Pub Date : 2026-01-12DOI: 10.1016/j.ijthermalsci.2026.110669
Ershuai Yin, Wenzhu Luo, Lei Wang, Enjian Sun, Qiang Li
Heat in gallium nitride (GaN) high-electron-mobility transistors (HEMTs) is typically generated as highly localized nanoscale hot spots and dissipates through GaN/substrate heterostructures, yet the impact of non-uniform heating on heterostructure thermal transport remains unclear. This work aims to elucidate the thermal transport mechanisms of GaN/substrate heterostructures under non-uniform heat sources. A heterostructure thermal transport model is developed by combining first-principles calculations with Monte Carlo simulations. The effects of heterostructure height, heat source width, and heat source height on thermal transport characteristics are analyzed for four typical GaN/substrate heterostructures: GaN/AlN, GaN/Diamond, GaN/Si, and GaN/SiC. The results show that non-uniform heating has only a minor effect on the average interfacial thermal conductance. However, it induces pronounced spatial non-uniformity when the heterostructure height is small, with substantially higher conductance near the hot-spot region. Increasing heat-source non-uniformity substantially elevates the total thermal resistance, reaching several times the value obtained under uniform heating. In contrast, conventional finite-element method significantly underestimates the total thermal resistance because it cannot capture the coupled effects of localized heating and size-dependent thermal transport. The findings can provide theoretical guidance for the thermal design and reliability assessment of GaN semiconductor devices.
{"title":"Thermal transport of GaN/substrate heterostructures under non-uniform heat source","authors":"Ershuai Yin, Wenzhu Luo, Lei Wang, Enjian Sun, Qiang Li","doi":"10.1016/j.ijthermalsci.2026.110669","DOIUrl":"10.1016/j.ijthermalsci.2026.110669","url":null,"abstract":"<div><div>Heat in gallium nitride (GaN) high-electron-mobility transistors (HEMTs) is typically generated as highly localized nanoscale hot spots and dissipates through GaN/substrate heterostructures, yet the impact of non-uniform heating on heterostructure thermal transport remains unclear. This work aims to elucidate the thermal transport mechanisms of GaN/substrate heterostructures under non-uniform heat sources. A heterostructure thermal transport model is developed by combining first-principles calculations with Monte Carlo simulations. The effects of heterostructure height, heat source width, and heat source height on thermal transport characteristics are analyzed for four typical GaN/substrate heterostructures: GaN/AlN, GaN/Diamond, GaN/Si, and GaN/SiC. The results show that non-uniform heating has only a minor effect on the average interfacial thermal conductance. However, it induces pronounced spatial non-uniformity when the heterostructure height is small, with substantially higher conductance near the hot-spot region. Increasing heat-source non-uniformity substantially elevates the total thermal resistance, reaching several times the value obtained under uniform heating. In contrast, conventional finite-element method significantly underestimates the total thermal resistance because it cannot capture the coupled effects of localized heating and size-dependent thermal transport. The findings can provide theoretical guidance for the thermal design and reliability assessment of GaN semiconductor devices.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110669"},"PeriodicalIF":5.0,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975207","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 : 2026-01-10DOI: 10.1016/j.ijthermalsci.2026.110670
Mingkai Guo , Guoshuai Qin , Chunsheng Lu , Cuiying Fan , Minghao Zhao
The regulation of carrier distributions in piezoelectric semiconductors through piezo-phototronic and pyro-phototronic effects offers a promising pathway for developing tunable optoelectronic devices. In this paper, we propose a nonlinear pyro-piezo-phototronic model that accounts for the combined influences of ultraviolet radiation and externally applied mechanical stress. Unlike previous approaches that consider only piezoelectric or photoexcitation effects, this work extends the perturbation method to include pyroelectric contributions, enabling a comprehensive analysis of electromechanical field distributions under multi-field coupling. Our findings reveal that the polarity and direction of polarization charges at both ends of a GaN PN junction can be reversibly modulated by adjusting ultraviolet irradiation and mechanical loading. This controllable switching of polarized charges highlights a new avenue for functional regulation in piezoelectric semiconductors and expands their potential applications in next-generation optoelectronic and multifunctional devices.
