Pub Date : 2026-01-29DOI: 10.1016/j.ijthermalsci.2026.110723
Zain Ali, Sri Addepalli, Yifan Zhao
Through-transmission pulsed thermography is widely recognised for offering higher defect resolution than reflection mode, yet its development has been hindered by challenges such as quantifying defect depth. This study addresses the depth quantification gap by introducing a novel depth estimation technique based on the relationship between defect depth and the Fourier number. The method is validated through both finite element modelling and laboratory experiments using calibration samples with embedded air-gap defects at known depths. Results show that depth estimation accuracy improves as defects approach the backwall, consistently across both simulation and experimental environments. Finite element analysis also demonstrates that the proposed technique outperforms the log second derivative method typically used in reflection mode. These findings advance the capability of through-transmission thermography for precise subsurface defect characterisation.
{"title":"Defect depth estimation using through-transmission pulsed thermography: A numerical and experimental investigation","authors":"Zain Ali, Sri Addepalli, Yifan Zhao","doi":"10.1016/j.ijthermalsci.2026.110723","DOIUrl":"10.1016/j.ijthermalsci.2026.110723","url":null,"abstract":"<div><div>Through-transmission pulsed thermography is widely recognised for offering higher defect resolution than reflection mode, yet its development has been hindered by challenges such as quantifying defect depth. This study addresses the depth quantification gap by introducing a novel depth estimation technique based on the relationship between defect depth and the Fourier number. The method is validated through both finite element modelling and laboratory experiments using calibration samples with embedded air-gap defects at known depths. Results show that depth estimation accuracy improves as defects approach the backwall, consistently across both simulation and experimental environments. Finite element analysis also demonstrates that the proposed technique outperforms the log second derivative method typically used in reflection mode. These findings advance the capability of through-transmission thermography for precise subsurface defect characterisation.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110723"},"PeriodicalIF":5.0,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074474","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 : 2026-01-29DOI: 10.1016/j.ijthermalsci.2026.110725
Bowen Yu, Zhiguo Xu
Droplet impingement on high-temperature solid surfaces is fundamental to numerous industrial technologies. While multilayered textured surfaces and electric field modulation are known to enhance evaporation, their coupled effects remain unexplored. In this work, the multilayered bio-inspired surface, designed based on the springtail cuticle reentrant surface and reef cilia, is proposed to regulate evaporation under a uniform electric field. The coupled lattice Boltzmann-immersed boundary method, accounting for multi-physics interactions, is utilized to systematically examine how Jakob number (Ja), flexible filament, electric capillary number, and Weber number affect the droplet evaporation. Results show that flexible filaments enhance evaporation on the bio-inspired surface, and this effect weakens at high Ja without an electric field but remains significant when the electric field is applied. Electric field-induced vortex redistribution (2.45 % peak vorticity increase at Ja = 0.27) and filament deformation (60.15 % increase in time-averaged contact length at Ja = 0.09) jointly enhance evaporation efficiency. The electric field governs evaporation behavior by promoting droplet expansion and inducing instability associated with detachment-contact dynamics: at Ja = 0.09, increasing the electric capillary number from 0.75 to 1.5 and 2.25 shortens the droplet lifetime by 29.25 % and 39.83 %, respectively; the shortening effect is more significant at Ja = 0.18, with reductions of 37.78 % and 43.65 %. The Weber number exhibits different influences on evaporation at low and high Ja, with a non-monotonic response occurring at Ja = 0.09, whereas at higher Ja (0.135–0.225), increasing Weber number shortens the droplet lifetime.
