USE OF A MODIFIED HARD-SPHERE MODEL FOR OIL-REFRIGERANT MIXTURES VISCOSITY CALCULATION

The present work is dedicated to the development of the model for calculating the viscosity of the oil-refrigerant solutions based on experimental data. The results of experimental studies of density and viscosity of the mixture of compressor lubricant ISO 10 with the refrigerant R134a over a temperature range from 273 to 353 K and oil mass concentration from 0.7 to 1 are presented. Description of liquid viscosity at various temperatures and pressures based on the rough hard sphere (RHS) model, in recent years successfully in use for hydrocarbons, including pure refrigerants ? derivatives of ethane and methane. Parameters of the modified RHS model were derived from experimental data for many polar liquids, including refrigerant R134a. The same model was used to describe the viscosity of binary and ternary refrigerant mixtures with the help of combination rules of molecular parameters for pure substances. We have modified the RHS model in order to apply it to the oil-refrigerant solutions. The obtained experimental viscosity data were introduced in the form of reduced viscosity, and the correlations of the reduced viscosity and density in the hard spheres model were determined with the empirical and universal for different fluids function of molar volume. Changes in the RHS model related to one of the combination rules of the molecular parameters and using an additional nonlinear term in the specified empirical polynomial function. As a result, the use of the hard spheres model for the viscosity of the oil-refrigerant mixtures was successful in spite of the task complexity (the viscosity of the lubricant is higher than the viscosity of the refrigerant by two to three orders of magnitude). The standard deviation for all compositions and temperatures was less than 6 %. Density and viscosity of the mixtures of synthetic polyolester lubricant oil ISO 10 with the refrigerant R134а have been measured over a temperature range from 273 до 353 K and a range of oil mass fraction from 0,7 to 1. The viscosity of liquid mixtures of lubricant oil-refrigerant is modeled with the modified rough hard-sphere method. The results are compared with the experimental data.