[Tomsho]

Hi all,

We try to solve the following problem using ANSYS Fluent:

We have a flow in a tube where we want to solve the tube body using transient solver. We know the heat transfer coefficient from the literature. Our tube is comprised of phase change material, hence it has a transient thermal behavior. we try to understand how to solve the conjugated heat transfer problem in ANSYS Fluent without simulating the tube flow.
We know that in the inner tube wall there is the following boundary condition:
q = h(Tm –Tw) where Tm is the mean temperature of the fluid flows in the tube and Tw is the inner tube wall temperature, the temperatures are functions of time and coordinate x, all the other boundaries are assumed insulated.

we formulated another transport equation for the tube flow (energy balance):
ρC_p A (∂T_m)/∂t+m_dot ̇C_p (∂T_m)/∂x=h(T_m (x,t)-T_w (x,t))

This is quite basic, but we could not find how to do it. I think the approach might involve using UDS, UDM and UDF.
I would like your help with ideas how to deal with this issue.
If something is not clear, please let me know.
Thanks.

[alainislas]

If you dont want to solve the flow, why would you go for CHT simulation then? If you already know the HTC at the tube wall, I'd stick with a thermal analysis in the solid only

[Tomsho]

Originally Posted by alainislas

If you dont want to solve the flow, why would you go for CHT simulation then? If you already know the HTC at the tube wall, I'd stick with a thermal analysis in the solid only

Thanks for your input.

I need Fluent since I want to activate the melting/solidification model.

I describe here a simplified problem that I believe that if I can solve it I can also solve my "real" problem.

[Tomsho]

Someone has any ideas?

[anan12345]

Can you elaborate on your problem, maybe with some pictures if that's okay? I'm not quite sure why you wouldn't want to solve the flow equations.

The flow equations can be disabled through GUI, so you can just solve the energy equations or your UDS's if you choose.

[Tomsho]

I dont want to solve the flow in the tube because my real problem is more complicated than the disscussed case.
solving the flow is computationally expensive (more equations, more cells).
I attach sechmatics of the physical system vs. the simplified geometry I want to solve.

what are you thoughts?


https://ibb.co/wsTzQGp

[jsm]

If you want to solve only thermal without flow and flow won't affect thermal behavior, just import the mesh for tube only.

You can solve melting/solidification model. It is possible.

[Tomsho]

Originally Posted by jsm

If you want to solve only thermal without flow and flow won't affect thermal behavior, just import the mesh for tube only.

You can solve melting/solidification model. It is possible.

The thing is that I don't know how to account for the boundary condition in the inner tube wall. The mean temperature of the flow (T_m) is a product of the conservation equation that is written in the figure I attached above.
This equation and the energy equation are coupled.

I tried and failed to understand how to define another transport equation to Fluent and how to link the two equations via the boundary.