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

Good convergence but without a good heat balance

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

Reply
 
LinkBack Thread Tools Display Modes
Old   June 27, 2007, 16:51
Default Good convergence but without a good heat balance
  #1
Juan Martin Catelén
Guest
 
Posts: n/a
Hello. I'm modelling a pool that is loosing heat trough a walls (one of them has velocity). Also, it has inlets of fluid with fixed temperatures and outlets where the temperatures are calculated. The problem I'm having is that although the residuals of the heat transfer are below 10-4, when I compare the heat entering to the pool through the temperature difference of inlets and outlets with the heat that is flowing through the walls, I see a difference of 20%. Is this possible with such a good convergence? What could be happening? The pool is of 22m long, 0.9m and 2.5m width. It has 750000 elements. I'll be waiting for help. Thanks in advance.
  Reply With Quote

Old   June 27, 2007, 16:56
Default Re: Good convergence but without a good heat balan
  #2
opaque
Guest
 
Posts: n/a
Dear Juan Martin,

Are you doing the comparison manually, or looking at the imbalance in the ANSYS CFX Solver Manager?

Do you have any Fluid Solid domain interfaces? The heat transfer reports are a bit different when they are present.

Opaque

  Reply With Quote

Old   June 27, 2007, 17:16
Default Re: Good convergence but without a good heat balan
  #3
Juan Martin Catelén
Guest
 
Posts: n/a
I'm doing the comparison with the CFX-Post functions in the table viewer. I'm taking the enthalpies at the inlets and at the outlets and comparing the diffrence with the areaint applied to the walls that are not adiabatic. I dont have solid fluid interfaces in the domain. What do you think? Should I continue the calculation?
  Reply With Quote

Old   June 27, 2007, 18:38
Default Re: Good convergence but without a good heat balan
  #4
Glenn Horrocks
Guest
 
Posts: n/a
Hi,

If you are looking for good heat balances then you should add this to the convergence criteria. This is usually caused by not running the simulation for enough physical time so the inlet flow fluid has reached the outlet and established steady state. Sometimes the timescale for the temperature to settle out is far long than for the flow so the default convergence options stop the run before the heat profile has reached steady state.

Glenn Horrocks
  Reply With Quote

Old   June 27, 2007, 18:41
Default Re: Good convergence but without a good heat balan
  #5
Juan Martin Catelén
Guest
 
Posts: n/a
Thanks.
  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
Problem of heat balance in Coal Boiler simulation DG FLUENT 9 December 25, 2008 20:57
Good book for heat transfer + FEA? Bren Main CFD Forum 0 November 24, 2008 19:54
Good CFD software for automotive heat exchanger Kiran Gaikwad Main CFD Forum 3 July 14, 2008 20:38
Two-Phase Buoyant Flow Issue Miguel Baritto CFX 4 August 31, 2006 12:02
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 15:55


All times are GMT -4. The time now is 07:31.