{"title":"Droplet evaporation on multilayered bio-inspired surfaces under a uniform electric field","authors":"Bowen Yu, Zhiguo Xu","doi":"10.1016/j.ijthermalsci.2026.110725","DOIUrl":"10.1016/j.ijthermalsci.2026.110725","url":null,"abstract":"<div><div>Droplet impingement on high-temperature solid surfaces is fundamental to numerous industrial technologies. While multilayered textured surfaces and electric field modulation are known to enhance evaporation, their coupled effects remain unexplored. In this work, the multilayered bio-inspired surface, designed based on the springtail cuticle reentrant surface and reef cilia, is proposed to regulate evaporation under a uniform electric field. The coupled lattice Boltzmann-immersed boundary method, accounting for multi-physics interactions, is utilized to systematically examine how Jakob number (<em>Ja</em>), flexible filament, electric capillary number, and Weber number affect the droplet evaporation. Results show that flexible filaments enhance evaporation on the bio-inspired surface, and this effect weakens at high <em>Ja</em> without an electric field but remains significant when the electric field is applied. Electric field-induced vortex redistribution (2.45 % peak vorticity increase at <em>Ja</em> = 0.27) and filament deformation (60.15 % increase in time-averaged contact length at <em>Ja</em> = 0.09) jointly enhance evaporation efficiency. The electric field governs evaporation behavior by promoting droplet expansion and inducing instability associated with detachment-contact dynamics: at <em>Ja</em> = 0.09, increasing the electric capillary number from 0.75 to 1.5 and 2.25 shortens the droplet lifetime by 29.25 % and 39.83 %, respectively; the shortening effect is more significant at <em>Ja</em> = 0.18, with reductions of 37.78 % and 43.65 %. The Weber number exhibits different influences on evaporation at low and high <em>Ja</em>, with a non-monotonic response occurring at <em>Ja</em> = 0.09, whereas at higher <em>Ja</em> (0.135–0.225), increasing Weber number shortens the droplet lifetime.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110725"},"PeriodicalIF":5.0,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074470","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 : 2026-01-29DOI: 10.1016/j.ijthermalsci.2026.110729
Song Yang, Liang Du, Jin Yuan, Xinlong Zhao, Wenbo Hu, Zhaoyang Zhang, Hongxing Wang
Modern electronics are continually evolving toward miniaturization and high performance, posing significant challenges for chip-level thermal management under ultra-high heat flux (>1000 W/cm2). Conventional heat sinks are inadequate for these demands. Diamond microchannel heat sinks, leveraging diamond's exceptional thermal conductivity, offer a promising solution. However, the high hardness and cost of diamond lead to elevated manufacturing costs for such heat sinks. Consequently, the co-optimization of thermal-hydraulic performance and manufacturing costs presents a critical challenge. This study employed a machine-learning-based multi-objective optimization approach to design diamond microchannel heat sinks, simultaneously considering thermal-hydraulic performance and manufacturing objectives. An artificial neural network predicted the thermal-hydraulic performance, and a genetic algorithm then identified Pareto-optimal solutions. First, a thermal-hydraulic dual-objective optimization was conducted to analyze the trade-off between the maximum temperature and pressure drop. Subsequently, two manufacturing objectives (aspect ratio and cross-sectional area) were introduced, thereby formulating a manufacturing-constrained multi-objective optimization problem. The results demonstrated clear trade-offs among these four objectives on the Pareto front. One notable optimal solution achieves a 61.6 % reduction in material cost and an estimated 58 % decrease in fabrication difficulty with only a 20 % compromise in thermal-hydraulic performance. Thus, this work provides a systematic design methodology that successfully balances performance with manufacturability, paving the way for the scalable industrial adoption of diamond microchannel heat sinks.
