Pub Date : 2026-01-21DOI: 10.1016/j.ijheatfluidflow.2026.110274
Jacek Szumbarski , Jakub Gałecki
This paper presents a numerical methodology for modeling unsteady flows of viscous incompressible fluids within internal domains containing multiple inlet and outlet sections. A new formulation for dissipative boundary conditions, incorporating nonlinear terms, is introduced. The approach enables the imposition of time-dependent flow rates and/or section-averaged pressures at the domain boundaries. The solution technique relies on the instantaneous superposition of Stokes problems. Fluid motion unsteadiness is addressed by combining Backward Differentiation Formulae (BDF) schemes with Operator-Integration-Factor splitting (OIFS) and polynomial extrapolation to manage the model’s nonlinearities. Numerical simulation results, generated using a spectral element solver applied to a two-dimensional test case, are also detailed.
{"title":"A new nonlinear dissipative boundary condition for internal incompressible flows","authors":"Jacek Szumbarski , Jakub Gałecki","doi":"10.1016/j.ijheatfluidflow.2026.110274","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110274","url":null,"abstract":"<div><div>This paper presents a numerical methodology for modeling unsteady flows of viscous incompressible fluids within internal domains containing multiple inlet and outlet sections. A new formulation for dissipative boundary conditions, incorporating nonlinear terms, is introduced. The approach enables the imposition of time-dependent flow rates and/or section-averaged pressures at the domain boundaries. The solution technique relies on the instantaneous superposition of Stokes problems. Fluid motion unsteadiness is addressed by combining Backward Differentiation Formulae (BDF) schemes with Operator-Integration-Factor splitting (OIFS) and polynomial extrapolation to manage the model’s nonlinearities. Numerical simulation results, generated using a spectral element solver applied to a two-dimensional test case, are also detailed.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110274"},"PeriodicalIF":2.6,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023350","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study presents the operational characteristics of a novel jet impingement oven through a combined numerical and experimental approach with an emphasis on its application in bread baking. The oven is designed for domestic use. It features arrays of air jets that enhance convective heat transfer. Computational simulations were carried out to model airflow, heat transfer and thermostatic control mechanisms. Results were validated using experimental measurements of jet velocities and temperature distributions. The bread baking process was simulated using a mathematical model incorporating phase change phenomena which was validated against experimental baking trials. Results demonstrate the capability of the device to deliver high rates of heat transfer thereby reduced baking times compared to conventional ovens. These findings suggest that jet impingement technology is a promising solution for improving thermal processes in domestic baking applications.
{"title":"Numerical and experimental study of a jet impingement oven and its application to bread baking","authors":"Ömer Abacı , Esin Selçuk , Özgül Altay , Funda Erdem Şahnali , S.Nur Dirim , Utku Şentürk , Figen Kaymak-Ertekin","doi":"10.1016/j.ijheatfluidflow.2026.110259","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110259","url":null,"abstract":"<div><div>This study presents the operational characteristics of a novel jet impingement oven through a combined numerical and experimental approach with an emphasis on its application in bread baking. The oven is designed for domestic use. It features arrays of air jets that enhance convective heat transfer. Computational simulations were carried out to model airflow, heat transfer and thermostatic control mechanisms. Results were validated using experimental measurements of jet velocities and temperature distributions. The bread baking process was simulated using a mathematical model incorporating phase change phenomena which was validated against experimental baking trials. Results demonstrate the capability of the device to deliver high rates of heat transfer thereby reduced baking times compared to conventional ovens. These findings suggest that jet impingement technology is a promising solution for improving thermal processes in domestic baking applications.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110259"},"PeriodicalIF":2.6,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023347","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.ijheatfluidflow.2026.110267
Mengfei Wang , Yang Zhang , Bingchen Liang , Bo Yang , Yonghui Liu
A three-twisted-blade pump was simulated using Delayed Detached Eddy Simulation (DDES) method with Arbitrary Mesh Interface (AMI) technique in OpenFOAM on a structured mesh. The study focused on the pump’s startup process, hydrodynamic behavior and the influence of velocity components on internal flow with different operating conditions. Results reveal that the internal flow rapidly evolves from an initially disordered, weakly turbulent state to a stable structure dominated by strong vortices. Vortices generated at the blade leading edge mark the onset of flow unsteadiness, while the trailing edge and volute regions serve as key areas for energy accumulation and transfer. The inlet pressure fluctuation amplitude increases linearly with flow rate and rotational speed, with slopes of 0.052 and 0.17, respectively. Within the impeller, radial fluid velocity increases and then decreases, peaking at 0.7 R (R: impeller radius). This trend remains consistent across flow rates (ranging from 0.75 Qn to 1.5 Qn, where Qn represents the nominal flow rate) and rotational speeds. At low flow rates and large rotational speeds, vortex shedding from the pressure side of the blade’s leading edge induces unstable, three-dimensional flow separation. As flow rates rise, the flow field becomes more uniform, turbulence decreases, and backflow is mitigated.
