BC convergence criterium or Stop condition

Hi to all,

i'm trying to solve a problem of heat transfer in porous medium in non local thermal equilibrium.

I use 2 ht modules linked by a source term to compute fluid and solid phase equations.

This model is ok when i use a BC like Tf=Ts=cost.

Now i want to apply this condition:

On fluid phase an heat flux: 100[W/m^2]-ht2.tfluxx where ht2fluxx is the flux on solid phase and is unknown.

On solid phase Tf=Ts where Tf=Ts is unknown

The model runs and reach a solution.

When I check this one i should find that ht.tfluxx+ht2.tfluxx=100 W/m2 indeed i find 90 W/m2.

So i would personalize a convergence criterium on BC or use a stop condition...i don't know.

I tried to use finer meshes and strong tolerance to check convergece (1e-10) but this unbalance still remain.

Thanks in advance.

Paolo