Modifying GMA equation of state for description of (P, ρ, T) relation of gas and liquids over an extended pressure range

Abstract

The main concern of this paper is on the improvement of the GMA equation of state (Fluid Phase Equilibr. 230 (2005) 170) which has been used for density calculation of components in liquid region with excellent accuracy. However, the GMA equation of state cannot predict the density of components in either the gas or gas-liquid transition region. The GMA equation of state is based on intermolecular potential energy; therefore, the potential energy of the GMA equation of state is corrected and an equation of state is obtained. The final form of the new equation of state is a regularity between (Z−1)v 3 and ρ for all temperatures, which is based on modified Lennard-Jones potential (9, 6, 3). The capability of the new equation of state is examined by comparing the results with experimental data in homo- geneous gas, homogeneous liquid and gas-liquid transition region from low to very high pressures. The new equation of state gives excellent results in homogeneous gas and homogeneous liquid region, while the predictions in the gas-liquid transition have more deviations. The average absolute deviation between calculated and experimental densities for 1979 data points of 24 components is 0.25% over the entire range of data with a maximum pressure of 1,000 MPa.