The Curl-Pitzer method (CP) may be used to predict the enthalpies and entropies for liquids and vapors. The enthalpy deviation is computed by using the principle of corresponding states, i.e., in terms of the reduced temperature, reduced pressure and the acentric factor. The critical temperature and pressure for the mixture is computed using the mixing rules of Stewart, Burkhart and Voo.
The method is limited to nonpolar mixtures and may be used for Pr up to 10.0, Tr for liquids in the range 0.35 to 4.0 and Tr for vapors in the range 0.6 to 4.0. For heavy ends, the saturated vapor Tr is less than 0.6 and the method must extrapolate. Extrapolation usually produces reasonable results.
See "Curl-Pitzer" under "Generalized Correlation Methods" in Chapter 2, Volume 1, of the PRO/II Reference Manual for more information.
Application Guidelines
Most hydrocarbon applications including natural gas and refinery processes. The method must extrapolate for vacuum columns and the Lee-Kesler method is recommended for this application.