International Journal of Heat and Mass Transfer最新文献

{"title":"Numerical simulation of compressible fluid-dynamics in the chamber of inertial fusion energy systems","authors":"Eric Cervi ,&nbsp;Antonio Cammi ,&nbsp;Carlo Fiorina ,&nbsp;Kirk Flippo ,&nbsp;Nahom Habtemariam ,&nbsp;Matteo Lo Verso","doi":"10.1016/j.ijheatmasstransfer.2025.126700","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126700","url":null,"abstract":"<div><div>This paper aims to establish new and innovative modeling capabilities for analyzing chambers in Inertial Fusion Energy (IFE) systems. IFE is emerging as a promising method to achieve fusion power production, but several challenges must be overcome to develop an IFE pilot plant or deploy commercial IFE systems. These challenges are both theoretical and technical, encompassing a deeper understanding of the underlying physical phenomena and the development of new technologies and materials. One of the needs is to develop mathematical models to describe IFE systems and numerical tools to simulate them. This paper contributes to this endeavor by presenting a new OpenFOAM solver for IFE systems, focusing on gas dynamics in their chambers. The analysis and development of chamber designs will play a significant role in the transition from single-shot experiments to high-repetition rates, as there is a need to protect the chamber walls from the intense radiation fields produced by fusion reactions. A promising design option, normally referred to as thick wall chamber design, consists in using lithium or molten salt jet arrays within the chamber. A critical phenomenon is the venting of high-pressure gases from the center to the external part of the chamber, passing through the blanket array. This process involves the propagation and attenuation of strong pressure waves, requiring suitable modeling approaches for compressible fluid-dynamics. The solver proposed in this work implements a multi-material hydrodynamics model tailored to accurately describe the non-linear propagation of pressure waves while avoiding numerical oscillation issues typical of high-velocity compressible simulation. This solver is verified against numerical test cases, validated against experimental data, and applied to the analysis of the High-Yield Lithium-Injection Fusion-Energy (HYLIFE-I) concept. The relevance of this paper is threefold. Firstly, it contributes to developing and testing modeling approaches for compressible fluid-dynamics phenomena, with specific focus on the new and unexplored topic of IFE thick-liquid-wall blanket modeling. Secondly, it marks one of the first applications of the OpenFOAM library in the research field of IFE systems. Finally, the investigated problem is of practical interest for IFE developers, as it provides useful indications about relevant phenomena in pressure wave propagation in the chamber of these systems.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126700"},"PeriodicalIF":5.0,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130574","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":"Heat and momentum transfer in Rayleigh–Bénard convection within a two-dimensional annulus under radial gravity","authors":"Abhiroop Bhadra ,&nbsp;Olga Shishkina ,&nbsp;Xiaojue Zhu","doi":"10.1016/j.ijheatmasstransfer.2025.126703","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126703","url":null,"abstract":"<div><div>We conduct direct numerical simulations (DNS) to explore Rayleigh–Bénard convection (RBC) within a two-dimensional (2D) annular domain, where the radius ratio (<span><math><mi>η</mi></math></span>) plays a crucial role in shaping the flow dynamics. In this study, we examine how varying <span><math><mi>η</mi></math></span> impacts the convection patterns when the inner shell is maintained at a higher temperature than the outer shell. Our simulations cover a broad range of radius ratios (<span><math><mrow><mi>η</mi><mo>=</mo><mn>0</mn><mo>.</mo><mn>2</mn></mrow></math></span> to 0.8) and Rayleigh numbers (<span><math><mrow><mi>R</mi><mi>a</mi><mo>=</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>7</mn></mrow></msup></mrow></math></span> to <span><math><mrow><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>10</mn></mrow></msup></mrow></math></span>), with a fixed Prandtl number of unity. To generate the buoyancy force, a gravity profile proportional to <span><math><mrow><mi>g</mi><mo>∼</mo><mn>1</mn><mo>/</mo><mi>r</mi></mrow></math></span> is applied, reflecting the radial dependence. Our findings reveal a distinct asymmetry in the flow field, which we further analyze by isolating the plume structures through conditional averaging. This approach allows us to examine how these structures influence the boundary layer behavior. Additionally, with the applied gravity profile, we derive exact relations between the driving forces and the kinetic and thermal dissipation rates. Using the Grossmann–Lohse theory, we incorporate these exact relations to determine prefactors specific to each <span><math><mi>η</mi></math></span> value, offering new insights into how geometry influences convection in this non-rotating cylindrical system.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126703"},"PeriodicalIF":5.0,"publicationDate":"2025-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130573","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}

