CFD Online Logo CFD Online URL
Home > Forums > CFX

problem with heat transfer

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

LinkBack Thread Tools Display Modes
Old   October 27, 2007, 12:07
Default problem with heat transfer
Posts: n/a
Hi I am trying to model a stack (2.5X1.6X0.5) with all walls except one adiabatic, on wall at T=const, inlet as static pressure=0 ant Tair=25 C, and outlet as const mass flow rate. I am modeling as steady state. With air at 25C And with thermal model with buoyancy turbulence

While the pressure, the velocities and the k-e are ok, the thermal model at the solution is very unsteady and the residuals are vey high.

Any ideas for this?

Also any ideas about BC so that I can run this as physical model (not to imply an outlet BC with mass flow rate, but to calculate the flow due to buoyancy)


  Reply With Quote

Old   October 27, 2007, 13:31
Default Re: problem with heat transfer
Posts: n/a
Have you set the initial temperature of the fluid?(Initial conditions dialog)? I had something similar occur to me and by Initializing the fluid temperature to the inlet condition (or suspected fluid temperature) I was able to get my thermal residuals to converge.

If we are talking about the same problem, then CFX basically sets the fluid temperature to the highest temperature set by the user (the hottest temperature in the model). This can cause the residuals to just "hang" at higher values. In my model they wouldn't converge until 1000+ iterations. Hope this helps. -W
  Reply With Quote

Old   October 28, 2007, 17:33
Default Re: problem with heat transfer
Glenn Horrocks
Posts: n/a

I think you will find there is no steady state solution. Often in turbulent convection driven problems you get large scale transient structures in the flow which cannot be "averaged" out with a turbulence model. The only way to proceed is to do a transient simulation.

At a minimum you should check the steady state solution gives the same answer as a transient solution.

Glenn Horrocks
  Reply With Quote

Old   October 31, 2007, 04:26
Default Re: problem with heat transfer
Posts: n/a
Thank you. I finally manage to get a result, with transient solution, but only in hybrid ventilation.

I still can't find bountary conditions for naturally ventilation

  Reply With Quote


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
Heat transfer problem at nucleate boiling MrStuebb FLUENT 12 March 14, 2017 14:31
Wall heat transfer coefficient (HTC) problem Mohamed khamis CFX 1 January 16, 2010 00:12
How can I increase Heat Transfer at Domain Interf? B.Simon CFX 3 October 28, 2008 19:53
Heat Transfer Problem Help JB FLUENT 2 October 18, 2006 18:54
heat transfer problem. vipin CFX 2 July 18, 2006 10:05

All times are GMT -4. The time now is 04:05.