Pub Date : 2025-02-11DOI: 10.1016/j.ijheatmasstransfer.2025.126788
Yanchi Liu , Baiquan Lin , Ting Liu , Zhiyong Hao
This study focuses on the heat transfer characteristics of crushed coal under axial compression in deep abandoned mines during geothermal extraction. By combining visualized experiments with CT image reconstruction, the study overcame the limitation in the simulation scale, increase the size of finite element model by tens of times. The transient conjugate heat transfer of multi-phase fluid flow process in real axial pressure crushed coal at macro scale is realized. The key findings are as follows: With regard to the thermal conductivity characteristics, the effective thermal conductivities of models filled with different fluids rise linearly with the increase in thermal conductivity of the matrix. As for conjugate heat transfer characteristics, dominant heat transfer paths significantly impact conjugate heat transfer during the non-steady-state phase. An increase in boundary velocity enhances heat extraction efficiency. However, when the boundary velocity increases to 0.001 m/s, the thermal breakthrough time decreases by 66.8 %. Additionally, an increase in the initial temperature difference enhances the heat extraction rate and thermal recovery rate. When gaseous CO₂ is used as the fluid, the temperature and conductive heat flux differences in the heat transfer model are mainly manifested as axial stratification. This research provides an important theoretical support for the development of digital core technology for heat transfer research.
{"title":"Conjugate heat transfer characteristics of crushed coal rock mass under axial compression: Coupling numerical analysis based on CT reconstruction and FEM","authors":"Yanchi Liu , Baiquan Lin , Ting Liu , Zhiyong Hao","doi":"10.1016/j.ijheatmasstransfer.2025.126788","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126788","url":null,"abstract":"<div><div>This study focuses on the heat transfer characteristics of crushed coal under axial compression in deep abandoned mines during geothermal extraction. By combining visualized experiments with CT image reconstruction, the study overcame the limitation in the simulation scale, increase the size of finite element model by tens of times. The transient conjugate heat transfer of multi-phase fluid flow process in real axial pressure crushed coal at macro scale is realized. The key findings are as follows: With regard to the thermal conductivity characteristics, the effective thermal conductivities of models filled with different fluids rise linearly with the increase in thermal conductivity of the matrix. As for conjugate heat transfer characteristics, dominant heat transfer paths significantly impact conjugate heat transfer during the non-steady-state phase. An increase in boundary velocity enhances heat extraction efficiency. However, when the boundary velocity increases to 0.001 m/s, the thermal breakthrough time decreases by 66.8 %. Additionally, an increase in the initial temperature difference enhances the heat extraction rate and thermal recovery rate. When gaseous CO₂ is used as the fluid, the temperature and conductive heat flux differences in the heat transfer model are mainly manifested as axial stratification. This research provides an important theoretical support for the development of digital core technology for heat transfer research.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126788"},"PeriodicalIF":5.0,"publicationDate":"2025-02-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377989","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-10DOI: 10.1016/j.ijheatmasstransfer.2025.126802
Shengkang Hu , Yuge Han , Qunqing Lin , Dengfeng Ren
The effect of excavation and soil recovery on the soil temperature field and surface infrared properties is a critical factor in shallow subsurface target detection, yet it has not been sufficiently addressed in existing research. This study employs a combined discrete element method and MIE scattering model to simulate the changes in soil surface morphology and physical properties after the shallow burial of metal blocks in sandy, loamy, and clay soils. By integrating soil heat and moisture transfer with an infrared radiation model, we simulate the resulting temperature field and infrared radiation characteristics of the surface after excavation. The results indicate that the granularity of sandy soils and the high cohesion of clay soils lead to relatively minor changes in surface morphology and physical parameters in comparison to loamy soils. Infrared imaging analysis reveals that buried materials are most easily detected in loamy and clayey soils, while detection is more challenging in sandy soils. Furthermore, the comparison of temperature differences between the surface center and surrounding environment demonstrates that the characteristics of buried objects in loamy and clay soils are most pronounced at 12:00 and 24:00, enhancing the feasibility of underground target detection at these times. The study also found that different excavation speeds had a minimal impact on soil parameters at the surface. Faster excavation speeds increase shear stresses at the subsurface interface, thereby enhancing the density of the subsurface layer. Additionally, stronger solar radiation was found to improve the detection of buried objects, reducing the difficulty of underground target identification. The methodology proposed in this paper provides a more realistic approach to underground target detection by accounting for the dynamic changes in soil properties during excavation and recovery processes.
