A unified correlation for predicting slug liquid holdup in viscous two-phase flow for pipe inclination from horizontal to vertical

This study presents new measured slug liquid holdup data for liquid viscosity ranging from 200 to 800 mPa s.The experiments were conducted using two different large pipe diameters (0.08 and 0.1 m) and pipe inclination angles of 0 degrees, 30 degrees, 60 degrees and 90 degrees from horizontal. To our best knowledge, most of the existing experimental data were limited to either vertical or horizontal flow and mostly performed using small pipe diameters. Based on the measured data, a new unified empirical correlation is developed to predict slug liquid holdup for viscous two-phase flow in horizontal, vertical and inclined pipes. The proposed correlation is simple and fully consistent with the trends of published experimental data. This study also investigates in details the performance of the existing liquid holdup correlations using different flow conditions. The investigation reveals several discrepancies associated with these correlations. Based on statistical analysis, the proposed correlation performs best as compared to the existing correlations using both the present measured data and data from three independent sources.