International Journal of Thermal Sciences最新文献

ANN-based optimization of disk-shaped microchannel heat exchanger for thermal and hydraulic performance improvement

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-19 DOI: 10.1016/j.ijthermalsci.2025.109805

Qi Jin , Xuemei Chen , Chaolei Yang , Jun Bao , Jiayi Zheng

In thermal management systems, achieving uniform temperature distribution and minimizing pressure drop in microchannel heat exchangers remains a critical challenge. This study proposes an innovative disk-shaped microchannel heat exchanger with flow tunnel (DMHX-FT) to improve temperature uniformity and reduce pressure drop while maintaining efficient heat transfer. The DMHX-FT features a dendritic fractal microchannel layout to enhance turbulence and fluid flow equalization, along with hub-shaped flow tunnels for efficient recirculation. A feedforward backpropagation Artificial Neural Network (ANN) was employed to analyze parameter impacts and develop a predictive performance model, followed by a genetic algorithm to identify optimal solutions balancing pressure drop and temperature difference. The DMHX-FT achieves a 45 % reduction in temperature difference across various heat fluxes and a 75 % reduction in pressure drop compared to traditional designs. Experimental results align closely with numerical predictions, with discrepancies confined to a maximum of 10 %. The DMHX-FT effectively addresses key challenges in microchannel heat exchangers, offering a promising solution for advanced thermal management, supported by a robust ANN and genetic algorithm optimization framework.

{"title":"ANN-based optimization of disk-shaped microchannel heat exchanger for thermal and hydraulic performance improvement","authors":"Qi Jin , Xuemei Chen , Chaolei Yang , Jun Bao , Jiayi Zheng","doi":"10.1016/j.ijthermalsci.2025.109805","DOIUrl":"10.1016/j.ijthermalsci.2025.109805","url":null,"abstract":"<div><div>In thermal management systems, achieving uniform temperature distribution and minimizing pressure drop in microchannel heat exchangers remains a critical challenge. This study proposes an innovative disk-shaped microchannel heat exchanger with flow tunnel (DMHX-FT) to improve temperature uniformity and reduce pressure drop while maintaining efficient heat transfer. The DMHX-FT features a dendritic fractal microchannel layout to enhance turbulence and fluid flow equalization, along with hub-shaped flow tunnels for efficient recirculation. A feedforward backpropagation Artificial Neural Network (ANN) was employed to analyze parameter impacts and develop a predictive performance model, followed by a genetic algorithm to identify optimal solutions balancing pressure drop and temperature difference. The DMHX-FT achieves a 45 % reduction in temperature difference across various heat fluxes and a 75 % reduction in pressure drop compared to traditional designs. Experimental results align closely with numerical predictions, with discrepancies confined to a maximum of 10 %. The DMHX-FT effectively addresses key challenges in microchannel heat exchangers, offering a promising solution for advanced thermal management, supported by a robust ANN and genetic algorithm optimization framework.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"213 ","pages":"Article 109805"},"PeriodicalIF":4.9,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143437630","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}

引用次数: 0

Hybrid optimization for structure of printed circuit heat exchanger with airfoil fins

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-18 DOI: 10.1016/j.ijthermalsci.2025.109803