{"title":"Manufacturing-constrained multi-objective optimization of diamond microchannel heat sinks via interpretable machine learning","authors":"Song Yang, Liang Du, Jin Yuan, Xinlong Zhao, Wenbo Hu, Zhaoyang Zhang, Hongxing Wang","doi":"10.1016/j.ijthermalsci.2026.110729","DOIUrl":"10.1016/j.ijthermalsci.2026.110729","url":null,"abstract":"<div><div>Modern electronics are continually evolving toward miniaturization and high performance, posing significant challenges for chip-level thermal management under ultra-high heat flux (>1000 W/cm<sup>2</sup>). Conventional heat sinks are inadequate for these demands. Diamond microchannel heat sinks, leveraging diamond's exceptional thermal conductivity, offer a promising solution. However, the high hardness and cost of diamond lead to elevated manufacturing costs for such heat sinks. Consequently, the co-optimization of thermal-hydraulic performance and manufacturing costs presents a critical challenge. This study employed a machine-learning-based multi-objective optimization approach to design diamond microchannel heat sinks, simultaneously considering thermal-hydraulic performance and manufacturing objectives. An artificial neural network predicted the thermal-hydraulic performance, and a genetic algorithm then identified Pareto-optimal solutions. First, a thermal-hydraulic dual-objective optimization was conducted to analyze the trade-off between the maximum temperature and pressure drop. Subsequently, two manufacturing objectives (aspect ratio and cross-sectional area) were introduced, thereby formulating a manufacturing-constrained multi-objective optimization problem. The results demonstrated clear trade-offs among these four objectives on the Pareto front. One notable optimal solution achieves a 61.6 % reduction in material cost and an estimated 58 % decrease in fabrication difficulty with only a 20 % compromise in thermal-hydraulic performance. Thus, this work provides a systematic design methodology that successfully balances performance with manufacturability, paving the way for the scalable industrial adoption of diamond microchannel heat sinks.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110729"},"PeriodicalIF":5.0,"publicationDate":"2026-01-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074473","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 : 2026-01-28DOI: 10.1016/j.ijthermalsci.2026.110726
Yixuan Yuwen , Jingzhi Zhou , Yuzhe He , Kai Zhang , Xunfeng Li
The flow and heat transfer characteristics of non-Newtonian power-law drilling fluids in helical tubes were investigated through combined experimental and numerical methods. The effects of fluid density, rheological parameters (consistency index K and power-law index n), and helical tube curvature ratio were systematically analyzed. The results indicate that lower fluid density and higher inlet temperature both enhance heat transfer performance. Reductions in K and n synergistically enhance convective heat transfer while simultaneously lowering flow resistance. Moreover, increasing the curvature ratio not only improves thermal-hydraulic performance but also amplifies the effect of K and n. Based on the experimental and numerical data, a friction factor correlation incorporating the effects of the Dean number, curvature ratio, and power-law index was developed, along with a corresponding predictive model for the Nusselt number. These findings provide valuable theoretical guidance for the engineering application and optimized design of power-law fluids in helical tube heat exchangers.
{"title":"Experimental and numerical study of flow and heat transfer of non-Newtonian power-law drilling fluids in helical tubes","authors":"Yixuan Yuwen , Jingzhi Zhou , Yuzhe He , Kai Zhang , Xunfeng Li","doi":"10.1016/j.ijthermalsci.2026.110726","DOIUrl":"10.1016/j.ijthermalsci.2026.110726","url":null,"abstract":"<div><div>The flow and heat transfer characteristics of non-Newtonian power-law drilling fluids in helical tubes were investigated through combined experimental and numerical methods. The effects of fluid density, rheological parameters (consistency index <em>K</em> and power-law index <em>n</em>), and helical tube curvature ratio were systematically analyzed. The results indicate that lower fluid density and higher inlet temperature both enhance heat transfer performance. Reductions in <em>K</em> and <em>n</em> synergistically enhance convective heat transfer while simultaneously lowering flow resistance. Moreover, increasing the curvature ratio not only improves thermal-hydraulic performance but also amplifies the effect of <em>K</em> and <em>n</em>. Based on the experimental and numerical data, a friction factor correlation incorporating the effects of the Dean number, curvature ratio, and power-law index was developed, along with a corresponding predictive model for the Nusselt number. These findings provide valuable theoretical guidance for the engineering application and optimized design of power-law fluids in helical tube heat exchangers.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110726"},"PeriodicalIF":5.0,"publicationDate":"2026-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074544","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 : 2026-01-27DOI: 10.1016/j.ijthermalsci.2026.110708
Zenan Yang, Yongjie Li, Chengke Li, Haiwei Yang, Ge Wang
The present study presents a numerical investigation into the heat transfer deterioration (HTD) mechanism during supercritical CO2 flowing upward in a vertical tube, with emphasis on the synergistic role of drastic variations in density and thermal conductivity near the pseudo-critical point. By selectively isolating property variations, the study reveals that abrupt density changes are a primary trigger of HTD, provoking buoyancy-induced flow re-laminarization and flow acceleration that suppress turbulent transport. Furthermore, sharp declines in thermal conductivity are shown to exacerbate HTD through a dual mechanism, that is, impairing heat conduction within the viscous sublayer and intensifying axial thermal gradients, which further amplify buoyancy and acceleration effects. These interactions collectively impair turbulent heat transfer efficiency. The results offer novel understanding of the coupled thermophysical pathways governing HTD and support the optimized design of heat exchange systems in supercritical CO2 power cycles.
