External Radiation Boundary Condition for Grid Interface
 

When I create Grid Interface, fluent automatically generate four walls, namely:

1. Boundary Zone 1
2. Boundary Zone 2
3. Interface Wall Zone 1
4. Interface Wall Zone 2

For Interface Wall Zone 1 and Interface Wall Zone 2 fluent automatically assign coupled boundary condition (thermal boundary condition).
For Boundary Zone 1 and Boundary Zone 2 fluent automatically assign heat flux = 0 boundary condition (thermal boundary condition).

These boundary conditions for all four walls are ok or we need to modify it?

If I want to use External Radiation Boundary Condition (Radiation heat transfer from body to fluid), in which wall I should use Radiation boundary condition?

Thanks and Regards