Pub Date : 2026-01-13DOI: 10.1016/j.ijheatmasstransfer.2026.128375
Ming Dong, Hui Jiang
Supercritical flow and heat transfer are critical in industrial applications such as shale gas extraction and deep geothermal systems. However, convective heat transfer of supercritical fluid at the micro- and nanoscale is poorly understood compared to the macroscale. In this study, the convective heat transfer processes of supercritical water in copper nanochannels are performed through molecular dynamics simulation. The effects of fluid density, surface wettability, flow velocity, and channel height on the convective heat transfer performance are investigated. The results show that the heat transfer enhances with increasing fluid density and surface wettability, and is almost independent of the flow velocity and channel height. In addition, both interfacial thermal resistance and slip length decrease with increasing fluid density and surface wettability. The interfacial thermal resistance hardly varies with flow velocity and channel height, while the slip length increases with flow velocity. Importantly, the convective heat transfer is dominated by interfacial thermal resistance rather than interfacial slip. The study establishes a clear correlation: the Nusselt number is inversely proportional to the interfacial thermal resistance and directly proportional to the peak density of the first fluid layer near the wall. These results provide fundamental understanding of supercritical convective heat transfer at the nanoscale and support applications in shale gas extraction and deep geothermal fields.
{"title":"Convective heat transfer of supercritical fluid in nanochannels: A molecular dynamics study","authors":"Ming Dong, Hui Jiang","doi":"10.1016/j.ijheatmasstransfer.2026.128375","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128375","url":null,"abstract":"<div><div>Supercritical flow and heat transfer are critical in industrial applications such as shale gas extraction and deep geothermal systems. However, convective heat transfer of supercritical fluid at the micro- and nanoscale is poorly understood compared to the macroscale. In this study, the convective heat transfer processes of supercritical water in copper nanochannels are performed through molecular dynamics simulation. The effects of fluid density, surface wettability, flow velocity, and channel height on the convective heat transfer performance are investigated. The results show that the heat transfer enhances with increasing fluid density and surface wettability, and is almost independent of the flow velocity and channel height. In addition, both interfacial thermal resistance and slip length decrease with increasing fluid density and surface wettability. The interfacial thermal resistance hardly varies with flow velocity and channel height, while the slip length increases with flow velocity. Importantly, the convective heat transfer is dominated by interfacial thermal resistance rather than interfacial slip. The study establishes a clear correlation: the Nusselt number is inversely proportional to the interfacial thermal resistance and directly proportional to the peak density of the first fluid layer near the wall. These results provide fundamental understanding of supercritical convective heat transfer at the nanoscale and support applications in shale gas extraction and deep geothermal fields.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128375"},"PeriodicalIF":5.8,"publicationDate":"2026-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974451","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}
A topology optimization framework for designing both micro- and macrostructures is developed for transient heat transfer in porous media. The proposed micro-macro optimization model incorporates the size effect of the microstructural surface area within a density-based and homogenization framework. As a density-based approach, the adjacent design variable is used to interpolate the heat transfer occurring at the microstructure’s interface, while other properties are determined using the standard power-law function. Optimal topologies for both micro- and macrostructures are obtained by solving two-scale optimization problems, which are addressed using a gradient-based optimizer and the proposed micro- and macro analytical sensitivity formulations. Numerical results demonstrate that the designed topologies from the proposed framework are consistent with steady-state benchmarks, while varying heating time leads to different optimized results. Furthermore, as the size effect increases, the optimized macrostructure in the steady-state condition begins to resemble the topology obtained in the unsteady-state condition.
