Extension of the IAPWS-95 formulation and an improved calculation approach for saturated properties

Abstract: The IAPWS-95 formulation explicit in Helmholtz free energy proposed by Wagner and Pruß (The IAPWS formulation 1995 for the thermodynamic properties of ordinary water substance for general and scientific use, Journal of Physical and Chemical Reference Data 2002 31(2), 387–535) is extended to calculate the volumetric property of the fluid water from 1GPa and 273K to 20GPa and 4273K. Comparison with large experimental and molecular dynamic simulation data above 1GPa shows that the equation of state can reproduce the volume of the fluid water with an average absolute deviation of 0.52%. Thus the original IAPWS-95 formulation together with the extended part can be used in a much larger temperature–pressure region: 273–4273K and 0–20GPa. In addition, this paper also reports a reliable and highly efficient method to calculate the saturated properties of water so that the equation of state can be conveniently applied in the study of fluid inclusion: calculating homogenization pressures, homogenization densities (or molar volumes) and isochores. Computer code of the model can be obtained from the first author. [Copyright &y& Elsevier]