited systematic investigation into the effects of key deposition strategies such as scanning strategy, interlayer cooling time, and deposition length. To address this, this study establishes a three-dimensional transient numerical model of DED-arc to systematically investigate how these strategies influence the melt pool's dynamics and formation characteristics. The results show that, increasing the interlayer cooling time from 0 s to 10 s significantly improves dimensional uniformity by approximately 19.7 %, achieved by decreasing the average deposition width by about 6.1 % and increasing the height by nearly 25.9 %. Furthermore, compared with unidirectional scanning, a bidirectional scanning strategy optimizes heat accumulation and enhances melt pool stability. Increasing the deposition length extends the stable formation zone, effectively mitigating the adverse impact of end instabilities on overall morphology. This study provides quantitative theoretical guidance for process optimization, parameter selection, and stable multi-layer formation in DED-arc.
{"title":"Influence of deposition strategy on melt pool behavior and forming morphology of directed energy deposition-arc","authors":"Qianru Wu , Maoqi Xu , Chengchun Zhang , Kuilin Huang , Jiachen Wang , Jiquan Yang , Changmeng Liu","doi":"10.1016/j.ijthermalsci.2025.110600","DOIUrl":"10.1016/j.ijthermalsci.2025.110600","url":null,"abstract":"<div><div>In directed energy deposition-arc (DED-arc), the melt pool's thermodynamic behavior significantly impacts component morphology. Most existing studies focus on the influence of individual process parameters, with limited systematic investigation into the effects of key deposition strategies such as scanning strategy, interlayer cooling time, and deposition length. To address this, this study establishes a three-dimensional transient numerical model of DED-arc to systematically investigate how these strategies influence the melt pool's dynamics and formation characteristics. The results show that, increasing the interlayer cooling time from 0 s to 10 s significantly improves dimensional uniformity by approximately 19.7 %, achieved by decreasing the average deposition width by about 6.1 % and increasing the height by nearly 25.9 %. Furthermore, compared with unidirectional scanning, a bidirectional scanning strategy optimizes heat accumulation and enhances melt pool stability. Increasing the deposition length extends the stable formation zone, effectively mitigating the adverse impact of end instabilities on overall morphology. This study provides quantitative theoretical guidance for process optimization, parameter selection, and stable multi-layer formation in DED-arc.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110600"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789450","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 : 2026-05-01Epub Date: 2026-01-05DOI: 10.1016/j.ijthermalsci.2025.110655
Jun-Meng Hou, Wan-Yuan Shi
Pendant droplets widely exit in various engineering technologies such as spray cooling and medical diagnostics whereas thermal Marangoni convection in pendant droplets is lack of clearly understanding. The present paper aims to the dynamic behaviors and heat transfer characteristics of thermal Marangoni convection in pendant droplets during evaporation. The results found that three types of Marangoni convection patterns successively occurred in droplet with evaporation, i.e., they were unsteady thermocapillary convection, longitudinal rolls, and BM convection. Their surface temperature patterns and internal flow fields were carefully analyzed and the critical conditions for incipience of Marangoni convection instabilities were determined. Their Nusselt numbers and evaporation rates were measured and the influences of substrate temperature on them were investigated. These findings will be helpful for realizing Marangoni convection instabilities of pendant droplets.
