A Multiparameter Viscosity Equation for 1,1-Difluoroethane (R152a) with an Optimized Functional Form

This paper presents a new formulation for the viscosity surface of 1,1-difluoroethane (R152a). The formulation is a multiparameter equation η=η (ρ,T ) obtained from an optimization technique of the functional form based on available experimental data. The equation is valid for temperatures from 240 to 440K and pressures up to 20MPa. Two lines of viscosity minima have been observed, and they have been analytically defined. A high accuracy equation of state for R152a was used to convert the experimental variables (P,T ) into the independent variables of the viscosity equation (ρ,T ). Comparisons with data are given to establish the accuracy of the viscosity values calculated using this equation. The obtained results are very satisfactory with an average absolute deviation of 0.27% for the selected 264 primary data points, and this is a significant improvement with respect to other equations in the literature.