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[GAMBIT] Modelling of Helical-rod inserted in the inner tube heat exchanger is required

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Old   February 23, 2010, 17:59
Default Modelling of Helical-rod inserted in the inner tube heat exchanger is required
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Fahad
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Dear friends,

I've got recently project mainly about heat transfer enhansment in a double pipe heat transfer and I am new to the Gambit software and I need some one to help me how to generate the attached geometry of the required system which consists of a double pipes, where the inner pipe fitted with a helical-rod inserts. Please step by step. Thank you
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File Type: jpg Double pipe_Heat transfer.jpg (38.4 KB, 124 views)
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Old   February 24, 2010, 02:29
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2 choices: either you create your geometry in a cad soft, and then export it into gambit, or you create your geometry within gambit
For the second option:
*create helical-rod
*create inner-tube
--> boolean operation: substract inner-tube with helical-rod.

Creating helical-rod should be done as follow:
-Create the section surface
-Sweep the surface, enable type perpendicular, option twist with angle 360.
You will have to give the right vector (path) which define a complete rotation of your section (360deg)
-Then copy the volume n-times for matching your geometry, and you can unite those volumes each other.
I post a picture of what you should obtain (blue face is the section you have to sweep)
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File Type: png helical-rod.png (84.3 KB, 89 views)
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Old   February 24, 2010, 15:48
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Quote:
Originally Posted by -mAx- View Post
2 choices: either you create your geometry in a cad soft, and then export it into gambit, or you create your geometry within gambit
For the second option:
*create helical-rod
*create inner-tube
--> boolean operation: substract inner-tube with helical-rod.

Creating helical-rod should be done as follow:
-Create the section surface
-Sweep the surface, enable type perpendicular, option twist with angle 360.
You will have to give the right vector (path) which define a complete rotation of your section (360deg)
-Then copy the volume n-times for matching your geometry, and you can unite those volumes each other.
I post a picture of what you should obtain (blue face is the section you have to sweep)

Thanks so much Mr. mAx
Is it possible to do that drawing in 2D instead of 3D?
if Yes ,could you explain more about that.
if No, Can you give more detaild in how to create the section surface because I did up to that point and I don't how to sweep the face?

Thank you again
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Old   February 24, 2010, 16:09
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I don't understand how you can draw your rod in 2d.
It must be in 3d.
The Sweep face icon appears if you stay clicking on the stich faces icon in the volume panel (the first icon on the left, you can see a small red triangle which means there are other icons)
Check Gambit help
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Old   August 11, 2010, 00:52
Default Double pipe exchanger
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@Mr. Max, if we subtract the helical rod from the inner cylinder, we'll be left with a void inside where meshing can't be done. How do we simulate the flow through inner cylinder then?
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Old   August 11, 2010, 01:29
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the substract operation shouldn't give you an empty volume.
Be sure the inner cylinder totally surrounds the rod.
Do you get any warning from Gambit?
You can post a picture if you want
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Old   August 11, 2010, 02:25
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Mr. Max,

I generated the helical inner cylinder & then created the outer cylinder ensuring that it covers the inner one properly. Images are attached for your reference. But when inner cylinder is subtracted from the outer one following boolean operation, it's obvious that only the "ANNULAR" portion will be left. (Images attached) thus creating void for the inner cylinder. With this geometry only flow past helical baffles can be simulated while Inner cylinder can't be.

I wanted to send you the pictures however could not do so because of size limitation. Could you please send me your email id so that I can send these images?

Thanks & Regards,

Subhasish
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Old   August 11, 2010, 07:05
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ok I saw the pictures.
But what is the problem?
The substraction gives you the fluid domain between the cylinder and the rod.
Are you expecting something else?
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Old   August 11, 2010, 08:00
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That's what I'm trying to emphasize that this arrangement gives me only the annular region but what if I want to simulate flow through the "INNER HELICAL" tube as well?

There should be 2 flow streams..1) annular region/shell side 2) (helical) tube side and I would like to simulate flow in both region.

How do I mesh the "tube part" which is void??
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Old   August 11, 2010, 08:14
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Since your rod is solid, I don't see how you can get a flowfield inside it.
Perhaps you need to "drill" a tube in the rod.
If you do the same operation as prior (eg: substract), you should see the second region
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