采用OpenFOAM软件中任意网格接口（AMI）技术的延迟分离涡流模拟（DDES）方法，在结构化网格上对三扭叶片泵进行了仿真。研究了不同工况下泵的启动过程、流体动力特性以及速度分量对内部流量的影响。结果表明，内部流动从最初的无序、弱湍流状态迅速演变为以强涡为主的稳定结构。在叶片前缘产生的涡标志着流动非定常的开始，而尾缘和蜗壳区域是能量积累和传递的关键区域。进口压力波动幅值随流量和转速线性增加，斜率分别为0.052和0.17。叶轮内径向流体速度先增大后减小，在0.7 R （R：叶轮半径）处达到峰值。这种趋势在流量（从0.75 Qn到1.5 Qn，其中Qn代表名义流量）和转速上保持一致。在低流量和大转速下，叶片前缘压力侧的涡脱落会引起不稳定的三维流动分离。随着流量的增加，流场变得更加均匀，湍流减少，回流减轻。
{"title":"Numerical analysis of unsteady vortex evolution and internal flow mechanisms in a three-twisted-blade pump using OpenFOAM","authors":"Mengfei Wang , Yang Zhang , Bingchen Liang , Bo Yang , Yonghui Liu","doi":"10.1016/j.ijheatfluidflow.2026.110267","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110267","url":null,"abstract":"<div><div>A three-twisted-blade pump was simulated using Delayed Detached Eddy Simulation (DDES) method with Arbitrary Mesh Interface (AMI) technique in OpenFOAM on a structured mesh. The study focused on the pump’s startup process, hydrodynamic behavior and the influence of velocity components on internal flow with different operating conditions. Results reveal that the internal flow rapidly evolves from an initially disordered, weakly turbulent state to a stable structure dominated by strong vortices. Vortices generated at the blade leading edge mark the onset of flow unsteadiness, while the trailing edge and volute regions serve as key areas for energy accumulation and transfer. The inlet pressure fluctuation amplitude increases linearly with flow rate and rotational speed, with slopes of 0.052 and 0.17, respectively. Within the impeller, radial fluid velocity increases and then decreases, peaking at 0.7 <em>R</em> (<em>R</em>: impeller radius). This trend remains consistent across flow rates (ranging from 0.75 <em>Q</em><sub>n</sub> to 1.5 <em>Q</em><sub>n</sub>, where <em>Q</em><sub>n</sub> represents the nominal flow rate) and rotational speeds. At low flow rates and large rotational speeds, vortex shedding from the pressure side of the blade’s leading edge induces unstable, three-dimensional flow separation. As flow rates rise, the flow field becomes more uniform, turbulence decreases, and backflow is mitigated.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110267"},"PeriodicalIF":2.6,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.ijheatfluidflow.2026.110266
Xiao-Fan Ping , Chun-Yu Guan , Jin-Huan Pu , Xuan-Kai Zhang , Xi Cao , Ming-Yi Liu , Ce Wang , Long Li , Jing-Feng Shi , Er-Sheng You , Ying-Huan Cui
A field synergy-guided design approach is proposed for the development of a variable cross-section serpentine-channel cold plate (SCP) to improve the thermal management performance of lithium-ion battery systems operating under high discharge rates. A validated numerical model is developed to evaluate the heat transfer behavior and coolant flow characteristics within the system. The thermal limitations of a conventional single SCP (SSCP) are systematically investigated across a range of inlet temperatures and coolant mass flow rates. To overcome these drawbacks, a novel variable cross-section double-channel SCP (VCDSCP) is introduced based on the field synergy principle. Guided by this principle, the VCDSCP is designed by redistributing the coolant flow and locally adjusting the channel cross-sections to reduce the velocity–temperature gradient synergy angle, particularly in high-temperature regions of the battery. Comparative results demonstrate that the VCDSCP achieves a significantly lower and more uniformly distributed synergy angle than the SSCP, leading to improved temperature control. Under high load conditions, the VCDSCP reduces the maximum battery temperature and temperature difference by 0.54 K (1.7 %) and 0.62 K (10.1 %), respectively. Furthermore, at a coolant mass flow rate of 0.2 g∙s−1, the design achieves up to 80.8 % reduction in pressure drop and a 25.5 % improvement in performance evaluation criteria. These results suggest that the proposed VCDSCP offers substantial advantages for next-generation battery thermal management systems with high operational demands.
