并行微通道内气液相分配规律

Gas-liquid flow distribution of parallel microchannels

微反应器的集成放大对于微化工技术的工业应用具有重要意义。利用高速摄像仪对4个并行微通道内气液两相流动状况及相分配规律进行了研究,考察了气液两相流量及液相黏度对两相分布均匀性的影响。实验所用液相为含0.3%表面活性剂十二烷基硫酸钠(SDS)的蒸馏水-甘油溶液,气相为氮气(N2)。实验观察到了6种典型的两相流型。对各支通道均为弹状流情况下气泡长度和气泡速度的分布规律进行了研究。在一定气相流率下,各支通道气泡长度的相对标准偏差随液相流率的增大而增大,气泡速度的相对标准偏差值随液相流率的增大先升高到一定值然后逐渐减小。气相分配不均匀性随液相流率和黏度的增大而增大,液相分配不均匀性随液相黏度的增大而减小,气相流率的变化对于两相分布影响不明显。研究结果有助于并行微通道的结构设计与优化,以实现更为均匀的气液两相流动分配。

The scale-up of microstructured reactor is an essential issue in order to achieve required throughput for industrial application. A high speed camera was used to observe gas-liquid flow pattern and phase distribution in four parallel microchannels. The influence of flow rate and viscosity on flow uniformity was investigated. The experimental liquid phase was deionized water with 0.3%（mass） surfactant sodium dodecyl sulfate （SDS）-glycerol, and the gas phase was nitrogen （N2）. Six types of two-phase flow patterns were observed in the parallel microchannels. For the situation of all slug flow in four branch channels, the distribution of bubble length and velocity was studied. At a given gas flow rate, the relative standard deviation （RSD） of bubble length in branch channels increased with increasing liquid flow rate, and the RSD of bubble velocity in branch channels increased with increasing liquid flow rate up to a maximum and then gradually decreased. Non-uniformity of gas phase distribution increased with the increase of liquid flow rate and viscosity, and non-uniformity of liquid phase distribution decreased with the increase of liquid viscosity. The influence of gas flow rate on two-phase distribution was not significant. The study is helpful for the design and optimization of parallel microchannel structure to realize the uniform two-phase distribution.