Phase behavior of the binary refrigerant mixture chlorodifluoro-ethane (R22)-1,1,1,2-tetrafluoro-ethane (R134a): experimental investigation and theoretical modelling using the perturbed-anisotropic-chain theory (PACT)

This study presents experimental data of the vapor-liquid phase behavior in the binary system of chlorodifluoro-ethane (R22) with 1,1,1,2-tetrafluoro-ethane (R134a). The main objective of the experimental work in this refrigerant system was to verify some unexpected findings with respect to its phase behavior reported earlier by Nishiumi et al. (1993). In the near-critical region of both pure components these authors found a three-phase equilibrium liquid-liquid-vapor with a negative slope in the pressure-temperature projection of this binary mixture. Although not impossible, to the best of our knowledge, this has never been reported in literature before. The present work did not confirm the existence of this three-phase region. In addition to the experimental work, the vapor-liquid data obtained here were modelled by an equation of state specifically designed to take directional forces into account. For that purpose the perturbed-anisotropic-hard-chain Theory (PACT) has been applied. Comparisons with the experimental data are very satisfactory, even without using any binary interaction parameters.