{"title":"Design of a field synergy-based variable cross-section cold plate for enhanced thermal management of lithium-ion batteries at high discharge rates","authors":"Xiao-Fan Ping , Chun-Yu Guan , Jin-Huan Pu , Xuan-Kai Zhang , Xi Cao , Ming-Yi Liu , Ce Wang , Long Li , Jing-Feng Shi , Er-Sheng You , Ying-Huan Cui","doi":"10.1016/j.ijheatfluidflow.2026.110266","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110266","url":null,"abstract":"<div><div>A field synergy-guided design approach is proposed for the development of a variable cross-section serpentine-channel cold plate (SCP) to improve the thermal management performance of lithium-ion battery systems operating under high discharge rates. A validated numerical model is developed to evaluate the heat transfer behavior and coolant flow characteristics within the system. The thermal limitations of a conventional single SCP (SSCP) are systematically investigated across a range of inlet temperatures and coolant mass flow rates. To overcome these drawbacks, a novel variable cross-section double-channel SCP (VCDSCP) is introduced based on the field synergy principle. Guided by this principle, the VCDSCP is designed by redistributing the coolant flow and locally adjusting the channel cross-sections to reduce the velocity–temperature gradient synergy angle, particularly in high-temperature regions of the battery. Comparative results demonstrate that the VCDSCP achieves a significantly lower and more uniformly distributed synergy angle than the SSCP, leading to improved temperature control. Under high load conditions, the VCDSCP reduces the maximum battery temperature and temperature difference by 0.54 K (1.7 %) and 0.62 K (10.1 %), respectively. Furthermore, at a coolant mass flow rate of 0.2 g∙s<sup>−1</sup>, the design achieves up to 80.8 % reduction in pressure drop and a 25.5 % improvement in performance evaluation criteria. These results suggest that the proposed VCDSCP offers substantial advantages for next-generation battery thermal management systems with high operational demands.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110266"},"PeriodicalIF":2.6,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.ijheatfluidflow.2025.110233
Qian Zhang , Jia Kang , Xing Zhang
With the trend of VR devices toward high-density integration and miniaturization, the collaborative heat dissipation challenges for multiple heat sources in compact spaces have emerged as a critical bottleneck constraining device performance. This study addresses the scientific question of “how to predict the minimal heat dissipation space for high heat flux electronic devices while ensuring safe thresholds for chip junction temperature and exhaust air temperature under coupled thermal-resource conditions in VR devices.” To tackle this, a systematic thermal management framework based on multi-physics coupling was established. This model includes dimensional selection criteria for graphene layers, a one-dimensional steady-state thermal analysis for flow in narrow channels, and thermal diffusion expressions for the MgAl framework. Third, a triple-nested optimization architecture is designed. It leverages coordinated feedback mechanisms across inner-loop multi-physics balancing, middle-loop channel parameter adjustment, and outer-loop fan characteristic optimization to dynamically match thermal performance with spatial constraints. The results demonstrate a 27.2% reduction in the required heat dissipation space volume for typical VR modules. Consequently, this work provides a theoretical tool for the synergistic co-optimization of spatial volume and thermal feasibility under fixed performance constraints in VR thermal management. The proposed threshold-triggered mechanism is also extendable to thermal design in other compact electronics, such as smart wearables and micro machine vision systems.
