Estimating the virial coefficients of small polar molecules

We adapt existing models for estimating the second and third virial coefficients of small molecules to the halogenated methanes and ethanes. We compare the results with the abundant new, high-qualityPVT data resulting from the search for alternative refrigerants. The present model provides an accurate method for calculating densities, and therefore it should provide reliable thermodynamic properties and fugacity coefficients. We give equations and parameters useful for estimating the properties of pure refrigerants and their mixtures when noPVT data are available.Nomenclature B Second virial coeficient - B₁₂ Mixture cross second virial - B_h Second virial of a hard sphere fluid - _i(T) Temperature function, second virial, Eq. (7) - C Third virial coefficient - C₁₁₂,C₁₂₂ Mixture cross third virials - C_h Third virial of a hard sphere fluid - N Avogadro's numberVirial Coefficients P_c Critical pressure - P_c12 Characteristic critical pressure of a binary mixture - T_c Critical temperature - T_c12 Characteristic critical temperature of a binary mixture - T_r Reduced temperature,T/T_c - Parameter measuring polar contribution toB, Eq. (3) - b Volume of a hard sphere molecule - f^(f) Polynomials determining temperature dependence of the nonpolar part ofB - k₁₂ Binary interaction parameter for mixtures, Eq. (9a) - _c Critical volume - _e Molecular polarizability - Dipole moment - _R Reduced dipole moment, Eq. (4) - _R12 Mixture reduced dipole moment, second virial - _R112,_R122 Mixture reduced dipole moment, third virial - Pitzer acentric factor - ₁₂ Mixture acentric factor - (r) Intermolecular potential - _c Critical density (1/_c)