A MODIFIED TREBBLE-BISHNOI EQUATION OF STATE - THERMODYNAMIC CONSISTENCY REVISITED

An inconsistency in thermodynamic property prediction using the Trebble-Bishnoi equation of state (TB EOS) was recently identified by scientists at the Shell research center in Amsterdam. Specifically, it was found that the TB EOS predicted negative values of isochoric heat capacity and imaginary values for speed of sound at extremely low temperatures. Subsequent investigation by the authors has led to the conclusion that any temperature dependence whatsoever in the co-volume term of van der Waals type equations will result in anomalies in the predicted thermodynamic properties of pure fluids at extreme conditions. This work presents a discussion of the implications of temperature dependence in the TB EOS parameters and describes a modification to the equation in which temperature dependence is completely removed from the co-volume term. By altering the temperature dependence in the attractive parameter we are able to correlate phase behavior with the modified equation more accurately than with the original equation, and the inconsistency has been corrected.