Learning Forum

[rajendrapor]

I am trying to solve a conjugate heat transfer (CHT) problem, where I have a solid (zone A) adjacent to a fluid and solid zone (zone B and C).

The conduction equation is solved for zone A which gives the temperature at interface. Now I wish to impose heat flux BC at walls of zone B & C, say half to the wall of zone B and half to wall of zone C.

I am confused about how to do it using UDFs. How to use the solution from fluent and input it as BC.

[Rob]

Where is the flux coming from? With CHT the heat transfer from solid to fluid is calculated by Fluent: ideally using a coupled wall bc.

[DrAmine]

Can you add a picture and tell us where you want to add the heat flux UDF in the picture as CHT will take care about transfer of heat between the zones.

[rajendrapor]

Thanks for the quick response!
Kindly see the schematic. Phase 1=fluid; Phase 2=solid.
In this case, I am denoting heat flux as BC to phases 1 and 2. However, I wish to ask further if a convective BC and heat flux BC could be applied separately to the left side of the wall also to different phases?.
I need to utilize the temperature (T_wall) obtained from the solver and implement it in the UDF. How can it be done? Of course, I need to decouple the walls for such an operation?

[Rob]

Assuming you're modelling the multiphase part of the system you just need to set the known temperature on the wall: check that's a known value on the surface and not in the free stream. If you include the solid thickness the solver will take care of the rest.

[rajendrapor]

Thanks for the response. I shall try this way and see the results. However, how should I use the obtained temperature at different time steps in the 2 different BCs.

[Rob]

If the input is a fixed temperature/heat flux I'd use that and monitor the temperatures. Otherwise you over constrain the model and force a result that's not physically correct.