International Journal of Thermal Sciences最新文献_第6页

Thermal-resistance modeling of free convection in metal foam for electronics cooling

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-29 DOI: 10.1016/j.ijthermalsci.2025.109901

N. Dukhan , H. Klatzke , M. Liang , M. Ghannam , D. Ramaswamy

Metal foams have been investigated for both forced and free convection heat transfer applications. However, there appear to be no engineering models for determining the thermal resistance of metal foams when used in free convection. In this paper, a new engineering model is presented to fill this gap. The model is developed from first principles of heat transfer and the concept of thermal resistance network. It identifies the various resistances present inside the foam, and the associated temperature difference for each resistance. A few coefficients were needed to calibrate the model, and they were determined from experimental data on an actual aluminum foam sample having 20 pores per inch (ppi) and a porosity of 76.4 %. The dimensions of the foam sample were 109 mm by 110 mm by 20 mm. The sample was subjected to three heat fluxes: 884.1 W/m², 1217.7 W/m² and 1884.9 W/m², and was cooled by room air. Subsequently, the model of the thermal resistance of the foam was validated by further experiments on three foam samples having different materials and morphological properties. These samples included aluminum and copper foam, and had porosities in the range 74.5 %–78.0 %. There was very good agreement between the thermal resistances of the foam as predicted by the model and their experimental counterparts. The heated wall temperature was predicted by the model within reasonable error. The model allows optimization of metal foam in terms of pore density and porosity for free convection. The model also shows that no advantage is gained by using copper foam as opposed to aluminum foam for passive cooling.

{"title":"Thermal-resistance modeling of free convection in metal foam for electronics cooling","authors":"N. Dukhan , H. Klatzke , M. Liang , M. Ghannam , D. Ramaswamy","doi":"10.1016/j.ijthermalsci.2025.109901","DOIUrl":"10.1016/j.ijthermalsci.2025.109901","url":null,"abstract":"<div><div>Metal foams have been investigated for both forced and free convection heat transfer applications. However, there appear to be no engineering models for determining the thermal resistance of metal foams when used in free convection. In this paper, a new engineering model is presented to fill this gap. The model is developed from first principles of heat transfer and the concept of thermal resistance network. It identifies the various resistances present inside the foam, and the associated temperature difference for each resistance. A few coefficients were needed to calibrate the model, and they were determined from experimental data on an actual aluminum foam sample having 20 pores per inch (ppi) and a porosity of 76.4 %. The dimensions of the foam sample were 109 mm by 110 mm by 20 mm. The sample was subjected to three heat fluxes: 884.1 W/m<sup>2</sup>, 1217.7 W/m<sup>2</sup> and 1884.9 W/m<sup>2</sup>, and was cooled by room air. Subsequently, the model of the thermal resistance of the foam was validated by further experiments on three foam samples having different materials and morphological properties. These samples included aluminum and copper foam, and had porosities in the range 74.5 %–78.0 %. There was very good agreement between the thermal resistances of the foam as predicted by the model and their experimental counterparts. The heated wall temperature was predicted by the model within reasonable error. The model allows optimization of metal foam in terms of pore density and porosity for free convection. The model also shows that no advantage is gained by using copper foam as opposed to aluminum foam for passive cooling.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109901"},"PeriodicalIF":4.9,"publicationDate":"2025-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143725180","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

Photon tunneling mechanism and performance analysis of near-field thermophotovoltaic system with plasmonic emitter

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-29 DOI: 10.1016/j.ijthermalsci.2025.109886

