Entropy, Absolute Temperature and Coldness in Thermodynamics: Boundary Conditions in Porous Materials

From the Preface: 'Thermodynamic processes are defined as the solution of the field equations that are based on the equations of balance of mass, momentum and energy and on constitutive relations for stress, heat flux and internal energy. Entropy is introduced as an additive constitutive quantity whose flux is also constitutive and whose production is non-negative. The requirement that this inequality hold for every thermodynamic process leads to some restrictions on the constitutive equations for stress, heat flux and internal energy. Most of these restrictions involve a function of the temperature and its time derivative which, under a suitable continuity assumption for the entropy flux, can be shown to be a universal function. This function will be called the coldness, its equilibrium value is the reciprocal of the absolute temperature.'