GAS ENTRAINMENT IN A LONG LIQUID SLUG ADVANCING IN A NEAR HORIZONTAL PIPE

The aeration of a liquid body advancing over a slow moving liquid layer in a pipe has been experimentally investigated with a conductance method. The 50 mm i.d. pipe section was close to horizontal and the fluids were air and water at atmospheric conditions. It has been found that net gas entrainment only occurs when the relative velocity between the advancing front and the liquid layer is greater than a limiting value. The rate of gas entrainment is proportional to the relative velocity between the advancing slug and the liquid layer, and to the interfacial width of the layer. Measured pressure drops, film heights and gas volume fractions in the advancing slug agree well with available correlations or with similar measurements taken under conditions of fully developed slug flow.