Song Li , Guoyun Wang , Jiduo Dong , Junming Zhao

Performance of thermophotovoltaic (TPV) system can be significantly improved by incorporating photon tunneling. In the near-field thermophotovoltaic system (NF-TPV) containing plasmonic emitter, where surface plasmon polaritons (SPPs) excited at the vacuum-plasmonic emitter interface may couple with total internal reflection (TR) mode to result in the TR-SPPs mode, or other electromagnetic modes. In this work, we investigate the photon tunneling mechanism and its impact on the performance of NF-TPV system with plasmonic emitter. Analytical formula of the dispersion relation of the TR-SPPs mode is derived. The mechanism of self-coupled SPPs mode is clarified. These mechanisms undergo transitions at different separation distances. As the distance decreases, TR-SPPs mode is suppressed, while the self-coupled SPPs mode progressively assumes a dominant role, which significantly enhances the spectral radiative heat flux surpassing the bandgap. The spectral changes increase the power density as the distance decreases. Especially, the efficiency can be significantly improved when NFRHT is primarily mediated by the self-coupled SPPs mode. These findings enhance the comprehension of photon tunneling mechanism and provide guidance for NF-TPV system design and optimization.

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引用次数: 0

Micro-CT investigation of urea crystal structures for frost analysis

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-27 DOI: 10.1016/j.ijthermalsci.2025.109893

A. Labuschagne, T. Zhu, W. Rohlfs

Frost formation poses a significant challenge to the design and efficiency of air-source evaporator units. To model frost formation, a detailed understanding of the evolving three-dimensional microstructures that influence thermal and mass transport properties is essential. However, direct measurement of frost microstructures remains challenging. This study demonstrates that Micro-CT, combined with finite-element modelling, is a viable method for evaluating transport properties in complex microstructures. Using urea mushy layers as a stable, non-melting analogue, we successfully validated the methodology by resolving microstructural influences on thermal conductivity and mass diffusivity.

Our results highlight the significant role of structural complexity in transport behaviour, with ‘simple’ and ‘complex’ formations influencing heat and mass transfer differently. Deviations of at least 26.6 % between measured properties and predictions from empirical bulk-property models confirm that conventional approaches fail to capture the effects of structural heterogeneity. While these findings do not directly translate to frost formation, the validated methodology offers a foundation for improving frost prediction models by incorporating high-resolution structural data, ultimately enhancing the accuracy of thermal system designs in frost-prone environments.

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引用次数: 0

Understanding the coupled thermo-electro-osmotic transport in asymmetrically charged nanochannels

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-27 DOI: 10.1016/j.ijthermalsci.2025.109872

Muhammad Farhan , Wenyao Zhang , Qiuwang Wang , Cunlu Zhao

Nanofluidic thermo-diffusion, encompassing both thermo-electric and thermo-osmotic effects, is gaining increasing attention for applications in low-grade thermal energy conversion, bio-molecular sensing, charge separation, and desalination. However, the influence of asymmetric surface charge density in thermally-driven nanochannel configurations has remained largely unexplored. This study presents a computational investigation using the extended Nernst–Planck–Poisson–Navier–Stokes and energy equations to examine the effects of Debye length and surface charge configurations (unipolar vs. bipolar) on thermo-electro-osmotic characteristics in nanochannels. Two electrolyte solutions, NaCl and NaI, were assessed, with a focus on ion-specific thermophobic and thermophilic behaviors. The results reveal that unipolar channels show a strong dependence on the Debye length, with significant effects on short-circuit current and Seebeck coefficient, while bipolar configurations exhibit rectified and monotonic behavior that is largely independent of surface charge density. Thermo-osmotic coefficients, evaluated under both short- and open-circuit conditions, demonstrate that bipolar channels accumulate responses with decreasing Debye length, contrasting with the discrete shifts observed in unipolar channels. The superior thermophoretic properties of

I^{-}

in NaI solutions consistently lead to higher performance compared to NaCl, particularly in specific bipolar configurations. These findings underscore the critical role of surface charge polarity and ionic mobility in influencing the magnitude and direction of thermo-electro-osmotic responses, highlighting the potential of asymmetric nanochannels to achieve controlled ionic transport and rectification. This work provides essential insights for the design of next-generation nanofluidic devices and advances our understanding of thermally-driven transport phenomena in nanofluidic systems.

