TABLE OF CONTENTS Methods are presented in this chapter for estimating the volumetric behavior of mixtures of gases and liquids as a function of temperature, pressure, and composition as expressed in mole, mass, or volume fractions. Section 5-2 introduces the extension of pure component models to mixtures, especially the concepts of mixing rules and combining rules. Their use in models based on the corresponding states principle (CSP) is discussed in Sec. 5-3. Techniques for estimation and calculation from equations of state (EoS) models, are given in Secs. 5-4 to 5-7. The models include the virial equation (Sec. 5-4), analytical density relations (EoS, mainly cubics, which can be solved analytically to find the volume of a fluid at a specified T, P and composition, Sec. 5-5), and more complex relations requiring numerical root-solving algorithms for the volume (Sec. 5-6). Section 5-7 summarizes our evaluation of mixing rules for volumetric properties. Sections 5-8 and 5-9 give estimation methods for saturated and compressed liquid densities that are not based on equations of state.
As in Chap. 4 for pure components, the discussion here is not comprehensive, and focuses on formulations of models for mixtures and on their application to volumetric properties. However, the treatments of composition here have implications for all other thermodynamic properties, since mathematical manipulations done on volumetric expressions with composition held constant provide calorimetric properties (such as internal energy, enthalpy and heat capacities) and free energy properties (such as Helmholtz and Gibbs energies). Chapter 6 describes...
