Refrigerant mixtures may be used to solve the ozone layer depletion problem as they offer the optimum combination of favorable technical performance with environmentally acceptable behavior. This work reports the thermodynamic properties and characteristics of the binary mixtures R-32/R-134a in compositions 20 80%, 30-70%, 40-60% by mass and of the ternary mixture R-407c: 23 wt% R-32 + 25 wt% R-125 + 52 wt% R-134a, A computer code has been developed for the phase equilibrium relationship of the binary mixtures using related activity and fugacity coefficients. Our results are in good agreement with existing experimental data. For the ternary blend, we present enthalpy and entropy correlations, diagrams illustrating the real gas behavior by means of k-type isentropic change exponents (k = c(p)/c(v), k(p),v,k(t),v,k(p),T) and figures for the refrigerating systems efficiency expressed by coefficient of performance values.