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

CFX - wall heat flux

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 1, 2006, 09:47
Default CFX - wall heat flux
  #1
divarano
Guest
 
Posts: n/a
I 've a question about sign convention in CFX. I made a simulation of steady state heat transfer of an insulated box, with internal T_in= 293 K, and outer of T= 213 K. I've to estimate the optimal thickness of insulating layer, so I created a boundary condition on the internal walls of heat transfer with heat source (energy). I've plotted the wall heat flux on a line across the layer, and noticed that heat flux varies with a peak in a range going from negative to positive values, whereas I expected that it decreases linearly, and in the best case it goes from 0 to negative flux equal to energy input source. Can you explain why this and what does it mean a negative heat flux? Thank you. Eng. Igor Di Varano

  Reply With Quote

Old   December 4, 2006, 13:54
Default Re: CFX - wall heat flux
  #2
Robin
Guest
 
Posts: n/a
Fluxes into the computational domain are positive, out are negative. A negative wall heat flux means heat is going into the wall, out of the fluid domain.

-Robin
  Reply With Quote

Old   December 4, 2006, 17:14
Default Re: CFX - wall heat flux
  #3
igor di varano
Guest
 
Posts: n/a
Thank you very much, I've found some information on help soon after my previous e-mail. Now there 's another point. I've plotted the wall heat flux through the thickness, but I have only a few points and I've been requested to enhance the number of points in the layer. I've tried to fit the mesh, but without success, as I have always the same points(7). I 've read on the handbook that wall heat flux is sensitive in proximity of wall surfaces, and in a lesser way within the wall. Is it true or with more elements I can expect the desired result? Thanks a lot. Igor
  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
Water subcooled boiling Attesz CFX 7 January 5, 2013 04:32
CFX Heat Transfer RJamison CFX 0 July 24, 2008 12:11
Wall Heat Flux Boundaries conditions Abigail FLUENT 2 July 24, 2007 09:34
wall heat flux between two fluid zone!!! Asghari FLUENT 2 August 25, 2006 10:11
Multicomponent fluid Andrea CFX 2 October 11, 2004 05:12


All times are GMT -4. The time now is 22:39.