Xin Gu, Jie Wang, Hanzhen Wang, Xin Liu, Yongqing Wang

The supercritical carbon dioxide (sCO₂) Brayton cycle is a highly efficient thermodynamic process. In the process, Printed Circuit Heat Exchanger (PCHE) is a promising heat transfer device with merits of under high pressures and temperatures. The airfoil fin, as a form of intermittent fin, has garnered considerable interest. Research involving experimental and simulation studies of airfoils primarily focuses on structural improvements, while the optimization of these improved structures remains relatively underexplored. To further enhance the thermal-hydraulic efficiency of Printed Circuit Heat Exchangers (PCHEs), both local and overall performance concerning flow dynamics and heat transfer of PCHEs with uniform airfoils are analyzed. Adopting the concept of enhancing heat transfer in different regions, combining the dense and sparse airfoil fin layouts at different positions, three types of mixed channels are presented. The hydraulic performance and thermal performance of the hybrid channel in various working conditions is compared. It is found that regional enhanced heat transfer is of big advantages to lower the overall pressure drop. Compared with uniform airfoil channel and the other two mixed channels, the total thermohydraulic efficiency of the low-temperature area in densified channel is the best, which is 1.099 time of that in the uniform channel. Compared to the channel in the high-temperature area, pressure drop in the low-temperature area can be reduced by up to 33.8 %. In addition, heat transfer efficiency is improved at a given mass flow rate while the overall pressure drop is significantly reduced in the low-temperature area of densified channel. Additionally, the enhanced flow passages in the low-temperature zone not only lead to a substantial reduction in overall pressure drop but also enhance heat transfer efficiency significantly. The research content and conclusion of this paper can provide a reference for the structure optimization of printed circuit heat exchangers and the optimization of sCO₂ Brayton circulation system.

{"title":"Hybrid optimization for structure of printed circuit heat exchanger with airfoil fins","authors":"Xin Gu, Jie Wang, Hanzhen Wang, Xin Liu, Yongqing Wang","doi":"10.1016/j.ijthermalsci.2025.109803","DOIUrl":"10.1016/j.ijthermalsci.2025.109803","url":null,"abstract":"<div><div>The supercritical carbon dioxide (sCO<sub>2</sub>) Brayton cycle is a highly efficient thermodynamic process. In the process, Printed Circuit Heat Exchanger (PCHE) is a promising heat transfer device with merits of under high pressures and temperatures. The airfoil fin, as a form of intermittent fin, has garnered considerable interest. Research involving experimental and simulation studies of airfoils primarily focuses on structural improvements, while the optimization of these improved structures remains relatively underexplored. To further enhance the thermal-hydraulic efficiency of Printed Circuit Heat Exchangers (PCHEs), both local and overall performance concerning flow dynamics and heat transfer of PCHEs with uniform airfoils are analyzed. Adopting the concept of enhancing heat transfer in different regions, combining the dense and sparse airfoil fin layouts at different positions, three types of mixed channels are presented. The hydraulic performance and thermal performance of the hybrid channel in various working conditions is compared. It is found that regional enhanced heat transfer is of big advantages to lower the overall pressure drop. Compared with uniform airfoil channel and the other two mixed channels, the total thermohydraulic efficiency of the low-temperature area in densified channel is the best, which is 1.099 time of that in the uniform channel. Compared to the channel in the high-temperature area, pressure drop in the low-temperature area can be reduced by up to 33.8 %. In addition, heat transfer efficiency is improved at a given mass flow rate while the overall pressure drop is significantly reduced in the low-temperature area of densified channel. Additionally, the enhanced flow passages in the low-temperature zone not only lead to a substantial reduction in overall pressure drop but also enhance heat transfer efficiency significantly. The research content and conclusion of this paper can provide a reference for the structure optimization of printed circuit heat exchangers and the optimization of sCO<sub>2</sub> Brayton circulation system.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"212 ","pages":"Article 109803"},"PeriodicalIF":4.9,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429780","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}

引用次数: 0

Effect of non-uniform nanofluid concentration on interferometric heat transfer measurements 非均匀纳米流体浓度对干涉传热测量的影响

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-18 DOI: 10.1016/j.ijthermalsci.2025.109802

Soheil Sahamifar, David Naylor, Jacob Friedman

The effect of non-uniform nanofluid concentration on the accuracy of interferometric heat transfer measurements has been investigated using a Mach-Zehnder interferometer. Because the refractive index is a function of concentration as well as temperature, concentration variations within the nanofluid can produce unwanted interference fringes, leading to temperature measurement errors. Measurement errors in the temperature gradient are demonstrated for conduction within a cavity heated from top to bottom, filled with an Al₂O₃-water nanofluid (0.16 wt%) produced using a standard two-step method. The results of the current measurements show that the temperature gradient can be overestimated by up to 100 % due to near-wall concentration gradients in an unstable nanofluid. The measurement problem is delineated, and several approaches to mitigate this source of measurement error are outlined. The technical trade-offs associated with designing interferometric heat transfer experiments to reduce the sensitivity to concentration differences are discussed. These trade-offs include selecting the nanofluid type and concentration, temperature differences, and the optical path length of the experimental model. It is shown that many interferometric studies in the literature were much more sensitive to concentration-induced errors than the current experiment. An isothermal stability test is recommended to detect nanofluid concentration gradients prior to temperature-based interferometry experiments.

