Prediction of PVT Properties of Pure Refrigerants Using ISM Equation of State

A three-parameter cubic equation of state has been proposed for predicting PVT of pure refrigerantssuch as R236ea, R236fa, R245fa, R245ca, R218, R227ea, and R717, from freezing point up to critical pointtemperature and pressures up 650 atm. We explore the theory of the equation of state from the view pointof Ihm–Song–Mason (ISM) equation of state, which has been derived on the basis of statistical mechanicalperturbation theory, and is characterized by three temperature dependent parameters, a, b, B2 , and a freeparameter λ. The second virial coefficients are calculated from a correlation based on the heat of vaporization,ΔHvap, and the liquid density at the normal boiling point, ρnb. α(T ) and b(T ) can also be calculated fromsecond virial coefficients by a scaling rule. The theory has considerable predictive power, since it permitsthe construction of the PVT surface from the heat of vaporization and the liquid density at the normal boilingpoint. The results indicate that the liquid densities can be predicted with very good agreement over a widerange of temperatures, 100–400 K.