An Experimental Investigation Of Condensation Heat Transfer And Pressure Drop Of HC600a-Oil Mixture In A Horizontal Micro-fin Tube

Refrigeration 134a , which has a zero ozone-depleting potential(ODP) value, has emerged as the new refrigeration for the automotive and commercial air-conditioning industry. However, its greenhouse warming potential(GWP) is relatively high among the newly developed hydroflourocarbons(HFCs), which seems to be an obstacle for the furtherance of the use of R-134a, especially in European countries. Hence many countries are looking for other refrigerants that do not contribute to global warming. Hydrocarbons R600a are receiving attention because their thermodynamic and thermophysical properties are similar to these of R12 and R134a and they have zero ODP and negligible GWP. Currently, limited information is available in the open literature on the performance and design of the air-conditioning and refrigerating systems using the hydrocarbons. So a great deal of work is still needed to do for using it properly.In this paper, recent development of condensation heat transfer of alternative refrigerants inside tubes are reviewed, including the comparison of heat transfer characteristics between alternative refrigerants and original refrigerants, the influence of lubricants on heat transfer and the enhancement of condensation heat transfer. On the basis of that, this paper investigates the saturated temperature of HC600a-oil mixtures, condensation heat transfer and pressure drop characteristics in a horizontal micro-fin tube for it. The experimental conditions are as follows: mass flux is 50~180kg/m2 s, the condensation temperature is from 36 ℃ to 42 ℃, the oil concentration is 1.81%~5.54%, 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 phenomenon can be 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 horizontalmicro-fin tube for HC600a-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. In this paper, the heat transfer coefficients based on the two different saturated temperatures-one is the real saturated temperature of the mixture and the other is the saturated temperature of pure refrigerant corresponding to the tested pressure of the mixture-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 oil concentration has negligible effect on the pressure drop of the mixture.