Flow behavior and film thickness of gas-oil two-phase flow in the single screw expander

Abstract The objective of this work is to study the flow behavior and oil film thickness in the vertical helical channel to improve the efficient operation of the single screw expander. The volume-of-fluid (VOF) model is adopted to examine various effects, including flow direction, oil viscosity, surface tension, flow rate, and oil inlet width on the liquid film thickness distribution and liquid holdup. An interesting phenomenon is found that the gas axial velocity is accelerated in the flow, and this has a profound influence on the liquid film thickness distribution and liquid holdup. The liquid film thickness exhibits a significant improvement as the downward flow is considered. The liquid film thickness becomes more symmetrical with increasing the oil viscosity, surface tension, oil flow rate, and inlet width, and more liquid are concentrated at the two endpoints of the channel. A higher viscosity oil or larger surface tension coefficient will result in a higher liquid holdup. These results and analysis are crucial for improving the performance of single screw expanders.