Influence of Liquid Properties on Gas-Liquid Flow Regimes and Pressure Drop in a Flat Microchannel

An urgent problem at the moment is to study various microchannel systems owing to the trend of miniaturization of devices. The present study is aimed at investigating the properties of the working liquid on the regimes of a two-phase flow and pressure drop in a flat microchannel 130 m high. The high-speed schlieren method is used for visualization of fast processes that occur in the microchannel. It is shown that the working liquid properties and microchannel wall wettability produce a significant effect on the two-phase flow regimes and transitions between them. Regions of jet, bubble, and churn flow regimes are observed at identical Weber numbers of the liquid and gas for different working liquids. The hydraulic resistance of various working liquids is studied. It is demonstrated that drastic jumps with an increase in the superficial gas velocity are observed for water during the transition to the churn flow regime. This feature is associated with washout of dry spots with an increase in the superficial liquid velocity owing to a significant effect of the hysteresis of the contact angle of wetting.