International Journal of Heat and Mass Transfer最新文献

{"title":"Data integrity resolving gas-solid interfacial heat transfer coefficient in porous media under low Reynolds number","authors":"Zeyang Song ,&nbsp;Jian Wang ,&nbsp;Shaotang Hui ,&nbsp;Renkun Dai","doi":"10.1016/j.ijheatmasstransfer.2025.127803","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127803","url":null,"abstract":"<div><div>Inverse computation of gas-solid interfacial heat transfer coefficient (<em>h</em>_sg) in porous media has remained a challenging issue. This work proposes a method using data integrity of both solid (<em>T</em>_s) and gas (<em>T</em>_g) temperatures in porous media to resolve this issue. The data integrity is accomplished by simultaneous measurement of <em>T</em>_s and <em>T</em>_g developed in our previous work. <em>h</em>_sg is approximately solved by the discretized gas energy conservation equation in a central difference scheme implemented with data integrity of <em>T</em>_s and <em>T</em>_g. This solution takes advantages in reducing both computation cost and numerical uncertainty since only one unknown parameter is directly calculated from one equation. An empirical correlation of <em>Nu</em> = 0.001(<em>Re</em>^1.66<em>Pr</em>^1/3) (<em>R</em>² = 0.93) is established for low-<em>Re</em> gas flow in porous media (5 mm ≤ <em>d</em>_p ≤ 15 mm and 13 ≤ <em>Re</em> ≤ 133) based on in total 54 studied cases considering four variables of Darcy flux, particle size, porous medium, and heating temperature. The proposed method is validated by the consistent <em>Nu</em> correlations in the literature. This work gives a new perspective of data integrity to resolve the challenging inverse models for heat transfer in porous media.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127803"},"PeriodicalIF":5.8,"publicationDate":"2025-09-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145019858","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}

{"title":"3D optimization of heat sink fins using adjoint-based optimization with a CAD-based parametrization","authors":"Praharsh Pai Raikar ,&nbsp;Nitish Anand ,&nbsp;Matteo Pini ,&nbsp;Carlo De Servi","doi":"10.1016/j.ijheatmasstransfer.2025.127722","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127722","url":null,"abstract":"<div><div>This study presents an automated shape optimization method for heat sinks. The computational framework has been developed by combining a conjugate heat transfer solver with adjoint capabilities, a CAD parametrization tool, and a gradient-based optimizer. The test case considers the design optimization of a water-cooled heat sink with pin fins, with the goal of concurrently enhancing heat transfer and minimizing pressure losses. Results show that the optimized fin geometry leads to an improvement of the average heat transfer coefficient by 24% while the pressure drop is lowered by 19%. The optimal fin array features an unconventional shape with an enlarged cross-section at the hub and the top with respect to mid-span, and a variation of the pin profile in the streamwise direction. The net effect is a reduction in flow blockage, an increase in fin efficiency, and a lower and more uniform temperature distribution in the heat sink base plate.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127722"},"PeriodicalIF":5.8,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145019855","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}

{"title":"Molecular investigation of thermal conduction and local phonon transport in graphene aerogels","authors":"Honglin Liu ,&nbsp;Zifeng Wang ,&nbsp;Xuzheng Tian ,&nbsp;Karl I. Jacob ,&nbsp;Youjiang Wang","doi":"10.1016/j.ijheatmasstransfer.2025.127713","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127713","url":null,"abstract":"<div><div>Graphene aerogels (GA), renowned for their exceptional mechanical and structural features, have garnered increasing attention for their unique thermal properties. By employing molecular dynamics (MD) simulations and phonon calculations, this study systematically investigates the relationship between thermal conductivity and local phonon transport behaviors of GA and its key structural parameters—including the average length and curvature of graphene sheets, pore diameter, density, porosity, tortuosity, carbon bond density, and specific surface area. The results reveal that increased graphene sheet curvature shifts localized phonon transport toward higher frequencies, diminishing thermal transport efficiency. Higher porosity further decreases thermal conductivity, whereas longer graphene sheets and higher carbon bond densities enhance heat conduction. Additionally, by incorporating new morphological descriptors into empirical equations for density- and porosity-dependent thermal conductivity of GA, the prediction accuracy improved by approximately 22% and 51%, respectively. These findings provide a reliable framework for evaluating, predicting, and optimizing the thermal performance of GA-based materials alongside other features, advancing their design and application space in thermal management and energy systems.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127713"},"PeriodicalIF":5.8,"publicationDate":"2025-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145019856","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}

