Gauss型粗糙表面对微通道流动与换热的影响

Effects of Guassian Rough Surface on Fluid Flow and Heat Transfer in Microchannels

摘要:

采用高斯分布描述粗糙表面形貌，提出了利用Coons曲面构造三维矩形粗糙微通道的方法，建立了光滑微通道和三条粗糙微通道。在等温壁面条件下，数值模拟了饱和水在微通道内的层流流动，分析了表面粗糙度对流动阻力特性及传热特性的影响。研究结果表明：区别于光滑微通道，粗糙微通道的Po和Nu高于理论值，不再保持常数，随着雷诺数的增大呈近似线性增加；受表面轮廓高度随机性的影响，沿程压降和Nux呈随机波动式变化，粗糙度越大波动越剧烈；Po和Nu随等效相对粗糙度的增加而变大，且在所研究Re范围内相对粗糙度对层流换热的强化作用比对流动阻力的影响更显著；微通道内等温线向粗糙度大的下表面偏移，温度分布呈现非对称性，随着粗糙度差距的变大，非对称性愈来愈明显。

Abstract:

Gaussian distribution was used to describe the rough surface, and a novel method was proposed to generate 3-D rectangular rough microchannel by using Coons surfaces. With this method, one smooth microchannel and three rough microchannels were created. Constant wall temperature condition was applied to simulate the laminar flow of the saturated water in microchannels, and the effects of the surface roughness on flow and heat transfer characteristics were all investigated. The results indicated that different from the smooth microchannel, Poiseuille number and average Nusselt number were larger than the theoretical values, and increase approximately linearly with Re. As the height of the surface profile changed randomly, both pressure drop and local Nusselt number along the channel fluctuated randomly. The larger the roughness was, the more intense the fluctuation was. Poiseuille number and average Nusselt number increased with increasing equivalent relative roughness. Furthermore, within the scope of the Re, the effect of relative roughness on laminar heat transfer was stronger than that on flow resistance. In the microchannel, isotherm migrated to the lower surface, where the roughness was larger. As a result, the temperature distribution was asymmetric. As the gap of the roughness got increasingly larger, the asymmetry was more and more distinct.