Cubic Equations of State-Which?

Abstract

An analysis is made of volume-cubic equations of state, starting with the most general generating equation from which all specific forms can easily be derived. One equation is shown to be both the simplest and the best in performance. A new quantity, the z-chart sum, is presented, which is a useful way to compare all equations of state, whether cubic or otherwise, while at the same time permitting excellent predictions of the second virial coefficient at the critical temperature from the critical compressibility factor. Extensive comparisons of reliable experimental PVT data with a number of equations of state are given for a wide range of substances from nonpolar to polar, and these demonstrate the superiority of the simplest two-term cubic equation.

Prediction of high pressure vapor-liquid equilibria with mixing rule using ASOG group contribution method.

“…For all the components except nitrogen, vki was calculated by applying Eqs. (9) or (10). For nitrogen, the value of vNl t was unity, which gave good agreement with the experimental vapor-liquid equilibria.…”

“…a=l%xMAi-RTfaytjlA ki=total number of atoms (other than hydrogen atoms) in group k in molecule / ; organic compound (9) vki=total number of atoms in group k in molecule /; inorganic compound (10) To express analytically the group activity coefficient in Eq. (8) …”

<b>Saturated properties prediction in critical region by a quartic equation of state</b>

“…On the other hand, Martin [8] pointed out that experimental data of fluids tend to follow quartic equation, and lots of quartic EOS were proposed since eighties of the last century [9][10][11][12].…”

Enhanced Models for Mixtures of Fluids in Chemical Equilibrium at High Pressures

“…A good review of the development of more complex, well-behaved, equations of state and their advantages has been done by Martin [23]. With the knowledge of appropriate thermodynamic relations, a good equation of state can be used to predict with high precision isothermal changes in heat capacity, enthalpy, entropy and fugacity, vapor pressure, latent heat of vaporization, activity coefficients, and vapor-liquid equilibria in mixtures.…”