Determination of the vapor-liquid coexistence curve and the critical parameters for refrigerant 502

Abstract

The vapor-liquid coexistence curve for refrigerant 502 (R 502) near the critical point has been determined by visual observation of the disappearance of the meniscus. Twenty-six saturated densities between 262 and 899 kg· m⁻³ have been obtained within an experimental error in temperature and density of ± 10 mK and ± 0.5%, respectively. Using these results along the vapor-liquid coexistence curve, the critical parameters, i.e., the critical temperature T _c =355.37 ±0.01 K and the critical density ρ _c =555±3kg · m⁻³, have been determined based on the disappearance of the meniscus level as well as on the intensity of the critical opalescence. A critical pressure P _c =4.070±0.002 MPa has been calculated from the existing vapor-pressure correlation using the present T _c value. In addition, the critical exponent β along the coexistence curve and the law of rectilinear diameter near the critical point are discussed.