Two-Phase Zero-Net Liquid Flow in Upward Inclined Pipes: Experiment and Modeling

Summary The effect of pressure on two-phase zero-net liquid flow (ZNLF) in upward inclined pipes has been studied experimentally and theoretically. Experimental data were acquired for four upward inclination angles, namely, 1,2, 5, and 9°, and for three system pressures of 14.7, 44.7, and 64.7 psia. A sequence of flow configuration was observed with increasing gas flow rate as follows: slug flow for low superficial gas velocities; protoslug for medium velocities; and pulsating, small-amplitude waves or roll waves at high velocities. At a particular velocity of gas, termed the blowout velocity, all the liquid was blown out of the pipe. An analysis of equilibrium stratified flow, at the limit of very low and zero liquid flow rates, has been carried out. It was found that, under these conditions, the flow is always unstable, resulting in intermittent or pulsating stratified flow. A model has been developed for the prediction of the blowout velocity, as well as average liquid holdup and pressure gradient under ZNLF conditions. A very good agreement was observed between the predictions of the proposed model and the experimental data.