Effect of vapour velocity on condensate retention between fins during condensation on low-finned tubes

The paper reports experimental results using simulated condensation on horizontal finned tubes in a vertical wind tunnel. Condensation was simulated using three liquids (water, ethylene glycol and R113) supplied to the tube via small holes between the fins along the top generator of the tubes. Eight tubes with different fin dimensions were used. The results indicate that when the retention angle (measured from the top of the tube to the position where the interfin space is completely filled with liquid) is less than about π/2 at zero air velocity, it increases with increasing air velocity. On the other hand, for cases where the retention angle is greater than about π/2 at zero air velocity it decreases with increasing air velocity. In all cases (all fluids and all tubes tested) the retention angle approaches a value near π/2 with increasing air velocity. Satisfactory agreement was found with observations taken during condensation.