{"title":"Understanding the coupled thermo-electro-osmotic transport in asymmetrically charged nanochannels","authors":"Muhammad Farhan , Wenyao Zhang , Qiuwang Wang , Cunlu Zhao","doi":"10.1016/j.ijthermalsci.2025.109872","DOIUrl":"10.1016/j.ijthermalsci.2025.109872","url":null,"abstract":"<div><div>Nanofluidic thermo-diffusion, encompassing both thermo-electric and thermo-osmotic effects, is gaining increasing attention for applications in low-grade thermal energy conversion, bio-molecular sensing, charge separation, and desalination. However, the influence of asymmetric surface charge density in thermally-driven nanochannel configurations has remained largely unexplored. This study presents a computational investigation using the extended Nernst–Planck–Poisson–Navier–Stokes and energy equations to examine the effects of Debye length and surface charge configurations (unipolar vs. bipolar) on thermo-electro-osmotic characteristics in nanochannels. Two electrolyte solutions, NaCl and NaI, were assessed, with a focus on ion-specific thermophobic and thermophilic behaviors. The results reveal that unipolar channels show a strong dependence on the Debye length, with significant effects on short-circuit current and Seebeck coefficient, while bipolar configurations exhibit rectified and monotonic behavior that is largely independent of surface charge density. Thermo-osmotic coefficients, evaluated under both short- and open-circuit conditions, demonstrate that bipolar channels accumulate responses with decreasing Debye length, contrasting with the discrete shifts observed in unipolar channels. The superior thermophoretic properties of <span><math><msup><mrow><mtext>I</mtext></mrow><mrow><mo>−</mo></mrow></msup></math></span> in NaI solutions consistently lead to higher performance compared to NaCl, particularly in specific bipolar configurations. These findings underscore the critical role of surface charge polarity and ionic mobility in influencing the magnitude and direction of thermo-electro-osmotic responses, highlighting the potential of asymmetric nanochannels to achieve controlled ionic transport and rectification. This work provides essential insights for the design of next-generation nanofluidic devices and advances our understanding of thermally-driven transport phenomena in nanofluidic systems.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109872"},"PeriodicalIF":4.9,"publicationDate":"2025-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714312","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

Forced convection in laminar flow with nonlinear viscoelastic fluids in non-circular ducts including viscous dissipation: Giesekus fluids

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-27 DOI: 10.1016/j.ijthermalsci.2025.109873

Gonzalo D. Álvarez, Mario F. Letelier, Dennis A. Siginer

Heat transfer enhancement for a steady, laminar, incompressible and axially fully developed flow of nonlinear viscoelastic shear-thinning fluids abiding by the Giesekus constitutive structure in straight microtubes of arbitrary non-circular contour under constant heat flux at the walls is investigated. The governing equations are solved based on an embedded double asymptotic series expansion pivoted around the elasticity measure Weissenberg number

W i

and a mapping parameter

ε .

The effects of the constitutive parameters of the Giesekus model as well as the dimensionless flow parameters on the flow and heat transfer in microtubes of a wide-ranging spectrum of non-circular cross-sectional contours are investigated. The flow and thermal fields of representative tubes with equilateral triangular, square, rectangular, and pentagonal cross-sections are investigated in detail. The analysis reveals that the constitutive mobility parameter

α

, viscosity ratio

β

and the Weissenberg number

W i

significantly influence the Nusselt number

N u

together with the flow characteristics, the Péclet Pe, Brinkman Br and Reynolds Re numbers. Effects of the viscous dissipation in wall cooling and wall heating is studied. At a given value of

W i

heat transfer is enhanced regardless the process considered at the boundary. In all cases, heat transfer is improved compared to Newtonian fluids, with the strongest enhancement observed in rectangular microtubes for low-inertia flows.

