Axial viewing studies of horizontal gas–liquid flows with low liquid loading

An axial viewing system is described which was used to investigate the behaviour of the liquid phase in two-phase gas–liquid flows in a 0.079 m diameter horizontal pipe. The region investigated was that of flows with relatively high gas velocities and low liquid loading. Such flows are typically experienced in gas-condensate lines. Axial images obtained using the new system, show that the bulk of the liquid flows within a layer at the bottom of the pipe; however, at higher gas or liquid velocities, a significant portion is entrained as droplets within the gas core and is seen to deposit around the pipe periphery. A process that appeared to contribute significantly to the entrainment was captured using a high speed video recording system. Waves on the liquid layer were observed to converge and breakup into rapidly moving spray droplets. This process appeared to be random, but more frequent with increase in gas or liquid velocities. Secondary droplet breakup was also observed; large droplets were seen to balloon out and burst. The video evidence obtained using the axial viewing method, clearly identified the process of entrainment and deposition as the dominant contributor to the liquid phase transfer to the upper part of the pipe wall.