A comparative study has been made on the predictive capabilities of a number of the more popular equations of state in use today. The equations were compared in their ability to predict the locus of points for which the Joule-Thomson coefficient is zero, the inversion curve.
The prediction of an inversion curve is an extremely severe test of an equation of state. To date inversion curves have been calculated only for the Van der Waals, Dieterici, Lennard-Jones and Devonshire, and DeBoer-Michels equations of state. This study covers the Van der Waals and Dieterici equations as well as the Virial, Berthelot, Redlich-Kwong, Beattie-Bridgeman, Benedict-Webb-Rubin, and Martin-Hou equations of state.
The results of the investigation show, among other things, that the Redlich-Kwong equation is quite unusual in that it predicts the inversion locus with more accuracy than any of the much more complex equations of state. Its predictive capabilities extend into the liquid region.