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llidito April 25, 2013 15:47

Repeated elements in a system – pressure drop
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Hi everyone,

I am a quite new foamer and I am having trouble dealing with the simulation of systems with repeated elements. The goal is to decrease the simulation-time by leaving these repeated elements out of the mesh and give as a known parameter for the simulation the corresponding pressure drop for each of these elements.

Firstly I will describe a simplified case. Let us consider the following heat exchanger (see picture A). The flow goes inside the exchanger through the inlet tube before entering the tank, continues through the tubes, goes to the tank and finally leaves the system through the outlet tube.

The pressure drop of each tube between the tanks is known and therefore they would not be meshed. The mesh would look like in picture B (only the tanks, the inlet and outlet tubes and a very small piece of the tubes at each side would make up the mesh; therefore there would be a gap in between these short tubes). The mesh is generated with Ansys and then converted to OF.

The difficulty arises when the pressure drop of each tube must be given/entered to OF and the way how to do it. I have tried the following methods but none of them are working out:

1) Fan BC between face A & face B (see pictures B & C). The problem here is with the mesh generated with Ansys. Because of the gap between the tanks the number of faces of face A is different from the number of faces of face B and therefore the utility createPatch (in order to obtain the cyclic Patches) will never work.
2) Groovy BC. I do not know how to relate the pressure and the velocity between the patchs face A and face B (see pictures B & C) in order to get the desired drop pressure and related velocity.

I do not know if the procedure is the correct one.

I hope someone can help me cause I am running out of ideas and I do not know what else should I try.

Have a nice weekend,
José.Attachment 21150

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