{"title":"Thermal Marangoni convection patterns and heat transfer characteristics in evaporating pendant droplets","authors":"Jun-Meng Hou, Wan-Yuan Shi","doi":"10.1016/j.ijthermalsci.2025.110655","DOIUrl":"10.1016/j.ijthermalsci.2025.110655","url":null,"abstract":"<div><div>Pendant droplets widely exit in various engineering technologies such as spray cooling and medical diagnostics whereas thermal Marangoni convection in pendant droplets is lack of clearly understanding. The present paper aims to the dynamic behaviors and heat transfer characteristics of thermal Marangoni convection in pendant droplets during evaporation. The results found that three types of Marangoni convection patterns successively occurred in droplet with evaporation, i.e., they were unsteady thermocapillary convection, longitudinal rolls, and BM convection. Their surface temperature patterns and internal flow fields were carefully analyzed and the critical conditions for incipience of Marangoni convection instabilities were determined. Their Nusselt numbers and evaporation rates were measured and the influences of substrate temperature on them were investigated. These findings will be helpful for realizing Marangoni convection instabilities of pendant droplets.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110655"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145922017","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}
Utilized within the present study is second law analysis as applied to experimentally-measured and numerically-predicted data within the turbulent boundary layers that develop along a constant heat flux test surface with an array of staggered dimples. Spatially-resolved second law results are provided over flow cross-sectional planes at different streamwise development locations, which are quantified using a characteristic temperature difference and freestream velocity. Considered are variations of entropy generation, as well as mass-averaged overall exergy destruction (both relative to freestream flow), as these quantities are determined using variations of local stagnation temperature only, variations of local flow stagnation pressure only, and stagnation pressure and stagnation temperature variations together. Resulting data provide detailed information on flow loss mechanisms which affect the thermal-fluid performance of surface dimples in augmenting surface heat transfer levels. Significant local variations of entropy generation and overall variations spatially-averaged exergy destruction are observed as spanwise-normal plane location, streamwise development location, freestream velocity, and characteristic temperature difference are altered. Additionally evident are gradients of local entropy generation from flow stagnation temperature, which are present near the surface beneath regions where local generation values are highest. These near-wall regions are associated with decreasing local flow temperatures, which are then locally lowest at the surface at the same locations where Nusselt numbers are locally augmented. Exergy destruction data based upon stagnation pressure consistently increase as freestream velocity becomes larger, with values that are 10–20 times lower relative to values based upon stagnation temperature only. Exergy destruction data values, based upon variations of stagnation temperature, and variations of stagnation temperature and stagnation pressure together, are higher by as much as 82 percent for ΔT = 15oC, compared to data associated with ΔT = 10oC. Responsible are a diversity of unsteady flow phenomena which originate due to the presence of individual dimple cavities, including secondary vortex pairs near dimple edges, primary vortex pairs shed from dimple central regions, and the shear layers which form across the top region of each dimple.
{"title":"Entropy generation from a staggered array of surface dimples with heat transfer and a constant heat flux boundary condition","authors":"Phillip M. Ligrani, Mason Hancock, Preston McMahan, Mauro Guevara-Ramon, Emily Mecklenburg, Nathan Knox","doi":"10.1016/j.ijthermalsci.2025.110645","DOIUrl":"10.1016/j.ijthermalsci.2025.110645","url":null,"abstract":"<div><div>Utilized within the present study is second law analysis as applied to experimentally-measured and numerically-predicted data within the turbulent boundary layers that develop along a constant heat flux test surface with an array of staggered dimples. Spatially-resolved second law results are provided over flow cross-sectional planes at different streamwise development locations, which are quantified using a characteristic temperature difference and freestream velocity. Considered are variations of entropy generation, as well as mass-averaged overall exergy destruction (both relative to freestream flow), as these quantities are determined using variations of local stagnation temperature only, variations of local flow stagnation pressure only, and stagnation pressure and stagnation temperature variations together. Resulting data provide detailed information on flow loss mechanisms which affect the thermal-fluid performance of surface dimples in augmenting surface heat transfer levels. Significant local variations of entropy generation and overall variations spatially-averaged exergy destruction are observed as spanwise-normal plane location, streamwise development location, freestream velocity, and characteristic temperature difference are altered. Additionally evident are gradients of local entropy generation from flow stagnation temperature, which are present near the surface beneath regions where local generation values are highest. These near-wall regions are associated with decreasing local flow temperatures, which are then locally lowest at the surface at the same locations where Nusselt numbers are locally augmented. Exergy destruction data based upon stagnation pressure consistently increase as freestream velocity becomes larger, with values that are 10–20 times lower relative to values based upon stagnation temperature only. Exergy destruction data values, based upon variations of stagnation temperature, and variations of stagnation temperature and stagnation pressure together, are higher by as much as 82 percent for ΔT = 15<sup>o</sup>C, compared to data associated with ΔT = 10<sup>o</sup>C. Responsible are a diversity of unsteady flow phenomena which originate due to the presence of individual dimple cavities, including secondary vortex pairs near dimple edges, primary vortex pairs shed from dimple central regions, and the shear layers which form across the top region of each dimple.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110645"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881179","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 : 2026-05-01Epub Date: 2026-01-03DOI: 10.1016/j.ijthermalsci.2025.110653
