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-   -   [GAMBIT] problem with meshing a heat exchanger (http://www.cfd-online.com/Forums/ansys-meshing/82164-problem-meshing-heat-exchanger.html)

 hittie November 18, 2010 17:08

problem with meshing a heat exchanger

hello everybody,

i need some help because i need to mesh a heat exchanger and the solid representig the heat exchanger is made from 2 rectangular bodies :the first one (heated volume) is the one supporting the "winglets" and the second one ( the heater) is pierced with 2 pipes. One of the two ducts is only a half pipe and the heat comes from the external surface of the pipes ( they are empty and the inside should not be meshed but only the external block). I joined the 2 bodies using the merge function and now it's a unique body .I want to mesh the body using map option but when i do this it says "vertex type not compatible".

How can i mesh it using map, submap or cooper option?

thanks for the help

PS: i linked the picture explainig a little bit more the situation :)
http://img339.imageshack.us/img339/9840/fig1.png

 -mAx- November 19, 2010 05:32

do you want to compute solid conduction?
if the body you showed, should be meshed, then you cannot mesh it with hex-element on the fly.
You need to decompose your volume into several smallest and simpliest subvolumes, which cacn be meshed with hexa

 hittie November 19, 2010 06:59

it is solid conduction and the heat is brought by the inner surfaces of the 2 pipes. There is no flow inside the pipes (it's a bore).
How should i divide teh volume because how can i consider the holes?

 -mAx- November 19, 2010 07:13

I never used Fluent for solid conduction.
Do you want absolutely full hexa (or cooper) mesh?
Becase you can use use the tetra-hexcore algorithm which filled your domain with hexa and boundaries are descibed with layer of tetra.
Very nice for complex geometries. (and it can be done on the fly)
Else you need to spend more time

 hittie November 19, 2010 07:22

on the picture i didn't represented the pipe containing the airflow ( englobing the winglets). I want to mesh the solid with a regular mesh such as "map" or "submap". I've already meshed the fluid volume using submap option.
The calculation will consists in measuring temperature and pressure in the flow volume to analyze the efficiency of the heat exchanger design and the bore transmit the heat. How can i spilt the volume for the meshing ?

 -mAx- November 19, 2010 08:25

ah ok your stuff in included in a pipe.
you will have to mesh your pipe at the end, because of your solid elements.
Mesh the solid elements, and then the surrounding pipe.
As I said, you have to ask yourself if you absolutely need full hexa mesh.

 hittie November 19, 2010 19:52

i've already meshed the surrounding pipe (air flow) which lies on the top of the solid body and englobing only the winglets using submap algorithm ( it's already approx. 1700000 elements including all Boundary Layers) but if i understand it could work well if i mesh the solid using the tetra-hexcore algo , but will it be so necessary to meshes it so precisely ? that's why i wanted to use the map or cooper option. By the way if i wanted to mesh it with map option how should i subdives the solid body to do so? should i mesh every winglets separately and after link the mesh with the mesh of the rectangular part? but doing so i don't know how to mesh only the outside of the 2 pipes.

Btw thanks a lot for the help:)

PS: when i try to mesh the solid volume using map it says : "logical cube for meshing was not found..." what should i do?

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