{"title":"The effect of excavation and soil recovery on soil temperature and ground infrared radiation containing a metal-bearing block","authors":"Shengkang Hu , Yuge Han , Qunqing Lin , Dengfeng Ren","doi":"10.1016/j.ijheatmasstransfer.2025.126802","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126802","url":null,"abstract":"<div><div>The effect of excavation and soil recovery on the soil temperature field and surface infrared properties is a critical factor in shallow subsurface target detection, yet it has not been sufficiently addressed in existing research. This study employs a combined discrete element method and MIE scattering model to simulate the changes in soil surface morphology and physical properties after the shallow burial of metal blocks in sandy, loamy, and clay soils. By integrating soil heat and moisture transfer with an infrared radiation model, we simulate the resulting temperature field and infrared radiation characteristics of the surface after excavation. The results indicate that the granularity of sandy soils and the high cohesion of clay soils lead to relatively minor changes in surface morphology and physical parameters in comparison to loamy soils. Infrared imaging analysis reveals that buried materials are most easily detected in loamy and clayey soils, while detection is more challenging in sandy soils. Furthermore, the comparison of temperature differences between the surface center and surrounding environment demonstrates that the characteristics of buried objects in loamy and clay soils are most pronounced at 12:00 and 24:00, enhancing the feasibility of underground target detection at these times. The study also found that different excavation speeds had a minimal impact on soil parameters at the surface. Faster excavation speeds increase shear stresses at the subsurface interface, thereby enhancing the density of the subsurface layer. Additionally, stronger solar radiation was found to improve the detection of buried objects, reducing the difficulty of underground target identification. The methodology proposed in this paper provides a more realistic approach to underground target detection by accounting for the dynamic changes in soil properties during excavation and recovery processes.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126802"},"PeriodicalIF":5.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-10DOI: 10.1016/j.ijheatmasstransfer.2025.126744
Mathis Grosso , Guillaume Bois , Adrien Toutant
This study investigates different temperature and flux coupling strategies in Direct Numerical Simulations (DNS) of bubbles at saturation, employing local one-dimensional thermal boundary layer sub-resolutions. Specifically, a laminar radial sub-resolution (LRS) near the interface is employed to address challenges in capturing sharp temperature variations, which is crucial for liquid–vapour heat transfer correlations. State-of-the-art techniques use analytical profiles to capture very thin boundary layers around single-rising objects for very high Prandtl or Schmidt numbers. The original approach proposed in Grosso et al. (2024) relies on a more general embedded sub-resolution still applicable at low Prandtl numbers and coarse grids. To accurately integrate the sub-layer variations into the CFD grid, the literature recommends using the sub-grid profiles to evaluate the Eulerian face fluxes instead of correcting cell temperature. From experience, it avoids excessive flux leakage from the sub-layer region at high Prandtl numbers. The present article investigates these coupling methods while proposing adaptations for thick boundary layers and very coarse grids in the context of LRS. Two test cases, pure diffusion acting around a sphere and a single rising bubble configuration, are explored, measuring heat flux at the interface and its transmission to the fluid domain serving as figures of merit for each coupling method. In low Prandtl bubbly flows (), and on coarse and affordable grids ( cells per bubble diameter), temperature coupling is found to be more stable though not conservative compared to flux coupling approaches. On the other hand, classical flux coupling strategies can exhibit artefacts and introduce potential instabilities with LRS. To overcome such problems, an improved local flux balance approach is proposed, demonstrating both robustness and efficiency in predicting and transmitting interfacial flux across the tested thermal layers’ thickness ranges.
