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

Flux+Temperature on a wall ?

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

Reply
 
LinkBack Thread Tools Display Modes
Old   August 11, 2006, 05:48
Default Flux+Temperature on a wall ?
  #1
tanphi
Guest
 
Posts: n/a
Hello,

I have a question : does anobody know if it's possible to have as boundary condition for a wall both temperature and heat flux ? (For example : a wall at 100C with a heat flux of 500W/m on it)

Thank you !

  Reply With Quote

Old   August 11, 2006, 08:28
Default Re: Flux+Temperature on a wall ?
  #2
Raj Kiran Grandhi
Guest
 
Posts: n/a
Hello,

I guess that would be too many constraints at the boundary.

It is like trying to specify the temperature, pressure and density of a gas at the same time. The moment you fix any two properties, the third is automatically fixed by the ideal gas equation. Likewise, for a given flow system, the moment you fix the wall temperature, the heat flux is fixed. Or if you specify the heat-flux, then the wall temperature becomes a derived quantity.

What is the physics behind what you are trying to simulate? Do you really have such a situation?

HTH, Raj Kiran
  Reply With Quote

Old   August 11, 2006, 08:46
Default Re: Flux+Temperature on a wall ?
  #3
Albert F.
Guest
 
Posts: n/a
Hello all,

I'm in same situation, I have asked it at fluent support and they have said me that fluent does not support the two conditions. You have to impose one or the other and it is a little bit complicate because when you impose a heat flux you mean that all is radiation but is difficult to impose a quantity for the convection. The surface is also important in this cases because is not the same emiting 2000 W in a small or in a high surface. In fact it is more complicated that seems.

I'll try to find out the best choice, I think that there is a tutorial specialized in this terms.

  Reply With Quote

Old   August 11, 2006, 09:40
Default Re: Flux+Temperature on a wall ?
  #4
tanphi
Guest
 
Posts: n/a
thank you for your answers

Raj, I think you're not right : you can have to specify heat flux and temperature at the same time on a wall, and to have the heat flux does not give automatically the temperature : For example if you want to know the temperature on the other side of the wall, to determine it you must have both temperature and flux.

Albert, I think I'll try to make a udf to force fluent to apply both conditions but I don't know if it will work.....

  Reply With Quote

Old   August 11, 2006, 09:50
Default Re: Flux+Temperature on a wall ?
  #5
Albert F.
Guest
 
Posts: n/a
Ok tanphi, I'll look for information about this type of boundary conditions but I thing that an UDF would be the right way...

  Reply With Quote

Old   August 17, 2006, 05:37
Default Re: Flux+Temperature on a wall ?
  #6
Albert F.
Guest
 
Posts: n/a
Look for this tutorial:

Thermal Model of Head Lamps using DO Radiation Model.

I think it can help.
  Reply With Quote

Old   August 19, 2006, 09:06
Default Re: Flux+Temperature on a wall ?
  #7
Mark Russell
Guest
 
Posts: n/a
Conductive heat flux through the solid is driven by the temperature gradient across it. i.e. Qx = -KA dt/dx. And so the two conditions are intimately connected. Hence I wonder why you feel you need both conditions. Please provide details of the case you are studying.

  Reply With Quote

Old   August 21, 2006, 02:28
Default Re: Flux+Temperature on a wall ?
  #8
Albert F.
Guest
 
Posts: n/a
I have a bulb that reamins at 900 C at the free stream but also emits 2000 W in radiation terms.
  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 with zeroGradient wall BC for temperature - Total temperature loss cboss OpenFOAM 10 March 5, 2015 07:57
Fluent3DMeshToFoam simvun OpenFOAM Other Meshers: ICEM, Star, Ansys, Pointwise, GridPro, Ansa, ... 48 May 14, 2012 05:20
assign both heat flux and temperature on wall qwerty753 FLUENT 2 July 14, 2010 08:09
No results for solid domain Gary Holland CFX 10 March 13, 2009 04:30
WALL HEAT FLUX tommy CFX 0 December 20, 2005 13:42


All times are GMT -4. The time now is 09:13.