Fluid flow in a heated flux media porous

Hello,

I pretend to built a model where I simulate the heat transfer to air flow through a porous media (in a channel with an inlet and outlet).
My fluid is the air and the porous structure is the SiC.

I stablished the following physics and boundary conditions:
- Brinkman equation: all structure
fluid and flow matrix properties: all structure and properties from the material
wall: no slip, u=0
inlet: velocity u=0,03 m/s
outlet: pressure without viscous stress, p=0,01 Pa

- Heat transfer in solids: porous structure (outer channel)
heat transfer in solids: properties from material (SiC)
thermal insulation: outside surfaces
initial values: 800°C (outer channel)
surface to surface radiation: emissivity 0,4; Tamb=20°C (describes the absorbed radiation on the front boundary of the structure)

- Heat transfer in Fluids: inner channel (air area)
heat transfer in fluids: properties from the material
thermal insulation: no tehrmal insulation
initial values: temperature=20°C (inner channel)
temperature : inlet T=100°C
outflow: outlet, convective flow
temperature: on the boundary cup-air T=800°C

After compute, an error appears:

"Failed to find a solution.
In segregated group 1:
Divergence of the linear iterations.
There was an error message from the linear solver.
Very ill-conditioned preconditioner.
The relative residual is more than 1000 times larger than the relative tolerance.
Returned solution is not converged.
- Feature: Stationary Solver 1 (sol1/s1)"

Please could you give any tipp or advice about what I should do?

I hope you can help me.
Thank you very much,

Ana