Thermodynamically Consistent Set of Equations

There are differential relations between properties of working fluid. By using the so-called thermodynamic potentials i.e. specific free energy (Helmholtz function f) and specific free enthalpy (Gibbs function g), which are related by the following equation:

g = f + P v

we can write:

where,
P= Pressure
T= Temperature
v= Specific volume
h= Specific enthalpy
s= Specific entropy
Any set of equations which satisfy the above mentioned relations is called a thermodynamically consistent set of equations. These equations can be based on experimentally obtained data.