{"title":"Effect of non-uniform nanofluid concentration on interferometric heat transfer measurements","authors":"Soheil Sahamifar, David Naylor, Jacob Friedman","doi":"10.1016/j.ijthermalsci.2025.109802","DOIUrl":"10.1016/j.ijthermalsci.2025.109802","url":null,"abstract":"<div><div>The effect of non-uniform nanofluid concentration on the accuracy of interferometric heat transfer measurements has been investigated using a Mach-Zehnder interferometer. Because the refractive index is a function of concentration as well as temperature, concentration variations within the nanofluid can produce unwanted interference fringes, leading to temperature measurement errors. Measurement errors in the temperature gradient are demonstrated for conduction within a cavity heated from top to bottom, filled with an Al<sub>2</sub>O<sub>3</sub>-water nanofluid (0.16 wt%) produced using a standard two-step method. The results of the current measurements show that the temperature gradient can be overestimated by up to 100 % due to near-wall concentration gradients in an unstable nanofluid. The measurement problem is delineated, and several approaches to mitigate this source of measurement error are outlined. The technical trade-offs associated with designing interferometric heat transfer experiments to reduce the sensitivity to concentration differences are discussed. These trade-offs include selecting the nanofluid type and concentration, temperature differences, and the optical path length of the experimental model. It is shown that many interferometric studies in the literature were much more sensitive to concentration-induced errors than the current experiment. An isothermal stability test is recommended to detect nanofluid concentration gradients prior to temperature-based interferometry experiments.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"212 ","pages":"Article 109802"},"PeriodicalIF":4.9,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429781","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}

引用次数: 0

Study on the temperature uniformity of workpieces inside an annealing furnace 退火炉内工件温度均匀性研究

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-18 DOI: 10.1016/j.ijthermalsci.2025.109798

Xuwen Wang , Zhanyong Long , Kai Zhou , Han Xiao , Xingbang Che , Junming Liao , Chunbo Li

A numerical analysis model of the transient temperature field was established to address the issue of temperature field measurement in a silicon carbide annealing furnace. Numerical simulations of the vacuum annealing process yielded temperature distributions at 550 °C, 1200 °C, and 1700 °C. Real-time temperature measurements using internal thermocouples were conducted at two points within the furnace, showing actual temperature variations. The comparison between simulated and measured data revealed that the maximum error during the holding stage was within 3 %. Based on this, an analysis of the temperature distribution inside the silicon carbide vacuum annealing furnace was performed. The results indicate that increasing the holding temperature during the annealing process effectively reduces the time needed for the workpieces to stabilize at a uniform temperature and improves temperature uniformity by the end of the process. Additionally, by the end of the annealing process, the highest temperatures of the workpieces are concentrated primarily in the middle pieces. The temperature difference among workpieces near the center is minimal, remaining within 2 °C. By the end of the holding phase, 43.64 % of the workpieces in the furnace meet the process requirements. This study offers valuable insights for the structural design and temperature control of silicon carbide vacuum annealing furnaces.

