NUMERICAL SIMULATION OF LIQUID FILM THICKNESS AND PRESSURE DROP IN MICROCHANNEL SLUG FLOW

Slug flow is a common flow regime in microchannel flow boiling cooling devices. The thickness of the liquid film around the bubble determines the heat transfer efficiency. Because of the existence of bubbles, the pressure drop of slug flow is different from that of single-phase flow. In this work, the two-phase flow with single gas slug in a 1-mm-diameter circular microchannel is numerically studied. Water and glycerol-water solution are used as the working liquid and air is used as the working gas. The results indicate that the bubble shape is stable at low velocity, while the bubble tail is wavy at high velocity. If the velocity increases further, the bubble will break. For slug flow at the same velocity, the film thickness of gas slug in glycerol-water solution/air condition is larger than that in water/air condition. The wall resistance of slug flow is mainly located at the bubble nose and tail, while the resistance in the middle of the bubble can almost be ignored.