{"title":"A pyro-piezo-phototronic regulation strategy for carrier modulation in a GaN PN junction","authors":"Mingkai Guo , Guoshuai Qin , Chunsheng Lu , Cuiying Fan , Minghao Zhao","doi":"10.1016/j.ijthermalsci.2026.110670","DOIUrl":"10.1016/j.ijthermalsci.2026.110670","url":null,"abstract":"<div><div>The regulation of carrier distributions in piezoelectric semiconductors through piezo-phototronic and pyro-phototronic effects offers a promising pathway for developing tunable optoelectronic devices. In this paper, we propose a nonlinear pyro-piezo-phototronic model that accounts for the combined influences of ultraviolet radiation and externally applied mechanical stress. Unlike previous approaches that consider only piezoelectric or photoexcitation effects, this work extends the perturbation method to include pyroelectric contributions, enabling a comprehensive analysis of electromechanical field distributions under multi-field coupling. Our findings reveal that the polarity and direction of polarization charges at both ends of a GaN PN junction can be reversibly modulated by adjusting ultraviolet irradiation and mechanical loading. This controllable switching of polarized charges highlights a new avenue for functional regulation in piezoelectric semiconductors and expands their potential applications in next-generation optoelectronic and multifunctional devices.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110670"},"PeriodicalIF":5.0,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975202","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 : 2026-01-10DOI: 10.1016/j.ijthermalsci.2026.110687
Ioannis Psihias, Eustathios S. Kikkinides, Stergios G. Yiantsios
We consider the issue of the effective thermal conductivity of open-cell foams. Spatially periodic structures based on the space-filling Kelvin's tetrakaidecahedron are examined over a range of porosities from 0.88 to 0.99, and a range of solid to fluid thermal conductivity ratios from 10 to 8200. The heat conduction problem is analyzed numerically employing the finite element and the front-tracking method. The attractive characteristic of the methods is that simple, fixed, structured numerical grids may be employed, despite the complicated two-phase geometries involved. The numerical results obtained are in satisfactory agreement with the extensive and widely acknowledged experimental data of Calmidi and Mahajan [J. Heat Transfer 121 (1999), 466–471] and with established models in the literature. Interestingly, the results are also in excellent agreement with theoretical relations based on effective medium theories and cluster expansion techniques for low density random dispersions, suggesting that these relations may be very useful for quantitative predictions of effective properties in open-cell foams.
{"title":"Effective thermal conductivity of open-cell foams: Numerical study in structures composed of the space-filling Kelvin's tetrakaidekahedron","authors":"Ioannis Psihias, Eustathios S. Kikkinides, Stergios G. Yiantsios","doi":"10.1016/j.ijthermalsci.2026.110687","DOIUrl":"10.1016/j.ijthermalsci.2026.110687","url":null,"abstract":"<div><div>We consider the issue of the effective thermal conductivity of open-cell foams. Spatially periodic structures based on the space-filling Kelvin's tetrakaidecahedron are examined over a range of porosities from 0.88 to 0.99, and a range of solid to fluid thermal conductivity ratios from 10 to 8200. The heat conduction problem is analyzed numerically employing the finite element and the front-tracking method. The attractive characteristic of the methods is that simple, fixed, structured numerical grids may be employed, despite the complicated two-phase geometries involved. The numerical results obtained are in satisfactory agreement with the extensive and widely acknowledged experimental data of Calmidi and Mahajan [J. Heat Transfer 121 (1999), 466–471] and with established models in the literature. Interestingly, the results are also in excellent agreement with theoretical relations based on effective medium theories and cluster expansion techniques for low density random dispersions, suggesting that these relations may be very useful for quantitative predictions of effective properties in open-cell foams.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110687"},"PeriodicalIF":5.0,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923776","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 : 2026-01-10DOI: 10.1016/j.ijthermalsci.2026.110679
Xing Qi Lim , Mohd Sharizal Abdul Aziz , C.Y. Khor
This study investigates the potential of a partially applied silver nanoparticle (AgNP) coating to enhance the thermal dissipation performance of the heat sink. Since the fully coated heat sink only showed marginal enhancement in the previous study, the heat sink is now partially coated on different surfaces. The simulation is completed using the ANSYS FLUENT software, and the accuracy of the setup is verified with an error percentage of less than 4 %. The heat sink with a front face coated (C3-AgNP) records the highest average overall heat transfer coefficient of 6.15379 W m−2 K−1, which is 1.141 % higher than the uncoated heat sink and 0.944 % better than the fully-coated (C1234-AgNP) heat sink. The C3-AgNP heat sink requires only a 5.4 mm3 AgNP coating, which is 96.655 % less than the 161.44 mm3 coating used by the C1234-AgNP heat sink. Although the presence of AgNP coating has adverse effects on the radiation heat loss of the heat sink, it enhances the heat dissipation process by facilitating heat flow from hotter regions to cooler regions. The AgNP coating promotes temperature uniformity in the heat sink, enabling greater heat loss through convection. This study reveals the possibility of unleashing the full potential of a coated heat sink through partial coating. It also contributes a solution for combining two or more different coatings, thereby optimizing heat sink performance in thermal management applications.
