Experimental studies on two phase flow patterns of air-water mixture in a pipe with different orientations

The experimental investigation of two-phase flow behavior in a pipe of 8 mm diameter and 2 m length with different orientations is presented in the study. Air and water are considered as the working fluids. The superficial velocities of water and air are varied over a wide range from 0.06 to 1 m/s and 0.06-15 m/s, respectively. The pipe is tilted at 0 degrees, 30 degrees, 45 degrees, 60 degrees and 90 degrees for investigating the effect of gravity on the two-phase flow behavior. The effect of pipe orientation and air-water velocities on two phase flow patterns, void fraction (alpha) and local drift velocity (U-gj) are presented. The flow regimes are observed using a high-speed video recorder and the comprehensive visualization of air-water two-phase flow is analyzed using image processing technique. The results show that the stratified flow is observed in the horizontal pipe but it does not appeared in the tilted pipe. For same velocities of water and air, the effect of turbulence is dominated when the angle of the pipe increases against the gravity that leads to churn flow. The experimentally obtained flow patterns are compared with the existing literature and observed that they are in good agreement. Further, the void fraction is measured experimentally, and it is compared with the predicted results of the famous correlations reported in the literature. Based on these studies, a new correlation is also developed and it is used to predict the void fraction of two phase flow at any angle from 0 degrees to 90 degrees.