Two dimensional modelling of annular two phase flow

Abstract

A two-dimensional model for analyzing annular two-phase flow through tubular geometry, based on the solution of continuity, momentum, and energy equations, is presented. The numerical approach employed is an adaptation of the Patankar-Spalding method, which was verified by solving the single-phase entrance flow problem. For evaluating Reynolds stresses, a mixing-length model has been postulated specifically for annular two-phase flow conditions. The model predicts a variety of annular two-phase flow characteristics, including dry-out phenomena, for both uniform and non-uniform heat flux distributions, within a single computational framework. Validation was performed against available experimental data from air-water, steam-water, and Freon-12 systems. Based on computational results, observations regarding the influence of heat flux and phase distribution on pressure drop are discussed. It was found that at high pressures, during the formation of annular two-phase flow, the entrained flow fraction is significantly high and remains above the level required for hydrodynamic equilibrium across all qualities.