Investigation Of The Viscosity Characteristics For Refrigerant Mixtures

Refrigeration and air conditioning technology has provided us comfortable living environment and the necessary conditions of production over the past one hundred years. However, the long-term use of chlorine-containing halogenated hydrocarbon substances as the refrigerant, which have the ozone depression potential (ODP), seriously damaged the ozone layer. In addition, the traditional refrigerants have the higher global warming potential (GWP) value. At present, the whole world is actively looking for new alternative refrigerants. The refrigerant mixture is one of the research focuses of alternative refrigerants.The process of alternating the traditional refrigerants is strict and careful. A large amount of comprehensive tests on the new refrigerants must be conducted in order to assess whether it meet the requirements. Viscosity is one of very important physical parameters for the design and optimization of refrigeration systems. However, the literature survey found that the experimental research on viscosity for new environmental friendly refrigerant mixtures was very little. Therefore, the viscosity characteristics of the new environmental friendly refrigerant mixtures should be studied in order to provide reliable physical property data for the alternative refrigerants.In this work, a new rotatable capillary viscometer was developed and designed for the need of viscosity measurement of volatile refrigerant mixtures. The rotatable capillary viscometer was embedded in a pressure vessel. It was adequate for the viscosity investigation of the low boiling point liquid mixtures. It combined the rotation method and the pressure vessel to realize the continuous experiment and eliminated the error brought from the deflation, which can repeat the viscosity measurement of the low boiling point liquid mixtures in the high pressure. The rotatable capillary viscometer was calibrated by HCFC-22and checked by HFO-1234yf. The absolute average relative deviation between experimental results and the literature for HFO-1234yf was1.11%and the maximum relative deviation was-1.62%. The viscosities of a binary refrigerant mixture HFC-22+HFC-134a (0.7+0.3, by mole) were measured from278.15K to278.15K on saturation state. The absolute average relative deviation of HFC-22+HFC-134a was1.33%and the maximum relative deviation was-1.97%, which further validated the experimental device developed in this paper could be used to measure the viscosity of the refrigerant mixtures. The viscosities of three kinds of binary refrigerant mixture HFC-134a+HFO-1234yf(0.5+0.5, bymole)、HFO-1234yf+HFC-152a (0.81+0.19, by mole)、HFC-134a+HFC-152a (0.29+0.71, by mole) were measured from278.15K to278.15K on saturation state. The modified Andrade correlation, the natural logarithm model, the hard sphere model, the freedom volume model and the local concentration model were used to correlate the experimental data.