A New Equation of State Formulation for Argon Covering the Fluid Region for Temperatures From the Melting Line to 2300 K at Pressures up to 50 000 MPa

Abstract

A new equation of state for argon has been developed in view to extend the range of validity of the equation of state previously proposed by Tegeler et al. (1999) and to obtain a better physical description of the experimental thermodynamic data for the whole fluid region (single-phase and coexistence states). As proposed by Tegeler et al., this equation is also based on a functional form of the residual part of the reduced Helmholtz free energy. However in this work, the fundamental equation for the Helmholtz free energy has been derived from the measured quantities CV(rho,T) and P(rho,T). The empirical description of the isochoric heat capacity CV is based on an original empirical description containing explicitly the metastable states. The new formulation is valid for the whole fluid region from the melting line to 2300 K and for pressures up to 50 000 MPa. It also predicts existence of a maximum of the isochoric heat capacity CV along isochors as experimentally observed in several other fluids