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引用次数: 0

Influences of wall materials on flow and thermal performance of S-CO2 at high pressure and heat flux

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-26 DOI: 10.1016/j.ijthermalsci.2025.109899

Yuan Ma , Gongnan Xie , Wujun Wang

Since supercritical carbon dioxide (S-CO₂) systems usually have to work at both high temperature, high pressure and high heat flux, selecting appropriate solid materials is of great important to their system safety. In this study, the thermofluidic characteristics of supercritical carbon dioxide (S-CO₂) in a horizontal rectangular channel have been investigated under high pressure and one-side-wall heated with high heat flux. Four different solid wall materials (253 MA, Inconel 617, Haynes 230 and Haynes 233) and three different heat flux values (1.5 MW/m², 2.0 MW/m² and 2.5 MW/m²) are selected for analyzing the impacts of wall material and heat flux boundary conditions. The results showed that the maximum wall temperature difference of all four wall materials can generally exceed 100 K under the minimum heat flux, and can reach 500 K for Haynes 233 at the heat flux of 2.5 MW/m². Considering the maximum allowable stress and creep characteristics, Inconel 617 has more obvious advantages as a solid material at the heat flux below 2 MW/m², while Haynes 230 is a better choice at the heat flux beyond 2 MW/m² because of the stronger mechanical properties. By exploring the effect of inlet temperature, it is found that the inlet temperature close to the pseudo-critical temperature is conducive to flow and heat transfer. Taking the effect of buoyancy into account, it is shown that the temperature of the heating surface is decreased, the deterioration of heat transfer is weakened and occurs early, and the difference on the cross sections of the wall temperature decreases.

{"title":"Influences of wall materials on flow and thermal performance of S-CO2 at high pressure and heat flux","authors":"Yuan Ma , Gongnan Xie , Wujun Wang","doi":"10.1016/j.ijthermalsci.2025.109899","DOIUrl":"10.1016/j.ijthermalsci.2025.109899","url":null,"abstract":"<div><div>Since supercritical carbon dioxide (S-CO<sub>2</sub>) systems usually have to work at both high temperature, high pressure and high heat flux, selecting appropriate solid materials is of great important to their system safety. In this study, the thermofluidic characteristics of supercritical carbon dioxide (S-CO<sub>2</sub>) in a horizontal rectangular channel have been investigated under high pressure and one-side-wall heated with high heat flux. Four different solid wall materials (253 MA, Inconel 617, Haynes 230 and Haynes 233) and three different heat flux values (1.5 MW/m<sup>2</sup>, 2.0 MW/m<sup>2</sup> and 2.5 MW/m<sup>2</sup>) are selected for analyzing the impacts of wall material and heat flux boundary conditions. The results showed that the maximum wall temperature difference of all four wall materials can generally exceed 100 K under the minimum heat flux, and can reach 500 K for Haynes 233 at the heat flux of 2.5 MW/m<sup>2</sup>. Considering the maximum allowable stress and creep characteristics, Inconel 617 has more obvious advantages as a solid material at the heat flux below 2 MW/m<sup>2</sup>, while Haynes 230 is a better choice at the heat flux beyond 2 MW/m<sup>2</sup> because of the stronger mechanical properties. By exploring the effect of inlet temperature, it is found that the inlet temperature close to the pseudo-critical temperature is conducive to flow and heat transfer. Taking the effect of buoyancy into account, it is shown that the temperature of the heating surface is decreased, the deterioration of heat transfer is weakened and occurs early, and the difference on the cross sections of the wall temperature decreases.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109899"},"PeriodicalIF":4.9,"publicationDate":"2025-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714313","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}

引用次数: 0

A novel spectral emissivity model for rough surfaces applicable beyond geometrical optics region 粗糙表面的新型光谱发射率模型，适用于几何光学以外的区域

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-25 DOI: 10.1016/j.ijthermalsci.2025.109887

Wu Jiangyuan , Wang Ningtao , Dong Wei , An Baolin , Peng Bo , Yang Zhen , Duan Yuanyuan

