Slug behavior and pressure drop of adiabatic slug flow in a narrow rectangular duct under inclined conditions

Abstract

A visualization-based investigation was carried out on slug behavior and pressure drop of air–water slug flow in a narrow rectangular duct with cross section of 43mm×3.25mm under inclined conditions. The velocity and length of slugs were obtained through image processing. Based on the liquid Reynolds number, slug flow was divided into laminar flow region (Rel<3000) and turbulent flow region (Rel⩾3000). Experimental results showed that both the slug velocity and the slug length increased with the inclination angle increasing in laminar flow region, while they were nearly unvaried in turbulent flow region. The slug length and slug frequency decreased with the gas superficial velocity increasing or the liquid superficial velocity decreasing for all cases. For laminar flow, the predictions of frictional pressure drop by Chisholm model, Mishima–Hibiki correlation and Lee–Lee correlation could be significantly improved by replacing the void fraction with the ratio of the slug velocity divided by the gas superficial velocity, us/jg; for turbulent region, all three models could well predict the experimental data if void fraction is calculated by the Jones–Zuber correlation.