porous media LTNE model - extra wall thermal boundary condition
 

I'm working on a natural porous media model for an underground pipe heat exchanger that's used for geothermal power generation. The ground is porous, and I've found that the fluid temperature differs from the rock temperature. So, I decided to use the Local Thermal Non-Equilibrium (LTNE) model.

When I try to apply the LTNE model to one of the layers, it generates a new domain and additional walls. For example, there are three walls where the heat exchanger connects with the grout, which is the layer between the heat exchanger and ground. Two of the walls are in the porous fluid zones, and I can easily apply a 'coupled' wall boundary condition to them. However, for the additional wall generated, I chose to use a 'via system coupling' boundary condition.

Unfortunately, I've noticed that there's no heat transfer at all from this wall with the 'via system coupling' boundary condition. I'm not sure if this is the correct boundary condition to use in this situation.

Looks like any other available thermal boundary conditions are not applicable as well.