CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Nusselt number in ribbed channel.

Register Blogs Members List Search Today's Posts Mark Forums Read

Like Tree1Likes
  • 1 Post By marluc

Reply
 
LinkBack Thread Tools Display Modes
Old   May 4, 2012, 04:33
Default Nusselt number in ribbed channel.
  #1
A7A
Member
 
AHMAD
Join Date: Apr 2012
Posts: 53
Rep Power: 5
A7A is on a distinguished road
Hi,

I am simulating a 2d ribbed channel heat transfer problem at (Re=10000 and wall heat flux q=1200 w/m2), and to simplify the solution i simulate half of the channel, but when computing Nusselt number from surface integrals i get a Nusselt number that is half of the right value of Nusslet number. (I am using the air temperature as reference temperature).

This is a picture of the geometry and mesh.

Thank you.
Attached Images
File Type: jpg geometry.jpg (20.9 KB, 30 views)
File Type: jpg mesh.jpg (86.6 KB, 36 views)
A7A is offline   Reply With Quote

Old   May 4, 2012, 04:45
Default
  #2
New Member
 
Yogesh Patil
Join Date: Nov 2009
Posts: 20
Rep Power: 7
foamcfd is on a distinguished road
Did you check the reference values in fluent. To report nusselt iot makes use of reference length which is set as default 1 in the refernce values.
foamcfd is offline   Reply With Quote

Old   May 4, 2012, 04:47
Default
  #3
A7A
Member
 
AHMAD
Join Date: Apr 2012
Posts: 53
Rep Power: 5
A7A is on a distinguished road
Thank you for your reply,

I used the hydraulic diameter of the channel as length reference value.
A7A is offline   Reply With Quote

Old   May 4, 2012, 12:26
Default
  #4
A7A
Member
 
AHMAD
Join Date: Apr 2012
Posts: 53
Rep Power: 5
A7A is on a distinguished road
Any solutions?
A7A is offline   Reply With Quote

Old   May 7, 2012, 09:37
Default
  #5
A7A
Member
 
AHMAD
Join Date: Apr 2012
Posts: 53
Rep Power: 5
A7A is on a distinguished road
Is this problem brcause of using standard k-w model, or because of using 2d study instead of using 3d study.

I hope that someone could advice me.
Thank you in advance.
A7A is offline   Reply With Quote

Old   June 8, 2012, 09:12
Default
  #6
Member
 
Luca
Join Date: Mar 2011
Location: Germany
Posts: 38
Rep Power: 6
marluc is on a distinguished road
Hi,

the 2D simulation is appropriate for ribbed channels with high aspect ratio (AR=depth x height). Anyway, RANS model hardly give accurate heat transfer results for flows with adverse pressure gradients (and thus recirculation).

You can check this paper:
A. Ooi, G. Iaccarino, P.A. Durbin, M. Behnia, Reynolds averaged simulation of flow and heat transfer in ribbed ducts, Int. Jou. Heat and Fluid Flow, 23, 2002
nenazarian likes this.
marluc is offline   Reply With Quote

Old   June 10, 2012, 08:24
Default
  #7
A7A
Member
 
AHMAD
Join Date: Apr 2012
Posts: 53
Rep Power: 5
A7A is on a distinguished road
Thank you for your reply, it was helpful.
A7A is offline   Reply With Quote

Old   August 4, 2012, 01:15
Default
  #8
New Member
 
Prem Chand
Join Date: Dec 2011
Posts: 3
Rep Power: 5
premchandpendota is on a distinguished road
Hi

Is your problem with the nusselt number solved? The problem i am working on also needs the variations of nusselt number across the area. But i am getting less values as you have mentioned.

If your problem got fixed, could you please tell me the changes i need to make in the numerical model? I have used the reference values just as you have mentioned in the previous posts.
premchandpendota is offline   Reply With Quote

Old   August 4, 2012, 09:49
Default
  #9
A7A
Member
 
AHMAD
Join Date: Apr 2012
Posts: 53
Rep Power: 5
A7A is on a distinguished road
Hi,

The main problem in my study was using 2d study (2d study can't predict the secondary flows that occur in the channel).
But if your study is 3d you could check the paper that marluc suggested, where you will find that also 3d study won't give you the same experimental results.

Quote:
Originally Posted by marluc View Post
You can check this paper:
A. Ooi, G. Iaccarino, P.A. Durbin, M. Behnia, Reynolds averaged simulation of flow and heat transfer in ribbed ducts, Int. Jou. Heat and Fluid Flow, 23, 2002

Last edited by A7A; August 5, 2012 at 08:50.
A7A is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Average Nusselt Number kamran651 FLUENT 7 August 20, 2014 18:58
Nusselt number in microchannel micro77 FLUENT 7 March 3, 2014 14:08
Mesh Refinement Luiz Eduardo Bittencourt Sampaio (Sampaio) OpenFOAM Mesh Utilities 41 January 17, 2013 03:43
BlockMeshmergePatchPairs hjasak OpenFOAM Native Meshers: blockMesh 11 August 15, 2008 07:36


All times are GMT -4. The time now is 06:02.