A model for predicting two-phase flow patterns transitions in an annulus: Inclinations from horizontal to near-vertical

Abstract

The concomitant flow of a mixture containing two phases is a complex phenomenon. One of the reasons is that the phases’ interactions depend on the variations of the operational condition imposing the formation of different flow patterns that, in turn, can undergo pattern transition depending on the geometric cross-section change. This paper proposes a model for any annulus inclination, from horizontal to near-vertical, and considers a concentric condition in the particular case of a pipe. The outcome is a generalized, two-phase flow pattern maps function of dimensionless parameters. The influence of the tube inclination is investigated for the transitions: stratified smooth/stratified wavy, stratified wavy/annular dispersed liquid, stratified/intermittent, annular dispersed liquid/intermittent, and intermittent/dispersed bubble. Also, mathematical relations for calculating the shear stress and velocity profile in annuli under inclinations are developed. A new methodology, based on geometric parameters, help obtain the wetted area and perimeters, reducing the classical set of equations.