{"title":"Thermal boundary layer modelling for bubbles at saturation: A posteriori analysis","authors":"Mathis Grosso , Guillaume Bois , Adrien Toutant","doi":"10.1016/j.ijheatmasstransfer.2025.126744","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126744","url":null,"abstract":"<div><div>This study investigates different temperature and flux coupling strategies in Direct Numerical Simulations (DNS) of bubbles at saturation, employing local one-dimensional thermal boundary layer sub-resolutions. Specifically, a laminar radial sub-resolution (LRS) near the interface is employed to address challenges in capturing sharp temperature variations, which is crucial for liquid–vapour heat transfer correlations. State-of-the-art techniques use analytical profiles to capture very thin boundary layers around single-rising objects for very high Prandtl or Schmidt numbers. The original approach proposed in Grosso et al. (2024) relies on a more general embedded sub-resolution still applicable at low Prandtl numbers and coarse grids. To accurately integrate the sub-layer variations into the CFD grid, the literature recommends using the sub-grid profiles to evaluate the Eulerian face fluxes instead of correcting cell temperature. From experience, it avoids excessive flux leakage from the sub-layer region at high Prandtl numbers. The present article investigates these coupling methods while proposing adaptations for thick boundary layers and very coarse grids in the context of LRS. Two test cases, pure diffusion acting around a sphere and a single rising bubble configuration, are explored, measuring heat flux at the interface and its transmission to the fluid domain serving as figures of merit for each coupling method. In low Prandtl bubbly flows (<span><math><mrow><mi>P</mi><msub><mrow><mi>r</mi></mrow><mrow><mi>l</mi></mrow></msub><mo>≤</mo><mn>5</mn></mrow></math></span>), and on coarse and affordable grids (<span><math><mrow><mo><</mo><mn>20</mn></mrow></math></span> cells per bubble diameter), temperature coupling is found to be more stable though not conservative compared to flux coupling approaches. On the other hand, classical flux coupling strategies can exhibit artefacts and introduce potential instabilities with LRS. To overcome such problems, an improved local flux balance approach is proposed, demonstrating both robustness and efficiency in predicting and transmitting interfacial flux across the tested thermal layers’ thickness ranges.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126744"},"PeriodicalIF":5.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377521","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Infrared Thermography and the heated thin foil heat flux sensor are employed to experimentally investigate the heat transfer characteristics of sweeping jets impinging on a flat surface. Multiple nozzle-to-target spacings ( and 10, where represents the width of the square exit nozzle throat) and feedback channel minimum passage widths ( and 0) are analyzed to evaluate the effects of these two parameters on the convective heat transfer of the investigated jets. The Reynolds number is set to for all the experiments performed. To assess the heat transfer behavior of the studied sweeping jet device, both time-averaged and phase-averaged analyses are conducted. This study demonstrates that the convective heat transfer of the impinging sweeping jet affects a broader area of the foil as the nozzle-to-target spacing increases, whereas the opposite effect is observed when reducing the minimum passage width of the feedback channels. Furthermore, the time-averaged analyses reveal that for , compared to the corresponding steady jet, sweeping jets enhance the convective heat transfer close to the impingement center of the target surface; instead, for the steady jet exhibits superior heat transfer performance near the stagnation region, while the sweeping jets generate a more uniformly distributed region of maximum convective heat transfer. Additionally, the analysis of the phase-averaged Nusselt number distributions across the target surface reveals that the maximum convective heat transfer region is situated on its uphill side, close to the stagnation point, resembling the behavior of inclined impinging jets.