{"title":"Investigation of enhanced pool boiling heat transfer with Fe magnetic thin films electrochemically deposited under different magnetic field orientations","authors":"Wei Yang ,&nbsp;Jianqiang Du ,&nbsp;Mengna Yuan ,&nbsp;Liting Tian ,&nbsp;Jin Wang ,&nbsp;Lidija Čuček ,&nbsp;Bengt Sundén","doi":"10.1016/j.ijheatmasstransfer.2025.126732","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126732","url":null,"abstract":"<div><div>Rapid development of energy technologies depends on the safe and stable operation of systems guaranteed by efficient cooling ability. To increase the heat flux transferred at a minor temperature difference, boiling has a significant advantage compared to other heat transfer methods. This study focuses on enhancing the pool boiling heat transfer using electrochemically deposited Fe magnetic thin films under various magnetic field orientations. It is found that the magnetic field orientation significantly affects the surface morphology of the Fe-thin film. Significant differences are observed for the diameter and arrangement of microcracks and pits on Fe-thin films grown with different magnetic field conditions, and these changes in surface morphology further affect the wettability of the Fe-thin film surface. The Fe-thin film surfaces are used to enhance the pool boiling heat transfer. The results show that by deposition of Fe-thin films, the boiling performance of copper surfaces is enhanced compared to that of the polished copper surface. The critical heat flux and heat transfer coefficient are improved maximally by 30.78 % and 27.55 %, respectively, compared to those without Fe-thin films. It is revealed that the presence of Fe-thin films increases the heat transfer area and nucleation sites due to the modified microstructure, increased roughness, and improved wettability, which jointly enhances the boiling heat transfer.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126732"},"PeriodicalIF":5.0,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130589","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":"Experimental diffusivity measurements using non-invasive laser-induced luminescence (PLIF & PLIF-I) in non-binary fluid multiphase domains","authors":"Johann Weigelt,&nbsp;Georg Brösigke,&nbsp;Jens-Uwe Repke","doi":"10.1016/j.ijheatmasstransfer.2025.126708","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126708","url":null,"abstract":"<div><div>Mass transfer in multiphase fluids represents a complex challenge that provides critical information for industry. We have applied, validated and extended the experimental approach for measuring diffusion coefficients initially introduced by (Jimenez et al.,2013) within a Hele-Shaw cell. The original measurement employed the inhibited planar laser-induced fluorescence (PLIF-I) method, utilizing the oxygen-sensitive ruthenium complex dye. The main results of our study demonstrate the successful transfer and extension of the original diffusivity measurement technique with PLIF-I to the planar laser-induced fluorescence (PLIF) principle using an additional but promising oxygen-sensitive dye, resazurin. Many scientific publications use a cuboid measuring chamber. In this work, the use of a cylindrical measuring chamber is also investigated. As a result, the experimental setup used involved two distinct measurement chambers: a cubic chamber with dimensions of 10 x 10 x 10 mm³, and a cylindrical chamber measuring 6<!--> <!-->mm in diameter and 10<!--> <!-->mm in height. We conducted a series of forty experiments utilizing a diverse range of eight different liquid–gas combinations, varying the viscosity. These combinations were primarily composed of a viscous mixture of glycerol and water and featured varying concentrations of oxygen. A motivating factor for our research was to explore the potential of the tracer dye resazurin for future studies involving mass transfer in film flows. This exploration was driven by the anticipated advantages, such as a superior noise-ratio, when compared to the ruthenium complex. Furthermore, our work makes a fundamental contribution to the understanding of complex non-binary fluid properties.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126708"},"PeriodicalIF":5.0,"publicationDate":"2025-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130479","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}

