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首页> 外文期刊>International Journal of Heat and Mass Transfer >Dilute gas flows through elliptic microchannels under H2 boundary conditions
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Dilute gas flows through elliptic microchannels under H2 boundary conditions

机译：稀释气体在H2边界条件下流经椭圆形微通道

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摘要

This work presents a numerical investigation of slip flow inside microchannels characterized by an elliptic cross-section. A gaseous flow is considered, in laminar steady state condition, in hydrodynamically and thermally fully developed forced convection, accounting for the rarefaction effect. The momentum and energy equations are solved resorting to the finite element method; the numerical results are compared with analytical values available in the literature for slip flow in elliptic cross sections and in circular ducts, to validate the numerical procedure. The temperature field is determined by considering the H2 boundary condition for different combinations of heated walls among the four branches constituting the elliptic perimeter. Nusselt numbers and normalized wall temperatures in the case of two or four heated sides are presented and discussed. The influence of the cross section aspect ratio and of the rarefaction effects on the fluid behavior are investigated. The numerical results point out that the Nusselt number decreases with the Knudsen number, and increases with the aspect ratio of the elliptical channel. To evaluate the Nusselt numbers for different values of aspect ratio and Knudsen number (in all analyzed cases) a simple polynomial correlation is proposed. Finally a comparison between rectangular and elliptic microchannels has been performed, when the whole perimeter of the cross-section is heated, showing that for values of the aspect ratio greater than 0.33 the elliptic microducts are characterized by better thermal performances.
机译：这项工作提出了以椭圆形横截面为特征的微通道内部滑流的数值研究。在层流稳态条件下，考虑到稀疏效应，在流体动力和热力充分发展的对流中考虑了气流。动量和能量方程通过有限元法求解。将数值结果与文献中针对椭圆形横截面和圆形管道中的滑流的分析值进行比较，以验证数值程序。通过考虑H2边界条件来确定温度场，该条件取决于构成椭圆周长的四个分支中加热壁的不同组合。介绍并讨论了在两个或四个加热侧的情况下的努塞尔数和归一化壁温。研究了横截面纵横比和稀疏效应对流体行为的影响。数值结果表明，努塞尔数随克努森数而减小，随椭圆形通道的长宽比而增大。为了评估宽高比和克努森数（在所有分析情况下）的不同值的Nusselt数，提出了一种简单的多项式相关性。最终，在加热整个横截面的周长时，进行了矩形和椭圆形微通道之间的比较，结果表明，对于长宽比大于0.33的椭圆形微管，其热性能更好。

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