Wei Dang , Wenqiang Deng , Jian Song , Kewei Song
A systematic numerical investigation is conducted to examine the influence of curved rectangular vortex generator (CRVG) placement on the thermal performance of circular-tube-fin heat exchangers. Transverse, longitudinal, and circumferential offsets are considered to identify configurations that maximize heat transfer while maintaining acceptable flow resistance. The results show that a transverse offset of Δz = 1 mm achieves the best overall performance in the Reynolds number (Re) range from 400 to 5000, the Nusselt number (Nu) increases by up to 34.2 %, while performance evaluation criterion (JF) first increases and then decreases, reaching its maximum value of 1.32 at Re = 1000. A longitudinal offset of Δx = 2 mm yields a peak JF of 1.30. Circumferential placement exhibits the strongest influence. Here, Δβ represents the circumferential offset angle. The optimal circumferential position for heat transfer enhancement depends on Re, with the highest JF of 1.29 occurring at Δβ = 0° for Re = 1000, whereas Δβ = +15° yields a JF of 1.18 at Re = 2000, reflecting enhanced heat transfer performance at higher Re. A strong dependence of Nu on secondary flow intensity (Se) is also established, confirming that vortex-induced secondary flow is the key mechanism governing heat transfer augmentation. Furthermore, empirical correlations relating Nu, friction factor (f), and JF to Re and CRVG positioning parameters are developed, providing practical tools for preliminary design, performance assessment, and optimization of circular-tube-fin heat exchangers.
{"title":"Heat transfer enhancement of circular-tube-fin heat exchangers: Optimal positioning and role of curved rectangular vortex generators","authors":"Wei Dang , Wenqiang Deng , Jian Song , Kewei Song","doi":"10.1016/j.ijthermalsci.2025.110653","DOIUrl":"10.1016/j.ijthermalsci.2025.110653","url":null,"abstract":"<div><div>A systematic numerical investigation is conducted to examine the influence of curved rectangular vortex generator (CRVG) placement on the thermal performance of circular-tube-fin heat exchangers. Transverse, longitudinal, and circumferential offsets are considered to identify configurations that maximize heat transfer while maintaining acceptable flow resistance. The results show that a transverse offset of Δ<em>z</em> = 1 mm achieves the best overall performance in the Reynolds number (<em>Re</em>) range from 400 to 5000, the Nusselt number (<em>Nu</em>) increases by up to 34.2 %, while performance evaluation criterion (<em>JF</em>) first increases and then decreases, reaching its maximum value of 1.32 at <em>Re</em> = 1000. A longitudinal offset of Δ<em>x</em> = 2 mm yields a peak <em>JF</em> of 1.30. Circumferential placement exhibits the strongest influence. Here, Δ<em>β</em> represents the circumferential offset angle. The optimal circumferential position for heat transfer enhancement depends on <em>Re</em>, with the highest <em>JF</em> of 1.29 occurring at Δ<em>β</em> = 0° for <em>Re</em> = 1000, whereas Δ<em>β</em> = +15° yields a <em>JF</em> of 1.18 at <em>Re</em> = 2000, reflecting enhanced heat transfer performance at higher <em>Re</em>. A strong dependence of <em>Nu</em> on secondary flow intensity (<em>Se</em>) is also established, confirming that vortex-induced secondary flow is the key mechanism governing heat transfer augmentation. Furthermore, empirical correlations relating <em>Nu</em>, friction factor (<em>f</em>), and <em>JF</em> to <em>Re</em> and CRVG positioning parameters are developed, providing practical tools for preliminary design, performance assessment, and optimization of circular-tube-fin heat exchangers.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110653"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881210","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}
Transpiration cooling using fuel is vital for scramjet combustor thermal protection and payload enhancement. However, the interaction between fuel pyrolysis combustion and shock waves is a complex and important subject worthy of study. This paper establishes a transpiration cooling model integrated with pyrolysis combustion reaction under the action of shock waves, and the influence of different shock wave incident intensity on the thermal protection/drag reduction effect of transpiration cooling is explored. The results indicate that pyrolysis combustion reaction reduces the ability of transpiration coolant film to resist shock wave interference to boundary layer; when pyrolysis combustion is considered, both the width and thickness of the turbulent boundary layer increase during shock wave impingement. Additionally, pyrolysis combustion reaction can oppose the impact of shock wave-induced unstable distribution of shear stress, thus contributing to the reduction of thrust loss in combustion chamber. Given the growth of the shock wave intensity, the flow deflection of coolant becomes more pronounced, and both the width of the local high-temperature region and the temperature peak value increase. These findings provide insights for the structural optimization of engine transpiration cooling systems.
