The effect of the spinodal curve condition on J T inversion curves for van der Waals real gas

This paper examines a consequence of spinodal curve condition on the Joule – Thomson inversion curves, for van der Waals real gas. To this end, we consider the differential form of Joule – Thomson coefficient, and concentrate on the parametrical algebraic equation of the corresponding family of curves in a P – V Cartesian frame of reference.  The aim of this work is not the prediction of Joule – Thomson inversion curves for the van der Waals Eos, but to derive inequality relations amongst the variables T, V and the parameters which appear in this constitutive law. Here, we should clarify beforehand that all proposed expressions concern only the intersection points between the set of inversion curves and the isothermal spinodal lines, which are drawn in the same P – V frame of reference.   Key words: JT inversion curves, spinodal curve condition, van der Waals Eos, P – V frame of reference.