Experimental study of two-phase flow regimes in slit microchannels

A two-phase flow in flat minichannels and microchannels with a height range of 50–1 mm and width range of 10–40 mm was experimentally investigated. The flow regimes were determined and regime maps were constructed. The characteristics of two-phase flows have been studied using laser-induced fluorescence and Schlieren methods. Transitions between two-phase flows and their formation have been investigated. Based on the developed methodology, criteria that accurately determine the boundaries between the two-phase flow regimes have been created. The two-phase flow regimes in microchannels were compared with theoretical models. For the Taitel and Dukler and Ullmann and Brauner models, an algorithm that calculates the regime maps for the given channel parameters was derived. It was shown that the Ullmann and Brauner model predicts quite well the transition to the stratified and annular regimes in channels with cross-sections of 0.05 × 20 mm 2 and 0.05 × 40 mm 2 . Regularities of the channel width influence on the transition to the annular regime were revealed. A criterion for the transition from the stratified to the annular regime, based on the discovered fact of liquid jet structuring along the channel, has been proposed.