{"title":"Hierarchical topology optimization for transient heat conduction in porous media with microstructure-dependent property","authors":"Naruethep Sukulthanasorn , Mao Kurumatani , Jaroon Rungamornrat , Kenjiro Terada , Junji Kato","doi":"10.1016/j.ijheatmasstransfer.2026.128366","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128366","url":null,"abstract":"<div><div>A topology optimization framework for designing both micro- and macrostructures is developed for transient heat transfer in porous media. The proposed micro-macro optimization model incorporates the size effect of the microstructural surface area within a density-based and homogenization framework. As a density-based approach, the adjacent design variable is used to interpolate the heat transfer occurring at the microstructure’s interface, while other properties are determined using the standard power-law function. Optimal topologies for both micro- and macrostructures are obtained by solving two-scale optimization problems, which are addressed using a gradient-based optimizer and the proposed micro- and macro analytical sensitivity formulations. Numerical results demonstrate that the designed topologies from the proposed framework are consistent with steady-state benchmarks, while varying heating time leads to different optimized results. Furthermore, as the size effect increases, the optimized macrostructure in the steady-state condition begins to resemble the topology obtained in the unsteady-state condition.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128366"},"PeriodicalIF":5.8,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974384","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 : 2026-01-12DOI: 10.1016/j.ijheatmasstransfer.2025.128278
Tianyou Xue , Jin Zhao , Haoyun Xing , Hang Yuan , Guice Yao , Dongsheng Wen
Acquiring instantaneous temperature and velocity distributions is critical for the thermal management of microchannel heat sinks in electronic devices. Although traditional machine learning data-driven approaches are capable of rapidly predicting physical fields, they often fail to precisely characterize local features in regions of high temperature gradient, particularly at the fluid-solid interface where hotspots predominately occur. To address such limitation in prediction performance at the interface, this work proposes a novel data-driven model named TC-Thermal, which integrates a convolutional neural network (CNN) encoder leveraging a self-attention mechanism decoder to predict the temperature and velocity distributions of a microchannel cooling system. By means of TC-Thermal, both temperature and velocity field are well reconstructed only with heat fluxes, inlet conditions and flow rates provided. The mean absolute percentage errors (MAPE) are as low as 0.02 % and 2.3 % for temperature and velocity prediction, respectively, compared with the numerical results. Particularly, the mean absolute error (MAE) of temperature prediction at the fluid-solid interface is 0.17 K, representing 22.27 % and 58.03 % improvements over the standalone Transformer model and the CNN model, respectively. The results demonstrated our proposed TC-Thermal architecture in capable of both capturing global and local thermal properties, which contributes to the application of data-driven method for predicting thermal dynamics with high temperature gradient.
{"title":"TC-thermal: A novel hybrid transformer-CNN architecture enhancing thermal flow reconstruction at fluid-solid interface for micro-channel heat sink","authors":"Tianyou Xue , Jin Zhao , Haoyun Xing , Hang Yuan , Guice Yao , Dongsheng Wen","doi":"10.1016/j.ijheatmasstransfer.2025.128278","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128278","url":null,"abstract":"<div><div>Acquiring instantaneous temperature and velocity distributions is critical for the thermal management of microchannel heat sinks in electronic devices. Although traditional machine learning data-driven approaches are capable of rapidly predicting physical fields, they often fail to precisely characterize local features in regions of high temperature gradient, particularly at the fluid-solid interface where hotspots predominately occur. To address such limitation in prediction performance at the interface, this work proposes a novel data-driven model named TC-Thermal, which integrates a convolutional neural network (CNN) encoder leveraging a self-attention mechanism decoder to predict the temperature and velocity distributions of a microchannel cooling system. By means of TC-Thermal, both temperature and velocity field are well reconstructed only with heat fluxes, inlet conditions and flow rates provided. The mean absolute percentage errors (MAPE) are as low as 0.02 % and 2.3 % for temperature and velocity prediction, respectively, compared with the numerical results. Particularly, the mean absolute error (MAE) of temperature prediction at the fluid-solid interface is 0.17 K, representing 22.27 % and 58.03 % improvements over the standalone Transformer model and the CNN model, respectively. The results demonstrated our proposed TC-Thermal architecture in capable of both capturing global and local thermal properties, which contributes to the application of data-driven method for predicting thermal dynamics with high temperature gradient.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128278"},"PeriodicalIF":5.8,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974448","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}
