Theoretical Analysis of Flow Characteristics of Multiphase Mixtures in a Vertical Pipe.

The purpose of the present investigation is to theoretically analyze the flow characteristics of the air-lift pump for the case where a transitional process from the solid-liquid two-phase mixture flow to the solid-gasliquid three-phase mixture flow by injecting gas-phase into the upriser through a gas-injector is present. The system of equations governing the liquid-solid two-phase mixture flow consists of two mass conservation equations, two momentum conservation equations and an equation for two-phase volume fractions. Again, the gasliquid-solid three-phase flow field after the position of gas injection is solved by three mass conservation equations, three momentum equations, a gas equation of state and an equation for the individual phase volume fractions. The transitions of the flow pattern of gas phase from the bubbly flow to the slug flow and from the slug flow to the churn flow are taken into account in the system of governing equations of three-phase flow. In order to verify the validity of the system of governing equations accounting for the transition of the flow patterns, the flow characteristics calculated on the basis of the present theoretical model have been compared with experimental data by several other investigators. As a result, we have found that the present theoretical model built up in this study gives good fit to the experimental data obtained by several investigators.