{"title":"Study on the temperature uniformity of workpieces inside an annealing furnace","authors":"Xuwen Wang , Zhanyong Long , Kai Zhou , Han Xiao , Xingbang Che , Junming Liao , Chunbo Li","doi":"10.1016/j.ijthermalsci.2025.109798","DOIUrl":"10.1016/j.ijthermalsci.2025.109798","url":null,"abstract":"<div><div>A numerical analysis model of the transient temperature field was established to address the issue of temperature field measurement in a silicon carbide annealing furnace. Numerical simulations of the vacuum annealing process yielded temperature distributions at 550 °C, 1200 °C, and 1700 °C. Real-time temperature measurements using internal thermocouples were conducted at two points within the furnace, showing actual temperature variations. The comparison between simulated and measured data revealed that the maximum error during the holding stage was within 3 %. Based on this, an analysis of the temperature distribution inside the silicon carbide vacuum annealing furnace was performed. The results indicate that increasing the holding temperature during the annealing process effectively reduces the time needed for the workpieces to stabilize at a uniform temperature and improves temperature uniformity by the end of the process. Additionally, by the end of the annealing process, the highest temperatures of the workpieces are concentrated primarily in the middle pieces. The temperature difference among workpieces near the center is minimal, remaining within 2 °C. By the end of the holding phase, 43.64 % of the workpieces in the furnace meet the process requirements. This study offers valuable insights for the structural design and temperature control of silicon carbide vacuum annealing furnaces.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"212 ","pages":"Article 109798"},"PeriodicalIF":4.9,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429782","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}

引用次数: 0

Numerical simulation on spray cooling with microencapsulated phase change material suspensions

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-18 DOI: 10.1016/j.ijthermalsci.2025.109796

Jiajie Zhang , Xu Wang , Rui Zhao , Yong Li , Suxia Ma

The flow and heat transfer features of spray cooling with microencapsulated phase change material suspension (MPCS) are studied numerically. The movement of spray droplet, the flow and heat transfer of the liquid film, and the latent heat absorption in MPCS are described with discrete phase model (DPM), Lagrangian wall film (LWF) model, and equivalent heat capacity method, respectively. The results indicate that the latent heat absorbing of MPCS can substantially improve the heat transfer compared to water, up to 21.6 %. The contradictory effect of latent heat ability and large viscosity of MPCS on the heat transfer makes it having the best heat transfer at 5 % concentration. A reduction in the droplet diameter can improve the heat transfer due to the increased disturbance within the liquid film. The Nu decreases with the growth of spray height at a reduction rate of approximately 7.4 % when H/D ≤ 8, but the decline clearly slows down when H/D > 8 with a reduction of only about 1.0 %. It exists a critical flow value of Q = 7.5 g/s for the influence of spray cone angle on the heat transfer, the evaporation rate and turbulent disturbance in the liquid film is dominant, respectively, when Q ≤ 7.5 g/s and Q > 7.5 g/s. Compared to the water, Nu for MPCS shows a peak within the phase change temperature range, and the optimal inlet temperature is θ = −0.11, which is slightly beneath the melting peak temperature of the MPCS.

{"title":"Numerical simulation on spray cooling with microencapsulated phase change material suspensions","authors":"Jiajie Zhang , Xu Wang , Rui Zhao , Yong Li , Suxia Ma","doi":"10.1016/j.ijthermalsci.2025.109796","DOIUrl":"10.1016/j.ijthermalsci.2025.109796","url":null,"abstract":"<div><div>The flow and heat transfer features of spray cooling with microencapsulated phase change material suspension (MPCS) are studied numerically. The movement of spray droplet, the flow and heat transfer of the liquid film, and the latent heat absorption in MPCS are described with discrete phase model (DPM), Lagrangian wall film (LWF) model, and equivalent heat capacity method, respectively. The results indicate that the latent heat absorbing of MPCS can substantially improve the heat transfer compared to water, up to 21.6 %. The contradictory effect of latent heat ability and large viscosity of MPCS on the heat transfer makes it having the best heat transfer at 5 % concentration. A reduction in the droplet diameter can improve the heat transfer due to the increased disturbance within the liquid film. The <em>Nu</em> decreases with the growth of spray height at a reduction rate of approximately 7.4 % when <em>H</em>/<em>D</em> ≤ 8, but the decline clearly slows down when <em>H</em>/<em>D</em> > 8 with a reduction of only about 1.0 %. It exists a critical flow value of <em>Q</em> = 7.5 g/s for the influence of spray cone angle on the heat transfer, the evaporation rate and turbulent disturbance in the liquid film is dominant, respectively, when <em><u>Q</u></em> ≤ 7.5 g/s and <em>Q</em> > 7.5 g/s. Compared to the water, <em>Nu</em> for MPCS shows a peak within the phase change temperature range, and the optimal inlet temperature is <em>θ</em> = −0.11, which is slightly beneath the melting peak temperature of the MPCS.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"212 ","pages":"Article 109796"},"PeriodicalIF":4.9,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429709","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}