本研究探讨了部分镀银纳米粒子（AgNP）涂层增强散热器散热性能的潜力。由于完全涂覆的散热器在之前的研究中仅表现出边际增强，因此现在将散热器部分涂覆在不同的表面上。利用ANSYS FLUENT软件完成了仿真，验证了该装置的精度，误差小于4%。前表面涂层（C3-AgNP）的平均总换热系数最高，为6.15379 W m−2 K−1，比未涂层的散热器高1.141%，比全涂层（C1234-AgNP）的散热器高0.944%。C3-AgNP散热器只需要5.4 mm3的AgNP涂层，比C1234-AgNP散热器使用的161.44 mm3涂层少96.655%。虽然AgNP涂层的存在对散热器的辐射热损失有不利影响，但它通过促进热量从较热区域流向较冷区域来增强散热过程。AgNP涂层促进了散热器的温度均匀性，通过对流实现了更大的热损失。这项研究揭示了通过部分涂层释放涂层散热器全部潜力的可能性。它还为组合两种或多种不同的涂层提供了解决方案，从而优化了热管理应用中的散热器性能。
{"title":"Strategic partial silver nanoparticles coating in enhancement of heat Sink's thermal performance","authors":"Xing Qi Lim , Mohd Sharizal Abdul Aziz , C.Y. Khor","doi":"10.1016/j.ijthermalsci.2026.110679","DOIUrl":"10.1016/j.ijthermalsci.2026.110679","url":null,"abstract":"<div><div>This study investigates the potential of a partially applied silver nanoparticle (AgNP) coating to enhance the thermal dissipation performance of the heat sink. Since the fully coated heat sink only showed marginal enhancement in the previous study, the heat sink is now partially coated on different surfaces. The simulation is completed using the ANSYS FLUENT software, and the accuracy of the setup is verified with an error percentage of less than 4 %. The heat sink with a front face coated (C3-AgNP) records the highest average overall heat transfer coefficient of 6.15379 W m<sup>−2</sup> K<sup>−1</sup>, which is 1.141 % higher than the uncoated heat sink and 0.944 % better than the fully-coated (C1234-AgNP) heat sink. The C3-AgNP heat sink requires only a 5.4 mm<sup>3</sup> AgNP coating, which is 96.655 % less than the 161.44 mm<sup>3</sup> coating used by the C1234-AgNP heat sink. Although the presence of AgNP coating has adverse effects on the radiation heat loss of the heat sink, it enhances the heat dissipation process by facilitating heat flow from hotter regions to cooler regions. The AgNP coating promotes temperature uniformity in the heat sink, enabling greater heat loss through convection. This study reveals the possibility of unleashing the full potential of a coated heat sink through partial coating. It also contributes a solution for combining two or more different coatings, thereby optimizing heat sink performance in thermal management applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110679"},"PeriodicalIF":5.0,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923777","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}
The thermal management challenge of modern servers is recognized to arise from highly non-uniform power densities. In this study, a single-phase immersion and cold plate hybrid cooling method is employed to address the cooling of discretely distributed server elements with different power. Three-dimensional steady-state Reynolds-averaged Navier-Stokes simulations with conjugate heat transfer are performed to evaluate the thermal behavior of a complete one-unit server. Five coolant flow configurations are examined and their orientations relative to gravity are evaluated. The effects of coolant temperatures and flow rates as well as immersion liquid conditions are quantified through a systematic parametric analysis and an orthogonal design method. The dual inlet and dual outlet configuration provides the best temperature uniformity for the central processing unit. The inlet temperature of coolant is identified as the dominant factor for the maximum temperature of central processing units, while the overall temperature difference is mainly governed by the cooling configuration arrangement and the coolant flow rate. The temperature of low power elements is controlled primarily by the inlet temperature of the immersion liquid. A maximum temperature difference of 1.34 K is obtained for the platform controller hub. A reduction of 62.98 % compared with related work is demonstrated, and superior temperature uniformity is shown to be achieved by the proposed system. The combined cooling strategy is shown to maintain low temperature gradients across discrete power elements and is expected to provide theoretical support for the design of thermal management systems in modern servers.
