An improved generalized equation of state

Abstract

Two forms of a generalized Benedict-Webb-Rubin Equation, BWR24 and BWR44, are proposed for dense gases which represent an improvement by a factor of about three in calculated pressures compared to reduced forms of this relationship in the literature. The method is also tested for accuracy in predicting enthalpy departures for pure components and mixtures. The proposed methods are marginally better than the best of other methods tested. Major advantages for the proposed equations are their relative simplicity, low computer storage requirements, and generality. No mixture interaction constants are required other than those already available in the literature.

Corresponding states. III. Henry's constants for nonpolar binary mixtures

“…The general applicability of these parameters is an important requirement in the development of a unified corresponding states theory for fluid mixtures. With the exception of nitrogen mixtures, which are discussed briefly later, values of Vcij and mij obtained in this work vary only a little from those calculated from empirical combining rules (Yamada, 1973). Similarly, values of kij do not differ greatly from those tabulated by Chueh and Prausnitz (1967).…”

“…The scaling volume, an approximation of the true critical volume, is calculated from liquid density at a reduced temperature of 0.6 at which accurate measurements are readily accomplished. V,, is defined The scaling volume has been used very successfully for a variety of corresponding states applications (Yamada, 1973;Gunn and Yamada, 1971), and a more detailed discussion of this parameter is given in the latter reference.…”

“…The expressions for Tsp, V,, and am used in this work are listed below. They have been selected for the reasons listed and have been used previously with considerable success (Yamada, 1973). For a binary mixture…”

Selected equation of state in the acentric factor system

“…A comparison of our fit with that for the 44 parameter equation of Yamada [6] is shown in Table III for a number of fluids using our data base. In general, we include a wider temperature and density range in our data base than did Yamada, as well as including some near critical data.…”

Using the noninteracting cluster theory to predict the properties of real vapor

“…Even in a dense vapor, nearly all the molecules are monomers or belong to small clusters; hence the formation energies of the smallest clusters are crucial to developing an accurate equation of state in the NIC model. The lack of an adequate expression for G i;s at small i is the major reason why the NIC theory has rarely been used to describe real vapor; scientists in need of a reliable equation of state for high density vapor have traditionally utilized phenomenological corresponding-states relations, such as the Benedict-Webb-Rubin equation 10,11].…”