With the rapid miniaturization and performance enhancement of electronic devices, high heat flux dissipation has emerged as a critical bottleneck restricting their reliable and stable operation. The Two-Phase Loop Thermosyphon (TPLT), as a representative passive phase-change heat transfer technology, boasts inherent advantages including a simple structure, no reliance on external power, and superior heat transfer efficiency, thus being widely recognized as a promising solution for high-heat-flux cooling scenarios. However, the complex internal gas-liquid two-phase flow mechanism leads to insufficient accuracy of existing models in predicting the coupling relationship between heat transfer performance and flow characteristics, limiting the optimized design of TPLT for target cooling scenarios. To address this gap, a one-dimensional steady-state momentum cycle model was established. Void fraction acts as the core intermediate variable linking flow and heat transfer: as heat flux density increases, void fraction gradually rises, regulating the balance between driving force and frictional resistance to drive the circulation flow rate to first increase and then decrease, while simultaneously affecting the dominant mode of heat transfer and thus the loop thermal resistance. Combined with experimental tests and visualization technology, the coupling characteristics of void fraction, circulation flow rate, flow regime, loop thermal resistance, and pressure drop were systematically analyzed under different filling ratios (30%, 60%, 80%) and heat flux densities (30∼390 W/cm²). The results demonstrate that the proposed model can effectively predict both the flow performance and heat transfer performance of TPLT, with the predicted trends of key parameters being highly consistent with experimental data. Further visualization observations and performance analyses under different filling ratios complement the mechanism clarification. Visualization results confirm that a low filling ratio (30%) causes early fragmentation of annular flow into droplet flow, leading to premature peak flow, increased thermal resistance, and poor heat transfer stability at high heat flux. In contrast, a high filling ratio (80%) maintains a continuous liquid phase in the flow regime across the entire heat flux range, achieving the latest peak flow, the highest flow efficiency, and the lowest thermal resistance at high heat flux, proving its suitability for high heat flux dissipation. This study clarifies the intrinsic coupling mechanism between the flow and heat transfer performance of TPLT, and the established model provides a reliable tool for predicting its key performance indicators under complex working conditions, offering valuable theoretical support for the optimized design of passive cooling systems in high-heat-flux electronic devices.
{"title":"Establishment of momentum model and analysis of heat transfer performance for two-phase loop thermosyphon","authors":"Yong Cai, Zihao Liu, Jingyi Lu, Yubai Li, Dawei Tang, Chengzhi Hu","doi":"10.1016/j.ijheatmasstransfer.2026.128344","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128344","url":null,"abstract":"<div><div>With the rapid miniaturization and performance enhancement of electronic devices, high heat flux dissipation has emerged as a critical bottleneck restricting their reliable and stable operation. The Two-Phase Loop Thermosyphon (TPLT), as a representative passive phase-change heat transfer technology, boasts inherent advantages including a simple structure, no reliance on external power, and superior heat transfer efficiency, thus being widely recognized as a promising solution for high-heat-flux cooling scenarios. However, the complex internal gas-liquid two-phase flow mechanism leads to insufficient accuracy of existing models in predicting the coupling relationship between heat transfer performance and flow characteristics, limiting the optimized design of TPLT for target cooling scenarios. To address this gap, a one-dimensional steady-state momentum cycle model was established. Void fraction acts as the core intermediate variable linking flow and heat transfer: as heat flux density increases, void fraction gradually rises, regulating the balance between driving force and frictional resistance to drive the circulation flow rate to first increase and then decrease, while simultaneously affecting the dominant mode of heat transfer and thus the loop