Conference Year
2016
Keywords
liquid viscosity, mixed refrigerant, HFO-1234yf, HFC-152a
Abstract
Refrigerants are improved with the development of refrigeration and air conditioning industry. Because of the long-term use of chlorine-containing halogenated hydrocarbon substances, the ozone depletion and global warming become important issues around the world. Searching for refrigerants with low GWP (Global Warming Potential) and zero ODP (Ozone Depletion Potential) is urgent. HFC-134a used to be a widely used refrigerant with zero ODP. However, its high GWP of 1300 and long atmospheric lifetime of 14 years would cause the problem of global warming. Thus, for the sake of environment, the substitution of HFC-134a is imperative. In recent years, HFO-1234yf has been regarded as one of the widely used substitutions of HFC-134a because of low GWP of 4 and similar thermophysical properties to HFC-134a. However, its COP is slightly smaller than that of HFC-134a. In order to make better use of HFO-1234yf, some HFO-1234yf + HFCs or HFO-1234yf + HCs binary mixtures were proposed as alternative refrigerants. HFC-152a with low GWP of 140 and a short atmospheric lifetime of 1.5 years was selected as component in refrigerant mixtures. The mixture HFO-1234yf + HFC-152a is a promising alternative refrigerant. Before the actual application of alternative refrigerants in the refrigeration and air conditioning systems, thermophysical properties of mixed refrigerants need to be carefully investigated. Knowledge of viscosity characteristics, as one of the major concerns in the study of the thermophysical properties of alternative refrigerants, has significant impact on heat transfer and pressure drop in the flow, and viscosity data with high accuracy are of considerable value in the calculation of heat transfer and fluid flow. Â Â Â Â Â Â Thus, in this work, the measurement of liquid viscosity of the mixture was carried out with a new type of gravitational capillary viscometer developed in our previous work. The liquid viscosity experimental system used in this paper consists of a gravitational capillary viscometer made of glass, a pressure vessel with sight glasses, a thermostatic bath system and a measurement system. The measurement system consists of a high accurate temperature measure system (the standard temperature uncertainty is less than 0.011K) and a high accurate pressure measure system (the standard pressure uncertainty is within 1.4 kPa). The expanded uncertainty of dynamic viscosity was 1.58 %. The reliability of the experimental apparatus has been validated with HFO-1234yf and the binary mixture HFC-22 + HFC-134a (0.7 + 0.3, by mole fraction) in previous work. Based on this, the gravitational capillary viscometer was firstly calibrated with HCFC-22, and then, the liquid viscosity data of the binary mixture HFO-1234yf + HFC-152a (0.81 + 0.19, by mole fraction) were given from 278.15 K to 333.15 K. Two most commonly used viscosity models based on the Andrade equation were used to correlate the experimental data of the mixture HFO-1234yf + HFC-152a (0.81 + 0.19, by mole fraction). The correlation results were discussed.