Approach for fluid cooled tube heat transfer

General Questions
1

I have a cooling tube with a heat load attached to the OD of the tube. Inside the tube is a fluid that is flowing at a known rate and pressure with a known fluid inlet temperature. Obviously the heat load will increase the fluid temperature as you get further and further down the tube, until, eventually it reaches the outlet and would be a some new, outlet temperature. Is there any way for PrePoMax to approximate what this outlet temperature would be? Any suggestions on how to set up this problem? I see the 1.4.1 DEV version can now have equation based loads, but I’m not sure if that could be utilized for this application.

Convective film isn’t really accurate because it uses a fixed sink temperature; whereas with this problem, the sink temperature would increase as you go further down the length of the tube.

For Surface flux, the flux would need to decrease as you go further down the length of the tube because the delta T would be decreasing, but the amount it decreases would still be unknown.

2

Well, you can’t simulate this multiphysics problem in PrePoMax or CalculiX directly. You would have to use preCICE which allows CalculiX to be coupled with OpenFOAM for FSI or CHT analyses but it’s not so easy. Thus, you will likely have to use some approximations. You could, for example, model the fluid volume or make some surface partitions inside the tube and apply convective films with different sink temperatures.

CalculiX subroutines for non-uniform thermal loads are yet another option but not an easy one too (they require Fortran coding skills).

3

Hi,
Maybe you could look at this approach.

4

I would advise a CFD analysis. Of course you could use open source software like Open Foam directly or the embedded OF module within Freecad.

5

CfdOF add-on workbench is great and should be sufficient even for non-isothermal flow but CHT (fluid+solid heat transfer) requires something more than that. Maybe solvers available in OpenFOAM would suffice (initial setup can be done in CfdOF and then it’s a matter of manual file edits) or coupling with preCICE would be useful.

6

Good to know.
I was not aware the Freecad OF could not perform Conjugate Heat Transfer.
Thank you.

7

Yeah, it supports buoyantSimpleFoam and buoyantPimpleFoam solvers (flow with heat transfer) but not chtMultiRegionFoam. Can be very helpful for the initial setup though.