{"title":"Thermal management of server with discrete power elements by localized cold plate enhanced single-phase immersion cooling and its orthogonal optimization","authors":"Yueting Zhou, Meiyan Xiong, Zhenwei Liu, Boyuan Wang, Feng Cao, Ping Li","doi":"10.1016/j.ijthermalsci.2026.110676","DOIUrl":"10.1016/j.ijthermalsci.2026.110676","url":null,"abstract":"<div><div>The thermal management challenge of modern servers is recognized to arise from highly non-uniform power densities. In this study, a single-phase immersion and cold plate hybrid cooling method is employed to address the cooling of discretely distributed server elements with different power. Three-dimensional steady-state Reynolds-averaged Navier-Stokes simulations with conjugate heat transfer are performed to evaluate the thermal behavior of a complete one-unit server. Five coolant flow configurations are examined and their orientations relative to gravity are evaluated. The effects of coolant temperatures and flow rates as well as immersion liquid conditions are quantified through a systematic parametric analysis and an orthogonal design method. The dual inlet and dual outlet configuration provides the best temperature uniformity for the central processing unit. The inlet temperature of coolant is identified as the dominant factor for the maximum temperature of central processing units, while the overall temperature difference is mainly governed by the cooling configuration arrangement and the coolant flow rate. The temperature of low power elements is controlled primarily by the inlet temperature of the immersion liquid. A maximum temperature difference of 1.34 K is obtained for the platform controller hub. A reduction of 62.98 % compared with related work is demonstrated, and superior temperature uniformity is shown to be achieved by the proposed system. The combined cooling strategy is shown to maintain low temperature gradients across discrete power elements and is expected to provide theoretical support for the design of thermal management systems in modern servers.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110676"},"PeriodicalIF":5.0,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145975210","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 : 2026-01-09DOI: 10.1016/j.ijthermalsci.2026.110658
Chunjie Zeng , Defang Mu , Hanrui Qiu , Mingjun Wang , Ge Wu , Wenxi Tian , Guanghui Su
The full-scale three-dimensional (3D) distribution characteristics of thermal-hydraulic parameters in a Steam Generator (SG) are crucial for the performance evaluation and safety analysis, which determine the economic efficiency and safety of nuclear power systems under long-term operation. Therefore, improving the prediction accuracy of the SG's 3D thermal-hydraulic field is one of the main development directions for SG analysis codes. A full-scale, tube-level computational model of the 55/19B steam generator (SG) was constructed using STEAM (Steam generator Tube-level thErmal-hydraulic Analysis platforM), a high-fidelity 3D code incorporating a two-fluid model developed by the Nuclear Thermal-hydraulic Laboratory at Xi'an Jiaotong University (XJTU-NuTHeL). Detailed thermal-hydraulic analysis was conducted for both the primary and secondary sides of the SG. Regarding the secondary side fluid domain, the simulation accurately reproduced the low void fraction distribution in the central bending tube region. Furthermore, areas susceptible to flow-induced vibration were pinpointed by analyzing crossflow energy. In the SG primary side flow domain, the characteristics of flow distribution in tube bundles were obtained, with a dimensionless standard deviation of 0.1 for the flow rates of the 4474 tubes. The influence of the channel head structure on flow distribution was also analyzed. Research on the high-fidelity tube-level 3D distribution characteristics of key thermal-hydraulic parameters on both sides of a full-scale SG can provide critical data support for SG flow-induced vibration analysis and design optimization.
