[ANSYS Meshing] Double pipe HE meshing problem

kola77 · May 24, 2011, 14:48

Hello all together,

I am currently busy with a simulation of a double pipe heat exchanger. However, I am having problems with the mesh generation of the geometry. The problem seems to appear in the solid domain (pipe wall), but only if the wall is too thin. As long as I operate with a wall thickness of about 1 cm the mesh can be easily generated, but as soon as I change it to about 5mm, I get the intersecting geometry error. I have no idea how to fix this, since I have created my geometry from scratch several times, tingled around with the spacing settings and I always get the same error. I would really appreciate it if somebody has any advice on how to solve this problem or any advice on how to do it whatsoever.
I'm using ANSYS 12, so the thin interface feature is not really an option.

In case anybody is kind enough to take a look, here is my workbench project: https://rapidshare.com/files/4084825686/doublepipe.zip

Thanks in advance!

shields · May 31, 2011, 09:59

I'm conducting a similar project in relation to heat transfer within a heat exchanger.

I've downloaded your files and meshed them using Ansys 13 for you - Mesh Conforming method. Its states that the CFX method is outdated and no longer used.

Hope this is of use.

Are you planning to use fluent to analyse the problem. I'm having problems getting Fluent to account for the conduction across the inner pipe boundary [the main point of interest as this is where the heat transfer is occurring]. I'm wondering how you plan to incorporate this in Fluent. Will you use conjugate heat transfer and if so how???

Any help is much appreciated. Heres a link to my post relating to my project

http://www.cfd-online.com/Forums/flu...two-pipes.html

Here are the updated meshed files for your project.
https://rapidshare.com/files/3335016585/doublepipe.rar

kola77 · May 31, 2011, 10:55

Thanks for your help, but I have managed to solve the problem by now. The solution was to mesh the solid domain using the ansys mechanical method, and the fluid domain using any other method (tetrahedral, even the outdated cfx-mesh method, etc) and joining them later on.

As for your problem, I am using CFX to run the analysis. I don't know if this is really an option for you, but it shouldn't be much more different than it is with FLUENT.

Anyway, here's how it goes:
First I have created three domains, one for the solid, and two for the fluids, hot and cold obviously. As you could see from my files, I have prepared some regions in advance, especially pay attention to the interface regions, which, later on, are used to connect both sides of the pipe wall with corresponding fluids. The results I have obtained using this strategy seem promising and realistic.

Unfortunately I have no idea how to use FLUENT, since my university only supplies me with a CFX license, but I imagine it shouldn't be much of a problem.

Thanks for the help once again, and I hope my thoughts on your problem help you at least a bit!
Cheers!

shields · May 31, 2011, 11:30

Thats good that you got a solution. Yes i'm trying to connect the fluid and solids regions. this is where I am having difficulty. My problems geometry is simpler than yours as I do not have the narrow inlet and outlet.

Would you be able to upload your cfx files, as I should be able to compare your methods then and possibly transfer them to fluent. I have a licence for CFX but I have not used it before, I should be able to follow the basics.

Thanks in advance, if this is not possible, no worries.

May 24, 2011, 14:48	Double pipe HE meshing problem	#1
kola77 New Member Marko Join Date: Sep 2010 Location: Slovenia/Portugal Posts: 13 Rep Power: 15	Hello all together, I am currently busy with a simulation of a double pipe heat exchanger. However, I am having problems with the mesh generation of the geometry. The problem seems to appear in the solid domain (pipe wall), but only if the wall is too thin. As long as I operate with a wall thickness of about 1 cm the mesh can be easily generated, but as soon as I change it to about 5mm, I get the intersecting geometry error. I have no idea how to fix this, since I have created my geometry from scratch several times, tingled around with the spacing settings and I always get the same error. I would really appreciate it if somebody has any advice on how to solve this problem or any advice on how to do it whatsoever. I'm using ANSYS 12, so the thin interface feature is not really an option. In case anybody is kind enough to take a look, here is my workbench project: https://rapidshare.com/files/4084825686/doublepipe.zip Thanks in advance!

May 31, 2011, 09:59	Hope this is helpful!	#2
shields New Member Killen Should Join Date: Jan 2011 Location: Ireland Posts: 10 Rep Power: 15	I'm conducting a similar project in relation to heat transfer within a heat exchanger. I've downloaded your files and meshed them using Ansys 13 for you - Mesh Conforming method. Its states that the CFX method is outdated and no longer used. Hope this is of use. Are you planning to use fluent to analyse the problem. I'm having problems getting Fluent to account for the conduction across the inner pipe boundary [the main point of interest as this is where the heat transfer is occurring]. I'm wondering how you plan to incorporate this in Fluent. Will you use conjugate heat transfer and if so how??? Any help is much appreciated. Heres a link to my post relating to my project http://www.cfd-online.com/Forums/flu...two-pipes.html Here are the updated meshed files for your project. https://rapidshare.com/files/3335016585/doublepipe.rar

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May 31, 2011, 10:55		#3
kola77 New Member Marko Join Date: Sep 2010 Location: Slovenia/Portugal Posts: 13 Rep Power: 15	Thanks for your help, but I have managed to solve the problem by now. The solution was to mesh the solid domain using the ansys mechanical method, and the fluid domain using any other method (tetrahedral, even the outdated cfx-mesh method, etc) and joining them later on. As for your problem, I am using CFX to run the analysis. I don't know if this is really an option for you, but it shouldn't be much more different than it is with FLUENT. Anyway, here's how it goes: First I have created three domains, one for the solid, and two for the fluids, hot and cold obviously. As you could see from my files, I have prepared some regions in advance, especially pay attention to the interface regions, which, later on, are used to connect both sides of the pipe wall with corresponding fluids. The results I have obtained using this strategy seem promising and realistic. Unfortunately I have no idea how to use FLUENT, since my university only supplies me with a CFX license, but I imagine it shouldn't be much of a problem. Thanks for the help once again, and I hope my thoughts on your problem help you at least a bit! Cheers!

May 31, 2011, 11:30		#4
shields New Member Killen Should Join Date: Jan 2011 Location: Ireland Posts: 10 Rep Power: 15	Thats good that you got a solution. Yes i'm trying to connect the fluid and solids regions. this is where I am having difficulty. My problems geometry is simpler than yours as I do not have the narrow inlet and outlet. Would you be able to upload your cfx files, as I should be able to compare your methods then and possibly transfer them to fluent. I have a licence for CFX but I have not used it before, I should be able to follow the basics. Thanks in advance, if this is not possible, no worries.