Thermodynamic properties of gaseous propane from model intermolecular potential functions

Abstract

A fourth-order virial equation of state was combined with isotropic model potentials to predict accurate volumetric and caloric thermodynamic properties of propane in the gas phase. The parameters in the model were determined in a fit to speed-of-sound data alone; no other data were used. The approximation employed for the fourth virial coefficient included interaction graphsthat contained at most one triplet potential. Predicted ordinary second and third virial coefficients are in good agreement with the experimental data of Thomas and Harrison (1982). Predicted compressibility factors deviated from experimental data by less than 0.05 % up to densities of 2 mol./dm³, or0.4^pc. Predicted isobaric heat capacity were in agreement with experimental data to within uncertainties of 0.4 % at pressures up to 12 bar. As examples of results obtained, at 333.15 K the following properties at saturation were obtained: pressure, 21.162 bar; density, 1.1227 mol./dm3; compressibility factor, 0.68051; C_p/R = 14.8304, Joule-Thomson coefficient, 1.9265 K/bar and the speed of sound, 193.858 m/s.

Keywords: Propane, equation of state, model potential functions, virial coefficients, speed of sound