Experimental study of water-air countercurrent flow characteristics in large scale rectangular channel

Water-air countercurrent flow in a rectangular channel is studied experimentally in this study. The experiment is carried out in a large scale facility that consists of a large scale flow channel and a rotatable operating platform which provides different inclination conditions. This paper focuses on the study of film behavior, such as film thickness and surface wave, in countercurrent flow. Optical thickness probe, hot wire anemometry and high speed camera are applied to perform the data measurement. The results show that the film thickness variation in the large scale channel under countercurrent flow condition is different from the results from small scale tests. The critical air velocity, which is usually considered as the proof of flooding onset, is discussed for different film Reynolds numbers. Moreover, the droplet entrainment plays an important role under high speed air flow conditions. The observation of the surface wave is also conducted to supplement the analysis of film surface variation.