{"title":"Multi objective heat dissipation space optimization feedback control algorithm based on threshold triggering","authors":"Qian Zhang , Jia Kang , Xing Zhang","doi":"10.1016/j.ijheatfluidflow.2025.110233","DOIUrl":"10.1016/j.ijheatfluidflow.2025.110233","url":null,"abstract":"<div><div>With the trend of VR devices toward high-density integration and miniaturization, the collaborative heat dissipation challenges for multiple heat sources in compact spaces have emerged as a critical bottleneck constraining device performance. This study addresses the scientific question of “how to predict the minimal heat dissipation space for high heat flux electronic devices while ensuring safe thresholds for chip junction temperature and exhaust air temperature under coupled thermal-resource conditions in VR devices.” To tackle this, a systematic thermal management framework based on multi-physics coupling was established. This model includes dimensional selection criteria for graphene layers, a one-dimensional steady-state thermal analysis for flow in narrow channels, and thermal diffusion expressions for the MgAl framework. Third, a triple-nested optimization architecture is designed. It leverages coordinated feedback mechanisms across inner-loop multi-physics balancing, middle-loop channel parameter adjustment, and outer-loop fan characteristic optimization to dynamically match thermal performance with spatial constraints. The results demonstrate a 27.2% reduction in the required heat dissipation space volume for typical VR modules. Consequently, this work provides a theoretical tool for the synergistic co-optimization of spatial volume and thermal feasibility under fixed performance constraints in VR thermal management. The proposed threshold-triggered mechanism is also extendable to thermal design in other compact electronics, such as smart wearables and micro machine vision systems.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110233"},"PeriodicalIF":2.6,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-20DOI: 10.1016/j.ijheatfluidflow.2026.110260
Hassan Abdelaty , Ahmed Omera , Mohamed Abdelgawad
Single-phase coolant flow in multi-layer microchannel heat sinks offers an effective alternative for removal of high heat fluxes generated by electronic devices and similar applications. This passive cooling technique enhances heat transfer without requiring additional external power, making it an attractive alternative to single-layer configurations. This study investigates the impact of number of layers and flow configurations on both thermal and hydraulic performances of microchannel heat sinks under a uniform heat flux up to 23.5 W/cm2. Four layers and three flow configurations, parallel, counter, and crossflow were investigated. Experiments were conducted on CNC-machined, pure copper channels with square cross-sections (500 μm × 500 μm). The evaluation focused on key performance metrics, including pressure drop, surface temperature distribution, and thermal resistance. The results demonstrate significant improvements in thermal performance compared to single-layer heat sinks under identical testing conditions. Specifically, at the lowest flow rate, the thermal resistance is reduced by 9.7%, 21%, and 25.2% for the Double, Triple and Four-layer configurations, respectively, compared to the single layer one. In addition, Flow arrangement was found to influence performance, with increased flow in lower layers yielding enhanced temperature uniformity, reduced surface temperature, and lower thermal resistance. Furthermore, increasing number of layers has a significant influence on the pressure drop. Specifically, transitioning from Single-layer to Double-, Triple-, and Four-layer configurations results in pressure drop reductions of 41.2%, 55.3%, and 67.3%, respectively, at the maximum tested flow rate of 5.075 g/s.
{"title":"Experimental evaluation of thermal and hydraulic performance in multi-layer microchannel heat sinks with various flow configurations","authors":"Hassan Abdelaty , Ahmed Omera , Mohamed Abdelgawad","doi":"10.1016/j.ijheatfluidflow.2026.110260","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110260","url":null,"abstract":"<div><div>Single-phase coolant flow in multi-layer microchannel heat sinks offers an effective alternative for removal of high heat fluxes generated by electronic devices and similar applications. This passive cooling technique enhances heat transfer without requiring additional external power, making it an attractive alternative to single-layer configurations. This study investigates the impact of number of layers and flow configurations on both thermal and hydraulic performances of microchannel heat sinks under a uniform heat flux up to 23.5 W/cm<sup>2</sup>. Four layers and three flow configurations, parallel, counter, and crossflow were investigated. Experiments were conducted on CNC-machined, pure copper channels with square cross-sections (500 μm × 500 μm). The evaluation focused on key performance metrics, including pressure drop, surface temperature distribution, and thermal resistance. The results demonstrate significant improvements in thermal performance compared to single-layer heat sinks under identical testing conditions. Specifically, at the lowest flow rate, the thermal resistance is reduced by 9.7%, 21%, and 25.2% for the Double, Triple and Four-layer configurations, respectively, compared to the single layer one. In addition, Flow arrangement was found to influence performance, with increased flow in lower layers yielding enhanced temperature uniformity, reduced surface temperature, and lower thermal resistance. Furthermore, increasing number of layers has a significant influence on the pressure drop. Specifically, transitioning from Single-layer to Double-, Triple-, and Four-layer configurations results in pressure drop reductions of 41.2%, 55.3%, and 67.3%, respectively, at the maximum tested flow rate of 5.075 g/s.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110260"},"PeriodicalIF":2.6,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-18DOI: 10.1016/j.ijheatfluidflow.2026.110253