{"title":"High-fidelity full-scale three-dimensional thermal-hydraulic characteristics analysis of the primary and secondary side in a steam generator","authors":"Chunjie Zeng , Defang Mu , Hanrui Qiu , Mingjun Wang , Ge Wu , Wenxi Tian , Guanghui Su","doi":"10.1016/j.ijthermalsci.2026.110658","DOIUrl":"10.1016/j.ijthermalsci.2026.110658","url":null,"abstract":"<div><div>The full-scale three-dimensional (3D) distribution characteristics of thermal-hydraulic parameters in a Steam Generator (SG) are crucial for the performance evaluation and safety analysis, which determine the economic efficiency and safety of nuclear power systems under long-term operation. Therefore, improving the prediction accuracy of the SG's 3D thermal-hydraulic field is one of the main development directions for SG analysis codes. A full-scale, tube-level computational model of the 55/19B steam generator (SG) was constructed using STEAM (Steam generator Tube-level thErmal-hydraulic Analysis platforM), a high-fidelity 3D code incorporating a two-fluid model developed by the Nuclear Thermal-hydraulic Laboratory at Xi'an Jiaotong University (XJTU-NuTHeL). Detailed thermal-hydraulic analysis was conducted for both the primary and secondary sides of the SG. Regarding the secondary side fluid domain, the simulation accurately reproduced the low void fraction distribution in the central bending tube region. Furthermore, areas susceptible to flow-induced vibration were pinpointed by analyzing crossflow energy. In the SG primary side flow domain, the characteristics of flow distribution in tube bundles were obtained, with a dimensionless standard deviation of 0.1 for the flow rates of the 4474 tubes. The influence of the channel head structure on flow distribution was also analyzed. Research on the high-fidelity tube-level 3D distribution characteristics of key thermal-hydraulic parameters on both sides of a full-scale SG can provide critical data support for SG flow-induced vibration analysis and design optimization.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110658"},"PeriodicalIF":5.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923774","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 : 2026-01-09DOI: 10.1016/j.ijthermalsci.2026.110674
Xilong Zhang , Rui Wang , Beibei Li , Zhicheng Zhou , Wenlin Dong
This study systematically compares six pin-fin configurations (Cases 0–5) in manifold microchannel heat sinks (MMCHS) through numerical simulation and experimental validation: Case 0 serves as the baseline conventional grooved structure, while Cases 1–5 explore novel designs including in-line rectangular pin-fins (Case 1), staggered rectangular pin-fins (Case 2), circular pin-fins with equilateral triangular pitch (Case 3), rhombus-shaped pin-fins rotated 45° (Case 4), and hybrid circular-rhombus configurations (Case 5). The results demonstrate that all pin-fin variants outperform the baseline by reducing fluid velocity and pressure drop, with Case 4 exhibiting the most significant performance enhancement – achieving 81.4 % thermal resistance reduction and 22.8 % higher convective heat transfer coefficient compared to Case 0. The rhombus-shaped pin-fins in Case 4 also demonstrate superior temperature uniformity, supported by field synergy angles that are 17.8 % lower than Case 0. Performance evaluation criterion (PEC) improvements range from 12.6 % for hybrid designs (Case 5) at high flow rates to 35.5 % for the optimal rhombic configuration (Case 4), with Cases 2 and 3 showing intermediate performance. This comprehensive analysis establishes the rhombic pin-fin structure as the most effective solution for simultaneously reducing thermal resistance and pumping power in MMCHS applications.
{"title":"Thermal-flow characteristics and field synergy principle analysis in pin-fin manifold microchannels","authors":"Xilong Zhang , Rui Wang , Beibei Li , Zhicheng Zhou , Wenlin Dong","doi":"10.1016/j.ijthermalsci.2026.110674","DOIUrl":"10.1016/j.ijthermalsci.2026.110674","url":null,"abstract":"<div><div>This study systematically compares six pin-fin configurations (Cases 0–5) in manifold microchannel heat sinks (MMCHS) through numerical simulation and experimental validation: Case 0 serves as the baseline conventional grooved structure, while Cases 1–5 explore novel designs including in-line rectangular pin-fins (Case 1), staggered rectangular pin-fins (Case 2), circular pin-fins with equilateral triangular pitch (Case 3), rhombus-shaped pin-fins rotated 45° (Case 4), and hybrid circular-rhombus configurations (Case 5). The results demonstrate that all pin-fin variants outperform the baseline by reducing fluid velocity and pressure drop, with Case 4 exhibiting the most significant performance enhancement – achieving 81.4 % thermal resistance reduction and 22.8 % higher convective heat transfer coefficient compared to Case 0. The rhombus-shaped pin-fins in Case 4 also demonstrate superior temperature uniformity, supported by field synergy angles that are 17.8 % lower than Case 0. Performance evaluation criterion (<em>PEC</em>) improvements range from 12.6 % for hybrid designs (Case 5) at high flow rates to 35.5 % for the optimal rhombic configuration (Case 4), with Cases 2 and 3 showing intermediate performance. This comprehensive analysis establishes the rhombic pin-fin structure as the most effective solution for simultaneously reducing thermal resistance and pumping power in MMCHS applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110674"},"PeriodicalIF":5.