Pitzer-Curl coefficient

The liquid-phase fugacity coefficient = /f/P may be calculated from a generalized correlation in terms of reduced temperature and pressure such as those of Lydersen et al.42 and Curl and Pitzer.15 Chao and Seader used a modified form of the Curl and Pitzer correlation. The correlation was modified by use of experimental data such that appropriate values of could be computed for the case where a component does not exist as a liquid and for the case of low temperatures. The following expression was proposed for the calculation of the fugacity coefficient for any component / in the liquid phase... 

Equation 25 was developed from an empirical representation of thg second virial coefficient correlation of Pitzer and Curl (I) parameter b was left unchanged at its classical value of 0.0866. Because of the substantial improvement in the prediction of and its temperature derivatives for nonsimple fluids, the Barner modification of the RK equation gave improved estimates of enthalpy deviations for nonpolar vapors and for vapor-phase mixtures of hydrocarbons. However, the new equation was unsuitable for fugacity calculations. 

It should be mentioned that the difference between Equations 37 and 27 is very small. The second virial coefficient calculated from Equation 25 using the new expression of f0(T) still agrees very well with the correlation of Pitzer and Curl (Equation 26). 

For non-polar molecules, Tsonopoulos [74-tso] modified the Pitzer and Curl [57-pit/cra] relationship for the reduced second virial coefficient in terms of T the temperature reduced by the critical temperature, and a third parameter, the acentric factor (O, which had been introduced to extend the application to non-spherical non-polar molecules, to give ... 

Pitzer and Curl [13] have shown that the second virial coefficient for a large number of fluids can be written as (16). 

A fluid that conforms to the Principle of Corresponding States has Ps.r = 0.1 at 7 = 0.7, i.e. cu = 0 for such a fluid. Non-conforming fluids have w > 0, and their second virial coefficients can conveniently be derived from Pitzer and Curl s equation ... 

---