{"title":"Heat transfer of impinging sweeping jets: Influence of nozzle-to-target spacing and feedback channel minimum passage width","authors":"Cristina D’Angelo, Gerardo Paolillo, Carlo Salvatore Greco, Gennaro Cardone, Tommaso Astarita","doi":"10.1016/j.ijheatmasstransfer.2025.126773","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126773","url":null,"abstract":"<div><div>Infrared Thermography and the heated thin foil heat flux sensor are employed to experimentally investigate the heat transfer characteristics of sweeping jets impinging on a flat surface. Multiple nozzle-to-target spacings <span><math><mi>H</mi></math></span> (<span><math><mrow><mi>H</mi><mo>/</mo><mi>w</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>5</mn><mo>,</mo><mn>1</mn><mo>,</mo><mn>1</mn><mo>.</mo><mn>5</mn><mo>,</mo><mn>2</mn><mo>,</mo><mn>4</mn><mo>,</mo><mn>6</mn><mo>,</mo><mn>8</mn></mrow></math></span> and 10, where <span><math><mi>w</mi></math></span> represents the width of the square exit nozzle throat) and feedback channel minimum passage widths <span><math><mi>g</mi></math></span> (<span><math><mrow><mi>g</mi><mo>/</mo><mi>w</mi><mo>=</mo><mn>1</mn><mo>,</mo><mn>0</mn><mo>.</mo><mn>83</mn><mo>,</mo><mn>0</mn><mo>.</mo><mn>67</mn><mo>,</mo><mn>0</mn><mo>.</mo><mn>50</mn><mo>,</mo><mn>0</mn><mo>.</mo><mn>33</mn><mo>,</mo><mn>0</mn><mo>.</mo><mn>17</mn></mrow></math></span> and 0) are analyzed to evaluate the effects of these two parameters on the convective heat transfer of the investigated jets. The Reynolds number is set to <span><math><mrow><mn>1</mn><mo>.</mo><mn>47</mn><mo>×</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>4</mn></mrow></msup></mrow></math></span> for all the experiments performed. To assess the heat transfer behavior of the studied sweeping jet device, both time-averaged and phase-averaged analyses are conducted. This study demonstrates that the convective heat transfer of the impinging sweeping jet affects a broader area of the foil as the nozzle-to-target spacing increases, whereas the opposite effect is observed when reducing the minimum passage width of the feedback channels. Furthermore, the time-averaged analyses reveal that for <span><math><mrow><mn>0</mn><mo>.</mo><mn>5</mn><mo>≤</mo><mi>H</mi><mo>/</mo><mi>w</mi><mo>≤</mo><mn>1</mn><mo>.</mo><mn>5</mn></mrow></math></span>, compared to the corresponding steady jet, sweeping jets enhance the convective heat transfer close to the impingement center of the target surface; instead, for <span><math><mrow><mi>H</mi><mo>/</mo><mi>w</mi><mo>></mo><mn>2</mn></mrow></math></span> the steady jet exhibits superior heat transfer performance near the stagnation region, while the sweeping jets generate a more uniformly distributed region of maximum convective heat transfer. Additionally, the analysis of the phase-averaged Nusselt number distributions across the target surface reveals that the maximum convective heat transfer region is situated on its uphill side, close to the stagnation point, resembling the behavior of inclined impinging jets.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126773"},"PeriodicalIF":5.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-10DOI: 10.1016/j.ijheatmasstransfer.2025.126799
HyunChul Kim , Soosung Kim , YongKwan Lee , Jae-Hong Shin , Donghyun Kim , SoongJu Oh , Kyoung-Tae Park
Electron beam melting (EBM), which is used to prepare ultra-high-purity refractory and rare metals with high melting points, is associated with an extremely high energy density of tens of megawatts per unit area. The shape and momentum of the electron beam can be adjusted by controlling the electromagnetic field within the electron-beam device to generate this high energy density. However, the energy density in EBM may decrease depending on the beam geometry and magnetic field strength of the focusing coil. To achieve high energy efficiency, the flux density generated by the focusing coil of the electron beam gun should be controlled such that the focusing point of the electron beam is on the surface of the molten material. In this study, the electron beam trajectory in the EBM process was altered by controlling the momentum of the electrons generated by the electric field and the shape of the electron beam produced under the magnetic field generated by the solenoid coil. Finite element analysis was performed to establish the process conditions required to form a beam with high energy efficiency and to minimize the electron bundle loss due to collisions with the inner wall. Our findings can be applied to the refinement of rare metals through high-efficiency energy-beam generation using electron-beam devices with various specifications. The necessary conditions for the electron beam to attain a Gaussian distribution are also outlined. To validate the simulation results, a real-time monitoring of a metal surface subjected to electron-beam irradiation was conducted using a thermal imaging camera. The predicted melting characteristics of titanium, based on electron beam trajectory and turbulence heat transfer models, were validated by ingot manufacturing experiments, confirming the model's applicability.