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923845","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 : 2026-01-09DOI: 10.1016/j.ijthermalsci.2026.110678
Tianxiang Yan , Muchun Lan , Huiqing Chen , Hucheng Chen
With the improvement of electronic device integration, the heat generated by electronic chips is greatly increasing. To meet the growing cooling demands of electronic chips and enhance the cooling performance of minichannel system, a cooling system integrating an annular valve piezoelectric pump (AVPP) and a leaf-vein minichannel heat sink (LMHS) is proposed. The AVPP with high flow rate and simple valve structure is used to drive the flow of coolant, and the LMHS with excellent heat transfer characteristics is responsible for removing the heat generated by the chip. The LMHS is designed inspired by the structural characteristics of leaf veins and compared with the three-branch minichannel heat sink (TMHS) and serpentine minichannel heat sink (SMHS). The performance of the LMHS, TMHS, and SMHS cooling systems driven by the AVPP is investigated through experiments and simulations. The results indicate that the LMHS cooling system has the better fluid transfer and cooling performance than the TMHS and SMHS cooling systems. When the driving voltage is 300 Vpp, the LMHS cooling system exhibits a high maximum flow rate of 91.85 g/min and a low maximum pressure drop of the heat sink. When the chip power is 30 W, the LMHS cooling system can stabilize the chip temperature at a low temperature of 55.9 °C and reach a high cooling efficiency of 64.2 %. The proposed cooling system has great potential in efficient thermal management of miniaturized electronic chips.
{"title":"Experimental study of a leaf-vein minichannel cooling system driven by piezoelectric pump","authors":"Tianxiang Yan , Muchun Lan , Huiqing Chen , Hucheng Chen","doi":"10.1016/j.ijthermalsci.2026.110678","DOIUrl":"10.1016/j.ijthermalsci.2026.110678","url":null,"abstract":"<div><div>With the improvement of electronic device integration, the heat generated by electronic chips is greatly increasing. To meet the growing cooling demands of electronic chips and enhance the cooling performance of minichannel system, a cooling system integrating an annular valve piezoelectric pump (AVPP) and a leaf-vein minichannel heat sink (LMHS) is proposed. The AVPP with high flow rate and simple valve structure is used to drive the flow of coolant, and the LMHS with excellent heat transfer characteristics is responsible for removing the heat generated by the chip. The LMHS is designed inspired by the structural characteristics of leaf veins and compared with the three-branch minichannel heat sink (TMHS) and serpentine minichannel heat sink (SMHS). The performance of the LMHS, TMHS, and SMHS cooling systems driven by the AVPP is investigated through experiments and simulations. The results indicate that the LMHS cooling system has the better fluid transfer and cooling performance than the TMHS and SMHS cooling systems. When the driving voltage is 300 V<sub>pp</sub>, the LMHS cooling system exhibits a high maximum flow rate of 91.85 g/min and a low maximum pressure drop of the heat sink. When the chip power is 30 W, the LMHS cooling system can stabilize the chip temperature at a low temperature of 55.9 °C and reach a high cooling efficiency of 64.2 %. The proposed cooling system has great potential in efficient thermal management of miniaturized electronic chips.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110678"},"PeriodicalIF":5.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923841","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 : 2026-01-09DOI: 10.1016/j.ijthermalsci.2026.110664
Xin Wang , Kuan Su , Ming Zhu , Wenchao Han , Lin Liang , Liang Cheng , Yanan Liu , Yaohua Chen , Dongliang Cui , Shuping Chen