Vassili Kitsios , Laurent Cordier , Terence J. O’Kane
A reduced-order model (ROM) of the global atmosphere is developed by projecting the hydrostatic equations of motion onto three-dimensional proper orthogonal decomposition (POD) modes. This approach transforms a system of partial differential equations dependent upon time and space, into a system of ordinary differential equations dependent upon only time and POD mode index. This massively reduces the dimensionality of the problem. Here we adopt the Climate Analysis Forecast Ensemble reanalysis dataset (CAFE-60), comprising of 96 realisations of the dynamically coupled atmosphere and ocean each month. Two POD bases are calculated from the atmospheric data, one for the velocity vector field, and another for the scalar temperature field. The POD ROM coefficients are calculated using a regression approach, with model errors accounted for via stochastic parameterisation. Temporal integrations of the POD ROM with dynamically coupled temperature and velocity fields are undertaken over a recent 40-year period. The statistical properties of the underlying data are broadly reproduced within the resolved modes for a range of truncation levels. Additionally, as more modes are retained in the POD ROM, the correlation of surface variance maps between the underlying data and the spatially reconstructed POD ROM output, approaches unity. The POD ROM coefficient learning and temporal integrations are completed in minutes on a laptop, as compared to the months of supercomputer time required to generate CAFE-60.
{"title":"Three-dimensional proper orthogonal decomposition reduced-order model of the global atmospheric climate","authors":"Vassili Kitsios , Laurent Cordier , Terence J. O’Kane","doi":"10.1016/j.ijheatfluidflow.2026.110253","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110253","url":null,"abstract":"<div><div>A reduced-order model (ROM) of the global atmosphere is developed by projecting the hydrostatic equations of motion onto three-dimensional proper orthogonal decomposition (POD) modes. This approach transforms a system of partial differential equations dependent upon time and space, into a system of ordinary differential equations dependent upon only time and POD mode index. This massively reduces the dimensionality of the problem. Here we adopt the Climate Analysis Forecast Ensemble reanalysis dataset (CAFE-60), comprising of 96 realisations of the dynamically coupled atmosphere and ocean each month. Two POD bases are calculated from the atmospheric data, one for the velocity vector field, and another for the scalar temperature field. The POD ROM coefficients are calculated using a regression approach, with model errors accounted for via stochastic parameterisation. Temporal integrations of the POD ROM with dynamically coupled temperature and velocity fields are undertaken over a recent 40-year period. The statistical properties of the underlying data are broadly reproduced within the resolved modes for a range of truncation levels. Additionally, as more modes are retained in the POD ROM, the correlation of surface variance maps between the underlying data and the spatially reconstructed POD ROM output, approaches unity. The POD ROM coefficient learning and temporal integrations are completed in minutes on a laptop, as compared to the months of supercomputer time required to generate CAFE-60.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110253"},"PeriodicalIF":2.6,"publicationDate":"2026-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-16DOI: 10.1016/j.ijheatfluidflow.2026.110255
Robert J. Kee, Kasra Taghikhani, Huayang Zhu, Oyvind Nilsen
This paper derives friction-factor Re and Nusselt-number Nu correlations for laminar, fully developed, parallel flow in curved rectangular channels. The correlations depend on the channel geometry as characterized by two dimensionless parameters—the channel aspect ratio and the radius of curvature ( and ). The analysis shows that the dimensionless correlations can be derived from an eigenvalue of the dimensionless conservation equations. The computational approach solves dimensionless circumferential momentum and thermal-energy equations with a high-resolution finite-element method. The analysis is restricted to parallel flow, with the circumferential velocity being the only velocity component (i.e., there are no radial and axial velocities). This assumption necessarily eliminates the possibility of Dean vortices, which are present in curved channels under flow circumstances that include high Reynolds numbers and small radius of curvature. The results are validated by comparisons with known limiting cases and with three-dimensional computational-fluid-dynamics simulations. The paper reports quantitative fits to the derived correlations (i.e., Re () and Nu().
