I'm trying to simulate combustion through an inert porous block. I was able to complete the simulation assuming local thermodynamic equilibrium between the solid and the fluid but since this would be quite inaccurate because of the high temperature of the fluid, I would like to improve the model by accounting for heat transfer between the solid matrix and the fluid.

FLUENT solves only one energy equation but I would like it to solve the energy equation twice in the porous zone and include the interface heat transfer. How do I write a UDF ( User Defined Function for this) ? If anybody already has this, I would be glad if you could share it with me.