CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Running, Solving & CFD

Energy balance error with high prandtl numbers.

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   January 20, 2011, 06:21
Default Energy balance error with high prandtl numbers.
  #1
Member
 
David
Join Date: Dec 2009
Location: Spain
Posts: 62
Rep Power: 16
David_010 is on a distinguished road
Hi to all,

I m using the buoyantBoussinesqSimpleFoam (with g=[0 0 0]) solver for a laminar flow inside a duct with constant heat flux at the walls (basically a fixedGradient b.c.). Inside the duct there is a moving device (moving walls).

When I use a low Prandtl number (like with air properties, Pr=0.7) the temperature field seems to be correct, and the energy balance between inlet, outlet and heat flux at the wall (q"*Area=m*cp(To-Ti)) is accomplished. But when I change the properties to a Pr=256 (corresponding to a propylene glycol) the temperature is higher than expected (specially near the heated walls) and therefore the energy balance is wrong.

What could be the problem? The high Pr number leads to a very low thermal diffusivity (DT), and the Laplacian therm could be negligible. I have tried to increase de DT value keeping the Pr constant, but I get the same results.

Thank you very much in advance for your help!

David
David_010 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
ATTENTION! Reliability problems in CFX 5.7 Joseph CFX 14 April 20, 2010 16:45
HELP!! Prandtl numbers in RNG k-e turbulence model maoasis FLUENT 0 April 24, 2006 11:51
Could anybody help me see this error and give help liugx212 OpenFOAM Running, Solving & CFD 3 January 4, 2006 19:07
HELP needed: Energy balance in gaseous combustion James Willie FLUENT 11 August 10, 2005 05:58
Multicomponent fluid Andrea CFX 2 October 11, 2004 06:12


All times are GMT -4. The time now is 00:49.