Two-phase bubbly flow structure in large-diameter vertical pipes

The two-phase flow structure of an air-water, bubbly, upward flow in a 20 cm diameter pipe is presented with particular emphasis on the local interfacial area concentration. The radial distribution of void fraction, bubble velocity, bubble size, bubble frequency, and interfacial area concentration were measured using a local dual-optical probe. The experimental results showed that the saddle-type distribution of void fraction and interfacial area concentration, which are common for bubbly flow in small diameter pipes, only appeared in the present experiments under conditions of very low area-averaged void fraction (<epsilon> < 0.04). The values for the interfacial area concentration were higher in large diameter pipes when compared with data obtained under the same flow conditions in small pipes The area-averaged void fraction data were correlated using the drift-flux model.