thermal resistance. Combined with experimental tests and visualization technology, the coupling characteristics of void fraction, circulation flow rate, flow regime, loop thermal resistance, and pressure drop were systematically analyzed under different filling ratios (30%, 60%, 80%) and heat flux densities (30∼390 W/cm²). The results demonstrate that the proposed model can effectively predict both the flow performance and heat transfer performance of TPLT, with the predicted trends of key parameters being highly consistent with experimental data. Further visualization observations and performance analyses under different filling ratios complement the mechanism clarification. Visualization results confirm that a low filling ratio (30%) causes early fragmentation of annular flow into droplet flow, leading to premature peak flow, increased thermal resistance, and poor heat transfer stability at high heat flux. In contrast, a high filling ratio (80%) maintains a continuous liquid phase in the flow regime across the entire heat flux range, achieving the latest peak flow, the highest flow efficiency, and the lowest thermal resistance at high heat flux, proving its suitability for high heat flux dissipation. This study clarifies the intrinsic coupling mechanism between the flow and heat transfer performance of TPLT, and the established model provides a reliable tool for predicting its key performance indicators under complex working conditions, offering valuable theoretical support for the optimized design of passive cooling systems in high-heat-flux electronic devices.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128344"},"PeriodicalIF":5.8,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974942","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 : 2026-01-12DOI: 10.1016/j.ijheatmasstransfer.2026.128334
Kai Tang , Guiping Lin , Keyi Huang , Tong Qiao , Yuandong Guo
The rapid advancement of the electronic chip industry has introduced increasingly severe thermal management challenges. Among emerging solutions, manifold microchannel heat sinks (MMCHSs) utilizing flow boiling are considered particularly promising for high–heat flux cooling. In this study, a full-scale visualized MMCHS was developed using HFE-7000 as the working fluid to investigate subcooled flow boiling characteristics. The experimental campaign elucidated the evolution of flow regimes and the mechanisms behind heat transfer degradation in conventional MMCHSs, and further assessed the effectiveness of diverging flow-path optimization strategy. Results revealed a heat-flux-driven transition from localized boiling to fully developed annular flow, accompanied by bubble retrograde growth phenomena. Under high heat fluxes, uniform-channel MMCHSs experienced pronounced vapor backflow and blockage, which impeded upstream liquid replenishment and induced intermittent dryout, ultimately triggering critical heat flux (CHF). To mitigate these limitations, a diverging flow-path configuration was proposed. By promoting forward liquid advection, the design effectively suppressed vapor blockage and backflow, thereby enhancing thermal-hydraulic performance. The optimized DD-MMCHS, which integrates two-level divergence in both the microchannel and manifold layout, achieved significant performance gains under identical conditions: an 18.8 °C reduction in heater temperature, a 40.7% decrease in pressure drop, and a 13% increase in CHF. These findings provide mechanistic insights and practical guidance for future studies on the thermal-hydraulic behavior and structural optimization of MMCHSs.
{"title":"Visualized flow boiling regime evolution and diverging flow paths enhancement in manifold microchannel heat sinks","authors":"Kai Tang , Guiping Lin , Keyi Huang , Tong Qiao , Yuandong Guo","doi":"10.1016/j.ijheatmasstransfer.2026.128334","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128334","url":null,"abstract":"<div><div>The rapid advancement of the electronic chip industry has introduced increasingly severe thermal management challenges. Among emerging solutions, manifold microchannel heat sinks (MMCHSs) utilizing flow boiling are considered particularly promising for high–heat flux cooling. In this study, a full-scale visualized MMCHS was developed using HFE-7000 as the working fluid to investigate subcooled flow boiling characteristics. The experimental campaign elucidated the evolution of flow regimes and the mechanisms behind heat transfer degradation in conventional MMCHSs, and further assessed the effectiveness of diverging flow-path optimization strategy. Results revealed a heat-flux-driven transition from localized boiling to fully developed annular flow, accompanied by bubble retrograde growth phenomena. Under high heat fluxes, uniform-channel MMCHSs experienced pronounced vapor backflow and blockage, which impeded upstream liquid replenishment and induced intermittent dryout, ultimately triggering critical heat flux (CHF). To mitigate these limitations, a diverging flow-path configuration was proposed. By promoting forward liquid advection, the design effectively suppressed vapor blockage and backflow, thereby enhancing thermal-hydraulic performance. The optimized DD-MMCHS, which integrates two-level divergence in both the microchannel and manifold layout, achieved significant performance gains under identical conditions: an 18.8 °C reduction in heater temperature, a 40.7% decrease in pressure drop, and a 13% increase in CHF. These findings provide mechanistic insights and practical guidance for future studies on the thermal-hydraulic behavior and structural optimization of MMCHSs.