Thermodynamic properties of pure fluids

In the previous Chapter we discussed the evaluation of physical, i.e. experimentally determinable, properties of pure fluids pressure-volume-temperature (PVT) relationships and heat capacities. In this Chapter we turn to thermodynamic properties, i.e. properties that cannot be measured directly. Rather, they are determined indirectly by using relationships that express them in terms of physical properties. These thermodynamic properties are  

Gibbs free energy (and the associated properties chemical potential and fugacity). 

We will concentrate our attention to the most important among them for chemical engineering applications entropy, enthalpy, and fugacity. 

We must emphasize again that thermodynamic properties are not measurable quantities. They are concepts, mathematical constructs in a strict sense, created for thermodynamics and their values are determined from experimentally measurable quantities through relationships developed by thermodynamics. Yet, these constructs are essential for the solution of everyday chemical engineering problems from the shaft work required for the compression of a gas (entropy and enthalpy), to the design of a distillation tower (fugacity and enthalpy). 

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X A. L. Lydersen, R. A Greenkom, and O. A Hougen, "Generalized Thermodynamic Properties of Pure Fluids, Unite Wisconsin, Eng. ExpL Sta. Rept. 4, 1955. 

The development of an equation of state typically commences with the representation of the thermodynamic properties of pure fluids and the functions are then extended to provide estimates of the properties of mixtures. The purpose of this chapter is to provide the methods used to permit this calculation... 

Having the scaling parameters for every fluid of interest, the model can predict all thermodynamic properties of pure fluids and mixtures. In case of mixtures, the mixing and combining rules of Equations 2.47, 2.48, 2.74, and 2.75 are used. Furthermore, combining rules are also used for... 

Values of these properties are essential in chemical engineering calculations (see Table 1.4 for example), such as the sizing of pipes and vessels, the evaluation of duties in heat exchangers, etc. In addition, they are required information in the determination of the Thermodynamic Properties of pure fluids, enthalpies, entropies, etc., that are considered in the next Chapter and of mixture properties. 

With this background, let us no V proceed with the main objective of this Chapter the evaluation of thermodynamic properties of pure fluids. 

In discussing physical and thermodynamic properties of pure fluids in Oi q>ters 8 and 9, we concluded that the main estimation techniques are ... 

We proceed with a limited discussion of Intermolecular Forces, which will help in understanding the Physical and Thermodynamic Properties of Pure Fluids which are considered next and, of course, the rest of the subject matter. 

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