{"title":"Numerical investigation on the interaction mechanism between pyrolysis combustion reaction and shock wave in transpiration cooling","authors":"Jiayue Zheng , Yuyang Bian , Xue Liu , Weixing Zhou","doi":"10.1016/j.ijthermalsci.2025.110615","DOIUrl":"10.1016/j.ijthermalsci.2025.110615","url":null,"abstract":"<div><div>Transpiration cooling using fuel is vital for scramjet combustor thermal protection and payload enhancement. However, the interaction between fuel pyrolysis combustion and shock waves is a complex and important subject worthy of study. This paper establishes a transpiration cooling model integrated with pyrolysis combustion reaction under the action of shock waves, and the influence of different shock wave incident intensity on the thermal protection/drag reduction effect of transpiration cooling is explored. The results indicate that pyrolysis combustion reaction reduces the ability of transpiration coolant film to resist shock wave interference to boundary layer; when pyrolysis combustion is considered, both the width and thickness of the turbulent boundary layer increase during shock wave impingement. Additionally, pyrolysis combustion reaction can oppose the impact of shock wave-induced unstable distribution of shear stress, thus contributing to the reduction of thrust loss in combustion chamber. Given the growth of the shock wave intensity, the flow deflection of coolant becomes more pronounced, and both the width of the local high-temperature region and the temperature peak value increase. These findings provide insights for the structural optimization of engine transpiration cooling systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110615"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145838093","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 : 2026-05-01Epub Date: 2025-12-27DOI: 10.1016/j.ijthermalsci.2025.110616
Qinghua Chen , Xin Sun , Song Cui , Jiadong Ji , Yin Hong , Huaibei Xie
In response to the issue of lithium battery performance degradation and safety risks caused by low-temperature environments in open-pit mines, this study proposes and optimizes a new type of integrated thermal management system for liquid indirect preheating and insulation based on an S-shaped dual-channel parallel flow heating plate. With the goal of improving temperature uniformity and reducing system energy consumption, the flow velocity, inlet temperature, and insulation layer thickness were selected as design variables, and the ΔTmax and ΔP were selected as objective functions. A high-precision quadratic regression model between the objective function and design variables was constructed using Box-Behnken experimental design combined with response surface methodology. Based on this model, a non-dominated sorting genetic algorithm was applied for multi-objective optimization to obtain the Pareto optimal solution set. Analysis of variance indicates: Flow velocity has a significant effect on both ΔTmax and ΔP. The inlet temperature significantly affects ΔTmax but has little effect on ΔP. The thickness of the insulation layer has a minor but significant effect on ΔP. Determine the optimal optimization point by comprehensively evaluating the power obtained from the fluid (PEF) and the distance from the ideal point. Compared with the initial design (V = 0.16 m/s, Ti = 25 °C, H = 5 mm), the optimized design (V = 0.138 m/s, Ti = 20 °C, H = 12.06 mm) reduced ΔTmax by 8.51 %, ΔP by 16.97 %, and PEF by 19.93 %. The results indicate that the designed thermal management system and its optimization method effectively enhance the temperature uniformity of mining lithium battery modules in low-temperature environments, while reducing system flow resistance and energy consumption.
