Accuratezza di alcune equazioni di stato

The present study analyzes the accuracy of some equations of state for determining the volumetric properties, towards fluids characterized by a different degree of acentricity and polarity. The examined equations are the Cubic equations of state (van der Waals, Redlich-Kwong, Redlich-Kwong-Soave and Peng-Robinson), the Lee-Kesler method and the Virial equation. The substances considered in this study are argon, which is a simple fluid, characterized by negligible values of the acentric factor and dipole moment, some light hydrocarbons and water, which has a strong dipole moment and high acentricity. The analysis shows that the Lee-Kesler method provides the best results for all the substances considered. Except for water, the mean errors are quite little, mostly lower than 1-2% in all the examined regions of a thermodynamic diagram, while in the case of water, the errors can be ever greater than 20%.