稀薄性对微通道气体流动换热特性影响数值分析

Numerical Simulation of Rarefaction Effects on Gaseous Flow and Heat Transfer in Microchannels

在微通道二维简化模型下,通过控制方程的无量纲化处理,对空气在滑移区稀薄性影响下的流动特性进行了研究与数值分析。研究结果表明,泊肃叶数(Po数)在进口与出口处较大,沿程其他位置的Po数为定值。随着克努森数(Kn数)的增加,稀薄性增强,壁面滑移变大,Po数减小。文中给出Po数的一维理论表达式,发现该公式与实验值较吻合。最后,通过对比验证表明,平均努塞尔数(Nu数)随着Kn数的增加而减小。

A flow and heat transfer numerical simulation was performed for a 2Dgaseous flow through microchannels in the slip regime to investigate the effects of rarefaction.In the paper,it denotes the normalized governing equations.The rarefaction is simulated by varying Knudsen numbers（Knnumbers）.The numerical results demonstrate that Poiseuille numbers（Po numbers）are significantly higher for the flow near the entrance and the exit.Then the downstream values of Po numbers change slightly along the channel.The lower Po number is expected,since the slip condition implies less shear stress against the wall and a higher Knnumber means larger slip.In general,our analytical formulas show good agreement with the related experimental data.In the end,it verifys that the average Nusselt number（Nunumber）decreases with the increase of Kn number.