{"title":"Modeling electron beam melting through electron trajectory control in electromagnetic fields for homogeneous titanium ingot manufacturing","authors":"HyunChul Kim , Soosung Kim , YongKwan Lee , Jae-Hong Shin , Donghyun Kim , SoongJu Oh , Kyoung-Tae Park","doi":"10.1016/j.ijheatmasstransfer.2025.126799","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126799","url":null,"abstract":"<div><div>Electron beam melting (EBM), which is used to prepare ultra-high-purity refractory and rare metals with high melting points, is associated with an extremely high energy density of tens of megawatts per unit area. The shape and momentum of the electron beam can be adjusted by controlling the electromagnetic field within the electron-beam device to generate this high energy density. However, the energy density in EBM may decrease depending on the beam geometry and magnetic field strength of the focusing coil. To achieve high energy efficiency, the flux density generated by the focusing coil of the electron beam gun should be controlled such that the focusing point of the electron beam is on the surface of the molten material. In this study, the electron beam trajectory in the EBM process was altered by controlling the momentum of the electrons generated by the electric field and the shape of the electron beam produced under the magnetic field generated by the solenoid coil. Finite element analysis was performed to establish the process conditions required to form a beam with high energy efficiency and to minimize the electron bundle loss due to collisions with the inner wall. Our findings can be applied to the refinement of rare metals through high-efficiency energy-beam generation using electron-beam devices with various specifications. The necessary conditions for the electron beam to attain a Gaussian distribution are also outlined. To validate the simulation results, a real-time monitoring of a metal surface subjected to electron-beam irradiation was conducted using a thermal imaging camera. The predicted melting characteristics of titanium, based on electron beam trajectory and turbulence heat transfer models, were validated by ingot manufacturing experiments, confirming the model's applicability.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126799"},"PeriodicalIF":5.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377520","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-10DOI: 10.1016/j.ijheatmasstransfer.2025.126779
Jiajun Zhang , Mengxuan Song , Xiaoling Wu , Zhenli Zhang , Kai Chen
Reduction of hot spot temperature is extremely important for power devices. Optimization equations using variational method are effective approaches to analyze convective heat transfer process. However, it is still lack of turbulent convective heat transfer optimization equations for minimization of hot spot temperature. In this work, the turbulent convective heat transfer optimization is investigated using variational method, with the aim of minimizing the hot spot temperature at customized regions. A continuous function that characterizes hot spot temperature is adopted as the objective function. The optimization equations with fixed total viscous dissipation are derived using the variational method, by solving which, the optimal flow field is obtained to achieve the minimum hot spot temperature. Subsequently, the developed optimization equations are applied to optimize the flow fields of the battery thermal management systems with different flow patterns. Numerical results demonstrate that the optimal flow fields from the developed optimization equations achieve lower hot spot temperature and temperature difference inside the battery pack, as compared to those obtained using extremum entransy dissipation in previous studies. Combined with the flow resistance network model, an iterative optimization strategy based on the optimal flow fields is further developed for structural design of the systems. The optimized systems exhibit superior performance in terms of hot spot temperature and temperature difference compared to the original systems before optimization. Finally, the effectiveness of this optimization strategy is validated by experiments. Compared with the systems before optimization, the experimental system with optimized parallel channel widths reduces the hot spot temperature and temperature difference by 6.3 K and 74 % respectively, and the system with optimized inlet defector reduces the hot spot temperature and temperature difference by 5.4 K and 67 % respectively. The optimal flow fields obtained from the developed optimization equations provide valuable insights for designing turbulent convective heat transfer systems which aim at reducing hot spot temperature, and the proposed strategy based on the optimal flow field shows great potential for efficient structural design of battery thermal management systems.
{"title":"Hot spot temperature optimization of turbulent heat convection systems: Application to battery thermal management systems","authors":"Jiajun Zhang , Mengxuan Song , Xiaoling Wu , Zhenli Zhang , Kai Chen","doi":"10.1016/j.ijheatmasstransfer.2025.126779","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126779","url":null,"abstract":"<div><div>Reduction of hot spot temperature is extremely important for power devices. Optimization equations using variational method are effective approaches to analyze convective heat transfer process. However, it is still lack of turbulent convective heat transfer optimization equations for minimization of hot spot temperature. In this work, the turbulent convective heat transfer optimization is investigated using variational method, with the aim of minimizing the hot spot temperature at customized regions. A continuous function that characterizes hot spot temperature is adopted as the objective function. The optimization equations with fixed total viscous dissipation are derived using the variational method, by solving which, the optimal flow field is obtained to achieve the minimum hot spot temperature. Subsequently, the developed optimization equations are applied to optimize the flow fields of the battery thermal management systems with different flow patterns. Numerical results demonstrate that the optimal flow fields from the developed optimization equations achieve lower hot spot temperature and temperature difference inside the battery pack, as compared to those obtained using extremum entransy dissipation in previous studies. Combined with the flow resistance network model, an iterative optimization strategy based on the optimal flow fields is further developed for structural design of the systems. The optimized systems exhibit superior performance in terms of hot spot temperature and temperature difference compared to the original systems before optimization. Finally, the effectiveness of this optimization strategy is validated by experiments. Compared with the systems before optimization, the experimental system with optimized parallel channel widths reduces the hot spot temperature and temperature difference by 6.3 K and 74 % respectively, and the system with optimized inlet defector reduces the hot spot temperature and temperature difference by 5.4 K and 67 % respectively. The optimal flow fields obtained from the developed optimization equations provide valuable insights for designing turbulent convective heat transfer systems which aim at reducing hot spot temperature, and the proposed strategy based on the optimal flow field shows great potential for efficient structural design of battery thermal management systems.