[liloM]

Hi , pleas i need help , i have a project of simulation a Conjugate Heat Transfer i mean cooling tow hot cpus (hot processor) attached to a motherboard with one Source of cold air (fan) ,so

what is the solver for my problem : circuit board cooling or chtMultiRegionSimpleFoam/heatExchanger ??

i start to create my geometry using Salome .

pleas i need your help .

[liloM]

http://www.process-visualization.com...board-cooling/

as here in this example .

[liloM]

somebody can help me , please?

[aminem]

Hi

You can use chtMultiRegionSimpleFoam or chtMultiRegionFoam. Make your simulation with OF 2.4.0 because there is a bug in OF 2.3.0 when you try to put a volumetric heat source.

If you have a complex geometry I think Salome is not a good solution.

You can use FreeCAD or DesignSpark Mechanical 2.0 (free software under windows).

Good luck

[liloM]

Originally Posted by aminem

Hi

You can use chtMultiRegionSimpleFoam or chtMultiRegionFoam. Make your simulation with OF 2.4.0 because there is a bug in OF 2.3.0 when you try to put a volumetric heat source.

If you have a complex geometry I think Salome is not a good solution.

You can use FreeCAD or DesignSpark Mechanical 2.0 (free software under windows).

Good luck

Thank you aminem for your response , i have OpenFoam 2.4.0 of course under Ubuntu 15.04 , i use linux 7 years ago ,

My geometry contain only a motherboard with 2 boxes represent a 2 CPUs and one cylinder as a obstacle ,

for the solver chtMultiRegionSimpleFoam there is heatExchanger and multiRegionHeaterRadiation wich one i should use , and what is the deference between chtMultiRegionFoam and chtMultiRegionSimpleFoam for my case .

If i use FreeCAD or DesignSpark ! wich converter i would use to OpenFoam ( Like ideasUnvToFoam for the .unv format ) .

Thank You for your help .

[aminem]

Hi
chtMultiRegionSimpleFoam solver contain two exemple:
multiRegionHeaterRadiation ==> simulation of convection, conduction and radiation
heatExchanger ==> simulation of convection and conduction

chtMultiRegionFoam: Combination of heatConductionFoam and buoyantFoam for conjugate heat transfer between a solid region and fluid region
chtMultiRegionSimpleFoam: Steady-state version of chtMultiRegionFoam

You can use FreeCAD or DesignSpark and export you geometry in stl format to be able to mesh him with snappyHexMesh

If you want to mesh you geometry under SALOME you can use this python script salomeToOpenfoam (ideasUnvToFoam is not necessary)

[liloM]

Thank You Sooo Match

Originally Posted by aminem

Hi
chtMultiRegionSimpleFoam solver contain two exemple:
multiRegionHeaterRadiation ==> simulation of convection, conduction and radiation
heatExchanger ==> simulation of convection and conduction

chtMultiRegionFoam: Combination of heatConductionFoam and buoyantFoam for conjugate heat transfer between a solid region and fluid region
chtMultiRegionSimpleFoam: Steady-state version of chtMultiRegionFoam

You can use FreeCAD or DesignSpark and export you geometry in stl format to be able to mesh him with snappyHexMesh

If you want to mesh you geometry under SALOME you can use this python script salomeToOpenfoam (ideasUnvToFoam is not necessary)

Thank you again , so i will choose heatExchanger to solve my problem give me your advice aminem ,

and FreeCad as design tool ,

whay ? (ideasUnvToFoam is not necessary) it work !.

[aminem]

Hi

Do you have understand that heatExchanger is an exemple and chtMultiRegionSimpleFoam is solver?

The choice of CAD software is depend on yout experience.

strategy

CAD (FreeCAD or DesignSpark) ==> export stl file ==> Mesh (snappyHexMesh) ==> OpenFoam

CAD (FreeCAD or DesignSpark) ==> export (stl, step,...) file ==> Mesh (SALOME) ==> export .unv (ideasUnvToFoam is necessary) ==> OpenFoam

CAD (SALOME) ==> Mesh (SALOME) ==> export .unv (ideasUnvToFoam is necessary) ==> OpenFoam

CAD (SALOME) ==> Mesh (SALOME) ==> use of python script salomeToOpenfoam (SALOME) ==> OpenFoam

Good luck

[macRC]

Originally Posted by aminem

Hi

You can use chtMultiRegionSimpleFoam or chtMultiRegionFoam. Make your simulation with OF 2.4.0 because there is a bug in OF 2.3.0 when you try to put a volumetric heat source.

Good luck

Hi aminem,

thanks for this post. This is maybe actually the bug I´m dealing with.

I set up a a simulation in OF 2.3.0 with chtMultiRegionSimpleFoam (convection + conduction + radiation), with a volumetric heat source and I have got a too slow convergence.
All together I have 5 regions, whereas 2 are made with the extrudeToRegionMesh utility.
May be the bug mentioned by you the reason for this extremely slow convergence?
What kind of bug is it exactly?

If you want, I can prepare my case folder for you, so that so can simulate it on your machine.

Thanks a lot in advance.
Best regards

[Tobi]

Dear all,

I just want to sum up this topic for you and give some more information. First of all I have a question to @aminem: Do you have the bug-issue number of the problem you mentioned in OpenFOAM-2.3.0? I think it would be great to have it here, that everybody who is using an old OpenFOAM version can check it out and remove it.

Convergence

Domi, as I can see from your stats I think you are not really aware of the numerics behind, right? If I am wrong, sorry. However, the convergence of the problem should not come directly from a source term bug. Of course it can but based on the fact that I do not know the bug in detail, I cannot say that it is related to that. Keep in mind that we are solving the system in a segregated way. That means, all domains separately. That means, that you should have at least a few outer loop in order to correct the explicit terms and to get an accurate solution (if you are using a transient solver). For steady-state solvers it looks different (relaxation factors, etc.). In addition, a bad convergence can be related to:

• Wrong or bad (in a numerical point of view) boundary conditions
• Bad initial conditions
• A mesh that can not handle your problem (like a fluid gap with 2 or 3 cells; solids are different)
• Bad relaxation factors
• Bad solvers
• Bad schemes
• .
• .
• .

In my personal opinion your bad convergence is related to one of the above mentioned points and not related to the source term. If you want to figure it out yourself, just remove your source and let it run (maybe set some other BC to get a well described problem).

Keep in mind that I am not an expert in OpenFOAM and all related stuff, so I can be wrong too or it might be that I missed something.