针对露天矿低温环境导致锂电池性能下降和安全风险的问题，本研究提出并优化了一种基于s型双通道平行流加热板的新型液体间接预热保温一体化热管理系统。以提高温度均匀性和降低系统能耗为目标，选取气流速度、进口温度和保温层厚度作为设计变量，并选取ΔTmax和ΔP作为目标函数。采用Box-Behnken试验设计结合响应面法，建立了目标函数与设计变量之间的高精度二次回归模型。在此模型的基础上，采用非支配排序遗传算法进行多目标优化，得到Pareto最优解集。方差分析表明：流速对ΔTmax和ΔP均有显著影响。进口温度对ΔTmax影响显著，对ΔP影响不大。保温层厚度对ΔP的影响虽小但很显著。通过综合评价从流体获得的功率（PEF）和到理想点的距离，确定最优优化点。与初始设计（V = 0.16 m/s, Ti = 25°C, H = 5 mm）相比，优化设计（V = 0.138 m/s, Ti = 20°C, H = 12.06 mm）降低ΔTmax 8.51%， ΔP 16.97%， PEF降低19.93%。结果表明，所设计的热管理系统及其优化方法有效提高了低温环境下矿用锂电池模块的温度均匀性，同时降低了系统流阻和能耗。
{"title":"Multi-objective optimization of a thermal management system for mining lithium-ion batteries in low-temperature environments","authors":"Qinghua Chen , Xin Sun , Song Cui , Jiadong Ji , Yin Hong , Huaibei Xie","doi":"10.1016/j.ijthermalsci.2025.110616","DOIUrl":"10.1016/j.ijthermalsci.2025.110616","url":null,"abstract":"<div><div>In response to the issue of lithium battery performance degradation and safety risks caused by low-temperature environments in open-pit mines, this study proposes and optimizes a new type of integrated thermal management system for liquid indirect preheating and insulation based on an S-shaped dual-channel parallel flow heating plate. With the goal of improving temperature uniformity and reducing system energy consumption, the flow velocity, inlet temperature, and insulation layer thickness were selected as design variables, and the <em>ΔT</em><sub><em>max</em></sub> and <em>ΔP</em> were selected as objective functions. A high-precision quadratic regression model between the objective function and design variables was constructed using Box-Behnken experimental design combined with response surface methodology. Based on this model, a non-dominated sorting genetic algorithm was applied for multi-objective optimization to obtain the Pareto optimal solution set. Analysis of variance indicates: Flow velocity has a significant effect on both <em>ΔT</em><sub><em>max</em></sub> and <em>ΔP.</em> The inlet temperature significantly affects <em>ΔT</em><sub><em>max</em></sub> but has little effect on <em>ΔP</em>. The thickness of the insulation layer has a minor but significant effect on <em>ΔP</em>. Determine the optimal optimization point by comprehensively evaluating the power obtained from the fluid (<em>PEF</em>) and the distance from the ideal point. Compared with the initial design (<em>V</em> = 0.16 m/s, <em>T</em><sub><em>i</em></sub> = 25 °C, <em>H</em> = 5 mm), the optimized design (<em>V</em> = 0.138 m/s, <em>T</em><sub><em>i</em></sub> = 20 °C, <em>H</em> = 12.06 mm) reduced <em>ΔT</em><sub><em>max</em></sub> by 8.51 %, <em>ΔP</em> by 16.97 %, and <em>PEF</em> by 19.93 %. The results indicate that the designed thermal management system and its optimization method effectively enhance the temperature uniformity of mining lithium battery modules in low-temperature environments, while reducing system flow resistance and energy consumption.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110616"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145838097","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 : 2026-05-01Epub Date: 2025-12-18DOI: 10.1016/j.ijthermalsci.2025.110605
Feng Liu , Wei Li , Zhongning Sun , Haozhi Bian , Ming Ding
The passive containment heat removal system (PCS), as a key cooling source within the new-generation nuclear containment, exerts a significant influence on the migration and stratification behaviors of hydrogen-steam-air multicomponent gas under severe accident conditions, which is crucial for hydrogen risk safety analysis. However, most existing studies generally overlook the impact of the PCS, which limits the ability of their conclusions to provide reliable guidance for hydrogen safety analysis under severe accident conditions. Therefore, this study conducts numerical simulations to investigate the migration of multicomponent gases and hydrogen stratification characteristics under the combined effect of the PCS and buoyant jet within a large enclosed space, focusing on the depressurization phase of severe accident (where the heat removal power of the PCS exceeds the enthalpy of the released gas). The results indicate that the gas temperature stratification and concentration stratification induced by the PCS can transform the multicomponent gas buoyant jet into a “negative buoyancy jet” during its upward migration. This transformation significantly inhibits the migration of multicomponent gases toward the top of the large enclosed space, and hydrogen accumulates below the stratification interface when the interaction Froude number Fri < 1. Within the range of parameters studied in this paper, the peak hydrogen concentration is significantly higher than that in the scenario without the PCS cold source. Furthermore, increasing the installation elevation of the PCS not only enhances its heat removal power but also alleviates hydrogen accumulation. These findings provide a critical theoretical basis for clarifying severe accident phenomena and optimizing hydrogen mitigation strategies in the new-generation nuclear containment.