引用次数: 0

Prediction method and influence mechanism of effective thermal conductivity of complex fractured coal based on CT image reconstruction simulation and machine learning training

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-18 DOI: 10.1016/j.ijthermalsci.2025.109792

Yanchi Liu , Jie Wang , Baiquan Lin , Jiayun Yang

The effective thermal conductivity (ETC) of coal body is a key parameter for geothermal design of abandoned mines, but due to the complex microscopic fracture structure of coal body after mining influence, the existing research lacks the prediction method of ETC the coal body considering the complex fracture structure. Therefore, in this study, finite element simulation was performed by inverse modelling of coal body CT slice data to form a dataset of 2200 sets. Six single machine learning (ML) prediction models of SVM, DT, KNN, BP, RF and XGBoost are trained by the dataset, and six stacking models are proposed on the basis of the single ML, and the prediction results are examined with the test set and the 3D modelling computation results by multiple indicators. The stacking prediction model with the best accuracy is finally screened, and SHapley Additive explanation (SHAP) analysis is performed to clarify the indicator influence mechanism. The resulting prediction procedure can batch calculate the ETC of coal bodies with real fissure structure in abandoned mines based on the coal mine core data, avoiding the sampling and testing of abandoned mines, and providing a reference for the engineering decision of heat extraction in the interior of abandoned mines.

{"title":"Prediction method and influence mechanism of effective thermal conductivity of complex fractured coal based on CT image reconstruction simulation and machine learning training","authors":"Yanchi Liu , Jie Wang , Baiquan Lin , Jiayun Yang","doi":"10.1016/j.ijthermalsci.2025.109792","DOIUrl":"10.1016/j.ijthermalsci.2025.109792","url":null,"abstract":"<div><div>The effective thermal conductivity (ETC) of coal body is a key parameter for geothermal design of abandoned mines, but due to the complex microscopic fracture structure of coal body after mining influence, the existing research lacks the prediction method of ETC the coal body considering the complex fracture structure. Therefore, in this study, finite element simulation was performed by inverse modelling of coal body CT slice data to form a dataset of 2200 sets. Six single machine learning (ML) prediction models of SVM, DT, KNN, BP, RF and XGBoost are trained by the dataset, and six stacking models are proposed on the basis of the single ML, and the prediction results are examined with the test set and the 3D modelling computation results by multiple indicators. The stacking prediction model with the best accuracy is finally screened, and SHapley Additive explanation (SHAP) analysis is performed to clarify the indicator influence mechanism. The resulting prediction procedure can batch calculate the ETC of coal bodies with real fissure structure in abandoned mines based on the coal mine core data, avoiding the sampling and testing of abandoned mines, and providing a reference for the engineering decision of heat extraction in the interior of abandoned mines.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"212 ","pages":"Article 109792"},"PeriodicalIF":4.9,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143429783","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}

引用次数: 0

The role of horizontal gaps on metal flow and heat transfer in bottom-locking welding joints

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-17 DOI: 10.1016/j.ijthermalsci.2025.109785

Biao Yang , Xiangbang Xu , Fuyun Liu , Wei Wang , Guoqing Chen , Houqin Wang , Xiaohui Han , Xiaoguo Song , Caiwang Tan

