Rising Behavior of Air–Water Two-phase Flows in Vertical Pipe of Poor Wettability

Abstract

Bubbles and slugs rising in vertical pipes of good and poor wettability were observed with a high-speed video camera. The mean rising velocity of bubbles on the pipe center line was slightly smaller in the poor wettability pipe than that in the good wettability pipe because the attachment of bubbles to the pipe wall took place in the former pipe, while that of slugs was hardly dependent on the wettability of the pipe. The mean vertical length of bubbles on the pipe center line was slightly larger in the pipe of poor wettability than that in the pipe of good wettability due to the coalescence of bubbles on the wall of the pipe of poor wettability. However, the mean vertical length of slugs was not dependent on the wettability of the pipe. An empirical equation was proposed for the mean vertical length of slugs.