Conformal solution correlation for the nitrogen‐oxygen‐argon system

Abstract

Conformal solution theory as developed by LonguetHiggins (1) and Brown ( 2 , 3 ) has severe theoretical limitations. It is a random mixture theory and, if the restrictions placed by Pitzer ( 4 ) on the universal potential function concept are observed strictly, the theory is applicable only to spherical molecules of the same size. The restriction to spherical molecules of the same size was loosened somewhat by Longuet-Higgins when he introduced the reference substance concept and stated that the resulting equations were restricted to "mixtures of spherical molecules (not necessarily equal in size) and mixtures of nonspherical molecules of the same shape and size." Nevertheless, application of the formalism associated with the theory to mixtures of engineering interest obviously requires that certain theoretical considerations be downgraded in importance.Despite the theoretical limitations, the conformal solution formalism offers important advantages as a starting point in the development of an improved correlation and predictive scheme for liquid mixture properties. The mathematical framework i s not based on a questionable physical model such as a lattice and it i s more readily usable than distribution function theory. The principle of corresponding states is invoked and the development suggests "scalereducing" parameters which are more accurate than reduced temperature, pressure, and volume for the prediction of excess properties. The corresponding states principle is combined with a perturbation approach which permits the representation of mixture properties in terms of the thermodynamic properties of a well-defined reference substance. The resulting equations are algebraically capable of fitting empirically all types of systems and are not restricted to miscible systems. Finally, the equations contain temperature and pressure terms which may permit the correlation parameters to be temperature and pressure independent. CO RR ESP0 N DI N G STATES EQU ATIONSThe two major assumptions in the initial development of conformal solution theory are (1) that only the configurational part of the partition function is changed in an isothermal mixing, and (2) that the potential energy between any pair of molecules at positions i and j in a mixture can be represented by a universal function (1) which is a function of distance only. These two assumptions permit manipulation of the configurational integral to provide the following corresponding states relationship between the configurational Gibbs free energies of pure substance a and a reference substance 0.

Correlation and Prediction of Excess Properties for Hydrocarbon Liquid Mixtures

“…However, all the equations are multicomponent in form and handle multicomponent systems as readily as binary ones if the &ab, cab constants are available for each binary pair in the mixture. Ternary predictions have been illustrated by Calvin and Smith (1971) and Houng and for the simple liquids. The correlation framework appears to work well for the Ce-Ci hydrocarbons.…”

“…Those changes are presented in this paper. Some are also described in two recently published papers by Calvin and Smith (1971) and Houng and Smith (1971) which cover work done more than 2 years ago. Five important improvements over the procedures described in those papers have been:…”

Principle of Corresponding States of Liquid Solutions

“…Leland and Fisher (1970) considered the shape factor of molecules in their development of the PCS of liquid solutions. Calvin and Smith (1971) used a perturbation approach. The molecular theory of the PCS of mixtures was reviewed by Rowlinson (1968) and by Leland and Chappelear (1968).…”