{"title":"A next-generation device for spreading volatiles substances into room air: Study of parameters affecting efficient dispersion","authors":"Abul Borkot Md Rafiqul Hasan ,&nbsp;Krishna M. Pillai ,&nbsp;Mason Ihrke ,&nbsp;M. Shahnawaz Ali ,&nbsp;Shama Mirza","doi":"10.1016/j.ijheatmasstransfer.2025.126709","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126709","url":null,"abstract":"<div><div>This study focuses on enhancing the efficacy of wick-based air fresheners by improving the evaporation rate and dispersion of volatile fragrances. It addresses the issue of reduced evaporation, primarily caused by the accumulation of non-volatile substances in the wicks of existing air fresheners. To tackle this problem, a prototype device was devised, featuring three wicks connected to a motor and shaft system capable of periodic immersion in a fragrant liquid, accompanied by a fan mounted on the reservoir's side to enhance airflow over the liquid. The test liquid used was a mixture of Decane (most volatile component), Dodecane, and Hexadecane. The study encompassed five test cases: reservoir on its own, reservoir with stationary wicks, wicks rotating without fan, stationary wicks with fan, and rotating wicks with fan. This research involved two phases: initially monitoring the gradual decrease in liquid mass over time using an in-house low-cost device capturing balance images. The results demonstrated a consistent increase in mass loss from 0.034 ± 0.011 gm/hr in Case 1 to 1.182 ± 0.256 gm/hr in Case 5, representing a 34-fold increase. The residual liquids in the tank from each case were preserved in vials for the subsequent Gas Chromatography analysis, which revealed a declining percentage of Decane (the most volatile component) from 46.84 % in Case 1 to 1.85 % in Case 5, a reduction by approximately 25 times. The study's findings revealed that the combination of rotating wicks and fan yielded the highest mass loss and the lowest remaining concentration of the volatile Decane fragrance component, confirming its effectiveness in optimizing fragrance evaporation. Consequently, the reservoir with a rotating wick coupled with a fan emerged as the most promising choice for the prototype design, based on its superior performance in terms of mass loss and volatile component dissipation. In summary, this research underscores the significance of factors like surface area, airflow velocity, and the relative concentration of volatile components in enhancing air freshener performance. Through improved fluid flow and evaporation, the developed prototype offers a potential solution to address the challenge of reduced evaporation in air fresheners. This study represents an advancement in air freshener technology and lays the foundation for the development of more efficient fragrance dispersal devices.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126709"},"PeriodicalIF":5.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130470","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":"AM micro-structures with bespoke permeability","authors":"Yeonse Kang ,&nbsp;Jan Seidler ,&nbsp;Jihwan Ahn ,&nbsp;Vicente Rubio ,&nbsp;Clemens Maucher ,&nbsp;Hans-Christian Möhring ,&nbsp;Fabian Hampp","doi":"10.1016/j.ijheatmasstransfer.2025.126674","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126674","url":null,"abstract":"<div><div>Additive manufacturing (AM) of high temperature alloys is increasingly used for the development of innovative heat and mass transfer applications including combustors and heat exchangers. The added design freedom of AM processes offers function integration into components, thereby offering exciting optimisation potential from improved performance to reduced emissions. However, AM processes inherently lead to relatively high surface roughness, e.g. due to partially adhering powder material, that can limit the achievable feature dimensions and tolerances. In the realisation of AM micro-structures, i.e. feature size <span><math><mo>≤</mo></math></span> 500<!--> <span><math><mi>μ</mi></math></span>m, the associated surfaces quality and tolerances can distinctly influence device performance and operability. In this context, co-optimisation of the AM process with fluid guiding structures is essential. In the current work we explore the capacity of creating AM micro-structures using laser-based powder bed fusion (PBF-LB/M) of Inconel 718 to innovate various injector and burner components. The results show, that such micro features can be realised and the control of their alignment can be used to design a permeability vector. Thereby, the degree of freedom of PBF-LB/M in the design phase can be further extended by function integration of bespoke fluid permeability. The seamless combination and integration of low pressure loss micro-channels with close-to deterministic percolating pore space, permeable structures with stochastic percolating pore space and gas-tight solid sleeves creates exciting opportunities to innovate hardware for heat and mass transfer applications. Additionally, a design correlation is provided to guide the engineering of these materials. The functionality of the PBF-LB/M process is validated through three case studies on injector and combustor hardware, showcasing its potential to drive innovation in energy and fluid handling technologies.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126674"},"PeriodicalIF":5.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130588","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}

