Learning Forum

[lars.hanschmann]

I have assigned new boundary conditions to every outer face in a thermal problem.
But the defaults Ambient Temperature / Convection in Air are still present and both have faces assigned.
How can I manage to get rid of these assignments?

[Gaurav Sharma]

Discoverytester

The ambient definition (coefficient and ambient  temperature) is used to calculate convective heat transfer.  By default any thermal setup has this convection BC and if user wants to get rid of it, you can simply use 0 as the convection coefficient and this should make the default BC redundant.  Unfortunately, deleting this BC doesn't appear possible.

While I tried and found this workaround to be working well for me, please let me know if you are having some unexpected observations with this approach.

[lars.hanschmann]

Gaurav_ANSYS 

it is not the point to set the BC to 0. I have assigned other BC for all faces to the outside. But there are still faces assigned to the default ambient definition. By the way wouldn't we receive an adiabatic BC if we set the film coefficient to be 0?

[Gaurav Sharma]

Discoverytester

The ambient temperature is the temperature of space surrounding the component. It doesn't enforce a temperature condition at any surface. Once you apply any BC to your model, say temperature, this will govern the behavior and the ambient temperature will only be used to calculate convective heat transfer.

In order to control the convective heat transfer, you can set a 0 convection coefficient. This would mean no heat transfer using default BC, but any other convection BC applied to this surface would still act and this approach does NOT enforce any adiabatic condition.

In a nutshell, zero convection coefficient only suppresses the default BC (as good as deleting the BC altogether) and the ambient temperature (which is used to calculate heat transfer) doesnt play any further role. So even if there are faces you see assigned to ambient temperature, it shouldn't be a problem since the faces are not forcefully assigned this temperature. Further, a zero coefficient does ensure no heat transfer through this surface using default BC.

I hope that answers your query.