{"title":"Numerical study on the effects of drastic variations in thermal conductivity on the supercritical CO2 heat transfer deterioration","authors":"Zenan Yang, Yongjie Li, Chengke Li, Haiwei Yang, Ge Wang","doi":"10.1016/j.ijthermalsci.2026.110708","DOIUrl":"10.1016/j.ijthermalsci.2026.110708","url":null,"abstract":"<div><div>The present study presents a numerical investigation into the heat transfer deterioration (HTD) mechanism during supercritical CO<sub>2</sub> flowing upward in a vertical tube, with emphasis on the synergistic role of drastic variations in density and thermal conductivity near the pseudo-critical point. By selectively isolating property variations, the study reveals that abrupt density changes are a primary trigger of HTD, provoking buoyancy-induced flow re-laminarization and flow acceleration that suppress turbulent transport. Furthermore, sharp declines in thermal conductivity are shown to exacerbate HTD through a dual mechanism, that is, impairing heat conduction within the viscous sublayer and intensifying axial thermal gradients, which further amplify buoyancy and acceleration effects. These interactions collectively impair turbulent heat transfer efficiency. The results offer novel understanding of the coupled thermophysical pathways governing HTD and support the optimized design of heat exchange systems in supercritical CO<sub>2</sub> power cycles.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110708"},"PeriodicalIF":5.0,"publicationDate":"2026-01-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074545","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The increasing heat flux in compact electronic devices necessitates advanced cooling solutions that exceed the capabilities of conventional microchannel heat sinks (MCHSs). This study presents a novel design using anisotropic gradient porous fins within MCHSs to achieve superior thermal performance while managing hydraulic penalties. The key innovation involves combining directional permeability anisotropy with graded Darcy numbers (10−1 – 10−4) to enable simultaneous heat transfer enhancement and flow resistance control. Eleven configurations, including a solid-fin baseline and various porous arrangements (uniform, stepwise, and linear gradients), were numerically investigated. The influence of Reynolds number (Re = 100–1000), fin thickness ratio (a1/a3 = 0.167–0.35), and fin height ratio (h2/a3 = 0.3–2.0) on thermohydraulic performance was systematically evaluated under a constant heat flux. Results show that Configuration 5 (stepwise decreasing permeability) achieved a 76.84 % reduction in thermal resistance and a 3594.71 % performance gain over the baseline at Re = 500. Increasing fin thickness from a1/a3 = 0.167 to 0.35 led to a 79.54 % drop in thermal resistance and a 4592.18 % increase in performance metric, while increasing height to h2/a3 = 2.0 resulted in a 5159.31 % improvement. Performance continued to rise with Reynolds number, reaching 4000 % improvement in performance metric at Re = 1000. These findings validate anisotropic gradient porous fins as a transformative approach for next-generation, high-flux thermal management systems.