The storage and transportation of large-scale liquid hydrogen (LH2) and liquid helium (LHe) face challenges such as evaporation losses and safety risks. This study proposes a thermal management strategy that combines an actively cooled thermal shield (ACTS) with multilayer insulation (MLI), employing a cold source medium to drive the ACTS in the temperature range of 77–87 K, establishing efficient thermal interception nodes. This approach overcomes the dependence of vapor-cooled shields (VCS) insulation on cold vapor medium and the energy efficiency limitations of active refrigeration technologies. An experimental platform was established to evaluate the insulation performance of ACTS, investigating the synergistic effects of ACTS temperature and MLI layer number on the insulation performance of the LHe tank. The temperature distribution patterns of ACTS and MLI were analyzed, along with the transient evaporation characteristics of cryogenic liquids. This study elucidates the active control strategy of ACTS in regulating insulation performance and assesses its economic benefits. The results indicate that the axial temperature difference of ACTS is strictly controlled within 0.5 K, effectively reshaping the MLI temperature field and significantly reducing the outermost radiation shield temperature, thereby suppressing radiative heat flux. In the LN2 temperature range, the optimal MLI layer count is 30, while in the LAr temperature range, this can be extended to 40 layers. The minimum heat flux of T-MLI is 0.0643 W/m2 (Case#5), representing a reduction of 87.8 %. The apparent thermal conductivity of T-MLI in the LHe temperature range is as low as 8.18 × 10−6 W/(m·K) (Case#2). In the application of a 40 m3 tank container, the average daily evaporation cost is reduced from $39,729 to $8,292, with the additional cost of the cold source medium being negligible. This results in significant return on investment and promising engineering applications. The experimental results validate the feasibility and economic viability of the ACTS insulation strategy, providing both theoretical and practical support for the safe storage and transportation of LH2 and LHe.
{"title":"Thermal management for cryogenic liquid storage systems: insulation control strategy using actively cooled thermal shields","authors":"Xin Wang , Kuan Su , Ming Zhu , Wenchao Han , Lin Liang , Liang Cheng , Yanan Liu , Yaohua Chen , Dongliang Cui , Shuping Chen","doi":"10.1016/j.ijthermalsci.2026.110664","DOIUrl":"10.1016/j.ijthermalsci.2026.110664","url":null,"abstract":"<div><div>The storage and transportation of large-scale liquid hydrogen (LH<sub>2</sub>) and liquid helium (LHe) face challenges such as evaporation losses and safety risks. This study proposes a thermal management strategy that combines an actively cooled thermal shield (ACTS) with multilayer insulation (MLI), employing a cold source medium to drive the ACTS in the temperature range of 77–87 K, establishing efficient thermal interception nodes. This approach overcomes the dependence of vapor-cooled shields (VCS) insulation on cold vapor medium and the energy efficiency limitations of active refrigeration technologies. An experimental platform was established to evaluate the insulation performance of ACTS, investigating the synergistic effects of ACTS temperature and MLI layer number on the insulation performance of the LHe tank. The temperature distribution patterns of ACTS and MLI were analyzed, along with the transient evaporation characteristics of cryogenic liquids. This study elucidates the active control strategy of ACTS in regulating insulation performance and assesses its economic benefits. The results indicate that the axial temperature difference of ACTS is strictly controlled within 0.5 K, effectively reshaping the MLI temperature field and significantly reducing the outermost radiation shield temperature, thereby suppressing radiative heat flux. In the LN<sub>2</sub> temperature range, the optimal MLI layer count is 30, while in the LAr temperature range, this can be extended to 40 layers. The minimum heat flux of T-MLI is 0.0643 W/m<sup>2</sup> (Case#5), representing a reduction of 87.8 %. The apparent thermal conductivity of T-MLI in the LHe temperature range is as low as 8.18 × 10<sup>−6</sup> W/(m·K) (Case#2). In the application of a 40 m<sup>3</sup> tank container, the average daily evaporation cost is reduced from $39,729 to $8,292, with the additional cost of the cold source medium being negligible. This results in significant return on investment and promising engineering applications. The experimental results validate the feasibility and economic viability of the ACTS insulation strategy, providing both theoretical and practical support for the safe storage and transportation of LH<sub>2</sub> and LHe.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110664"},"PeriodicalIF":5.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923773","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 : 2026-01-09DOI: 10.1016/j.ijthermalsci.2026.110675
Heng Lin , Li Zhang , Chun-Mei Wu , You-Rong Li
