A thermodynamic approach to heat and electric conduction in solids

Heat and electric conduction in a rigid solid is investigated in the framework of extended irreversible thermodynamics. This allows us to apply directly the original procedure of Onsager to the analysis of the reciprocal relations. A non-local constitutive equation for the heat flux previously obtained is compared with microscopic equations used for the analysis of second sound in solids. A hydrodynamical analogy of this equation leads to the possibility of a turbulent phonon flow under some specific physical conditions.