An Experimental Investigation Of Condensation Heat Transfer And Pressure Drop Of HC290-Oil Mixture In A Horizontal Micro-fin Tube

Owing to the negative influence of CFC and HCFC refrigerant on environment,seeking and using natural substitutes for CFC and HCFC refrigerant has become more and more urgent. Propane (HC290),a new natural refrigerant,is one of the most promising substitutes. Much information concerning HC290 is available in the present literature,however a great deal of work is still needed to do for using it properly.On the basis of the investigation on the related literature of new refrigerant substitutes,the in-tube condensation of refrigerant and refrigerant-oil mixtures,this paper investigates the saturated temperature of HC290-oil mixtures,condensation heat transfer and pressure drop characteristics in a horizontal micro-fin tube for it. The experimental conditions are as follows:the oil concentration is 1.95%-5.28%,mass flux is 40-220 kg/m2 s,and the condensation temperature is from 40C to 45C,the vapor quality is 1 at the inlet of the test section and 0.1-0.25 at the outlet of the test section. The conclusions reached are as follows:(1) The saturated temperature of refrigerant-oil mixture is higher than that of pure refrigerant at a same pressure. The temperature difference,which is called superheat temperature of refrigerant-oil mixture,increases as the oil concentration and the vapor quality are increased at a certain saturated pressure and pressure has negligible effect on the superheat temperature of the mixture. This is explained with the viewpoint of oil concentration change in the liquid phase of the refrigerant-oil mixture.(2) The investigation on the condensation heat transfer characteristics in a horizontal micro-fin tube for HC290-oil mixture shows:a) The condensation heat transfer coefficient of the mixture increases with the increasing of the mass flux.b) The mean condensation heat transfer coefficient decreases with the increase of the oil concentration.c) The condensation temperature has negligible effect on the mean heat transfer coefficient at a same oil concentration.(3) The saturated temperature of refrigerant-oil mixture has different definitions because of the superheat temperature of the mixture. One is the real saturatedtemperature of the mixture and the other is the saturated temperature of pure refrigerant corresponding to the tested pressure of the mixture. In this paper,the heat transfer coefficients based on the two different saturated temperatures are compared and the results showed the latter is larger.(4) A heat transfer correlation is developed by comparing the experimental data with the past correlations. And the deviation between the predicted and experimental values is 30%.(5) The experiment on the condensation resistance characteristics of HC290-oil mixture shows the oil concentration has negligible effect on the pressure drop of the mixture.