The accurate prediction of emissivity for rough surfaces is critical in fields such as solar thermal energy and radiation thermometry. For practical rough surfaces, directly solving electromagnetic equations is computationally intensive and often lacks analytical solutions. Geometrical optics approximation offers computational efficiency and, in some cases, explicit formulas. However, their applicability is inherently limited, particularly for surfaces with steep slopes or small σ/λ ratios. This paper introduces a formula for calculating a roughness factor based on Gaussian random rough surfaces and presents a concise, wide-range emissivity model that integrates the Finite-Difference Time-Domain (FDTD) method. Results demonstrate that the predicted roughness factor deviates by less than 5 % compared to measurements of sandblasted surfaces, while the derived emissivity values exhibit a maximum relative deviation of less than 3 % from experimental results. In regions where geometrical optics approximation is invalid, emissivity is governed by two dimensionless parameters: σ/τ and σ/λ, within specific ranges. By incorporating an effective roughness factor related to σ/λ into the geometrical optics model, the proposed approach significantly extends the model's applicability. The new model reduces the maximum absolute error compared to FDTD results from 0.43 (using conventional geometrical optics models) to 0.09. This study addresses the limitations of existing emissivity models for rough surfaces where geometrical optics approximation fails, while advancing the understanding of how surface morphology influences emissivity.

{"title":"A novel spectral emissivity model for rough surfaces applicable beyond geometrical optics region","authors":"Wu Jiangyuan , Wang Ningtao , Dong Wei , An Baolin , Peng Bo , Yang Zhen , Duan Yuanyuan","doi":"10.1016/j.ijthermalsci.2025.109887","DOIUrl":"10.1016/j.ijthermalsci.2025.109887","url":null,"abstract":"<div><div>The accurate prediction of emissivity for rough surfaces is critical in fields such as solar thermal energy and radiation thermometry. For practical rough surfaces, directly solving electromagnetic equations is computationally intensive and often lacks analytical solutions. Geometrical optics approximation offers computational efficiency and, in some cases, explicit formulas. However, their applicability is inherently limited, particularly for surfaces with steep slopes or small <em>σ</em>/<em>λ</em> ratios. This paper introduces a formula for calculating a roughness factor based on Gaussian random rough surfaces and presents a concise, wide-range emissivity model that integrates the Finite-Difference Time-Domain (FDTD) method. Results demonstrate that the predicted roughness factor deviates by less than 5 % compared to measurements of sandblasted surfaces, while the derived emissivity values exhibit a maximum relative deviation of less than 3 % from experimental results. In regions where geometrical optics approximation is invalid, emissivity is governed by two dimensionless parameters: <em>σ</em>/<em>τ</em> and <em>σ</em>/<em>λ</em>, within specific ranges. By incorporating an effective roughness factor related to <em>σ</em>/<em>λ</em> into the geometrical optics model, the proposed approach significantly extends the model's applicability. The new model reduces the maximum absolute error compared to FDTD results from 0.43 (using conventional geometrical optics models) to 0.09. This study addresses the limitations of existing emissivity models for rough surfaces where geometrical optics approximation fails, while advancing the understanding of how surface morphology influences emissivity.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109887"},"PeriodicalIF":4.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143696150","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

Element mixing and solidification behavior during multi-track overlapping laser deposition of Cr-based alloys

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-25 DOI: 10.1016/j.ijthermalsci.2025.109890

Gaosong Li , Xinjian Yin , Yanqing Lai , Wenfeng Bai , Suai Zhang , Zhenya Wang

Multi-track overlapping laser deposition has been applied more widely than single track laser deposition in engineering practices. However, it is difficult to predict the solidification behavior and element mixing of multi-track overlapping laser deposition layers under existing conditions. Hence, in this paper, we not only derive the formula for calculating the arbitrary arc length of the overlapping cross-section, but also establish a three-dimensional multi-track overlapping laser deposition element mixing and solidification behavior prediction model. By the proposed model, the solidification behaviors of multi-track overlapping deposition layer and element concentrations of iron (Fe), nickel (Ni) and chromium (Cr) are predicted. The element redistribution and remelting solidification characteristics of the overlapping zone are further investigated. The results reveal that the element of Cr in the overlapping zone is 2 wt % higher than the first track non-overlapping zone. With the increase of deposition track, the concentrations of elements in the deposition layer tend to be uniform. The Peclet_m number, convection time and mixing velocity of the melt pool in the track joint decrease significantly, but these values are still 1.5, 3.5 and 1.5 times higher than at the beginning (35 ms) of first track, respectively. Meanwhile, the change in crystal size and morphology of deposition layer is predicted according to cooling rate (