{"title":"Study on migration characteristics of multi-component gases driven by the cold source of passive containment cooling system in a large enclosed space","authors":"Feng Liu , Wei Li , Zhongning Sun , Haozhi Bian , Ming Ding","doi":"10.1016/j.ijthermalsci.2025.110605","DOIUrl":"10.1016/j.ijthermalsci.2025.110605","url":null,"abstract":"<div><div>The passive containment heat removal system (PCS), as a key cooling source within the new-generation nuclear containment, exerts a significant influence on the migration and stratification behaviors of hydrogen-steam-air multicomponent gas under severe accident conditions, which is crucial for hydrogen risk safety analysis. However, most existing studies generally overlook the impact of the PCS, which limits the ability of their conclusions to provide reliable guidance for hydrogen safety analysis under severe accident conditions. Therefore, this study conducts numerical simulations to investigate the migration of multicomponent gases and hydrogen stratification characteristics under the combined effect of the PCS and buoyant jet within a large enclosed space, focusing on the depressurization phase of severe accident (where the heat removal power of the PCS exceeds the enthalpy of the released gas). The results indicate that the gas temperature stratification and concentration stratification induced by the PCS can transform the multicomponent gas buoyant jet into a “negative buoyancy jet” during its upward migration. This transformation significantly inhibits the migration of multicomponent gases toward the top of the large enclosed space, and hydrogen accumulates below the stratification interface when the interaction Froude number <em>Fr</em><sub><em>i</em></sub> < 1. Within the range of parameters studied in this paper, the peak hydrogen concentration is significantly higher than that in the scenario without the PCS cold source. Furthermore, increasing the installation elevation of the PCS not only enhances its heat removal power but also alleviates hydrogen accumulation. These findings provide a critical theoretical basis for clarifying severe accident phenomena and optimizing hydrogen mitigation strategies in the new-generation nuclear containment.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110605"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789367","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 : 2026-05-01Epub Date: 2025-12-18DOI: 10.1016/j.ijthermalsci.2025.110599
Zongjie Luo , Jinhui Fan , Peng Hao , Cheng Bao
Horizontal tube falling film evaporators have found extensive applications in absorption heat pumps, a sustainable technology for building cooling systems. In practical film descent processes, continuous and complete liquid film coverage cannot be maintained throughout the entire system, and the formation of dry spots represents a frequently observed phenomenon. The discontinuous liquid film formation on the tube surface significantly deteriorates the system's heat transfer efficiency, yet this phenomenon remains insufficiently investigated in existing literature. Two-dimensional mathematical model of a horizontal tube bundle under different arrangements is developed in the present study, the liquid film coverage and heat transfer coefficient of the bundle are numerically simulated under different liquid flow rates. The results demonstrate that liquid film coverage progressively decreases along the tube bundle during film descent, with dry patches significantly impairing the system's heat transfer efficiency. While increased flow rates enhance film coverage by suppressing dry patch formation, turbulent effects in the rotating triangular configuration establish an optimal regime at Re = 1580. Beyond this critical Reynolds number, structural optimization of the tube bundle can further improve liquid film coverage by shifting the optimal operation point to higher Re values (>1580), consequently achieving superior heat transfer efficiency.
