Fluid flow and heat transfer in two-segmented microchannels within the slip flow regime

IF 5.4 3区工程技术 Q2 ENERGY & FUELS

Thermal Science and Engineering Progress Pub Date : 2025-06-03 DOI:10.1016/j.tsep.2025.103751

Younes Azizi , Moslem Fattahi , Arman Sadeghi

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引用次数: 0

Abstract

We theoretically investigate gaseous slip flow and heat transfer in circular microchannels with two different wall materials in the lateral direction. The flow is considered as steady and fully-developed, and constant but different wall heat fluxes are assumed for the channel segments. While infinite series solutions are obtained for the velocity and temperature distributions as well as the Nusselt number, finite-element numerical simulations are also performed to confirm the validity of the analytical solutions developed. It is demonstrated that the average Nusselt number of the channel depends on several parameters comprising the Knudsen number, the Prandtl number and specific heat ratio of the gas, the momentum and thermal accommodation coefficients, and the angular span of either channel segment as well as the heat flux ratio of the two segments. It is further illustrated that the fluid velocity is strongly non-uniform in the angular direction when the channel segments have different momentum accommodation coefficients. This significantly affects the heat transfer rates, especially at high Knudsen numbers where the rarefaction effects are more significant. An inspection of the dimensionless average velocity variations shows that reducing the momentum accommodation coefficient of one channel segment while keeping that of the other one constant leads to higher average velocities, whereas the opposite is true for the influence of the thermal accommodation coefficient on the average Nusselt number. Finally, it is shown that the Nusselt number is a maximum for a symmetric wall heating.

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滑移流动状态下两段微通道内的流体流动和传热

本文从理论上研究了两种不同壁材的圆形微通道的横向滑动流动和传热。流动被认为是稳定和充分发展的，并且假定通道段的壁面热通量恒定但不同。在得到速度和温度分布以及努塞尔数的无穷级数解的同时，还进行了有限元数值模拟以证实所开发的解析解的有效性。结果表明，通道的平均努塞尔数取决于气体的克努森数、普朗特数和比热比、动量和热容纳系数、通道段的角跨度以及两段的热流密度比等参数。进一步说明，当通道段的动量调节系数不同时，流体速度在角方向上具有强烈的不均匀性。这显著影响传热速率，特别是在高克努森数时，稀薄效应更为显著。对无量纲平均速度变化的检查表明，在保持另一通道段的动量调节系数不变的情况下，降低一通道段的动量调节系数会导致更高的平均速度，而热调节系数对平均努塞尔数的影响则相反。最后，证明了对称壁面加热的努塞尔数是一个最大值。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Thermal Science and Engineering Progress Chemical Engineering-Fluid Flow and Transfer Processes

CiteScore

7.20

自引率

10.40%

发文量

327

审稿时长

41 days

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