VDNS Expansion: For dsat of the Liquid or Gas phase

dsat = dc + a1×t0.35 + åai+1×ti ; where the summation is from i = 1 to nTerms -1.

dc = the critical density and t = 1 - T/Tc, where Tc is the critical temperature.

NOTE: The TDE program truncates this equation based upon the extent and quality of the fitted data.