不凝气体对R123凝结换热的影响

对氟利昂 R123 在水平单管外的凝结换热性能进行了试验研究,试验管为光管和五根强化管.目的是获得不凝气体对 R123 蒸气凝结时最佳肋密度的影响.试验结果表明:光管管外 Nusselt 理论值与实验数据偏差在±5%以内.对于含 8%不凝气体的 R123 在低肋管外的凝结换热,在肋密度为 1475 翅/米时可以获得最佳的换热性能.含不凝气体的 R123凝结换热系数显著下降,其管外换热系数约为纯蒸气的 20%～25%.随着肋密度的减小,不凝气体对凝结换热的影响逐渐减弱,但其最佳肋间隙仍保持不变,均为 0.32 mm.

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, andthe 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.