{"title":"Machine learning assisted convective wall heat transfer models for wall fire modeling","authors":"Jie Tao ,&nbsp;Ning Ren ,&nbsp;Yi Wang ,&nbsp;Haifeng Wang","doi":"10.1016/j.ijheatmasstransfer.2025.126684","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126684","url":null,"abstract":"<div><div>A significant source of error arising from wall fire modeling is the convective wall heat transfer model, especially when a thermal boundary layer along a wall is highly under-resolved, i.e., the size of the first grid cell from the wall is much greater than the viscous layer thickness. Traditional convective wall heat transfer models developed for forced or natural convection in a turbulent boundary layer tend to fail when used in a wall fire problem due to different challenges like the effect of blowing pyrolysis gas from a wall. In this work, machine learning with the random forest model is employed to construct a data-driven convective wall heat transfer model to provide an assessment of the feasibility and potential of using machine learning for enhancing wall fire predictions. To improve the predictions of convective heat flux to a wall in wall-modeled large-eddy simulations (LES) of wall fire, an amplification factor <span><math><mi>β</mi></math></span> is introduced for the improvement of the calculation of the heat flux that accounts for the sub-filter scale effect. The factor <span><math><mi>β</mi></math></span> compensates for the under-resolution of temperature gradient on the wall normal to its surface when the thermal boundary layer is under-resolved. A fine-resolution LES of a fire case along a vertical wall is conducted to provide the training data for machine learning. The fine-resolution LES uses a grid size a few times larger than the viscous layer thickness but reasonably captures the inner thermal boundary layer. Different choices of input parameters for the machine learning models are examined. Several models for <span><math><mi>β</mi></math></span> are constructed by using machine learning. Three different strategies for machine learning training are compared. Both <em>a priori</em> testing and <em>a posteriori</em> testing are performed in the vertical wall fire case to examine the performance of the developed machine learning models. The machine learning model is also tested in an intermediate-scale parallel-wall fire spreading case (0.6 m wide and 2.4 m high) which has not been seen by the trained model. Overall, the results show the promise of using machine learning approaches to enhance wall fire predictions.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126684"},"PeriodicalIF":5.0,"publicationDate":"2025-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130698","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":"Non-Oberbeck–Boussinesq effects on the convective stability in a transient natural convection boundary layer for water","authors":"Junhao Ke,&nbsp;S.W. Armfield,&nbsp;N. Williamson","doi":"10.1016/j.ijheatmasstransfer.2025.126670","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126670","url":null,"abstract":"<div><div>The non-Oberbeck–Boussinesq effects on the linear stability of a vertical natural convection boundary layer are investigated using the linearised disturbance equation for water flows up to a temperature difference of <span><math><mrow><mi>Δ</mi><mi>T</mi><mo>=</mo><mn>40</mn></mrow></math></span> K at two ambient temperatures, <span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>∞</mi></mrow></msub><mo>=</mo><mn>293</mn></mrow></math></span> K and <span><math><mrow><msub><mrow><mi>T</mi></mrow><mrow><mi>∞</mi></mrow></msub><mo>=</mo><mn>333</mn></mrow></math></span> K. Results reveal that the instability of the natural convection boundary layer in water is completely driven by buoyancy. The neutral stability curves are shown to be sensitive to the choice of reference temperature — when evaluated at the film temperature <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>f</mi></mrow></msub></math></span>, the flow is stabilised by heating at small Grashof number near the critical point; but is destabilised at higher Grashof number. An increased ambient temperature is also shown to have a stabilising effect on the flow. For the buoyancy-driven instability, we propose a reference temperature for the purpose of generalising the neutral stability curves at different <span><math><mrow><mi>Δ</mi><mi>T</mi></mrow></math></span> and <span><math><msub><mrow><mi>T</mi></mrow><mrow><mi>∞</mi></mrow></msub></math></span> values.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126670"},"PeriodicalIF":5.0,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130355","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}