{"title":"Modeling the role of beam oscillation in reducing element segregation during dissimilar laser welding of steel and nickel alloys","authors":"Changshuai Dou ,&nbsp;Xiaoying Liu ,&nbsp;Hui-Ping Wang ,&nbsp;Yaqi Wang ,&nbsp;Chendong Shao ,&nbsp;Fenggui Lu","doi":"10.1016/j.ijheatmasstransfer.2025.127782","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127782","url":null,"abstract":"<div><div>This study presents a three-dimensional numerical model to investigate the influence of laser beam oscillation on element segregation during the welding of 9Cr steel and nickel-based dissimilar alloys. The model simulates molten pool dynamics and solidification behavior under three oscillation conditions: no oscillation, circular oscillation, and infinity-pattern oscillations. Without oscillation, significant Fe segregation occurs on the 9Cr steel side, with blocky patterns in the upper weld and band-like formations in the middle, reaching an area fraction of 25.82 %. Circular and infinity-pattern oscillations effectively reduce segregation to 7.08 % and 4.48 %, respectively. The segregation is driven by the interplay between molten pool flow and solidification dynamics, with Marangoni forces drawing Fe-rich melt toward the 9Cr side. Laser beam oscillation enhances molten pool convection, disrupting Fe accumulation and promoting mixing. Notably, infinity-pattern oscillation, characterized by higher velocity and greater backward displacement, provides superior post-heating and stirring effects. At 50 Hz frequency and 0.6 mm amplitude, it achieves the most effective suppression of Fe segregation. These findings provide valuable insights into optimizing oscillation strategies for improving weld quality in dissimilar metal joining.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127782"},"PeriodicalIF":5.8,"publicationDate":"2025-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145010099","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}

{"title":"Dynamic behaviors and stability limit of sessile droplet on dielectric surface under external electric field","authors":"Xiaoye Ren,&nbsp;Wan-Yuan Shi,&nbsp;Lang Liu,&nbsp;Meng Li","doi":"10.1016/j.ijheatmasstransfer.2025.127804","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127804","url":null,"abstract":"<div><div>Unlike droplets on conductive substrates, sessile droplets on dielectric surfaces exhibit constrained charge transportation under an external electric field, leading to distinct dynamic behaviors that remain insufficiently elucidated up to date. The present paper aims to address this issue by specifically investigating the stability limit and transient deformation response behavior of water droplets on a dielectric polyimide polymer surface through experiments. The results found that two deformation modes of droplets appeared successively with increasing electric field intensity, i.e., the tensile mode and ejection mode. For the tensile mode, the electric field, charge, and electrostatic force at droplet apex and tensile height of droplet are nonlinearly related to external electric field intensity. The tensile height is also affected by droplet volume, film thickness, and electrode-film distance. For ejection mode, the ejection frequency and length depend on droplet volume, electrode-film distance, and film thickness, but the ejection width is not affected by these parameters. The physical mechanism of ejection behavior is clarified through numerical simulation. The stability limit of droplets is elucidated through the energy minimization theory. This study provides a scientific basis and technical guidance for the manipulation and control of droplet behavior on dielectric surfaces.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127804"},"PeriodicalIF":5.8,"publicationDate":"2025-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145010153","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}

