Van der Waals equation of state and PVT properties of real fluid

TL;DR

This paper analyzes the Van der Waals equation of state, demonstrating its ability to accurately describe PVT properties and phase equilibrium of argon under various parameter definitions, especially near the critical point.

Contribution

It provides a detailed quantitative analysis of how different parameter choices in the Van der Waals equation affect its accuracy in modeling argon's PVT properties and phase behavior.

Findings

Exact parametric solutions describe saturated pressure dependencies on temperature and density.

The Van der Waals equation accurately models argon's PVT data near the critical point.

Different parameter definitions influence the qualitative and quantitative agreement with experimental data.

Abstract

It is shown that: in the case when two parameters of the Van der Waals equation of state are defined from the critical temperature and pressure the exact parametrical solution of the equations of the liquid-vapor phase equilibrium of the Van der Waals fluid quantitatively describes the experimental dependencies of the saturated pressure of argon on the temperature and reduced vapor density, and it gives the quantitative description of the temperature dependencies of the reduced densities near critical point. When the parameters are defined from the critical pressure and density the parametric solution describes quantitatively the experimental dependencies of the saturated pressure of argon on the density and reduced temperature, it can describe qualitatively the dependencies of the vapor and liquid densities on the reduced temperature, and it gives the quantitative description of the dependencies of the densities on the reduced temperature near critical point. If the parameters are defined from the critical temperature and density then the exact solution describes quantitatively the experimental dependencies of the reduced saturated pressure of argon on the density and temperature, it describes qualitatively the temperature dependencies of the vapor and liquid densities of argon, and it gives the quantitative description of the temperature dependencies of the vapor and liquid densities near critical point. It is also shown that the Van der Waals equation of state describes quantitatively the reference experimental PVT- data for the gas and supercritical fluid states for the under-critical densities of argon, the dependencies of the saturation pressure on the temperature and vapor density, and the dependence of the vapor density of argon on temperature if the parameters are defined from the critical pressure and temperature.