Consistency of Steady-State Models Using Insight about Extensive Variables?

Fundamental consistency relationships exist between the effect of changes in extensive variables under steady-state conditions. These relationships are derived by use of physical insight about scaling of extensive variables. The relationships may be used to obtain data for or to check consistency of linear steady-state models used in process control and design. The derivation and use of these relationships is very similar to that of the Gibbs-Duhem equation of thermodynamics. Surprisingly, these scaling consistency relationships seem be unknown in the chemical engineering community and examples demonstrate inconsistency in some widely used published models.