{"title":"Friction-factor and Nusselt-number correlations for low-Reynolds-number flow in curved and helical rectangular channels","authors":"Robert J. Kee, Kasra Taghikhani, Huayang Zhu, Oyvind Nilsen","doi":"10.1016/j.ijheatfluidflow.2026.110255","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110255","url":null,"abstract":"<div><div>This paper derives friction-factor Re<span><math><mi>f</mi></math></span> and Nusselt-number Nu correlations for laminar, fully developed, parallel flow in curved rectangular channels. The correlations depend on the channel geometry as characterized by two dimensionless parameters—the channel aspect ratio <span><math><mi>α</mi></math></span> and the radius of curvature <span><math><mi>ξ</mi></math></span> (<span><math><mrow><mn>0</mn><mo>.</mo><mn>1</mn><mo>≤</mo><mi>α</mi><mo>≤</mo><mn>5</mn></mrow></math></span> and <span><math><mrow><mn>0</mn><mo>.</mo><mn>1</mn><mo>≤</mo><mi>ξ</mi><mo>≤</mo><mn>5</mn></mrow></math></span>). The analysis shows that the dimensionless correlations can be derived from an eigenvalue of the dimensionless conservation equations. The computational approach solves dimensionless circumferential momentum and thermal-energy equations with a high-resolution finite-element method. The analysis is restricted to parallel flow, with the circumferential velocity being the only velocity component (i.e., there are no radial and axial velocities). This assumption necessarily eliminates the possibility of Dean vortices, which are present in curved channels under flow circumstances that include high Reynolds numbers and small radius of curvature. The results are validated by comparisons with known limiting cases and with three-dimensional computational-fluid-dynamics simulations. The paper reports quantitative fits to the derived correlations (i.e., Re<span><math><mi>f</mi></math></span> (<span><math><mrow><mi>α</mi><mo>,</mo><mi>ξ</mi></mrow></math></span>) and Nu(<span><math><mrow><mi>α</mi><mo>,</mo><mi>ξ</mi></mrow></math></span>).</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110255"},"PeriodicalIF":2.6,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974047","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-15DOI: 10.1016/j.ijheatfluidflow.2026.110256
Yogesh Chouksey, Nitin Shrivastava, Sunil Kumar
Cooling compact electronics, such as laptops, is challenging due to strict size limitations and the low thermal capacity of air. While rectangular fins are commonly used, dovetail fins with tip clearance may offer improved thermal performance. This study investigates the thermal–hydraulic behaviour of rectangular and dovetail fin heat sinks under these constraints. Initially, a rectangular channel heat sink was designed and later modified to a channel heat sink incorporating a rectangular fin with tip clearance. This fin was further adapted into three dovetail fin variants by varying the root and tip thicknesses to evaluate the feasibility of replacing rectangular fins. CFD analyses were conducted in ANSYS Fluent for inlet air velocities ranging from 1 to 6 m/s (corresponding Reynolds number varies from 2054–12323), with the top surface of the heat sink maintained at a constant temperature of 360 K. Temperature distribution, heat transfer, pressure drop, and effectiveness were evaluated, considering weight in the performance comparison. Dovetail fins outperformed the rectangular fin, enhancing heat convection by up to 20.6% but with a 66.7% increase in weight and substantially higher pressure drops. The dovetail variant with weight equal to the rectangular fin achieved up to 2.2% higher performance with only a marginal increase in pressure drop, indicating its potential as a promising alternative.
