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Old   October 15, 2009, 06:28
Default Heat Transfer
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Dear all,

I would like to simulate a heat transfer problem.
- Which solver is adaquat for that?
- Is it possible with rhoSimpleFoam?

I have a fluid (air 200K) and a solid (fin) above that fluid. The top of the solid (Tube) is warmed (350K) and i want to study the convective heat transfert inside the solid .
Thanks in advance
Help please!
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Old   October 15, 2009, 06:47
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Hi Ronaldo,

I think the chtMultiRegionFoam solver is adequate for your problem. It solves the energy, navier-stokes and mass conversation equations separately for solid and fluid regions. I did natural convection over a hot plate with this solver. If you use OpenFOAM-1.6 there must be a tutorial case which you can use at sample case.
If you have further problems feel free to ask.

Best regards,
Lars

Last edited by LarsPT; October 15, 2009 at 07:03.
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Old   October 15, 2009, 07:01
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Thank you very much!
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Old   October 15, 2009, 08:03
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Hi LarsPT,

I use OpenFOAM-1.6. There are two Tutorials case of chtMultiRegionFoam. There appear to be complicated.

- Please could you tell how to set the RegionPropeties?
- What about this bottomAir and topAir Directories in the "Constant" 'Directory

Please Help me!
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Old   October 15, 2009, 08:22
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So, just give me some minutes to prepare my case as a tutorial which is easier to understand because it is 2D and has only tow regions.

Anyway, the folders in the constant folder are needed to set the properties of the fluid regions. Furthermore, a folder for each region in the constant directory is necessary to convert results to VTK afterwards. You will see!

Be a bit patient, please!
Lars
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Old   October 15, 2009, 09:04
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So, it's done. The problem is quite easy. There's a copper plate heated at the bottom. Over the plate there is air. I decreased mesh resolution because I calculated it on a cluster with 8 CPUs.

Setting the case works like this.
1. Create the whole domain and a mesh with blockMesh
2. Create cell set out of several cells (makeCellSets)
3. Convert cell sets to cell zones
4. Convert cell zones finally to regions (0.001 directory is created automatically)
5. Change the BCs at the intersection of the two regions, e.g. velocity is 0 directly at the plate and so on
6. Remove unnecessary field from both regions, e.g. solid needs no turbulence properties
7. Copy polyMesh data from regions to the constant/region directory, important for post processing
8. Run the solver
9. Convert results to VTK

The creation of the regions is summarized in the mesh.sh script, all the other stuff in the run.sh script. So you might first run mesh.sh and afterwards run.sh to perform a complete simulation.

Hope this helps!

Best regards
Lars
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File Type: zip CHTconvection.zip (67.0 KB, 101 views)

Last edited by LarsPT; October 15, 2009 at 09:46.
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Old   October 15, 2009, 15:01
Default my case
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Thank you so much LarsPT!

I would try right now.
Please here is my case (just for give you more information about my case). It is very important for me!

Last edited by ronaldo; October 22, 2009 at 04:53.
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Old   October 16, 2009, 08:08
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It looks like a heat echanger, isn't it? Is the fin supposed to optimize the heat flux from the hot pipes to the air? Furthermore, there is one thing that is not clear to me. Is the air able to flow around the find completely? It seems that the fin is like an obstacle in the channel.

Best Regards
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Old   October 16, 2009, 08:34
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Quote:
Originally Posted by LarsPT View Post
Hi Ronaldo,

I think the chtMultiRegionFoam solver is adequate for your problem. It solves the energy, navier-stokes and mass conversation equations separately for solid and fluid regions. I did natural convection over a hot plate with this solver. If you use OpenFOAM-1.6 there must be a tutorial case which you can use at sample case.
If you have further problems feel free to ask.

Best regards,
Lars
Quote:
Originally Posted by LarsPT View Post
It looks like a heat echanger, isn't it? Is the fin supposed to optimize the heat flux from the hot pipes to the air? Furthermore, there is one thing that is not clear to me. Is the air able to flow around the find completely? It seems that the fin is like an obstacle in the channel.

