Generalized crossover description of the thermodynamic and transport properties in pure fluids

Abstract

We have developed a generalized cubic (GC) EOS for pure fluids, which incorporates non-analytic scaling laws in the critical region and in the limit ρ→0 is transformed into the ideal gas equation EOS. The GC EOS contains 10 adjustable parameters and reproduces the thermodynamic properties of pure fluids with high accuracy, including the asymptotic scaling behavior of the isochoric heat capacity in the one- and two-phase regions. Unlike the crossover cubic EOS developed earlier [Fluid Phase. Equilibr. 147 (1998) 7], the GC EOS is based on the crossover sine model and can be extended into the metastable region for representing analytically connected van der Waals loops. In addition, using the GC EOS and the decoupled-mode theory (DMT) we have developed a generalized GC + DMT model, which reproduces the singular behavior of the thermal conductivity of pure fluids in and beyond the critical region. Unlike the DMT model based on the asymptotic crossover equation of state CREOS-97, the GC + DMT model is valid in the entire fluid state region at T≥ T b (where T b is the binodal temperature), and at ρ→0 reproduces the dilute gas contributions for the transport coefficients.