Two-phase flow through pipe branch junctions

Abstract

Detailed distributions of void fraction and velocity are observed for flow in the vicinity of a junction where a side branch draws a flow from a vertical main pipe flow of a gas-liquid mixture in the froth-bubbly flow regime. Velocity ratio, momentum and energy distribution parameters determined from these needle void probe measurements are then combined with the equations for compressible mixture flow to facilitate the determination of the branch junction force and pressure loss coefficients. Values of these coefficients were found to be of comparable magnitude to those found in single-phase flow through a junction, although some significant variations due to the larger proportion of the gas phase diverted to the branch were observed. This larger proportion of gas phase division to the branch increased with the mixture void fraction and overall branch flow rate. Whilst the branch flow was stratified, it was found to be significantly less intermittent in nature than the main inlet and outlet flows. Pulsations in the void fraction were between 0.2 of the local mean void fraction in the branch and 0.6 in the main outlet flow, which also tended to exhibit a characteristic frequency of voidage pulsation.