Thermodynamic foundations of dried materials in elastic range

The thermodynamics of irreversible processes deals with systems that are in a thermodynamic non-equilibrium. We have accepted tacitly in our previous considerations that the thermodynamic parameters of state, and thus also the thermodynamic functions, are defined in some way during drying processes. However, the issue of determination of these parameters is not quite clear, since the systems are heterogeneous and the parameters undergo continuous changes in time as in space during irreversible processes in general, and in particular in drying processes. At least some thermodynamic parameters are not constant but are functions of drying time and position in the dried body. Therefore, an issue arises of how to determine the magnitude of these parameters varying continuously in time and space.