Best Regards
Lars

It is! I have 4m/s Velocity Inlet. The fin supposed to optimize the heat flux. It looks like "Bild fin" after the Simulation with Fluent. Yes the air able to flow around the find completely.

I would send you another Graphic! Thank you for your Help

Last edited by ronaldo; October 19, 2009 at 10:15.
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Old   October 16, 2009, 09:12
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Hi LarsLP,

this is the Graphic.

Last edited by ronaldo; October 22, 2009 at 04:41.
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Old   October 19, 2009, 04:16
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Hi LarsTP,

it donīt work. I tried, but no success.

- I read a Fluent.msh mesh file using fluentMeshToFoam, so i donīt have " blockMeshDict" . I also have following problems:

- How could i set the makeCellSet " (* * *)(* * *)", mesh.sh, file?
- How could i find nFaces and startFace (air_to_plate for example)

have a good Day!
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Old   October 19, 2009, 08:54
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Hi,

first of all I have to confess that I have never worked with fluent so far. So, I can't help at this point, sorry.

The makeCellSets file is necessary to group cells which build a region.
It can be edited to your own purposes by using topoSetSources which can be found in OpenFOAM/OpenFOAM-1.6/applications/mesh/manipulation/cellSet/cellSetDict, e.g. a cylinder or a sphere.

I am not sure with the last point you mentioned. In my cases I don't need to know the start faces. A further boundary file is created somewhere in the 0/regionName directory after splitting up the mesh and creating the regions. There you should find the values for both parameters.

Best regards
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Old   October 19, 2009, 09:19
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Thank you for your Reply! I would try now

The only problem i have is to simulate using Openfoam (not Fluent)!
please could i post my case here? Maybe you could find out what happend.
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Old   October 19, 2009, 09:37
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Yes, of course you can post your case and I'll have a look at it. But make sure that you post no information protected by any copyright laws!
As university courses start today I can't say when I have time to look at it, but I'll try as soon as possible.
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Old   October 20, 2009, 05:39
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Quote:
Originally Posted by LarsPT View Post
Yes, of course you can post your case and I'll have a look at it. But make sure that you post no information protected by any copyright laws!
As university courses start today I can't say when I have time to look at it, but I'll try as soon as possible.


Hi LarsTp,

this is my case. I have tried, but i still have problems. I post only " Boundary" in the PolyMesh folder. It is ok?
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File Type: zip chtMultiRegionFoam.zip (14.6 KB, 24 views)
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Old   October 20, 2009, 10:01
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Hi LarsTP,

i run only "splitMeshRegions -cellZones" and 0.001 directory is created automatically.
I also got 4 region ( 3 for air and ane for solid).
For every Region under 0.001, i got automatically a folder polyMesh and cp,.......U file.
I am on the right way or not?

tell me please!
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Old   October 20, 2009, 12:09
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I didn't have the time to look in your case yet, but the way you described sounds very good. It has to be this way!
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Old   October 20, 2009, 17:33
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Thank you LarsTP!

i would try to ameliorate my case tonigth and post it tomorrow here.
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Old   October 22, 2009, 02:25
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Quote:
Originally Posted by LarsPT View Post
I didn't have the time to look in your case yet, but the way you described sounds very good. It has to be this way!

Hi LarsTP,

i have only one Problem now. How to set my makeCellSets file.
I did it but i became the following error:

Cell 0 with centre (0.024 0.000155 8.003e-05) is multiple zones. This is not allowed. It is in zone c1 and c2.
I donīt know if i could send you the geometry to Email thereby you set this makeCellSets for me.

sorry but i have tried

Last edited by ronaldo; October 26, 2009 at 07:54.
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Old   October 22, 2009, 04:42
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Hi Ronaldo,

the mentioned problem can be solved easily. As it simply says there is a cell which is part of two zones. If a cell is part of a particular zone depends on the position of the centre of the specific cell.
The fact that a cell is part of two different zones often appears when a mesh with a odd number of cells is divided in two zones, or something similar.
Being brief it means that the boundary of a zone/region is not allowed to cut a cell. Check your and look for this kind of problem.

Hope this helps, good luck!

Best Regards
Lars
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