Effect of Inclination on Distribution of Entrainment Flow Rate in an Inclined Upward Annular Flow.

Abstract

The droplet entrainment in an annular flow plays an important role in heat and mass transfer. owever the fundamental experimental data such as film thickness, entrainment flow rate and disturbance wave velocity in the case of an inclined upward annular flow are very few compared with similar data in the case of two-phase flow in vertical and horizontal pipelines. In this paper, experimental data on the distribution of entrainment flow rate and the onset of liquid entrainment in an inclined upward annular flow are presented and the effects of the inclination angle are examined. In this experiment, the isokinetic sampling probe technique was used for the measurement of the entrained droplet flow rate and the ranges of inclination angle examined were 0, 30, 45, 60°and 75°from horizontal. As a result, it was clarified that the difference in droplet mass flux between the upper and lower tubes becomes small as pipe inclination increases, the entrainment fraction increases as both the flow rate and the inclination increase and the critical gas velocity for the onset of entrainment becomes small as the liquid film Reynolds number and the inclination increase. Furthermore, Ishii & Mishima's correlation for the entrainment fraction was modified for application to the inclined upward annular flow.