CONDENSATION HEAT TRANSFER ENHANCEMENT BY RIDGES ON INTEGRAL FIN SURFACES

A finned tube having ridges on the fin surface, called an R-tube, was investigated using R113 as a condensing medium. Heal transfer performance, including a local heal transfer coefficient along a circumferential direction, for the horizontal R-tube was compared with that of an integral finned tube and a commercial Thermoexcel-C tube produced by Hi-tachi, LId. Because the ridges increase the thin condensate film areas on the fin surface, the mean condensation heat transfer coefficient of the R-tube was the highest among the tubes tested and was two times that of the integral finned tube. From measurements of the circumferential distribution of the heal flux, the local heal flux was highest at the top of the tube, but has a second peak approximately phi >= 110 degrees from the top.