Analyses of the effects of channel inclination and rotation on two-phase flow characteristics and pressure drop in a rectangular channel

This paper presents a broad study on gas-liquid flow in inclined channels with rectangular cross section. Experimental data are presented for flow patterns, pressure drop and bubble shape during air-water flows for channel inclinations ranging from -90 degrees to +90 degrees relative to the horizontal plane, and channel axial rotations of 0, 45 and 60 degrees. The test section is 6.0 mm deep, 6.5 mm wide, and 1.2 m long. Experiments were performed for mass velocities ranging from 90 to 760 kg/m(2)s, corresponding to gas and liquid superficial velocities ranging from 0.09 to 19.4 m/s, and from 0.1 to 0.76 m/s, respectively. Flow patterns were identified based on flow images captured with a high-speed video camera and on the k-means clustering method based on an analysis of pressure drop and optical signals. It was found that duct inclination and channel rotation affect the flow pattern transitions. Moreover, two-phase stratification effects were enhanced by rotating the channels, and the effect of channel rotation on pressure drop was found negligible. On the other hand, the channel inclination affects significantly the pressure drop, whereas gravitational pressure drop parcel was the main parcel of the total pressure drop for most of non-horizontal conditions. The influence of flow pattern transitions on the pressure drop was inferred based on changes of the pressure drop behavior.