宽高比及表面粗糙度对矩形微尺度通道流动特性的影响

Influence of aspect ratio and roughness on flow behavior in rectangle microchannels

实验研究了不同宽高比矩形金属微尺度通道的流动特性,并与硅通道对比来探究表面粗糙度的影响。金属微尺度通道宽为0.4mm,通道宽高比分别为0.50、0.67、和1.00,相对表面粗糙度范围为0.1609%~0.214 5%。硅通道宽度及高度都为0.4mm,相对表面粗糙度为0.003 25%。实验工质为空气,实验的雷诺数范围是250~3 000。实验结果表明:在粗糙微尺度通道会发生转捩提前,并且转捩雷诺数随着宽高比增大而减小。在层流区,微尺度矩形通道摩擦因数随着雷诺数增大而减小,在转捩区出现明显增大后再减小。表面粗糙度很小时,未发现转捩提前现象。

The influence of aspect ratio on the flow behavior in metallic rectangle microchannels was experimentally investigated.The results of flow behavior in silicon microchannels were compared to investigate the influence of roughness.The width of metallic microchannels was 0.4 mm and the aspect ratios were 0.50,0.67,1.00,respectively;and the relative roughness of the metallic microchannels ranged from 0.160 9% to 0.214 5%.The widths and heights of the silicon microchannels were both 0.4 mm,and the relative roughness was 0.003 25%.All experiments were performed with air.The experiments were completed with Reynolds number within the range of 250-3000.Results of experiments showed that the onset of transition from laminar flow to turbulent flow occurred earlier in unsmooth microchannels.And the critical Reynolds number decreased with the increase of aspect ratio.In laminar region,the friction factors for all the rectangle microchannels decreased roughly with the increase of Reynolds numbers.In transition region,the friction factors increased then decreased.At very low roughness,the transition enhancement was not found.