The calculation of excess molar enthalpies of liquid mixtures at high pressures and temperatures from measurements at ambient conditions

In this paper, a new approach for calculating the excess molar enthalpies of liquid mixtures at high pressures and temperatures based on the experimental excess molar enthalpy (HE) data at low pressure is proposed. This model (we call it the GE–EOS(HE) model) is an equation of state (EOS) (original Peng–Robinson (PR) EOS with a conventional mixing rule) combined with an excess Gibbs energy model (NRTL equation). This approach has been tested by calculating excess molar enthalpies of seven binary systems. The binary parameters in the NRTL equation were determined only from the low-pressure excess molar enthalpy data. The calculated results show that the GE–EOS(HE) model can calculate excess molar enthalpies over a wide range of temperatures and pressures on the basis of low-pressure data.