Experimental Evaluation of the Effect of Pipe Inclination Angle on Minimum and Maximum Liquid Film Thickness in Two-Phase Flow

In this study, the effect of limited inclination angle on two-phase flow in a vertical pipe was investigated, focusing on the formation of liquid film thickness using image recording and processing techniques. To generate annular flow patterns, non-homogeneous air-water flow was utilized in three transparent pipes with diameters ranging from 25 to 75 millimeters. After analyzing the flow pattern results for various superficial gas and liquid velocities, Reynolds numbers, and different pipe diameters, both the maximum and minimum liquid film thicknesses were calculated and presented, along with their ratios. Additionally, the dimensionless equivalent liquid film thicknesses for inclined pipes were provided concerning the uniform film thickness in the fully vertical condition. The results indicated an increase in the ratio of maximum to minimum film thickness with a change in inclination angle from 90 to 85 degrees. Furthermore, the dimensionless equivalent liquid film thickness decreased with inclination angle, consistent with prior research findings. The uncertainty analysis revealed a maximum uncertainty of 4.9 percent in the experimental assessment of the liquid film thickness, which falls within an acceptable range.