G s ∙ R s

) and morphological parameters (G/R). The crystal size gradually increases from the top to the bottom of the deposition layer, and the morphology changes from equiaxed dendritic, columnar, and cellular crystals to planar crystals. In addition, the element distribution at the edge of multi-track overlapping laser deposition is uneven than in other regions.

{"title":"Element mixing and solidification behavior during multi-track overlapping laser deposition of Cr-based alloys","authors":"Gaosong Li , Xinjian Yin , Yanqing Lai , Wenfeng Bai , Suai Zhang , Zhenya Wang","doi":"10.1016/j.ijthermalsci.2025.109890","DOIUrl":"10.1016/j.ijthermalsci.2025.109890","url":null,"abstract":"<div><div>Multi-track overlapping laser deposition has been applied more widely than single track laser deposition in engineering practices. However, it is difficult to predict the solidification behavior and element mixing of multi-track overlapping laser deposition layers under existing conditions. Hence, in this paper, we not only derive the formula for calculating the arbitrary arc length of the overlapping cross-section, but also establish a three-dimensional multi-track overlapping laser deposition element mixing and solidification behavior prediction model. By the proposed model, the solidification behaviors of multi-track overlapping deposition layer and element concentrations of iron (Fe), nickel (Ni) and chromium (Cr) are predicted. The element redistribution and remelting solidification characteristics of the overlapping zone are further investigated. The results reveal that the element of Cr in the overlapping zone is 2 wt % higher than the first track non-overlapping zone. With the increase of deposition track, the concentrations of elements in the deposition layer tend to be uniform. The Peclet<sub>m</sub> number, convection time and mixing velocity of the melt pool in the track joint decrease significantly, but these values are still 1.5, 3.5 and 1.5 times higher than at the beginning (35 ms) of first track, respectively. Meanwhile, the change in crystal size and morphology of deposition layer is predicted according to cooling rate (<span><math><mrow><mi>G</mi><mi>s</mi><mo>∙</mo><mi>R</mi><mi>s</mi></mrow></math></span>) and morphological parameters (<em>G/R</em>). The crystal size gradually increases from the top to the bottom of the deposition layer, and the morphology changes from equiaxed dendritic, columnar, and cellular crystals to planar crystals. In addition, the element distribution at the edge of multi-track overlapping laser deposition is uneven than in other regions.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109890"},"PeriodicalIF":4.9,"publicationDate":"2025-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143714317","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

Physical model and multiple moth-flame optimization fusion temperature field prediction in large-space building fires

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-24 DOI: 10.1016/j.ijthermalsci.2025.109892

Bin Sun

To achieve accurate and fast temperature field prediction in large-space building fires, a fusion method is developed, which combines a developed physical model based on heat transfer as well as physical characteristics and an improved multiple moth-flame optimization. The artificial intelligence-based method has advantages like real-time prediction, physical explanations, and no prior data training. According to these advantages, the method can meet the real firefighting application requirements. Supported by two numerical cases of temperature predictions in a large underground parking fire and a large logistics warehouse fire, the results support that the developed method is effective and superior to the traditional moth-flame optimization algorithm and its variant. The developed fusion method of the physical model and multiple Moth-flame optimization can support an effective and useful tool to achieve quick temperature field prediction in large-space building fires for better fire rescue.

