INVESTIGATING THE HYDRODYNAMIC BEHAVIOUR OF TWO-PHASE FLOW NEAR THE TRANSITION TO CHURN FLOW IN A VERTICAL PIPE

Abstract

Information on the transition from slug to churn flow regime, a two-phase flow, in a vertical pipe is currently scanty. As a result of this, this research was set up to provide useful information on the parameters needed for the transition of the flow and their impacts. The study was carried out to evaluate the hydrodynamic behaviour of two-phase flow, from slug to churn in a vertical pipe, using silicon oil and air as the working fluids. The needed parameters evaluated include; structure velocity, frequency, void fraction in the slug and pressure drop. The study comprised a vertical pipe flow rig, containing twin Electrical Capacitance Tomography (ECT) planes and Wire Mesh Sensor (WMS). The gas and liquid superficial velocities used were 0.047 to 4.727 m/s, 0.047 to 0.378 m/s respectively. The results were analysed using PDF, structured velocity, power spectral density, and dominant velocity. It was discovered that the transition from slug to churn flow regime was first noticed in the void fraction between 0.68 to 0.99. It is evident that slug flow occurred at a gas superficial velocity (0.288 to 0.544 m/s), while that of the transition flow, from slug to churn, occurred at 0.709 to 0.945 m/s gas superficial velocity. The churn flow regime was established at 1.41 to 4.727 m/s, with the liquid superficial velocity observed 0.047 to 0.378 m/s. As the gas superficial velocity increases, there was a change in the flow regime which led to the transition. Slug flow has dual peak at the low and high void fractions, but changed as it transited to churn flow. It could be established that an increase in gas superficial velocity would lead to decrease in the gravitational pressure gradients.