{"title":"Performance evaluation of dovetail fin variants derived from a rectangular fin for laptop heat sinks","authors":"Yogesh Chouksey, Nitin Shrivastava, Sunil Kumar","doi":"10.1016/j.ijheatfluidflow.2026.110256","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110256","url":null,"abstract":"<div><div>Cooling compact electronics, such as laptops, is challenging due to strict size limitations and the low thermal capacity of air. While rectangular fins are commonly used, dovetail fins with tip clearance may offer improved thermal performance. This study investigates the thermal–hydraulic behaviour of rectangular and dovetail fin heat sinks under these constraints. Initially, a rectangular channel heat sink was designed and later modified to a channel heat sink incorporating a rectangular fin with tip clearance. This fin was further adapted into three dovetail fin variants by varying the root and tip thicknesses to evaluate the feasibility of replacing rectangular fins. CFD analyses were conducted in ANSYS Fluent for inlet air velocities ranging from 1 to 6 m/s (corresponding Reynolds number varies from 2054–12323), with the top surface of the heat sink maintained at a constant temperature of 360 K. Temperature distribution, heat transfer, pressure drop, and effectiveness were evaluated, considering weight in the performance comparison. Dovetail fins outperformed the rectangular fin, enhancing heat convection by up to 20.6% but with a 66.7% increase in weight and substantially higher pressure drops. The dovetail variant with weight equal to the rectangular fin achieved up to 2.2% higher performance with only a marginal increase in pressure drop, indicating its potential as a promising alternative.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110256"},"PeriodicalIF":2.6,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974050","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-01-15DOI: 10.1016/j.ijheatfluidflow.2026.110258
Wei Ye, Tao Liang, Wanwu Xu, Zhiyan Li
The mixing layer array in the MSE exhibits complex and unique behaviors. To address this gap, this study develops a slidable pitot pressure rake with a 2 mm horizontal resolution to characterize the mixing features of the MSE under both starting and operating modes. Additionally, a new method is proposed to define the edges, thickness, and thickness growth rate of the mixing layer. Results indicate that under operating mode, the convective Mach number (Mc) ranges from 1.03 to 1.21, while the static pressure ratio at the nozzle outlet(PR) varies between 0.493 and 0.763. Unlike the traditional growth trends, the mixing layer array in the MSE undergoes a synergistic evolution involving positive growth, expansion, and negative growth. The corresponding flow field are analyzed. Specifically, the growth rate of mixing layer thickness () ranges from −0.139 to 0.245 at the PR = 0.513, Mc = 1.18 condition. While ranges from −0.045 to 0.144 at the PR = 0.763, Mc = 1.03 condition. Besides, the mixing layer array covers the secondary flow path at x/la ∈ [2.857, 4.571] under small PR conditions, but it is not observed until x/la = 9.714 under large PR conditions.
{"title":"Investigation on the mixing characteristics of the multi-strut ejector","authors":"Wei Ye, Tao Liang, Wanwu Xu, Zhiyan Li","doi":"10.1016/j.ijheatfluidflow.2026.110258","DOIUrl":"10.1016/j.ijheatfluidflow.2026.110258","url":null,"abstract":"<div><div>The mixing layer array in the MSE exhibits complex and unique behaviors. To address this gap, this study develops a slidable pitot pressure rake with a 2 mm horizontal resolution to characterize the mixing features of the MSE under both starting and operating modes. Additionally, a new method is proposed to define the edges, thickness, and thickness growth rate of the mixing layer. Results indicate that under operating mode, the convective Mach number (<em>Mc</em>) ranges from 1.03 to 1.21, while the static pressure ratio at the nozzle outlet<em>(PR</em>) varies between 0.493 and 0.763. Unlike the traditional growth trends, the mixing layer array in the MSE undergoes a synergistic evolution involving positive growth, expansion, and negative growth. The corresponding flow field are analyzed. Specifically, the growth rate of mixing layer thickness (<span><math><msup><mrow><mi>δ</mi></mrow><mo>′</mo></msup></math></span>) ranges from −0.139 to 0.245 at the <em>PR</em> = 0.513, <em>Mc</em> = 1.18 condition. While <span><math><msup><mrow><mi>δ</mi></mrow><mo>′</mo></msup></math></span> ranges from −0.045 to 0.144 at the <em>PR</em> = 0.763, <em>Mc</em> = 1.03 condition. Besides, the mixing layer array covers the secondary flow path at <em>x/l<sub>a</sub></em> ∈ [2.857, 4.571] under small <em>PR</em> conditions, but it is not observed until <em>x/l<sub>a</sub></em> = 9.714 under large <em>PR</em> conditions.</div></div>","PeriodicalId":335,"journal":{"name":"International Journal of Heat and Fluid Flow","volume":"119 ","pages":"Article 110258"},"PeriodicalIF":2.6,"publicationDate":"2026-01-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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