{"title":"Anisotropic gradient porous fins for microchannel heat sinks: A new paradigm in thermal management design","authors":"Hamid-Reza Bahrami , Amir-Erfan Sharifi , Mahziyar Ghaedi","doi":"10.1016/j.ijthermalsci.2026.110706","DOIUrl":"10.1016/j.ijthermalsci.2026.110706","url":null,"abstract":"<div><div>The increasing heat flux in compact electronic devices necessitates advanced cooling solutions that exceed the capabilities of conventional microchannel heat sinks (MCHSs). This study presents a novel design using anisotropic gradient porous fins within MCHSs to achieve superior thermal performance while managing hydraulic penalties. The key innovation involves combining directional permeability anisotropy with graded Darcy numbers (10<sup>−1</sup> – 10<sup>−4</sup>) to enable simultaneous heat transfer enhancement and flow resistance control. Eleven configurations, including a solid-fin baseline and various porous arrangements (uniform, stepwise, and linear gradients), were numerically investigated. The influence of Reynolds number (Re = 100–1000), fin thickness ratio (a<sub>1</sub>/a<sub>3</sub> = 0.167–0.35), and fin height ratio (h<sub>2</sub>/a<sub>3</sub> = 0.3–2.0) on thermohydraulic performance was systematically evaluated under a constant heat flux. Results show that Configuration 5 (stepwise decreasing permeability) achieved a 76.84 % reduction in thermal resistance and a 3594.71 % performance gain over the baseline at Re = 500. Increasing fin thickness from a<sub>1</sub>/a<sub>3</sub> = 0.167 to 0.35 led to a 79.54 % drop in thermal resistance and a 4592.18 % increase in performance metric, while increasing height to h<sub>2</sub>/a<sub>3</sub> = 2.0 resulted in a 5159.31 % improvement. Performance continued to rise with Reynolds number, reaching 4000 % improvement in performance metric at Re = 1000. These findings validate anisotropic gradient porous fins as a transformative approach for next-generation, high-flux thermal management systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110706"},"PeriodicalIF":5.0,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146024190","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 : 2026-01-24DOI: 10.1016/j.ijthermalsci.2026.110722
Weifeng Deng , Wenjie Zhang , Yaosong Huang
This paper investigates silica particles behavior during large-size fused silica glass synthesis by multi-burner CVD method using a comprehensive numerical model that couples turbulent flow, chemical reactions, and particle dynamics. We systematically analyze how three key process parameters—the height of the deposition surface, the number of burners, and the hydrogen/oxygen equivalence ratio— affect particle growth and deposition. The results show that the deposition height and burner count alter particle size, spatial distribution, and deposition uniformity by modifying the flow-field structure and the spatial distribution of heat release. The hydrogen/oxygen equivalence ratio controls particle nucleation and growth by altering the flame environment and vapor supersaturation. A deposition height of H = 0.6 m, a stoichiometric equivalence ratio (φ = 1.0), and four burners together produce the most uniform particle growth and the highest deposition efficiency. Under these conditions, heat and mass transport are balanced, which improves both the optical quality and the dimensional stability of the synthesized glass. This study offers quantitative guidance for scaling up production of high-performance fused silica glass with enhanced optical homogeneity.
{"title":"Effects of process parameters on the growth and deposition of silica particles during multi-burner CVD synthesis of large-size fused silica glass","authors":"Weifeng Deng , Wenjie Zhang , Yaosong Huang","doi":"10.1016/j.ijthermalsci.2026.110722","DOIUrl":"10.1016/j.ijthermalsci.2026.110722","url":null,"abstract":"<div><div>This paper investigates silica particles behavior during large-size fused silica glass synthesis by multi-burner CVD method using a comprehensive numerical model that couples turbulent flow, chemical reactions, and particle dynamics. We systematically analyze how three key process parameters—the height of the deposition surface, the number of burners, and the hydrogen/oxygen equivalence ratio— affect particle growth and deposition. The results show that the deposition height and burner count alter particle size, spatial distribution, and deposition uniformity by modifying the flow-field structure and the spatial distribution of heat release. The hydrogen/oxygen equivalence ratio controls particle nucleation and growth by altering the flame environment and vapor supersaturation. A deposition height of <em>H</em> = 0.6 m, a stoichiometric equivalence ratio (φ = 1.0), and four burners together produce the most uniform particle growth and the highest deposition efficiency. Under these conditions, heat and mass transport are balanced, which improves both the optical quality and the dimensional stability of the synthesized glass. This study offers quantitative guidance for scaling up production of high-performance fused silica glass with enhanced optical homogeneity.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110722"},"PeriodicalIF":5.0,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074395","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 : 2026-01-24DOI: 10.1016/j.ijthermalsci.2026.110718
Jun Zheng (郑俊) , Yibiao Chen (陈一镖) , Nuo Chen (陈诺) , Decai Li (李德才) , Hongming Zhou (周宏明) , Yanjuan Zhang (张艳娟) , Qi Pan (潘琦)
Ferrofluid, valuable for its fluidity and magnetic response, is extensively employed in sealing applications. The sealing capability of ferrofluid is limited by temperature elevation resulting from viscous dissipation, with heat transfer efficiency strongly dependent on thermal conductivity. Although magnetic fields are recognized to modulate the thermal conductivity of ferrofluids, the governing mechanisms under high-field sealing conditions, particularly the impact of excessive aggregation, remain inadequately elucidated. This study employs a multiscale methodology integrating microstructure analysis with macroscopic thermal transport modeling. A modified effective medium theory incorporating magnetic aggregation effects is coupled with microscale heat transfer simulations and experimental validation. Through this framework, the influence of magnetic aggregation on thermal transport under high magnetic fields is systematically examined. The findings indicate that the synergistic action of intense magnetic fields and spatial confinement promotes excessive particle aggregation, giving rise to dense transverse aggregates that ultimately restrict the enhancement of macroscopic thermal conductivity. The elucidated multiscale evolution mechanism offers theoretical insights and technical guidance for advancing thermal management strategies in high-end equipment, precision manufacturing, and energy systems.