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128334"},"PeriodicalIF":5.8,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974450","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 : 2026-01-12DOI: 10.1016/j.ijheatmasstransfer.2026.128353
Junhua Gong , Chonghai Huang , Qi Xiao , Bo Yu , Yujie Chen , Dongxu Han , Dongliang Sun , Kun Li , Bin Chen
To address the high heat flux dissipation requirements of electronic devices, flow boiling in mini-channels has become a critical research focus due to its superior phase-change heat transfer performance. Usually, the bubble interface tends to appear spherical in shape in the mini-channel under the effect of surface tension. Therefore, in this study, a numerical simulation method based on a three-dimensional sphere-based curved interface reconstruction algorithm (SCIR) is employed to systematically investigate the flow pattern evolution and heat transfer characteristics during saturated flow boiling in rectangular mini-channels. The typical flow pattern and temperature distribution are repoduced by the SCIR algorithm. The microlayer evaporation significantly promotes the formation of slug flow and plays a dominant role in heat dissipation within the channel, with evaporative heat accounting for 75.84% to 82.76% of total input heat. With the increasing heat flux, the local dry patch appears with higher wall superheat than surrounding microlayer regions. When the heat flux exceeds 1400 kW/m2, bubble coalescence leads to the formation of elongated slug bubbles, accompanied by prolonged dryout of the microlayer. The formation of large dry patches leads to local heat accumulation and a pronounced increase in wall superheat, ultimately triggering the boiling crisis. Besides, there is almost no difference in the wall superheat between saturated flow boiling and that with 20 K subcooling, owing to the significant contribution of microlayer evaporation to heat dissipation, which is revealed for the first time by numerical simulation. This work contributes to a deeper understanding of flow pattern evolution and heat transfer mechanisms in mini-channels.
{"title":"Investigation of saturated flow boiling heat transfer in mini-channel based on the SCIR algorithm","authors":"Junhua Gong , Chonghai Huang , Qi Xiao , Bo Yu , Yujie Chen , Dongxu Han , Dongliang Sun , Kun Li , Bin Chen","doi":"10.1016/j.ijheatmasstransfer.2026.128353","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128353","url":null,"abstract":"<div><div>To address the high heat flux dissipation requirements of electronic devices, flow boiling in mini-channels has become a critical research focus due to its superior phase-change heat transfer performance. Usually, the bubble interface tends to appear spherical in shape in the mini-channel under the effect of surface tension. Therefore, in this study, a numerical simulation method based on a three-dimensional sphere-based curved interface reconstruction algorithm (SCIR) is employed to systematically investigate the flow pattern evolution and heat transfer characteristics during saturated flow boiling in rectangular mini-channels. The typical flow pattern and temperature distribution are repoduced by the SCIR algorithm. The microlayer evaporation significantly promotes the formation of slug flow and plays a dominant role in heat dissipation within the channel, with evaporative heat accounting for 75.84% to 82.76% of total input heat. With the increasing heat flux, the local dry patch appears with higher wall superheat than surrounding microlayer regions. When the heat flux exceeds 1400 kW/m<sup>2</sup>, bubble coalescence leads to the formation of elongated slug bubbles, accompanied by prolonged dryout of the microlayer. The formation of large dry patches leads to local heat accumulation and a pronounced increase in wall superheat, ultimately triggering the boiling crisis. Besides, there is almost no difference in the wall superheat between saturated flow boiling and that with 20 K subcooling, owing to the significant contribution of microlayer evaporation to heat dissipation, which is revealed for the first time by numerical simulation. This work contributes to a deeper understanding of flow pattern evolution and heat transfer mechanisms in mini-channels.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128353"},"PeriodicalIF":5.8,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974385","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 : 2026-01-12DOI: 10.1016/j.ijheatmasstransfer.2026.128346
