矩形和圆形微通道内流体流动特性的实验研究

流体在微米级通道中的流动规律与常规通道不同,其区别主要体现在摩擦因子、转捩雷诺数和泊肃叶数等方面。针对上述问题,实验研究了水在水力直径为167~195 m矩形硅通道和水力直径为168~399 m圆形玻璃微管中的流动特性。结果表明,对水力直径为167~195 m的矩形通道,其转捩雷诺数发生在1 300~1 480;对水力直径为168~399 m的圆形通道,其转捩雷诺数位于2 600~2850,且二者的摩擦因子和泊肃叶数与理论值基本一致,这说明了微通道的形状对流动阻力特性没有明显影响。通道S-3的长径比为173,其入口段长度比常规管道入口段略长,说明微通道的入口效应较明显。实验测量了微通道的局部阻力压降随流量变化的关系。结果表明,突变微通道内水流动的局部阻力符合常规理论曲线。

Experimental Study on Flow Characteristics in Rectangular and Circular Microchannels

Flow characteristics in channels with micron dimension are different from macroscale channels,which mainly embodies three aspects friction factor,transition Reynolds number and Poiseuille number.With this background,the flow characteristics of water were experimentally investigated in rectangular silicon microchannels with hydrodynamic diameter ranging from 167 m to 195 μm and 168 m to 399 m for circular glass microtubes.The experimental results show that the values of the critical Reynolds number fall between 1 300 and 1 480 in rectangular microchannels with the hydrodynamic diameter of 167 m to 195 m while falling between 2 600 and 2 850 in circular microtubes with the hydrodynamic diameter of 168 m to 399 m;Besides,the friction factor and Poiseuille number of both rectangular microchannels and circular microtubes are consistent with the theoretical values,which indicates geometric features have no significant influence on flow resistance.The entrance length in channel S-3 with length-diameter ratio of 173 is slightly more than that of conventional channel,which shows that the entrance effect is obvious in micro-scale channel.Investigation of the relationship of local resistance versus the flow rate in rectangular silicon microchannel shows good agreement between theoretical curves and experimental results.