Parameter optimization on condensation heat transfer of R134a over integral-fin tubes

Abstract

Experimental studies of film condensation of R134a on one horizontal smooth tube and five integral-fin tubes have been conducted. The fin number per inch varies from 19 to 56. The objective is to enrich the basic data for film condensation of R134a on enhanced tubes and to optimum fin density for the condensation of R134a on integral-fin tubes. Wilson plot technique was used to obtain the condensation heat transfer coefficients. The results indicate that the predicted condensation heat transfer coefficients of R134a on smooth tube from Nusselt theory agree with the experimental data within 10 percent. It is found that the condensation heat transfer coefficient increases with the increase of fin density, so the optimum fin density is about 46 to 56 fpi for R134a condensing outside integral-fin tubes. Compared with the smooth tube, at a saturation temperature of 40 C and for the identical temperature difference, the enhancement factors of the five enhanced tubes(56fpi, 46fpi, 38fpi, 26fpi, 19fpi) are 7.7-10.2, 7.2-10.1, 6.6-8.2, 6.5-7.0, 5.4-5.5, respectively.