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126779"},"PeriodicalIF":5.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-10DOI: 10.1016/j.ijheatmasstransfer.2025.126747
Vijay Kuberan, Sateesh Gedupudi
Surface modification results in substantial improvement in pool boiling heat transfer. Thin film-coated and porous-coated substrates, through different materials and techniques, significantly boost heat transfer through increased nucleation due to the presence of micro-cavities on the surface. The existing models and empirical correlations for boiling on these coated surfaces are constrained by specific operating conditions and parameter ranges and are hence limited by their prediction accuracy. This study focuses on developing an accurate and reliable Machine Learning (ML) model by effectively capturing the actual relationship between the influencing variables. Various ML algorithms have been evaluated on the thin film-coated and porous-coated datasets amassed from different studies. The CatBoost model demonstrated the best prediction accuracy after cross-validation and hyperparameter tuning. For the optimized CatBoost model, SHAP analysis has been carried out to identify the prominent influencing parameters and interpret the impact of parameter variation on the target variable. This model interpretation clearly justifies the decisions behind the model predictions, making it a robust model for the prediction of nucleate boiling Heat Transfer Coefficient (HTC) on coated surfaces. Finally, the existing empirical correlations have been assessed, and new correlations have been proposed to predict the HTC on these surfaces with the inclusion of influential parameters identified through SHAP interpretation.
{"title":"Modelling of nucleate pool boiling on coated substrates using machine learning and empirical approaches","authors":"Vijay Kuberan, Sateesh Gedupudi","doi":"10.1016/j.ijheatmasstransfer.2025.126747","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126747","url":null,"abstract":"<div><div>Surface modification results in substantial improvement in pool boiling heat transfer. Thin film-coated and porous-coated substrates, through different materials and techniques, significantly boost heat transfer through increased nucleation due to the presence of micro-cavities on the surface. The existing models and empirical correlations for boiling on these coated surfaces are constrained by specific operating conditions and parameter ranges and are hence limited by their prediction accuracy. This study focuses on developing an accurate and reliable Machine Learning (ML) model by effectively capturing the actual relationship between the influencing variables. Various ML algorithms have been evaluated on the thin film-coated and porous-coated datasets amassed from different studies. The CatBoost model demonstrated the best prediction accuracy after cross-validation and hyperparameter tuning. For the optimized CatBoost model, SHAP analysis has been carried out to identify the prominent influencing parameters and interpret the impact of parameter variation on the target variable. This model interpretation clearly justifies the decisions behind the model predictions, making it a robust model for the prediction of nucleate boiling Heat Transfer Coefficient (HTC) on coated surfaces. Finally, the existing empirical correlations have been assessed, and new correlations have been proposed to predict the HTC on these surfaces with the inclusion of influential parameters identified through SHAP interpretation.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126747"},"PeriodicalIF":5.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377415","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-10DOI: 10.1016/j.ijheatmasstransfer.2025.126792
Wenning Zhou , Ruotong Li , Lin Lin , Yanhui Feng
Paraffin is a stable organic phase change material (PCM); however, its broad application is constrained by its inherently low thermal conductivity. Incorporation high thermal conductivity nano-additives has proven to be an effective strategy for enhancing the thermal performances of paraffin. In this study, the thermal properties of pure octadecane paraffin, octadecane/copper oxide (CuO), and octadecane/carbon nanotube (CNT) composite PCMs are investigated using molecular dynamics simulations. Furthermore, the mechanisms underlying the thermal conductivity enhancements achieved with these nano-additives are explored. The results indicate that both CuO and CNT nano-additives substantially increase the thermal conductivity across a range of temperatures but decrease its self-diffusion coefficient of pure paraffin. Specifically at 323 K, the thermal conductivities have been increased by 22.6 % and 52.0 % by adding CuO and CNT into pure octadecane, respectively. Notably, distinct mechanisms of the thermal conductivity enhancements induced by CuO and CNT have been observed. The presence of CuO nanoparticles changes the conformation of octadecane molecules from linear to curved state but exhibits minimal influence on the molecular arrangement. In contrast, the incorporation of CNT not only makes the molecular conformation of octadecane more stretched but also facilitates a hierarchical crystal-like arrangement. Both CuO and CNT nano-additives contribute to the formation of a dense interfacial layer, with the layer showing a more ordered structure for CNT. It is concluded that, for paraffin/CuO composites, the increased collision frequency of particles within the dense layer is likely the main reason for the enhancement in thermal conductivity. Whereas for paraffin/CNT composites, the formation of an ordered crystal-like arrangement of octadecane molecules near the interface might be responsible for the thermal conductivity improvement.