{"title":"Semiconductor field-effect near-field thermal control skin with tunable emission via voltage-controlled plasmon polariton","authors":"Guoyun Wang ,&nbsp;Deyu Xu ,&nbsp;Junming Zhao","doi":"10.1016/j.ijheatmasstransfer.2025.127801","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127801","url":null,"abstract":"<div><div>Variable emissivity coatings can manage heat flow and regulate temperature in small satellites operating under strict weight and power constraints, but their limited tuning ranges and discontinuous tunability affect their overall effectiveness. This study proposes two types of field-effect near-field thermal control skins (FENFS) to address these limitations: a <em>p</em>-<em>n</em> type with the same initial doped levels and an <em>n</em>-<em>n</em> type with different initial doped levels. Both designs enable active and continuous emissivity modulation through voltage-controlled plasmon polariton mode conversion. Results show that the maximum emissivity tuning range can reach 0.8 for the <em>p</em>-<em>n</em> type within [−3.8, 20] V and 0.7 for the <em>n</em>-<em>n</em> type within [−12.1, 3.2] V, with the <em>p</em>-<em>n</em> type achieving an emissivity below 0.1, which is suitable for heat preservation. By applying appropriate voltages, both FENFS effectively mitigate satellite surface temperature swings caused by fluctuating internal and external heat fluxes and can even maintain the surface temperature at a preset target temperature. The <em>p</em>-<em>n</em> type is better suited for low internal heat flux scenarios, whereas the <em>n</em>-<em>n</em> type performs better under higher internal heat flux cases. This study advances active emissivity control strategies for small satellite thermal management and expands the application of near-field radiative heat transfer in spacecraft systems.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127801"},"PeriodicalIF":5.8,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145004916","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}

{"title":"A novel CFD-DPM model of adaptive gridded particle for particle deposition and heat transfer analysis in wire-wrapped rod bundles","authors":"Yan Deng ,&nbsp;Huo Liang ,&nbsp;Yanfeng Huang ,&nbsp;Dong Li","doi":"10.1016/j.ijheatmasstransfer.2025.127797","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127797","url":null,"abstract":"<div><div>Lead-bismuth eutectic (LBE), employed as a coolant in lead-bismuth fast reactors, exhibits strong corrosiveness and can erode metallic components within the reactor, thereby generating corrosion particles. As the coolant circulates, these particles may accumulate along the wire-wrapped fuel assembly, potentially causing blockages and overheating, which posing serious risks of nuclear accidents. Previous studies primarily investigated the effects of blockages on coolant flow and heat transfer by artificially inserting obstruction blocks. However, in practical scenarios, particle deposition rarely results in a single, well-defined blockage. This study focuses on the behavior of particle deposition and heat transfer processes in wire-wrapped rod bundles. First, the thermal-hydraulic characteristics of LBE are evaluated using computational fluid dynamics. The discrete phase model is applied to calculate the deposition of corrosion particles, while an energy balance model is employed to determine the criteria for particle deposition upon collision with wall. Subsequently, an adaptive gridded particle coupling time amplification algorithm is proposed to accelerate the simulation of long-term particle deposition by converting particles into computational grids. This method is used to explore the impact of particle deposition on the thermal-hydraulic behavior of wire-wrapped rod bundles. Finally, six cases with varying particle diameters and mass fraction are conducted to analyze their influence on flow blockage and heat transfer. The results indicate that increased particle deposition leads to elevated peak wall temperatures and greater inlet-outlet pressure differentials. With a particle diameter of 15 μm and mass fraction of 8.95 × 10⁻¹⁰ wt%, after 138,890 h, the peak temperature of the wall increases by 48.12 K compared to the baseline scenario without particle injection.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127797"},"PeriodicalIF":5.8,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145004918","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}

