Gas-liquid Interfacial Friction Factor under Flooding Conditions in Vertical Pipes

In our previous studies, we carried out air-water counter-current flow experiments under flooding conditions in vertical pipes of 40 mm diameter with combinations of sharp-edged or rounded top and bottom ends to measure counter-current flow limitation (CCFL), pressure gradient dP/dz, and void fraction αG. We obtained the wall and interfacial friction factors, fw and fi, and proposed a correlation of fw. In the present study, we carried out similar experiments with sharp-edged top and bottom ends, and obtained fw and fi. We proposed a correlation of fi for all flow patterns including smooth film (SF) and rough film (RF) due to flooding at the top and bottom ends, respectively. By using the one-dimensional annular flow model and the proposed fw and fi correlations, we computed the liquid volume fraction αL,cal and compared it with the experimental data αL,exp. The computation gave two solutions of αL,cal for SF and RF, which agreed relatively well with the αL,exp values for SF and RF in the regions of low gas superficial velocity JG and high JG, respectively.