几何尺寸对矩形微通道液体流动和传热性能的影响

基于连续介质方法数值研究液体在不同几何结构微通道中的流动和传热性能。在相同热边界条件下,通过比较水力直径、通道长度和宽高比等几何参数对液体微流动的影响,得到各参数对泊肃叶数(Po)和努塞尔数(Nu)的影响关系。研究发现,截面宽高比越大,Po数越小,且雷诺数对泊肃叶数基本无影响;雷诺数(Re)小于500情况下,水力直径小于0.545 mm时,Po数随水力直径减小而减小,水力直径大于0.545 mm时,水力直径变化对Po数基本无影响;Po数不随通道长度变化而变化,但略受流动雷诺数影响;在Re=20～1 800时,Nu数正比于水力直径和宽高比,但是通道长度对Nu数的作用受流动Re数的影响;在通道材料和流动介质相同的条件下,Nu数和Re数之间的关系受通道几何参数的影响,并且拟合得到其关系式。

Effects of Geometry on Liquid Flow and Heat Transfer in Microchannels

The geometric effects on the liquid flow are investigated in microchannel based on the numerical simulation method.Effects of geometry are shown obviously on the microflow by comparing the results of different geometric characteristics covered hydraulic diameter,length and aspect ratio.Thermal boundary conditions are same for different cases in the numerical simulation.The effects of geometric parameters on the Poiseuille number and the Nusselt number are investigated.The Poiseuille number decreases with the increasing of the aspect ratio while the Reynolds number has no effect on it for the same aspect ratio microchannels.For Re<500,when the hydraulic diameter Dh<0.545 mm,Po decreases with the Dh,but Po does not change when Dhis larger.The length of the microchannel has no effect on Po while Reynolds number has a little influence on it.When Re is 20-1 800,Nu is proportional to the hydraulic diameter and aspect ratio of the microchannel.Effects of the length on the Nusselt number vary at different Reynolds number.The relation of Nu and Re can be fitted,which is affected by the geometry of microchannels for the same substrate and flow liquid.