Comparison of Thermodynamical and Dynamical Approaches
There are many reasons to study dynamical effects instead of limiting ourselves to a purely thermodynamic analysis. First, as we have repeatedly stressed, it is important to recall that thermodynamic arguments cannot be automatically extrapolated to non-equilibrium steady states. Indeed, it is not clear a priori whether the classical thermodynamic stability criteria, such as, for instance, those based on the derivatives of the chemical potential with respect to the concentration, may be used or not in non-equilibrium steady states. In Sect. 7.1 we provide a dynamical basis to the stability criteria (6.38) and (6.39) used in Chap. 6, and analyse their conditions of applicability. It turns out that, in some occasions, the stability criteria of classical thermodynamics must be modified in presence of the flow.