Experimental investigation of force balance at vapour condensation on a cylindrical fin

Experimental investigation of vapour condensation on single cylindrical fin has been carried out under various gravity conditions: 1g0, 1.8g0 and 0.05g0. For the first time, a balance of forces acting on the condensate flow is analyzed. The fin surface is divided in seven areas, each one being characterized by the main force acting on the liquid motion: gravitational vs surface-tension pressure gradient. The magnitude of the areas does not depend on the gravity level. This confirms the correctness of the fin surface segmentation, as used by various authors, to simplify the condensation modelling. It has been shown that the most intensive vapour condensation takes place in the areas, where the surface-tension pressure gradient is higher than the gravity force. Analysis of the heat load shows that each region affected by the surface-tension pressure gradient provides 10–15% of the total heat load, a contribution that is not negligible and should be taken into account. In case of low gravity, the most intensive condensation takes place at the corner of the fin tip, where the curvature gradient is maximum, and on its cylindrical part. The heat loads in these regions are comparable.