Author(s)

M. H. S. Zangana & B. J. Azzopardi

Abstract

Systematic experiments have been carried over the ranges of 0.02–0.1m/s and 6.2–16.5 m/s liquid and gas superficial velocities respectively. In the experiments the total pressure drop, liquid film thickness and wall shear stress in vertical upward pipes of air–water two phase flow are measured simultaneously on the 127 mm closed loop facility at Nottingham University. For the overall pressure difference over a length of test section a differential pressure cell was employed. Circumferentially averaged and local film thicknesses were obtained using conductance rings and local pin probes respectively in different locations on the test section. Both magnitude and directional wall shear stress also measured employing the hot film based techniques. In addition, the data were supported by some high speed video images through a visualization campaign. The time series of film thickness show that the interface between the gas and the liquid is rough and that this roughness is visibly influenced by variation in liquid and gas velocities. There are consequent effects in wall shear stress and total pressure drop. From the directional wall shear stress data and the high speed videos is noted that no completely unidirectional upward flow has been observed over the conditions studied. This applies at the upper end of the range of gas velocity studied, a rather unexpected. This might be linked to the characteristics of wave on the liquid film. Keywords: gas–liquid flows, liquid film properties, film thickness, pressure drop, wall shear stress, large diameter pipes.

Keywords

gas–liquid flows, liquid film properties, film thickness, pressure drop, wall shear stress, large diameter pipes.