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 refrigerants such as R236ea, R236fa, R245fa, R245ca, R218, R227ea, and R717, from freezing point up to critical point temperature and pressures up 650 atm. We explore the theory of the equation of state from the view point of Ihm–Song–Mason (ISM) equation of state, which has been derived on the basis of statistical mechanical perturbation theory, and is characterized by three temperature dependent parameters, a, b, B2 , and a free parameter 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 from second virial coefficients by a scaling rule. The theory has considerable predictive power, since it permits the construction of the PVT surface from the heat of vaporization and the liquid density at the normal boiling point. The results indicate that the liquid densities can be predicted with very good agreement over a wide range of temperatures, 100–400 K.