A validated numerical simulation model coupling multiple phases and physics is developed. The role of horizontal gaps in the laser-arc hybrid welded bottom-locking joints is focused. A new adjustment method for the surface tension momentum source is proposed to suppress the spontaneous closure of internal gaps. The weld profile, metal flows, keyhole dynamics and heat flux distribution under different gap sizes are compared. The results indicated that horizontal gaps deteriorated the weld formation. The weld depth was lower than 3 mm when the gap size reached 0.8 mm, which failed to meet the design requirements. In addition, horizontal gaps induced a split-flow once the molten metal penetrated the upper butt part. The split-flow reduced the density of upward back flows on the gap side while hardly affected that on the other side. Consequently, more keyhole wall humps formed under the unbalanced upward flows compared with gap-free conditions. Moreover, more severe keyhole fluctuations hindered the laser beam from reaching the keyhole bottom. The average keyhole depth was thus reduced with the increase of gap sizes. Correspondingly, the heat transfer was also affected. Higher heat flux was obtained when no gap existed while more heat energy was located at the keyhole wall under gap conditions, which was responsible for the reduction of the weld depth. This study clarifies weld pool dynamics of bottom-locking joints and will provide more modeling guidance on welding CFD analysis involving gap conditions.

{"title":"The role of horizontal gaps on metal flow and heat transfer in bottom-locking welding joints","authors":"Biao Yang , Xiangbang Xu , Fuyun Liu , Wei Wang , Guoqing Chen , Houqin Wang , Xiaohui Han , Xiaoguo Song , Caiwang Tan","doi":"10.1016/j.ijthermalsci.2025.109785","DOIUrl":"10.1016/j.ijthermalsci.2025.109785","url":null,"abstract":"<div><div>A validated numerical simulation model coupling multiple phases and physics is developed. The role of horizontal gaps in the laser-arc hybrid welded bottom-locking joints is focused. A new adjustment method for the surface tension momentum source is proposed to suppress the spontaneous closure of internal gaps. The weld profile, metal flows, keyhole dynamics and heat flux distribution under different gap sizes are compared. The results indicated that horizontal gaps deteriorated the weld formation. The weld depth was lower than 3 mm when the gap size reached 0.8 mm, which failed to meet the design requirements. In addition, horizontal gaps induced a split-flow once the molten metal penetrated the upper butt part. The split-flow reduced the density of upward back flows on the gap side while hardly affected that on the other side. Consequently, more keyhole wall humps formed under the unbalanced upward flows compared with gap-free conditions. Moreover, more severe keyhole fluctuations hindered the laser beam from reaching the keyhole bottom. The average keyhole depth was thus reduced with the increase of gap sizes. Correspondingly, the heat transfer was also affected. Higher heat flux was obtained when no gap existed while more heat energy was located at the keyhole wall under gap conditions, which was responsible for the reduction of the weld depth. This study clarifies weld pool dynamics of bottom-locking joints and will provide more modeling guidance on welding CFD analysis involving gap conditions.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"212 ","pages":"Article 109785"},"PeriodicalIF":4.9,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143420651","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}

引用次数: 0

Characterization of flow and heat transfer in flexible electroconductive pumps at various bending modes

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-17 DOI: 10.1016/j.ijthermalsci.2025.109794

Yice Shao , Juanjuan Liu , Hong Wang , Quan Peng , Yuchen Tian , Xun Zhu , Yudong Ding , Rong Chen , Qiang Liao

As flexible electronic devices are increasingly applied in fields such as healthcare and life sciences, the need for efficient fluid pumping and thermal management is steadily growing. The electroconductive pump, characterized by the absence of mechanical components and ease of integration, is considered an ideal solution for flexible pumping applications. This study uses the open-source software OpenFOAM to conduct numerical simulations on the flow and heat transfer characteristics of flexible electroconductive pumps under various bending modes. The results indicate that localized bending of wide electrodes can reduce Coulomb resistance by 15 %, leading to a 20.11 % increase in the outlet flow rate at a 90° bend. However, bending of narrow electrodes results in a decrease in positive Coulomb force and an increase in negative Coulomb force, which leads to a reduction in flow, with a maximum decrease of 20 %. In terms of heat transfer characteristics, channel bending generally has a detrimental effect on heat transfer performance, particularly with narrow electrode bending, which significantly hinders heat exchange. This study not only deepens the understanding of electroconductive pumps but also provides valuable insights for the design and application of flexible electroconductive pumps.

