Parameter optimization on condensation heat transfer of R22 outside horizontal integral-fin tubes

Experimental studies of film condensation of R22 on single horizontal smooth tube and five enhanced tubes have been conducted. The objective is to obtain optimum fin density on condensation heat transfer characteristics. The results indicate that the predicted condensation heat transfer coefficients of smooth tube from Nusselt theory agree within ± 10 percent with the experimental data. Experimental results show that integral-fin can effectively enhance condensation heat transfer. It is found that the optimum fin density is 1720fpm from the present study when R22 condensing outside the integral-fin tube. At a saturation temperature of 40°C and for the same values of heat flux, average enhancement factors of five enhanced tubes C21-C25 are 10.36, 11.46, 9.19, 7.69, 5.63, and for the same values of temperature difference, the average factors are 5.78, 6.24, 5.28, 4.62, 3.65 respectively. It is found that the enhancement of condensation heat transfer is larger than that of the area increase for R22 condensing outside integral-fin tubes.