Numerical investigation of flow behavior and film thickness in the single screw expander

Abstract The need to understand the flow behavior and film thickness in the single screw expander is very crucial since it is known to be a complex system due to the existence of various flow patterns. The present work reports a computational fluid dynamic analysis of two-phase flow behavior and film thickness through a vertical helical rectangular channel using the volume of fluid (VOF) model. The numerical model is validated against available experimental data of annular flow in the helical rectangular channel. The numerical predictions of velocity field, pressure field and liquid phase distribution are presented as each fluid flows into the helical channel. It is found that the inlet flow inclined angle has a significant influence on the liquid film distribution at the outer side of the helical channel. The effects of curvature ratio and dimensionless pitch on the liquid film distribution, film thickness and liquid holdup are illustrated in detail. In addition, the new relationship between the average liquid film thickness and the liquid holdup is also given, and these results are necessary for the optimization design of the single screw expander prototype.