Explicit conditions for local thermal equilibrium in porous media heat conduction

Based on the traditional formulation of heat transfer in porous media it is demonstrated that Local Thermal Equilibrium (Lotheq) applies generally for any boundary conditions that are a combination of constant temperature and insulation. The resulting consequences are being analysed and discussed. Among these consequences it is shown that the linear relationship between the average temperature difference of the two phases and the heat transferred over the fluid-solid interface is inappropriate for use in connection with conditions of Lack of Local Thermal Equilibrium (La Lotheq).