A Mechanistic Model for Gas/Liquid Flow in Upward Vertical Annuli

In this study, a mechanistic model is developed to predict flow patterns, pressure gradient, and liquid holdup for gas/liquid flow in upward vertical annuli. The flow-pattern-transition model consists of a modified Zhang et al. (2003a) unified model for dispersed-bubble flow and annular-flow-pattern transitions, a Caetano (1986) model for bubbly-flow transition, and a modified Kaya et al. (2001) model for slug- to churn-flow transition. The hydrodynamic models are developed on the basis of the dynamics of slug flow, and the film zone is used as the control volume. The two liquid films are taken into account in the annulus-slug-flow and annular-flow model developments. The churn-flow model is developed on the basis of the Zhang et al. (2003a) unified model for pipe flow by using a much shorter slug length.