Congren Zheng , Xuhui Liu , Tianyan Liu , Youchuang Chao , Zijing Ding
We present a systematic linear stability analysis of Taylor–Couette flows with non-ideal fluids, taking carbon dioxide near its critical point as a representative working fluid. By exploring different thermodynamic states (subcritical, transcritical, and supercritical), rotational configurations (single-, co-, and counter-rotation), and multiple equations of state, we reveal how thermodynamic non-ideality, compressibility, and rotational shear synergistically impact the flow stability. We show that the subcritical state is the most unstable state under counter-rotation, the transcritical state is the most complex state, and the supercritical state generally suppresses instability. However, compressibility exhibits state-dependent behavior: instability is enhanced with increasing fluid compressibility in the subcritical state but varies non-monotonically in the transcritical state. Significant discrepancies are found between real-fluid and ideal-gas predictions, particularly near the critical point, underscoring the necessity of an accurate thermodynamic model. Furthermore, modal analysis demonstrates that disturbances with azimuthal wavenumbers typically dominate, although higher-order modes may prevail under strong counter-rotation. Finally, by performing the energy budget analysis, we identify that the shear production is the primary energy source, while non-ideality modifies energy transfer via coupling thermal and velocity perturbations. Our findings may advance the fundamental understanding of Taylor–Couette flows with non-ideal fluids and provide insights for predicting and controlling the stability of real-fluid systems that operate near critical conditions.
{"title":"Linear instability in Taylor–Couette flows with non-ideal fluids","authors":"Congren Zheng , Xuhui Liu , Tianyan Liu , Youchuang Chao , Zijing Ding","doi":"10.1016/j.ijheatmasstransfer.2026.128346","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128346","url":null,"abstract":"<div><div>We present a systematic linear stability analysis of Taylor–Couette flows with non-ideal fluids, taking carbon dioxide near its critical point as a representative working fluid. By exploring different thermodynamic states (subcritical, transcritical, and supercritical), rotational configurations (single-, co-, and counter-rotation), and multiple equations of state, we reveal how thermodynamic non-ideality, compressibility, and rotational shear synergistically impact the flow stability. We show that the subcritical state is the most unstable state under counter-rotation, the transcritical state is the most complex state, and the supercritical state generally suppresses instability. However, compressibility exhibits state-dependent behavior: instability is enhanced with increasing fluid compressibility <span><math><mrow><mi>P</mi><mi>r</mi><mi>E</mi><mi>c</mi></mrow></math></span> in the subcritical state but varies non-monotonically in the transcritical state. Significant discrepancies are found between real-fluid and ideal-gas predictions, particularly near the critical point, underscoring the necessity of an accurate thermodynamic model. Furthermore, modal analysis demonstrates that disturbances with azimuthal wavenumbers <span><math><mrow><mi>n</mi><mo>=</mo><mn>0</mn><mo>−</mo><mn>2</mn></mrow></math></span> typically dominate, although higher-order modes may prevail under strong counter-rotation. Finally, by performing the energy budget analysis, we identify that the shear production is the primary energy source, while non-ideality modifies energy transfer via coupling thermal and velocity perturbations. Our findings may advance the fundamental understanding of Taylor–Couette flows with non-ideal fluids and provide insights for predicting and controlling the stability of real-fluid systems that operate near critical conditions.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128346"},"PeriodicalIF":5.8,"publicationDate":"2026-01-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974944","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.ijheatmasstransfer.2026.128363
Ali Pourfathi
This study establishes a novel theoretical and computational framework for the inverse design of cooling variables in continuous steel slab casting, with a focused investigation into a previously overlooked aspect: the systematic influence of design-variable selection on the optimization outcome. The problem is formulated as an inverse heat-transfer problem, constrained by a target solidification front derived from a second-order Stefan approximation. This front inherently embeds critical metallurgical constraints — the Niyama criterion for porosity and a breakout threshold — to ensure defect-aware solidification control.