引用次数: 0

Optimization of tapered pin fins for enhanced heat transfer in microchannel heat sink 优化锥形针翅片以增强微通道散热器的传热效果

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences

Pub Date : 2025-03-24 DOI: 10.1016/j.ijthermalsci.2025.109889

Tabish Alam , Md Muslim Ansari , Kishor S. Kulakrni , Injamamul Haque , Naushad Ali

Microchannel heat sinks (MHSs) are critical components in thermal management applications, such as photovoltaic thermal (PVT) collectors, where efficient heat dissipation is essential to enhance system performance and maintain temperature stability. Despite the growing adoption of MHS, there remain research gaps concerning the optimization of pin fin geometries for improved thermohydraulic performance. This study investigates tapered-angle pin fins with angles of 15°, 20°, 25°, 30°, and 35° along with similar dissected ribs on the wall in MHS under laminar flow conditions with Reynolds numbers ranging from 100 to 900. Numerical simulations were conducted to evaluate the effects of these pin fin angles on key performance parameters: Nusselt number, friction factor, pumping power, and Thermo-hydraulic Performance Parameter (THPP). The results indicate that smaller taper angles (e.g., θ = 15°) are more effective at lower Reynolds numbers (e.g., Re = 100), achieving a Nusselt number of 9.81. However, as the flow rate increases (e.g., Re = 900), larger taper angles such as θ = 30° perform better, with the Nusselt number reaching approximately 30.62. The friction factor data reveal that larger angles, while enhancing heat transfer, also increase flow resistance, impacting the overall hydraulic efficiency. At Re = 900, the highest friction factor is observed for θ = 35° (0.191). THPP values consistently remain above 1, confirming the effectiveness of pin fin designs, with θ = 30° achieving the highest value (1.77) at Re = 900. These findings highlight the importance of selecting optimal taper angles to balance thermal performance and hydraulic efficiency, filling existing research gaps and advancing the design of MHS for PVT collectors and other high-performance applications.

{"title":"Optimization of tapered pin fins for enhanced heat transfer in microchannel heat sink","authors":"Tabish Alam , Md Muslim Ansari , Kishor S. Kulakrni , Injamamul Haque , Naushad Ali","doi":"10.1016/j.ijthermalsci.2025.109889","DOIUrl":"10.1016/j.ijthermalsci.2025.109889","url":null,"abstract":"<div><div>Microchannel heat sinks (MHSs) are critical components in thermal management applications, such as photovoltaic thermal (PVT) collectors, where efficient heat dissipation is essential to enhance system performance and maintain temperature stability. Despite the growing adoption of MHS, there remain research gaps concerning the optimization of pin fin geometries for improved thermohydraulic performance. This study investigates tapered-angle pin fins with angles of 15°, 20°, 25°, 30°, and 35° along with similar dissected ribs on the wall in MHS under laminar flow conditions with Reynolds numbers ranging from 100 to 900. Numerical simulations were conducted to evaluate the effects of these pin fin angles on key performance parameters: Nusselt number, friction factor, pumping power, and Thermo-hydraulic Performance Parameter (THPP). The results indicate that smaller taper angles (e.g., θ = 15°) are more effective at lower Reynolds numbers (e.g., Re = 100), achieving a Nusselt number of 9.81. However, as the flow rate increases (e.g., Re = 900), larger taper angles such as θ = 30° perform better, with the Nusselt number reaching approximately 30.62. The friction factor data reveal that larger angles, while enhancing heat transfer, also increase flow resistance, impacting the overall hydraulic efficiency. At Re = 900, the highest friction factor is observed for θ = 35° (0.191). THPP values consistently remain above 1, confirming the effectiveness of pin fin designs, with θ = 30° achieving the highest value (1.77) at Re = 900. These findings highlight the importance of selecting optimal taper angles to balance thermal performance and hydraulic efficiency, filling existing research gaps and advancing the design of MHS for PVT collectors and other high-performance applications.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"214 ","pages":"Article 109889"},"PeriodicalIF":4.9,"publicationDate":"2025-03-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143685416","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