Gas-liquid-liquid three-phase flow in cross microchannels has been widely used in flow chemistry and process intensification. At present, the flow and mass transfer characteristics in this microchannel are not well understood. In this work, the hydrodynamics and liquid-liquid mass transfer characteristics of gas-liquid-liquid three-phase flow were systematically investigated. For the gas-liquid-liquid hydrodynamics, the bubble/droplet size prediction model based on the multiphase cooperative behavior was proposed, which could be used in predicting droplet/bubble size in flow systems. For the gas-liquid-liquid mass transfer process, the semi-empirical prediction formula of the mass transfer coefficient was obtained by considering the vortex strength, the interfacial area and the effective mass transfer area. This work could be the comprehensive study of gas-liquid-liquid three-phase flow and liquid-liquid mass transfer under gas enhancement in the cross microchannel.

The droplet generation mechanism in the step T-junction remains unknown, especially for the transition stage from dripping to jetting . In this work, the droplet generation mechanism was systematically investigated in a novel modified step T-junction. We found that under different fluid regimes, different factors take action. In dripping regime, the interfacial tension dominated the formation mechanism when the surfactant concentration was controlled below micelle concentration (CMC). In jetting regime, our experimental results showed that the influence of the surfactant concentration on the size of generated droplets was rather negligible while the phase ratio indeed determined such a parameter. In the dripping-jetting transition stage, an abnormal increase of droplet size was observed despite the increase of continuous phase flow. To the best for our knowledge, it is the first study to report generation mechanism in modified step T-junction from dripping to jetting regimes.