Two distinct inverse strategies are formulated and compared: one optimizes heat flux, superheat, and casting velocity (OPQ), while the other optimizes heat-transfer coefficient, spray water temperature, and casting velocity (OPH). Both are solved using a projected steepest descent algorithm. A rigorous comparative analysis reveals that the fundamental choice of design variables dictates numerical performance and physical interpretation. The OPH strategy demonstrates superior convergence efficiency and reliability, better captures radiative heat transfer, and yields a lower defect risk profile. In contrast, the OPQ strategy reduces model nonlinearity and yields a convection-dominated cooling profile.
The proposed in silico framework presents a mathematically grounded methodology for inverse solidification design. It provides a systematic comparative study of variable selection within the proposed framework and offers a robust offline design capability for initial process parameterization, effectively decoupling the complex design phase from reliance on extensive experimental trial-and-error procedures.
{"title":"Inverse optimization of solidification via the Stefan problem in continuous steel slab casting","authors":"Ali Pourfathi","doi":"10.1016/j.ijheatmasstransfer.2026.128363","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128363","url":null,"abstract":"<div><div>This study establishes a novel theoretical and computational framework for the inverse design of cooling variables in continuous steel slab casting, with a focused investigation into a previously overlooked aspect: the systematic influence of design-variable selection on the optimization outcome. The problem is formulated as an inverse heat-transfer problem, constrained by a target solidification front derived from a second-order Stefan approximation. This front inherently embeds critical metallurgical constraints — the Niyama criterion for porosity and a breakout threshold — to ensure defect-aware solidification control.</div><div>Two distinct inverse strategies are formulated and compared: one optimizes heat flux, superheat, and casting velocity (OPQ), while the other optimizes heat-transfer coefficient, spray water temperature, and casting velocity (OPH). Both are solved using a projected steepest descent algorithm. A rigorous comparative analysis reveals that the fundamental choice of design variables dictates numerical performance and physical interpretation. The OPH strategy demonstrates superior convergence efficiency and reliability, better captures radiative heat transfer, and yields a lower defect risk profile. In contrast, the OPQ strategy reduces model nonlinearity and yields a convection-dominated cooling profile.</div><div>The proposed <em>in silico</em> framework presents a mathematically grounded methodology for inverse solidification design. It provides a systematic comparative study of variable selection within the proposed framework and offers a robust offline design capability for initial process parameterization, effectively decoupling the complex design phase from reliance on extensive experimental trial-and-error procedures.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128363"},"PeriodicalIF":5.8,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145940845","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}
This study presents a topology optimization framework for the design of water-cooled heat sinks that incorporate voided lattice structures, formulated using a two-layer Darcy–Forchheimer model. Conventional porous heat sinks often suffer from excessive pressure drop due to their intricate geometry, which limits their practical applicability. To address this issue, the proposed method introduces an explicit representation of both void and porous regions, together with graded lattice density, within a multi-material optimization framework. The two-layer Darcy–Forchheimer model enables efficient reduced-order simulations, allowing direct consideration of the heterogeneous porous-void distribution during the optimization process. The optimized designs are reconstructed into full-scale lattice geometries and validated through coupled thermo-fluid finite element analyses under fixed pressure-drop conditions. The results demonstrate that voided lattice configurations significantly outperform conventional plate-fin and uniform lattice heat sinks, achieving approximately 20%–30% higher maximum Nusselt numbers while maintaining lower pressure losses.
