
FLUENT solves the standard energy transport equation (Equation 13.21) in porous media regions with modifications to the conduction flux and the transient terms only. In the porous medium, the conduction flux uses an effective conductivity and the transient term includes the thermal inertia of the solid region on the medium:
where
=  total fluid energy  
=  total solid medium energy  
=  porosity of the medium  
=  effective thermal conductivity of the medium  
=  fluid enthalpy source term 
Effective Conductivity in the Porous Medium
The effective thermal conductivity in the porous medium, , is computed by FLUENT as the volume average of the fluid conductivity and the solid conductivity:
where
=  porosity of the medium  
=  fluid phase thermal conductivity (including the turbulent contribution, )  
=  solid medium thermal conductivity 
The fluid thermal conductivity and the solid thermal conductivity can be computed via userdefined functions.
The anisotropic effective thermal conductivity can also be specified via userdefined functions. In this case, the isotropic contributions from the fluid, , are added to the diagonal elements of the solid anisotropic thermal conductivity matrix.