Hydrodynamics of gas-liquid countercurrent flow in internally finned monolithic structures

The flooding behaviour of gas-liquid countercurrent flow was studied in a set of small diameter internally finned tubes that were bundled in a hexagonal arrangement so that a monolith like structure was obtained. The liquid outlet of the tubes was bevelled at an angle of 70 degrees to enhance the countercurrent flow. In order to investigate the effect of the fins, the flooding behaviour was compared with countercurrent flow in a bundle of unfinned tubes, having almost the same cross-sectional area. It was found that because of the stabilising effect of the fins, a transition regime exists between the wavy annular film flow regime and the total flooding regime. This regime, which is characterised by pressure drop fluctuations that are in the order of 10%, is completely reversible without hysteresis to occur. Experiments with various liquid outlets demonstrated that not the liquid drainage but the way of feeding the gas has the largest effect on the flooding limits. (C) 1997 Elsevier Science Ltd.