Characteritic of Low-Mass-Velocity Vertical Gas-Liquid Two-Phase Flow.

Abstract

Low-mass-velocity two-phase flow in a vertical pipe shows lower void fraction than high-mass-velocity two-phase flow even though their qualities are the same. In order to clarify the flow characteristics of the low-mass-velocity two-phase flow, air, water two phase flow experiments were conducted under the froth or annular flow conditions. Experimental results show that wall shear stress is positive even though both gas and liquid superficial velocities are positive. Measured water film average velocity is negative under this condition. These results indicate that local flow reversal should exist along the channel wall. This local flow reversal gives rise to the low void fraction in low-mass-velocity two-phase flow. It is also clarified that the drift flux model can be applied to the low-mass-velocity two-phase flow with local flow reversal.