{"title":"Characterization of flow and heat transfer in flexible electroconductive pumps at various bending modes","authors":"Yice Shao , Juanjuan Liu , Hong Wang , Quan Peng , Yuchen Tian , Xun Zhu , Yudong Ding , Rong Chen , Qiang Liao","doi":"10.1016/j.ijthermalsci.2025.109794","DOIUrl":"10.1016/j.ijthermalsci.2025.109794","url":null,"abstract":"<div><div>As flexible electronic devices are increasingly applied in fields such as healthcare and life sciences, the need for efficient fluid pumping and thermal management is steadily growing. The electroconductive pump, characterized by the absence of mechanical components and ease of integration, is considered an ideal solution for flexible pumping applications. This study uses the open-source software OpenFOAM to conduct numerical simulations on the flow and heat transfer characteristics of flexible electroconductive pumps under various bending modes. The results indicate that localized bending of wide electrodes can reduce Coulomb resistance by 15 %, leading to a 20.11 % increase in the outlet flow rate at a 90° bend. However, bending of narrow electrodes results in a decrease in positive Coulomb force and an increase in negative Coulomb force, which leads to a reduction in flow, with a maximum decrease of 20 %. In terms of heat transfer characteristics, channel bending generally has a detrimental effect on heat transfer performance, particularly with narrow electrode bending, which significantly hinders heat exchange. This study not only deepens the understanding of electroconductive pumps but also provides valuable insights for the design and application of flexible electroconductive pumps.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"212 ","pages":"Article 109794"},"PeriodicalIF":4.9,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143420650","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}

引用次数: 0

Modelling of near isothermal liquid piston gas compressor employing porous media for compressed air energy storage systems

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-17 DOI: 10.1016/j.ijthermalsci.2025.109775

Lee Haney , Robert Prosser , Alexander Lanzon , Yasser Mahmoudi

The liquid piston gas compressor (LPGC) is a method of compressing gases with improved efficiency. Key to the success of this device is its operation in as close to an isothermal state as possible. This paper presents high-fidelity, three-dimensional, unsteady Reynolds-averaged Navier–Stokes (uRANS) simulations to better understand the heat transfer and fluid physics involved in the liquid-piston-driven compression process. Furthermore, the uRANS is coupled with conjugate heat transfer to study using porous media inserts to manage the temperature increase. We simulate the entire cylinder/porous media arrangement using the volume of fluid (VOF) method to analyse the turbulent, multiphase physics and the fluid–structure interaction, providing a greater understanding of this process. It also investigates how porous media inserts perform against the no-insert (baseline) cases in producing a near-isothermal process. The porous mediums used are parallel plates, interrupted plates, and metal foam, all produced from aluminium. Results show that temperature rises within the cylinder can be reduced by as much as 120 K, depending on the choice of porous insert. This temperature reduction translates to an increase of up to 13% in compression efficiency.

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引用次数: 0

The enhancement of mixed convection in a metal foam-filled elliptic annulus by a spatially variable heat flux

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-02-17 DOI: 10.1016/j.ijthermalsci.2025.109747

I. Boukhalfa, M. Afrid

Thermal performance enhancement is obtained when the same heat input that is uniformly imposed on a conduit wall is concentrated over short axial bands that are separated by adiabatic bands. This study explores numerically the heat transfer enhancement, with a variable concentrated heat flux, for the three-dimensional mixed convection in a metal foam-filled elliptic annulus. This work studies the effect and synergy of the spatially periodic or aperiodic heat flux, the metal foam structure, the annulus orientation and geometry and the dynamic and thermal controlling parameters on the mixed convection heat transfer performance, the axial evolution of the cross-section temperature difference and the annulus pressure drop. The results of the spatially variable heat flux are compared with those of the constant and uniform heat flux. For the same heat input and the same flow rate, in most of the considered cases in this study, the spatial variation of the heat flux enhances the heat transfer, decreases slightly the pressure drop but increases the cross-section temperature variation along the heated bands. A totally adiabatic end portion of the annulus is found to considerably enhance the homogenization of the cross-section temperature towards the annulus exit.

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引用次数: 0