Steam Absorption inside Small Bore Tubes and Its Modelling

Abstract

Previously, numerical model for absorption within vertical pipes was proposed. Agreements were good for pipes with OD 25-15mm except 10mm or smaller. For smaller diameters, the difference between the surface area of the falling liquid film and that of the outer surface of the pipe is not negligible and the thickness of the liquid film is neither negligible. A new model is formulated in cylindrical coordinates and experiments using pipes with 9.52mm and 7mm OD are done. Smooth pipes and two kinds of internally finned pipes, which are originally developed and used to enhance the heat transfer characteristics of evaporator and condenser of refrigerator using HFC as refrigerant, are tested in the experiments. The absorption performance is enhanced by 30% compared to the smooth pipes, but the difference between the finned pipes are small.