{"title":"Numerical investigation of dry spot evolution and heat transfer degradation in falling film evaporation over tube bundle","authors":"Zongjie Luo , Jinhui Fan , Peng Hao , Cheng Bao","doi":"10.1016/j.ijthermalsci.2025.110599","DOIUrl":"10.1016/j.ijthermalsci.2025.110599","url":null,"abstract":"<div><div>Horizontal tube falling film evaporators have found extensive applications in absorption heat pumps, a sustainable technology for building cooling systems. In practical film descent processes, continuous and complete liquid film coverage cannot be maintained throughout the entire system, and the formation of dry spots represents a frequently observed phenomenon. The discontinuous liquid film formation on the tube surface significantly deteriorates the system's heat transfer efficiency, yet this phenomenon remains insufficiently investigated in existing literature. Two-dimensional mathematical model of a horizontal tube bundle under different arrangements is developed in the present study, the liquid film coverage and heat transfer coefficient of the bundle are numerically simulated under different liquid flow rates. The results demonstrate that liquid film coverage progressively decreases along the tube bundle during film descent, with dry patches significantly impairing the system's heat transfer efficiency. While increased flow rates enhance film coverage by suppressing dry patch formation, turbulent effects in the rotating triangular configuration establish an optimal regime at <em>Re</em> = 1580. Beyond this critical Reynolds number, structural optimization of the tube bundle can further improve liquid film coverage by shifting the optimal operation point to higher <em>Re</em> values (>1580), consequently achieving superior heat transfer efficiency.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110599"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789371","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 : 2026-05-01Epub Date: 2025-12-16DOI: 10.1016/j.ijthermalsci.2025.110594
Qunwei Zhang , Hongwei Xing , Qiqi Liang , Aimin Yang , Jie Li , Yang Han
Heat transfer in blast furnace cooling staves exhibits nonlocal thermal memory and transient multi-scale coupling characteristics. Traditional integer-order models have prediction deviations due to neglecting historical thermal effects. This paper proposes a fractional-order Physics-Informed Neural Network (PINN) framework: A heat transfer equation based on the Caputo fractional derivative is constructed to characterize the thermal memory effect, and solved using the Grünwald-Letnikov discretization scheme with short-memory correction; a PINN architecture embedded with fractional operators is designed, and combined with receding horizon optimization and transfer learning to realize inversion of heat transfer parameters and thermal state prediction. Validation results show that the model converges stably. When the optimal fractional order , the global temperature prediction RMSE reaches 0.99 °C, significantly outperforming integer-order models, and the temperature field simulation is consistent with actual operating conditions. Multi-scale simulations reveal the micro-mechanism: The power-law relaxation characteristics of Al2O3-SiO2 lattices and nonlocal thermal diffusion induced by microcrack networks are consistent with the characteristics of the fractional-order model. Finally, a health early-warning framework is established based on fractional parameters, providing a new method for intelligent regulation of blast furnace cooling systems.