To understand the flow and transport characteristics in the entrance region of Poiseuille-Rayleigh-Bénard (P-R-B) double diffusive convection within horizontal channel, a series of three-dimensional numerical simulations are conducted to assess the impact of aspect ratio (B), Reynolds number (Re), buoyancy ratio (N), and Rayleigh number (Ra), with the following ranges: 1≤B ≤ 10, 0≤Re ≤ 25, −0.3≤N ≤ 0.3, and 40≤Ra≤1.2 × 105. The results indicate that the vertical velocity exhibits periodic sinusoidal fluctuations in both space and time as transverse rolls (TRs) develop. The amplitude of these fluctuations increases with Ra and N, while the fundamental frequency decreases as N rises. In the presence of longitudinal rolls (LRs), the vertical velocity is symmetrically distributed in the spanwise direction. If LRs do not fully develop in the entrance region, the vertical velocity will not form regular periodic fluctuations. When stable TRs occupy the entrance region, both temperature and concentration fields fluctuate sinusoidally over time with identical fundamental frequency. Correspondingly, Nusselt (Nu) and Sherwood (Sh) numbers show sinusoidal variations in the streamwise direction, and their amplitudes increase with Ra and N. Moreover, for LRs, the entrance lengths for the onset of secondary flow (L1) and for its full development (L2) decrease with Ra and N, but increase with Re and B. Meanwhile, at high Ra or large positive N, the reductions of L1 and L2 become less pronounced. In addition, the overall transport performance is not improved monotonically with increasing B. Based on simulation data, correlations for L1 and L2 were proposed. Ultimately, the thermal and solute transport correlations including the entrance region were also derived. These findings provide a theoretical foundation for the dimensional design of chemical reactors, heat and mass transfer equipment, and other systems involving P-R-B double diffusive convection.
{"title":"Flow and transport characteristics in the entrance region of Poiseuille-Rayleigh-Bénard double diffusive convection of binary fluid in a horizontal channel","authors":"Heng Lin , Li Zhang , Chun-Mei Wu , You-Rong Li","doi":"10.1016/j.ijthermalsci.2026.110675","DOIUrl":"10.1016/j.ijthermalsci.2026.110675","url":null,"abstract":"<div><div>To understand the flow and transport characteristics in the entrance region of Poiseuille-Rayleigh-Bénard (P-R-B) double diffusive convection within horizontal channel, a series of three-dimensional numerical simulations are conducted to assess the impact of aspect ratio (<em>B</em>), Reynolds number (<em>Re</em>), buoyancy ratio (<em>N</em>), and Rayleigh number (<em>Ra</em>), with the following ranges: 1≤<em>B</em> ≤ 10, 0≤<em>Re</em> ≤ 25, −0.3≤<em>N</em> ≤ 0.3, and 40≤<em>Ra</em>≤1.2 × 10<sup>5</sup>. The results indicate that the vertical velocity exhibits periodic sinusoidal fluctuations in both space and time as transverse rolls (TRs) develop. The amplitude of these fluctuations increases with <em>Ra</em> and <em>N</em>, while the fundamental frequency decreases as <em>N</em> rises. In the presence of longitudinal rolls (LRs), the vertical velocity is symmetrically distributed in the spanwise direction. If LRs do not fully develop in the entrance region, the vertical velocity will not form regular periodic fluctuations. When stable TRs occupy the entrance region, both temperature and concentration fields fluctuate sinusoidally over time with identical fundamental frequency. Correspondingly, Nusselt (<em>Nu</em>) and Sherwood (<em>Sh</em>) numbers show sinusoidal variations in the streamwise direction, and their amplitudes increase with <em>Ra</em> and <em>N</em>. Moreover, for LRs, the entrance lengths for the onset of secondary flow (<em>L</em><sub>1</sub>) and for its full development (<em>L</em><sub>2</sub>) decrease with <em>Ra</em> and <em>N</em>, but increase with <em>Re</em> and <em>B</em>. Meanwhile, at high <em>Ra</em> or large positive <em>N</em>, the reductions of <em>L</em><sub>1</sub> and <em>L</em><sub>2</sub> become less pronounced. In addition, the overall transport performance is not improved monotonically with increasing <em>B</em>. Based on simulation data, correlations for <em>L</em><sub>1</sub> and <em>L</em><sub>2</sub> were proposed. Ultimately, the thermal and solute transport correlations including the entrance region were also derived. These findings provide a theoretical foundation for the dimensional design of chemical reactors, heat and mass transfer equipment, and other systems involving P-R-B double diffusive convection.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110675"},"PeriodicalIF":5.0,"publicationDate":"2026-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145923775","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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