Insights into the transition from plug to slug flow in a horizontal pipe: An experimental study

Abstract

A thorough understanding of the behaviour of the transition from plug to slug flow is imperative based on the fact that the transition can trigger an abrupt radial pressure variation. This can bring about major vibrations to the pipeline and also lead to big differences in pressure gradient and wall temperature. Unfortunately, the transition from plug to slug flow is poorly understood due to the scarce availability of experimental data. Furthermore, a considerable amount of research on the transition from plug to slug flow in the literature is based on an air–water system. In this work, the transition behaviour from plug to slug flow in a horizontal pipeline was experimentally investigated using electrical capacitance tomography (ECT). Working fluids are air–silicone oil. The work was carried out over a range of liquid and gas superficial velocities of 0.05–0.47 m/s and 0.05–4.7 m/s, respectively. Wave growth and wave characteristics mechanisms were observed to be responsible for the transition from plug to slug flow based on the obtained experimental results. Both liquid and gas superficial velocities have a major influence also on these mechanisms. The drift flux parameters for the transition from plug to slug flow was determined. A reasonably good agreement was observed from the comparison between present experimental data against hitherto published empirical models and correlations.