{"title":"Multi-scale topology optimization of porous heat sinks with voided lattice structure using a two-layer Darcy–Forchheimer model","authors":"Tatsuki Saito , Yuto Kikuchi , Kuniharu Ushijima , Kentaro Yaji","doi":"10.1016/j.ijheatmasstransfer.2025.128324","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.128324","url":null,"abstract":"<div><div>This study presents a topology optimization framework for the design of water-cooled heat sinks that incorporate voided lattice structures, formulated using a two-layer Darcy–Forchheimer model. Conventional porous heat sinks often suffer from excessive pressure drop due to their intricate geometry, which limits their practical applicability. To address this issue, the proposed method introduces an explicit representation of both void and porous regions, together with graded lattice density, within a multi-material optimization framework. The two-layer Darcy–Forchheimer model enables efficient reduced-order simulations, allowing direct consideration of the heterogeneous porous-void distribution during the optimization process. The optimized designs are reconstructed into full-scale lattice geometries and validated through coupled thermo-fluid finite element analyses under fixed pressure-drop conditions. The results demonstrate that voided lattice configurations significantly outperform conventional plate-fin and uniform lattice heat sinks, achieving approximately 20%–30% higher maximum Nusselt numbers while maintaining lower pressure losses.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128324"},"PeriodicalIF":5.8,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974940","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.ijheatmasstransfer.2026.128331
Pooja Singh, Sourav Mondal
We focus on the immiscible displacement within a radial Hele-Shaw cell using a phase-changing medium. The high-viscosity oil is displaced by methanol vapour, along with its condensate. The condensed methanol liquid migrates toward the fingertip, exerting dominant control over the flow dynamics. The coexistence of vapour and liquid in the displacing phase induces anisotropy and heterogeneity in the viscous fingering pattern, markedly distinctive from the classical observations in Hele-Shaw cell experiments and exhibits non-intuitive pattern formations.
The study explores displacement in porous media where a high-viscosity cold fluid is replaced by a low-viscosity hot fluid (vapour liquid mixture). Thermal front movement is impeded due to heat transfer between the fluids as well as the large time scale of thermal diffusion to the other side of the quartz plate, causing the thermal front to lag behind the fluid front. Initially, momentum diffusion governs heat transfer, followed by thermal diffusion dominance. Interfacial oscillations induced by the Marangoni effect stemming from temperature-induced interfacial tension gradients, are observed. Numerical simulations of the multiphase transport process involving heat transfer, reveal non-trivial variations in the viscous fingering pattern concerning influential parameters such as the surface tension and fluid volume fraction.
{"title":"Viscous fingering with phase-changing (condensing) fluid displacement in radial Hele-Shaw cell","authors":"Pooja Singh, Sourav Mondal","doi":"10.1016/j.ijheatmasstransfer.2026.128331","DOIUrl":"10.1016/j.ijheatmasstransfer.2026.128331","url":null,"abstract":"<div><div>We focus on the immiscible displacement within a radial Hele-Shaw cell using a phase-changing medium. The high-viscosity oil is displaced by methanol vapour, along with its condensate. The condensed methanol liquid migrates toward the fingertip, exerting dominant control over the flow dynamics. The coexistence of vapour and liquid in the displacing phase induces anisotropy and heterogeneity in the viscous fingering pattern, markedly distinctive from the classical observations in Hele-Shaw cell experiments and exhibits non-intuitive pattern formations.</div><div>The study explores displacement in porous media where a high-viscosity cold fluid is replaced by a low-viscosity hot fluid (vapour liquid mixture). Thermal front movement is impeded due to heat transfer between the fluids as well as the large time scale of thermal diffusion to the other side of the quartz plate, causing the thermal front to lag behind the fluid front. Initially, momentum diffusion governs heat transfer, followed by thermal diffusion dominance. Interfacial oscillations induced by the Marangoni effect stemming from temperature-induced interfacial tension gradients, are observed. Numerical simulations of the multiphase transport process involving heat transfer, reveal non-trivial variations in the viscous fingering pattern concerning influential parameters such as the surface tension and fluid volume fraction.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"259 ","pages":"Article 128331"},"PeriodicalIF":5.8,"publicationDate":"2026-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145974943","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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