{"title":"Fractional-order physics-informed neural network for predicting and inverting heat transfer in blast furnace cooling staves","authors":"Qunwei Zhang , Hongwei Xing , Qiqi Liang , Aimin Yang , Jie Li , Yang Han","doi":"10.1016/j.ijthermalsci.2025.110594","DOIUrl":"10.1016/j.ijthermalsci.2025.110594","url":null,"abstract":"<div><div>Heat transfer in blast furnace cooling staves exhibits nonlocal thermal memory and transient multi-scale coupling characteristics. Traditional integer-order models have prediction deviations due to neglecting historical thermal effects. This paper proposes a fractional-order Physics-Informed Neural Network (PINN) framework: A heat transfer equation based on the Caputo fractional derivative is constructed to characterize the thermal memory effect, and solved using the Grünwald-Letnikov discretization scheme with short-memory correction; a PINN architecture embedded with fractional operators is designed, and combined with receding horizon optimization and transfer learning to realize inversion of heat transfer parameters and thermal state prediction. Validation results show that the model converges stably. When the optimal fractional order <span><math><mrow><mi>α</mi><mo>=</mo><mn>0.8</mn></mrow></math></span>, the global temperature prediction RMSE reaches 0.99 °C, significantly outperforming integer-order models, and the temperature field simulation is consistent with actual operating conditions. Multi-scale simulations reveal the micro-mechanism: The power-law relaxation characteristics of Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub> lattices and nonlocal thermal diffusion induced by microcrack networks are consistent with the characteristics of the fractional-order model. Finally, a health early-warning framework is established based on fractional parameters, providing a new method for intelligent regulation of blast furnace cooling systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110594"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789444","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 : 2026-05-01Epub Date: 2025-12-31DOI: 10.1016/j.ijthermalsci.2025.110610
Zhi Zhang , Si Fu , Zhengbo Li , Yundong Cao , Zhengkang Li , Jing Cao
As the primary source of metal vapor particles in vacuum arcs, cathode spots are fundamental to the control and regulation of arcs in vacuum interrupters. This study investigates the influence of contact rotation on the generation and evolution of cathode spots by simulating the formation of craters on a copper cathode surface under a constant current carried by a single basic cathode spot unit. To accurately reflect the impact of the vacuum arc on the contact, optical emission spectroscopy (OES) is employed to diagnose plasma parameters under different rotational speeds, determining electron temperature and electron density. The derived electron heat flux density is used to estimate the energy flux density received by a single cathode spot from the arc column, which serves as a boundary condition for modeling cathode spot formation and evolution at various rotation speeds. The three-dimensional model integrates fluid dynamics equations, heat transfer equations, and a modified level-set equation. The study explores cathode spot surface temperature, molten pool width, erosion volume, and droplet ejection behavior under different rotational interruption scenarios. Results show that direct-pull interruption causes more severe droplet splashing compared to rotational interruption. In the direct-pull case, splashed material at the molten pool edge forms a “serrated” morphology. With the introduction of rotation, surface erosion is alleviated, the velocity of droplet ejection from a single cathode spot increases, but the total droplet volume decreases. The splashed morphology transitions to a “ring-shaped” shape, and the overall erosion mass is reduced.
{"title":"Analysis on microscopic characteristics of cathode spot ablation of vacuum contact under different interruption modes","authors":"Zhi Zhang , Si Fu , Zhengbo Li , Yundong Cao , Zhengkang Li , Jing Cao","doi":"10.1016/j.ijthermalsci.2025.110610","DOIUrl":"10.1016/j.ijthermalsci.2025.110610","url":null,"abstract":"<div><div>As the primary source of metal vapor particles in vacuum arcs, cathode spots are fundamental to the control and regulation of arcs in vacuum interrupters. This study investigates the influence of contact rotation on the generation and evolution of cathode spots by simulating the formation of craters on a copper cathode surface under a constant current carried by a single basic cathode spot unit. To accurately reflect the impact of the vacuum arc on the contact, optical emission spectroscopy (OES) is employed to diagnose plasma parameters under different rotational speeds, determining electron temperature and electron density. The derived electron heat flux density is used to estimate the energy flux density received by a single cathode spot from the arc column, which serves as a boundary condition for modeling cathode spot formation and evolution at various rotation speeds. The three-dimensional model integrates fluid dynamics equations, heat transfer equations, and a modified level-set equation. The study explores cathode spot surface temperature, molten pool width, erosion volume, and droplet ejection behavior under different rotational interruption scenarios. Results show that direct-pull interruption causes more severe droplet splashing compared to rotational interruption. In the direct-pull case, splashed material at the molten pool edge forms a “serrated” morphology. With the introduction of rotation, surface erosion is alleviated, the velocity of droplet ejection from a single cathode spot increases, but the total droplet volume decreases. The splashed morphology transitions to a “ring-shaped” shape, and the overall erosion mass is reduced.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"223 ","pages":"Article 110610"},"PeriodicalIF":5.0,"publicationDate":"2026-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145881183","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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