An application of statistical chain theories on thermodynamic properties of hydrocarbon refrigerants

Abstract

The paper features the mathematical modeling to compute the equilibrium thermodynamic properties in the fluid phase of pure hydrocarbons with the aid of classical thermodynamics and statistical associating chain theories. In the present paper, we calculated thermodynamic properties for methane, ethane, n-butane and propane as the examples of hydocarbon substances. To calculate the thermodynamic properties of real fluid the models on the basis of Lennard–Jones intermolecular potential and statistical associating fluid theory were applied. We developed expressions for semi-theoretical Liu–Li–Lu model (LLL) and purely analytical Tang–Lu (TL) model obtained on the basis of salvation Orestein–Zernike EOS. To calculate the thermodynamic properties of real fluid with the aid of classical thermodynamics, we used Miyamoto–Watanabe (MW) equations developed in terms of Helmhotz energy. We developed the mathematical model for the calculation of all the thermodynamic functions of state for pure hydrocarbons. The analytical results obtained by statistical thermodynamics are compared with the MW model and show relatively good agreement.