Void Fraction Distribution of Upward Bubbly Flow in a Vertical Pipe with Sudden Expansion

Abstract

Experimental study was made on the multi-dimensional behavior of upward gas-liquid two-phase flow through a vertical pipe with an axisymmetric sudden expansion. In this study, the measurement on the void fraction distribution was carried out for the sudden expansion channel. The void fraction distributions below and above the sudden expansion point were measured at the different axial and radial positions using a point-electrode resistivity probe for various gas and liquid flow conditions. The results of measured void fraction distributions showed that how the two-phase flow develops along the direction of the downstream of the sudden expansion. Furthermore, the development of the void fraction distribution also revealed quite complicated behaviors depending upon flow rates of gas and liquid phases and bubble size. Based on the measured void fraction distribution in the sudden expansion, cross-sectional averaged void fraction and phase distribution parameter were evaluated at the different tube cross sections in the sudden expansion. As a result, it revealed that the void fraction along the flow direction in the sudden expansion might be predicted by using the appropriate distribution parameter representing the void fraction distributions in the sudden expansion.