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April 18, 2014, 12:36 |
heat exchanger with perforated fins ... help
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#1 |
New Member
ayad
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Hi
I have cross flow finned tube heat exchanger with perforated annular fins as shown below. http://s10.postimg.org/hhq4dfxih/Sna...BIT_Solver.png after finishing the mesh and geometry and applied boundary condition by using GAMBIT i had exporting the case to fluent. the problem, there is no connection between the duct and heat exchanger, in the other word the air doesn't collide with finned tube, so there is no stagnation and heat transfer. Notes 1- constant temp. B.C applied to inner diameter of the pipe 2- the true result must be as shown in fig. below http://s10.postimg.org/w9uu4s3ft/perforated_fin.jpg |
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April 21, 2014, 08:04 |
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#2 |
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ayad
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Really need help
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April 21, 2014, 22:37 |
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#3 |
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Real Name :)
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Sounds like you didn't subtract the inner part from the outer enclosure. Gambit won't automatically subtract the two in a boolean manner just because you set the boundary conditions appropriately. I would check your order of operations or, worst-case, post your journal file for us to review.
ComputerGuy |
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April 22, 2014, 09:21 |
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#4 |
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ayad
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thank u for your reply
subtract doesn't used here because i have no smooth pipe. I thing split volume must be used in my case. I used volume option to split the two volumes, Bidirectional and connected options were selected, Retain option was unselected. is this right way please? |
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April 22, 2014, 13:28 |
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#6 |
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ayad
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thank u for your reply
right I do that, but there is no connection between (fluid and solid) volumes I think the true result gained by use true method to split the two volumes. |
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April 22, 2014, 13:42 |
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#8 |
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ayad
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Never mind, thank u so much
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April 28, 2014, 01:36 |
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#9 | |
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Maxime Perelli
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Quote:
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April 28, 2014, 03:02 |
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#10 |
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ayad
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Hi max thank u for your reply
As you see there is no temp. variation in the air temp. |
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April 28, 2014, 03:06 |
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#11 |
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Maxime Perelli
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I never did such computation, but I assume you have to handle thermal conduction within thin wall
check here: https://www.sharcnet.ca/Software/Flu...e253.htm#33023
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April 28, 2014, 03:28 |
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#12 |
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ayad
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Indeed i have select the Coupled option B.C. in the fluent .
I think the problem in the gambit, because there is no connection between the pipe and the duct. any method make a stagnation between fins and air will be solve the problem. |
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April 28, 2014, 03:38 |
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#13 |
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Maxime Perelli
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do you have "shadow" walls?
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April 28, 2014, 03:41 |
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#14 |
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ayad
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Yes, I have.
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April 28, 2014, 03:46 |
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#15 |
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Maxime Perelli
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are you coupling the good surface with its shadow surface?
if I see your picture you at least need 5 coupling
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April 28, 2014, 03:51 |
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#16 |
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ayad
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No, I didn't do that.
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April 28, 2014, 03:54 |
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#17 |
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Maxime Perelli
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then what did you do?
display the list of your bc (wall and shadow) and explain what you did
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April 28, 2014, 04:19 |
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#18 |
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ayad
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firstly i specified two zones fluid zone (duct), and solid zone (pipe and fin). then, inter: fin surface area (coupled B.C.) P: duct outlet (pressure outlet B.C) S: Inner diam. of the pipe (constant temp. B.C.) V: duct inlet (velocity inlet B.C) WS: 4 wall of the duct wall: I dont know why is appear |
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April 28, 2014, 04:27 |
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#19 |
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Maxime Perelli
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*wall contains all outer surfaces on which you didn't set any BC, and Gambit set them automatically as wall
ok, now display the BC on inter and inter:012 and show me its geometry (how did you set the BC? did you pick inter and inter:012 or only inter, then inter:012?)
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April 28, 2014, 04:47 |
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#20 |
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ayad
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thank you for your time,and I'm sorry for delay, there is a problem in fluent because i connect the computer with internet, So i can't take a picture.
But, the fin and pipe surface area are the geometry of inter. only inter gave B.C (coupled), and i had neglect inter:012. |
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