Transition From Stratified to Annular Flow in a Flat Minichannel at High Liquid and Gas Velocities

This study is devoted to the experimental investigation of the transition from stratified to annular flow in a flat minichannel at various gas and liquid velocities, including condition of turbulent flow. Water and air were used as the components of the two-phase flow. It was found that the transition to annular flow at high liquid and gas flow rates occurred not only due to side wall wetting, as reported in the literature, but also due to drop entrainment. Moreover, when the influence of side wall wettability was eliminated by placing fibers into recesses near the side walls of the minichannel, the transition to annular flow at high liquid and gas flow rates occurred solely due to drop entrainment from the wavy gas-liquid interface, which, to the best of the authors knowledge, was obtained for the first time.