{"title":"Thermal performance evaluation of shaped sweeping jet film cooling at simulated engine condition using emissivity-corrected infrared thermometry","authors":"Kechen Wang ,&nbsp;Zhe Shi ,&nbsp;Yang Li ,&nbsp;Yihong He ,&nbsp;Wenwu Zhou ,&nbsp;Xin Wen ,&nbsp;Yingzheng Liu","doi":"10.1016/j.ijheatmasstransfer.2025.126699","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126699","url":null,"abstract":"<div><div>Sweeping jet (SJ) is a periodic, self-excited flow generated by a fluidic oscillator, showing promising potential for film cooling applications. With continuous structural improvements, the shaped sweeping jet (SSJ) design has achieved a proper size and demonstrated excellent film cooling performance at low-speed conditions. However, its overall cooling effectiveness at engine-relevant conditions remains to be fully validated. This study investigates the thermal performance of the SSJ compared to the baseline 777 hole at simulated engine conditions. Experiments were conducted on a high-pressure guide vane with a row of SSJ on both the pressure and suction surface. Emissivity-corrected infrared (IR) thermometry was employed to measure the vane surface temperature across several blowing ratios (0.5 ≤ <em>M</em> ≤ 3.0), providing an evaluation of overall cooling effectiveness. This method incorporates three-dimensional reconstruction and emissivity correction to address temperature measurement errors caused by directional emissivity. The results indicate up to a 42 % improvement in overall cooling effectiveness for the SSJ compared to the baseline 777 hole, further validating the SSJ film cooling at simulated engine conditions and highlighting its potential for advanced turbine cooling applications.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126699"},"PeriodicalIF":5.0,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130359","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":"Experimental study on flow boiling in microchannel evaporators with top gap structures","authors":"Lulu Li ,&nbsp;Yaning Guo ,&nbsp;Bo Zhang ,&nbsp;Xiangji Guo","doi":"10.1016/j.ijheatmasstransfer.2025.126710","DOIUrl":"10.1016/j.ijheatmasstransfer.2025.126710","url":null,"abstract":"<div><div>The efficient cooling of high-power electronic equipment requires developing a simple and effective method for enhancing boiling heat transfer. This study utilized R245fa as a refrigerant in a closed pump-driven two-phase system to enhance boiling heat transfer performance. The effects of the boiling curves, overall heat transfer performance, radial local heat transfer coefficients, and along-length local heat transfer coefficients were analyzed under five different mass fluxes and four top gap height structures. The results indicate that a top gap height of 0.9 mm leads to a higher critical heat flux compared to a structure without a top gap. For a given mass flux, the overall heat transfer coefficient peaks at a top gap height of 0.9 mm. The difference in radial local heat transfer coefficient (Δ<span><math><msub><mi>h</mi><mi>r</mi></msub></math></span>) consistently exceeds zero across different vapor qualities and mass flux conditions. As the vapor quality increased, the overall trend of the along-length heat transfer coefficient showed a significant increase at the <span><math><mrow><msub><mi>L</mi><mrow><mi>n</mi><mi>d</mi></mrow></msub><mspace></mspace></mrow></math></span>= 0 position. Among the top gap structures, the 0.9-mm top gap height exhibits the highest and most uniform along-length heat transfer coefficient. The average local heat transfer coefficients for the 0.9-mm top gap were 1.17-, 1.20-, 1.21-, 1.11-, and 1.09 times higher than those of a gapless structure as the mass flux increased from 89 to 535 kg/m²/s. This study provides deeper insight into how the top gap height enhances the fluid redistribution and rewetting mechanisms in flow boiling within microchannels.</div></div>","PeriodicalId":336,"journal":{"name":"International Journal of Heat and Mass Transfer","volume":"241 ","pages":"Article 126710"},"PeriodicalIF":5.0,"publicationDate":"2025-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143130358","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}