激光全息干涉测定微通道内气液传质

Measurement of Gas-Liquid Mass Transfer in Microchannel using Microscopic Laser Holographic Interferometry

为了进一步理解微通道内气液两相传质过程机理,利用激光全息干涉条纹与流体折射率以及折射率与流体浓度的关系,采用激光显微全息干涉测试系统对微通道入口处Taylor气泡形成过程中的液相侧浓度分布进行了测定。微通道尺寸为深100μm,宽2000μm,长4cm。气相采用CO2,液相使用无水乙醇。利用图像采集系统对干涉条纹的变化过程进行实时记录,并利用自编图像处理软件对干涉条纹图像进行处理,得到了Taylor气泡形成过程中液相侧浓度分布和近界面浓度边界层厚度。结果表明,在Taylor气泡形成过程中有较强的传质发生,液相近界面浓度和浓度边界层厚度均随着气液相流速的增大而减小。结果显示,利用激光显微全息干涉测试系统,对微观尺度通道内部的气液传质过程进行实时测定研究,可得到清晰的图像和满意的结果。

In order to understand further the gas-liquid two-phase mass transfer process mechanism in microchannel, by using the relationship between stripes and fluid refractive index and that between refractive index and the fluid concentration, the microscopic laser holographic interferometry is used to study the concentration distributions on the liquid side during the formation of Taylor bubble at the inlet of microchannel. The dimension of microchannel is 100 μm in depth, 2000μm in width, and 4 cm in length. C02 is used as gas phase and ethanol is used as liquid phase. The shift of the interference stripes during the absorption is recorded by image acquisition system, and the images are treated by a self-designed digital image processing system. Experimental results show that there is obvious mass transfer during the generation processes of Taylor bubbles, and both the liquid side concentration near the interface and the thickness of concentration boundary layer decrease with the increment of liquid and gas velocities. The results show that, for real-time determination of gas-liquid mass transfer process, microscopic laser holographic interferometry testing system can obtain clear images and satisfactory results in the micro scale channels.