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

How to find Mean Nusselt Number?

Register Blogs Community New Posts Updated Threads Search

Like Tree1Likes
  • 1 Post By azizi0407

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   December 21, 2012, 04:00
Default How to find Mean Nusselt Number?
  #1
New Member
 
Abhishek
Join Date: Dec 2012
Posts: 1
Rep Power: 0
abhishek4890 is on a distinguished road
I am doing an computational analysis on natural convection heat transfer through rectangular fins attached to a wall. After the simulation, Surface Nusselt number for hot wall which I am getting in higher than (twice) the experimental results. The way I am following for finding the mean nusselt number is : Report--> Surface Integrals-->Facet Average-->Wall Fluxes-->Surface Nusselt number.
Please provide me the solution. Also let me know whether I am using the right way of finding the nusselt number or not. If not then please provide me an alternate way of finding the Average Nusselt Number.
abhishek4890 is offline   Reply With Quote

Old   December 22, 2012, 03:24
Default
  #2
Senior Member
 
Lucky
Join Date: Apr 2011
Location: Orlando, FL USA
Posts: 5,747
Rep Power: 66
LuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura aboutLuckyTran has a spectacular aura about
Two things:

1) Heat transfer coefficient needs a reference temperature
2) Nusselt number needs a reference length scale.

Both of these reference quantities are specified on the reference values task pane. Did you remember to specify them?

I have always used area-weighted average and not facet average, but I believe they yield similar results. You should be able to get the average Nusselt number the way you are doing.
LuckyTran is offline   Reply With Quote

Old   December 12, 2016, 08:21
Question hi
  #3
New Member
 
Djamila
Join Date: May 2016
Location: Algeria
Posts: 16
Rep Power: 10
djamila77 is on a distinguished road
Quote:
Originally Posted by LuckyTran View Post
Two things:

1) Heat transfer coefficient needs a reference temperature
2) Nusselt number needs a reference length scale.

Both of these reference quantities are specified on the reference values task pane. Did you remember to specify them?

I have always used area-weighted average and not facet average, but I believe they yield similar results. You should be able to get the average Nusselt number the way you are doing.
What you mean by length scale, when I use length in a rectangular cavity do you mean depth ( hydrolics diameter )
djamila77 is offline   Reply With Quote

Old   December 12, 2016, 10:50
Default
  #4
New Member
 
a0407
Join Date: Aug 2016
Posts: 10
Rep Power: 10
azizi0407 is on a distinguished road
Hi, u need to precribed the bulk temperature and characteristic length in the reference value in order to calculate the Nusselt number.
djamila77 likes this.
azizi0407 is offline   Reply With Quote

Old   December 12, 2016, 15:15
Default i already did
  #5
New Member
 
Djamila
Join Date: May 2016
Location: Algeria
Posts: 16
Rep Power: 10
djamila77 is on a distinguished road
Quote:
Originally Posted by azizi0407 View Post
Hi, u need to precribed the bulk temperature and characteristic length in the reference value in order to calculate the Nusselt number.
i already did
but my Question is what means length in CFD when you use 3dpp.
My problem is in three dimensional
length is it the hydraulics Diameter
djamila77 is offline   Reply With Quote

Reply


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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Average Nusselt Number kamran651 FLUENT 8 April 2, 2016 09:41
same geometry,structured and unstructured mesh,different behaviour. sharonyue OpenFOAM Running, Solving & CFD 13 January 2, 2013 23:40
there is a problem with fully developed Nusselt number eeman Fluent UDF and Scheme Programming 4 September 24, 2012 02:36
CFX problem in ubuntu (linux) Vigneshramaero CFX 0 July 13, 2012 11:22
[snappyHexMesh] snappyHexMesh won't work - zeros everywhere! sc298 OpenFOAM Meshing & Mesh Conversion 2 March 27, 2011 22:11


All times are GMT -4. The time now is 07:25.