Effect of non-condensible gas on condensation heat transfer of R123

Experimental studies of film condensation of R123 on single horizontal smooth tube and five enhanced tubes are conducted. The objective is to reveal the influence of non-condensible gas on optimum fin density for the condensation of R123. The results indicate that the predicted condensation heat transfer coefficients of pure R123 on smooth tube from Nusselt theory agree well with the experimental data within ±5 percent. It is found that the optimum fin density is about 1475 fpm for R123 condensing outside integral-fin tubes, with non-condensible gas bulk concentration of 8 percent. The heat transfer rate is deteriorated sharply with the existence of non-condensible gas, and the condensation heat transfer coefficients are about 20~25 percent of those of pure refrigerant gas. The effect of non-condensible gas is weakened with the decrease of fin density, but the optimum fin spacing is kept constant at about 0.32 mm.