Thermodynamic Properties from Helmholtz Energy Equations of State

7 Thermodynamic Properties from Helmholtz Energy Equations of State 

The following equations give the relations among the common thermodynamic properties including those frequently measured for fluids of engineering importance. These relations are derived from the fnndamental equation. Properties can be expressed in either molar or mass nnits depending on the valne used for the gas constant R. 

In eq 12.52 p is the mass density. Equations 12.45 through 12.52 are used for the calculation of thermodynamic properties. Other properties can also be calculated by differentiation of the fundamental equation. 

Problems that arise from calculating properties with fundamental equations usually result from the choice of independent variables. Any combination of variables that are different from T and p , for example, (rjat, T and / , and requires one or two-dimensional iterations to determine the corresponding values of temperature and density. Details for algorithms suitable to achieve the transformation have been given by Span in general, the recommendation is to use available programs and so avoid the inherent problems with these iterative procedures. 

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