Experimental study on condensation heat transfer enhancement by various kinds of integral finned tubes.

Condensation on the outer surface of an integral finned tube, Thermoexcel-C, and a finned tube having ridges on the fin surface (called the R-tube) was investigated by using R 113 as a condensing medium. Heat transfer performances including a local heat-transfer coefficient in a circumferential direction were compared. The mean hcat-transfer coefficient of the R-tube was 30 %-40 % higher than that of Thermoexcel-C, and two times that of the integral finned tube. Since the ridges on the fin surface of the R-tube enlarged thin condensate film area in the upper part of the tube and promoted a convective heat transfer in the condensate film in the lower part : the heat-transfer performance of the R-tube was the best.