{"title":"Correlation between microstructure and macroscopic thermal transport: Mechanism of thermal conductivity variation in ferrofluids in a sealed high magnetic field","authors":"Jun Zheng (郑俊) , Yibiao Chen (陈一镖) , Nuo Chen (陈诺) , Decai Li (李德才) , Hongming Zhou (周宏明) , Yanjuan Zhang (张艳娟) , Qi Pan (潘琦)","doi":"10.1016/j.ijthermalsci.2026.110718","DOIUrl":"10.1016/j.ijthermalsci.2026.110718","url":null,"abstract":"<div><div>Ferrofluid, valuable for its fluidity and magnetic response, is extensively employed in sealing applications. The sealing capability of ferrofluid is limited by temperature elevation resulting from viscous dissipation, with heat transfer efficiency strongly dependent on thermal conductivity. Although magnetic fields are recognized to modulate the thermal conductivity of ferrofluids, the governing mechanisms under high-field sealing conditions, particularly the impact of excessive aggregation, remain inadequately elucidated. This study employs a multiscale methodology integrating microstructure analysis with macroscopic thermal transport modeling. A modified effective medium theory incorporating magnetic aggregation effects is coupled with microscale heat transfer simulations and experimental validation. Through this framework, the influence of magnetic aggregation on thermal transport under high magnetic fields is systematically examined. The findings indicate that the synergistic action of intense magnetic fields and spatial confinement promotes excessive particle aggregation, giving rise to dense transverse aggregates that ultimately restrict the enhancement of macroscopic thermal conductivity. The elucidated multiscale evolution mechanism offers theoretical insights and technical guidance for advancing thermal management strategies in high-end equipment, precision manufacturing, and energy systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110718"},"PeriodicalIF":5.0,"publicationDate":"2026-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146074471","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 : 2026-01-23DOI: 10.1016/j.ijthermalsci.2026.110720
Tairu Chen , Wenbin Fei , Guillermo A. Narsilio
The efficiency of both thermal energy storages and borehole ground heat exchangers in shallow geothermal systems depends on the energy storage and heat transfer rate of the backfilling materials used. Phase change materials (PCMs) can store and release heat at a relatively constant temperature (large latent heat). Incorporating PCMs into backfills can improve overall thermal energy density and thus benefit thermal energy storage and shallow geothermal energy systems. However, due to the low thermal conductivity of PCMs, the overall heat transfer rate through these backfill mixtures may be reduced. Therefore, other additives are needed to increase heat transfer efficiency, while maintaining the enhanced thermal storage effect on the backfill material. Graphite is a candidate for this purpose given its superior thermal conductivity. In addition, glass fines are used in this work, to explore a novel approach for recycling glass waste. Dry mixtures are prepared with different proportions of encapsulated PCMs (EPCMs), graphite and glass fines, and their heat capacity and thermal conductivity are measured in the laboratory. Furthermore, the internal structure of the mixture is observed via imagining techniques including scanning electron microscope and computed tomography. Grain-scale numerical simulations based on the obtained images reveals the particle-scale heat transfer pattern in the proposed backfill mixture materials. Experimental results show that incorporating EPCMs and graphite can lead to an average of 40 % increase in heat capacity without sacrificing thermal conductivity. The advanced numerical modelling shows that heat transfer is mainly determined by the contacts and distribution of glass fines in the mixtures, and that EPCMs under phase transition hinder overall heat transfer.