{"title":"LES of a hydrogen flame controlled by mass flow oscillations and rotating shear layer disturbance","authors":"Karol Wawrzak,&nbsp;Agnieszka Wawrzak,&nbsp;Artur Tyliszczak","doi":"10.1016/j.ijheatmasstransfer.2025.127742","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127742","url":null,"abstract":"&lt;div&gt;&lt;div&gt;The paper presents the results of investigations on a low-Reynolds-number nitrogen-diluted hydrogen turbulent flame subjected to different types of inlet perturbations, including (1) high/low turbulence intensity and large/small turbulent length scales and (2) two-term excitation composed of mass flow oscillation and a radial velocity disturbance rotating along the nozzle lip. The ratio of axial to radial excitation frequency, &lt;span&gt;&lt;math&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt;, is considered as the control parameter. The research is conducted using the Large Eddy Simulation (LES) method employing a high-order numerical code. A laminar chemistry approach and a detailed chemical reaction kinetic scheme (9 species, 21 reactions) are used to model the combustion process. In case (1), small-scale turbulent fluctuations prevent flame attachment to the nozzle, lifting it to a distance of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;25&lt;/mn&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;8&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;6&lt;/mn&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; (&lt;span&gt;&lt;math&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; - the nozzle diameter) for low/high turbulence intensity, respectively. The induced small-scale mixing process enhances combustion, leading to a doubling of the flame volume and an increase in the average temperature of approximately 100 K at a distance of &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mn&gt;30&lt;/mn&gt;&lt;mi&gt;D&lt;/mi&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. In case (2), three &lt;span&gt;&lt;math&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;/math&gt;&lt;/span&gt; values are selected based on current knowledge of non-reacting jet control: &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;mo&gt;,&lt;/mo&gt;&lt;mspace&gt;&lt;/mspace&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;27&lt;/mn&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;. The excitation markedly impacts the dynamics and the shape of the flame. For &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;0&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; and &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;, bifurcating and fifth-armed flames form, respectively. The value &lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;27&lt;/mn&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt; is chosen based on a recent discovery by Y. Li et al. (J. Fluid Mech. 991 (2024)) - a rotating two-arm jet (double-helix). We demonstrate that all these patterns can be reproduced in reactive flows. The cases with five flame arms and rotating arms are presented and discussed for the first time. Analysis of lift-off heights reveals local flame front oscillations at frequencies exactly matching those of large-scale vortex shedding (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mn&gt;5&lt;/mn&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;) and flame rotation (&lt;span&gt;&lt;math&gt;&lt;mrow&gt;&lt;mi&gt;R&lt;/mi&gt;&lt;mo&gt;=&lt;/mo&gt;&lt;mn&gt;2&lt;/mn&gt;&lt;mo&gt;.&lt;/mo&gt;&lt;mrow&gt;&lt;mo&gt;(&lt;/mo&gt;&lt;mn&gt;27&lt;/mn&gt;&lt;mo&gt;)&lt;/mo&gt;&lt;/mrow&gt;&lt;/mrow&gt;&lt;/math&gt;&lt;/span&gt;). The oxidizer engulfing the separated arms, along with the induced large-scale mixing, results i","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127742"},"PeriodicalIF":5.8,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145004921","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}

