Computational and experimental study of multiphase flow in inclined pipes

This work presents a computational and experimental investigation on the effects of liquid properties on multiphase flow in horizontal and upward-inclined pipes. The overall aim of the research is to gain more insight into the effects of viscosity, density, and surface tension on multiphase flow behaviour. The computational part of the study simulated the drift velocity of an elongated gas bubble, commonly referred to as Taylor bubbles in a 2D domain. The computational efficiency of 2D simulation makes it a preferred option for parametric studies, where different operational parameters are systematically varied to understand their impact on the flow behaviour. By simplifying the geometry to 2D, it becomes easier to explore a wide range of parameters and assess their effects. In this work, 78 simulations were run at six different pipe inclinations to study the effects of 13 different liquids. The simulation results show that liquid density alone has little or no influence on the Taylor bubble’s velocity at all pipe inclinations, while the bubble’s velocity is heavily influenced by liquid viscosity at all pipe inclinations. However, surface tension appears to show unique effects on the Taylor bubble, when the pipe inclination is less than 45 degrees, surface tension seems to have no effect on Taylor bubble’s drift velocity, the effects of surface tension only become notable when the flow inclination is at 45 degrees or above. This behaviour has not been reported by previous researchers based on the review done, as no previous work has singled out one liquid physical property to study its effect while keeping the other properties constant. Experimental study on the effects of liquid properties was also carried out to generate two-phase flow data using three different liquids, water, surfactant solution, and glycerol solution in a 19 mm ID pipe and 4m length. The experimental campaign was carried out in horizontal and 15 degrees upward inclinations. Two-phase flow regime and slug frequency data were acquired using a high-speed camera, quick-action solenoid valves were used to collect liquid holdup data, and a differential pressure transducer was used to measure the pressure drop across the flow section. The effects of liquid properties and variation of inclination angles on different flow parameters including flow regime, pressure drop, liquid holdup, and slug frequency were investigated and reported. Flow regime maps were also developed for all flow orientations investigated. The data generated would be a useful contribution to the gas/liquid flow database and could potentially be used to develop or improve multiphase flow correlations.