The excess Gibbs free energy-equation of state "(" "G" ^"E" "-EoS) " is a new method for predicting the vapor liquid equilibrium (VLE) with respect to the equation of state (EoS) and activity coefficient method. In this study

the Peng Robinson (PR) equation of state was employed in combination with the Wong-Sandler (WS) mixing rule to predict binary and ternary systems coupled with the activity coefficient model: the modified universal quasichemical functional group activity coefficient (UNIFAC) used in the predictive Soave-Redlich-Kwong (PSRK). So a gas-liquid equilibrium prediction model of the mixture (PRWS-UNIFAC-PSRK) was constructed EoS (PRWS-UNIFAC-PSRK model). The to calculated VLE data of R161/R1234yf

R32/R125/R134a

and the strong zeotropic ternary system of R1234yf/R170/R14 were calculated. The results indicated that for R161/R1234yf

the relative deviation of the pressures and the absolute deviation of the vapor phase mass fraction between the experimental and calculated data were within ±1.5% and ±0.02

respectively

which were better than those found using the REFPROP9.0 software

while the deviations for R32/R125/R134a were within ±4% and ±0.02

respectively. The calculated VLE data and three-dimensional phase equilibrium diagrams showed that the temperature glide phenomenon of R1234yf/R170/R14 was the most obvious at the mass fraction ratio of 0.4/0.2/0.4

and the maximum sliding temperature reached 72.5 K. The dew-point and bubble-point temperatures increased with the increase in the mass fraction of R1234yf.