{"title":"Enhancing thermal properties: Understanding the combined effect of granular phase change materials and graphite in dry mixtures","authors":"Tairu Chen , Wenbin Fei , Guillermo A. Narsilio","doi":"10.1016/j.ijthermalsci.2026.110720","DOIUrl":"10.1016/j.ijthermalsci.2026.110720","url":null,"abstract":"<div><div>The efficiency of both thermal energy storages and borehole ground heat exchangers in shallow geothermal systems depends on the energy storage and heat transfer rate of the backfilling materials used. Phase change materials (PCMs) can store and release heat at a relatively constant temperature (large latent heat). Incorporating PCMs into backfills can improve overall thermal energy density and thus benefit thermal energy storage and shallow geothermal energy systems. However, due to the low thermal conductivity of PCMs, the overall heat transfer rate through these backfill mixtures may be reduced. Therefore, other additives are needed to increase heat transfer efficiency, while maintaining the enhanced thermal storage effect on the backfill material. Graphite is a candidate for this purpose given its superior thermal conductivity. In addition, glass fines are used in this work, to explore a novel approach for recycling glass waste. Dry mixtures are prepared with different proportions of encapsulated PCMs (EPCMs), graphite and glass fines, and their heat capacity and thermal conductivity are measured in the laboratory. Furthermore, the internal structure of the mixture is observed via imagining techniques including scanning electron microscope and computed tomography. Grain-scale numerical simulations based on the obtained images reveals the particle-scale heat transfer pattern in the proposed backfill mixture materials. Experimental results show that incorporating EPCMs and graphite can lead to an average of 40 % increase in heat capacity without sacrificing thermal conductivity. The advanced numerical modelling shows that heat transfer is mainly determined by the contacts and distribution of glass fines in the mixtures, and that EPCMs under phase transition hinder overall heat transfer.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"224 ","pages":"Article 110720"},"PeriodicalIF":5.0,"publicationDate":"2026-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146023756","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 : 2026-01-22DOI: 10.1016/j.ijthermalsci.2026.110707
Amjid Rashid , Tenglong Cong , Hanyang Gu
In order to guarantee that electronics modules function at their design temperature for enhanced production and duration, thermal management is essential. The quantity of heat that needs to be dissipated per area rises in parallel with the compactness and power density of modern electronic equipment. The design of heat sinks that can sustain a low operational temperature and a small packing environment is therefore required. The geometric flexibility offered by topology optimization makes it a valuable tool for creating passive heat sinks that can reject as much heat as feasible in a constrained area. Convective heat transference problem established on the power law type non-Newtonian fluid is subjected to topology optimization. By optimizing non-Newtonian cooling device topology utilizing a material distribution-based optimization approach, a heat transfer maximization problem is investigated. Expending a design variable, specifically the “material density” to distinguish between the fluid and solid domains, is the methods core principle. An adjoint-based analysis procedure is used to update it depending on the gradient information. A numerical investigation is conducted into the non-Newtonian effect on the ideal arrangements of thermal devices. Our findings demonstrate that as the pressure differential or heat generation rises, extra branching flow channels are seen in the ideal designs. As compared to previous results, the current finding shows that the best arrangement is dependent on the power law index, and an advanced power law index can lead to lower flow rates and more complicated setups. Furthermore, the flow distribution design might offer the lowest hydrodynamic resistance, while the heat transfer increase design can reduce thermal resistance. Under the same conditions, the optimum design of the maximum power index problem performs significantly well in terms of heat transmission than the low index one. Our research could provide a mechanism for non-Newtonian fluid-based TO thermal devices, such as non-Newtonian heat sinks. The suggested design approach can be applied as a tool to offer cooling solutions for electronic components having a large heat flow thermal management.
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