{"title":"Different enhancement mechanisms of heat conduction for paraffin phase change materials by adding CuO and CNT nanoparticles","authors":"Wenning Zhou , Ruotong Li , Lin Lin , Yanhui Feng","doi":"10.1016/j.ijheatmasstransfer.2025.126792","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126792","url":null,"abstract":"<div><div>Paraffin is a stable organic phase change material (PCM); however, its broad application is constrained by its inherently low thermal conductivity. Incorporation high thermal conductivity nano-additives has proven to be an effective strategy for enhancing the thermal performances of paraffin. In this study, the thermal properties of pure octadecane paraffin, octadecane/copper oxide (CuO), and octadecane/carbon nanotube (CNT) composite PCMs are investigated using molecular dynamics simulations. Furthermore, the mechanisms underlying the thermal conductivity enhancements achieved with these nano-additives are explored. The results indicate that both CuO and CNT nano-additives substantially increase the thermal conductivity across a range of temperatures but decrease its self-diffusion coefficient of pure paraffin. Specifically at 323 K, the thermal conductivities have been increased by 22.6 % and 52.0 % by adding CuO and CNT into pure octadecane, respectively. Notably, distinct mechanisms of the thermal conductivity enhancements induced by CuO and CNT have been observed. The presence of CuO nanoparticles changes the conformation of octadecane molecules from linear to curved state but exhibits minimal influence on the molecular arrangement. In contrast, the incorporation of CNT not only makes the molecular conformation of octadecane more stretched but also facilitates a hierarchical crystal-like arrangement. Both CuO and CNT nano-additives contribute to the formation of a dense interfacial layer, with the layer showing a more ordered structure for CNT. It is concluded that, for paraffin/CuO composites, the increased collision frequency of particles within the dense layer is likely the main reason for the enhancement in thermal conductivity. Whereas for paraffin/CNT composites, the formation of an ordered crystal-like arrangement of octadecane molecules near the interface might be responsible for the thermal conductivity improvement.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"242 ","pages":"Article 126792"},"PeriodicalIF":5.0,"publicationDate":"2025-02-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-08DOI: 10.1016/j.ijheatmasstransfer.2025.126758
Shakyajit Paik , Somnath Bhattacharyya , Bernhard Weigand
Thermoelectric transport driven by an imposed temperature gradient of an ionized liquid through a charged hydrophobic conical nanopore in a membrane separating two reservoirs is studied in the context of conversion of waste heat to electricity and to generate a liquid flow through the pore. We have also considered the impact of an imposed pressure gradient to enhance the thermoelectric transport. The thermoelectric field arises due to the interplay between the thermophoresis created by the Soret effect, thermoosmosis of ions and the induced electric field governed electrophoretic transport of ions along with the EOF. In addition, the geometric asymmetry of the conical pore also generates an ionic concentration gradient. We consider a modified model for the electrokinetics which incorporates the hydrodynamic steric interactions of finite-sized ions and the viscosity of the suspension medium is considered to vary with the local ionic volume fraction. This modification extends the present model to become valid for a larger range of surface charge density for which the ionic volume fraction can become . While the counterion saturation created by the steric effect attenuates the surface charge screening, an enhanced viscosity near the charged surface creates a larger hydrodynamic friction and reduced ionic flux. Based on the modified model we have analyzed the impact of surface charge density and slip length of the membrane on the thermoelectric field by considering the temperature dependent viscosity, dielectric permittivity and ionic diffusivity for a wide range of the bulk ionic concentration. The occurrence of the ion concentration polarization in the conical pore and its impact on the thermoelectric field is analyzed.