{"title":"Hot shear flows promote instabilities of liquid wall films","authors":"Keito Murakami,&nbsp;Yoshiaki Kamada,&nbsp;Zhenying Wang,&nbsp;Chihiro Inoue","doi":"10.1016/j.ijheatmasstransfer.2025.127783","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127783","url":null,"abstract":"<div><div>Liquid films are common in thermal and multiphase flow systems, while the mechanisms of their interfacial instability driven by shear, heat, and evaporation remain elusive. By combining experimental flow visualization with theoretical modeling, this study examines annular gas–liquid two-phase flows under non-isothermal conditions, in which a hot turbulent airflow (<span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>g</mi></mrow></msub><mo>=</mo><mn>290</mn><mo>∼</mo><mn>440</mn><mspace></mspace><mi>K</mi></mrow></math></span>, <span><math><mrow><mi>N</mi><mi>u</mi><mo>∼</mo><mi>O</mi><mrow><mo>(</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>2</mn></mrow></msup><mo>)</mo></mrow></mrow></math></span>) heats a room-temperature water film (<span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>l</mi></mrow></msub><mo>=</mo><mn>290</mn><mspace></mspace><mi>K</mi></mrow></math></span>). Under a fully developed hot airflow and a uniform water film, we observe an enhancement in interfacial instability of three-dimensional ripple wave structures on the wall film: the axial wavelength of ripple waves reduces to approximately half compared to the isothermal case. This remarkable trend is attributed to the cooling effect of the water film on the gas stream, which leads to thinning of the gas-side velocity boundary layer and amplification of shear-induced instabilities visible as the shortened film wavelength. Despite the heating of the liquid film — which decreases surface tension and promotes evaporation — the cooling of the airflow dominates the mechanism for promoted instability. Incorporating the thinning gas-side boundary layer thickness, we formulate the ripple wavelengths under non-isothermal conditions through Kelvin–Helmholtz and Rayleigh–Taylor instability frameworks, well validated by experimental results. Moreover, large-scale disturbance waves are likely to emerge due to increased shear stress at elevated airflow temperatures, with their onset corresponding to a film Weber number of unity. The elucidated mechanism and derived formulation advance the understanding of gas–liquid dynamics with interfacial heat transfer.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127783"},"PeriodicalIF":5.8,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145004920","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}

{"title":"Subcooled flow boiling in microchannels: Heat transfer enhancement via topology optimization and transient characteristics of microbubble emission","authors":"Jianhong Zhou,&nbsp;Yuanle Zhang,&nbsp;Qiang Li,&nbsp;Xuemei Chen","doi":"10.1016/j.ijheatmasstransfer.2025.127799","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.127799","url":null,"abstract":"<div><div>In recent years, subcooled flow boiling in microchannels has attracted extensive research attention due to its applications in high heat flux cooling scenarios. In this study, subcooled flow boiling in microchannels with a baseline configuration (BC) and two topologically optimized configurations (TOC-I and TOC-II) is investigated through flow visualization experiments. The effects of mass flux (330.1, 660.2, and 1320.3 kg/m²·s), inlet subcooling (40, 60, and 80 K), and heater heat flux (0-700 W/cm²) on two-phase flow patterns and thermo-hydraulic characteristics are examined. Particular focus is given to the bubble dynamics and transient responses of wall temperature and pressure drop associated with the microbubble emission boiling (MEB) phenomenon. The results show that all three configurations exhibit Type-I Bubbly Flow (TIBF), Slug Flow (SF), and Droplet Flow (DF). In contrast, Type-II Bubbly Flow (TIIBF) and Annular Flow (AF) are unique to BC, while Evaporated Flow (EF) appears exclusively in TOC-I and TOC-II. TOC-II exhibits the lowest wall superheat under identical heat flux conditions, owing to its large heat transfer area and the micro pin fins with topologically optimized configuration, which enhances fluid mixing and disrupts the formation of the thermal boundary layer. Compared to BC, the maximum reduction in wall superheat reaches 29.5 K. Under most operating conditions, TOC-I demonstrates a higher heat transfer coefficient than both BC and TOC-II, reaching a peak value of 80.4 kW/m²·K under the SF regime, which is 40.2 % higher than the peak value of 57.3 kW/m²·K observed in BC. The time-averaged pressure drop in TOC-I is comparable to that in BC and slightly lower than that in TOC-II, under most operating conditions. Notably, MEB with two distinct evolution modes is observed in BC, with a complete evolution cycle lasting approximately 30-70 ms. Furthermore, during intense MEB activity, a transient and anomalous drop in wall superheat is observed as heat flux increases, accompanied by temperature and pressure drop oscillations with amplitudes of up to 8 K and 6.4 kPa, respectively.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"255 ","pages":"Article 127799"},"PeriodicalIF":5.8,"publicationDate":"2025-09-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145004917","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}