Analysis of Thermodynamic Complexes and Density Data for SF6 on the Saturation Line Near the Critical Point

The article considers complexes containing the properties (liquid and gas densities) of sulfur hexafluoride on the saturation line and representing the order parameter, the average diameter, the ur = fd/fs complex, etc. A number of equations focused on thermophysical (TF) calculations in a wide neighborhood of the critical point (CP) for SF6 are studied The purpose of the research is, first, to estimate the errors of data on SF6 in the range (2 10-8< τ <10-2). In so doing, it is planned to use reliable experimental values and recommendations of the critical phenomena scaling theory (ST). Second, it is planned to clarify the functions fs(τ), fd(τ), Dρl(τ), ... and to estimate numerically some thermodynamic complexes in the specified temperature range. In accordance with the chosen purpose, problems I–III were analyzed. From the methodological point of view, several stages were carried out: setting up of the initial data array containing reliable experimental data in the range 2 10-8< τ <0.3; development of empirical equations Zl eff(x1, x2, τ), Zg eff(x1, x2, τ), which have a simple structure and contain the coefficients x1, x2 calculated by statistically processing the experimental data; elaboration of the methodology aimed at finding the coefficients x1, x Within the framework of solving problems I and II, numerical information on the binodal shape was obtained when using the coordinates Dρl, |Dρg|, τ and Zl, Zg, urbas. Some advantages of the second version of coordinates over the first one are shown. As a result of solving problem III, the empirical functions Zl eff(x1, x2, τ) and Zg eff(x1, x2, τ) are constructed. On their basis, numerical data are obtained, which confirm that these functions meet the requirements of ST in the CP neighborhood. Some applied calculations are performed, in which these empirical models are used. The proposed methodological developments and the results of the performed calculations are of interest for specialists in thermal physics who work on CT problems, including those who perform various calculations focused on the thermodynamic properties of SF6 in the CT neighborhood.