{"title":"Effects of thermoosmosis and thermophoresis of finite-sized ions along with a pressure-driven flow on the thermoelectric field in a conical hydrophobic nanopore","authors":"Shakyajit Paik , Somnath Bhattacharyya , Bernhard Weigand","doi":"10.1016/j.ijheatmasstransfer.2025.126758","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126758","url":null,"abstract":"<div><div>Thermoelectric transport driven by an imposed temperature gradient of an ionized liquid through a charged hydrophobic conical nanopore in a membrane separating two reservoirs is studied in the context of conversion of waste heat to electricity and to generate a liquid flow through the pore. We have also considered the impact of an imposed pressure gradient to enhance the thermoelectric transport. The thermoelectric field arises due to the interplay between the thermophoresis created by the Soret effect, thermoosmosis of ions and the induced electric field governed electrophoretic transport of ions along with the EOF. In addition, the geometric asymmetry of the conical pore also generates an ionic concentration gradient. We consider a modified model for the electrokinetics which incorporates the hydrodynamic steric interactions of finite-sized ions and the viscosity of the suspension medium is considered to vary with the local ionic volume fraction. This modification extends the present model to become valid for a larger range of surface charge density for which the ionic volume fraction can become <span><math><mrow><mo>∼</mo><mi>O</mi><mrow><mo>(</mo><mn>0</mn><mo>.</mo><mn>1</mn><mo>)</mo></mrow></mrow></math></span>. While the counterion saturation created by the steric effect attenuates the surface charge screening, an enhanced viscosity near the charged surface creates a larger hydrodynamic friction and reduced ionic flux. Based on the modified model we have analyzed the impact of surface charge density and slip length of the membrane on the thermoelectric field by considering the temperature dependent viscosity, dielectric permittivity and ionic diffusivity for a wide range of the bulk ionic concentration. The occurrence of the ion concentration polarization in the conical pore and its impact on the thermoelectric field is analyzed.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126758"},"PeriodicalIF":5.0,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143349638","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-02-08DOI: 10.1016/j.ijheatmasstransfer.2025.126784
Lingzi Wang , Yiling Liao , Junyu Niu , Yi Guo , Jianmei Feng , Xueyuan Peng
The ionic liquid compressor is a newly proposed hydrogen compression technology, which has irreplaceable advantages in the application of high-pressure hydrogen refueling stations. In the gas compression chamber, the suction and discharge of the hydrogen are controlled by the self-acting valve, however, the existence of the ionic liquid piston brings challenges to the design of the self-acting valves. In this paper, a three-dimensional two-phase model was established for the compression chamber in the ionic liquid compressor, in which the motion of the valve plate is controlled by the fluid-structure interaction (FSI) model. The accuracy of the model was verified by experiment. Based on this model, the valve plate motion and the two-phase flow characteristics in the compressor chamber were investigated, with a focus on the influence of the number of flow passages (1, 2, 4, 6, 8, 10) in the valve. When taking the gas-liquid heat-transfer performance and fluid discharge characteristics as the primary evaluation factors and ignoring the delayed closure of the discharge valve. The results indicated that 4 or 6 flow passages optimized fluid discharge characteristics and gas-liquid heat transfer performance. In these two cases, the liquid discharge rates were 8.35 % and 8.90 %, respectively, while the hydrogen temperatures remained within the optimal control range of a small increment of 4.7 % (14 K) and 2.3 % (7 K) in temperature after one cycle.
{"title":"Investigation of the number of flow passages in the self-acting valve applied in the hydrogen ionic liquid compressor","authors":"Lingzi Wang , Yiling Liao , Junyu Niu , Yi Guo , Jianmei Feng , Xueyuan Peng","doi":"10.1016/j.ijheatmasstransfer.2025.126784","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126784","url":null,"abstract":"<div><div>The ionic liquid compressor is a newly proposed hydrogen compression technology, which has irreplaceable advantages in the application of high-pressure hydrogen refueling stations. In the gas compression chamber, the suction and discharge of the hydrogen are controlled by the self-acting valve, however, the existence of the ionic liquid piston brings challenges to the design of the self-acting valves. In this paper, a three-dimensional two-phase model was established for the compression chamber in the ionic liquid compressor, in which the motion of the valve plate is controlled by the fluid-structure interaction (FSI) model. The accuracy of the model was verified by experiment. Based on this model, the valve plate motion and the two-phase flow characteristics in the compressor chamber were investigated, with a focus on the influence of the number of flow passages (1, 2, 4, 6, 8, 10) in the valve. When taking the gas-liquid heat-transfer performance and fluid discharge characteristics as the primary evaluation factors and ignoring the delayed closure of the discharge valve. The results indicated that 4 or 6 flow passages optimized fluid discharge characteristics and gas-liquid heat transfer performance. In these two cases, the liquid discharge rates were 8.35 % and 8.90 %, respectively, while the hydrogen temperatures remained within the optimal control range of a small increment of 4.7 % (14 K) and 2.3 % (7 K) in temperature after one cycle.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126784"},"PeriodicalIF":5.0,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143348569","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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