Study of Flow Patterns and Void Fraction in Inclined Two Phase Flow

Abstract

In the field of multiphase flow, much research has been done on flow patterns and void fraction in vertical upward, vertical downward and horizontal pipes with only very little investigation done in inclined pipes. Experimental investigation was conducted in present study over six pipe orientations (+5, +10, +20, -5, -10 & -20 degrees) using air-water as fluid combination in a 12.7 mm diameter pipe. Flow visualization was conducted for flow pattern identification, flow pattern maps were developed showing effect of pipe orientation on flow pattern transition boundaries and 700 void fraction data points were measured and analyzed. Effect of pipe orientation on void fraction was also observed and reported. Fourteen void fraction correlations were selected for experimental data prediction based on previous works and the best performing void fraction correlation for upward inclined pipe, downward inclined pipe and near horizontal pipe orientation was determined. A unique phenomenon called flow reversal in co-current two phase flow was observed in upward inclined pipe orientation and investigated in present study. Flow reversal was investigated using Bernoulli's equation and dimensionless numbers (Froude, Reynolds & Weber number) which gave in-depth analysis of this phenomenon.