**3. Numerical modeling**

The thermophysical properties of the air such as density, thermal conductivity and specific heat are assumed to be functions of the temperature. Usually, the pressure drop through the porous burner is not that high (with high porosity of PM) and its effect on the thermophysical properties can be neglected. In general, the properties of the solid phase may be assumed to be constant and assumed that there is thermal non-equilibrium between the gas and solid phases. Therefore, there are two energy equations to model the energy transport in the system. The porous material can be assumed as a scattering, emitting and absorbing medium. Gaseous radiation is assumed to be negligible compared to the solid radiation.
