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

Operation Temperature for Boussimesq Approx

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

Reply
 
LinkBack Thread Tools Display Modes
Old   December 12, 2013, 12:16
Default Operation Temperature for Boussimesq Approx
  #1
Member
 
Tom Marquardt
Join Date: May 2013
Posts: 33
Rep Power: 4
TomM is on a distinguished road
Hey guys,

I'm trying to solve a natural convection melting problem. Boussinesq approximation is valid because *(T-T0)<<1.

I'm not sure how to set the reference density rho(0) and temperature T(0). I have data regarding the density in solid (890kg/m) and liquid phase (760kg/m) and I know the melting temperature is 306 K.

What would I use for operation temperature and density in this case? Might be a silly question but I'm not sure about this.

Thanks for your help!
TomM is offline   Reply With Quote

Old   December 12, 2013, 13:57
Default
  #2
Senior Member
 
Join Date: Jan 2010
Location: Germany
Posts: 268
Rep Power: 8
Zaktatir is on a distinguished road
The Buossinesq model is valid when the temperature fullfill the condition delta T * thermal expansion coeff smaller than one. Beyond that you should be using a compressible model.

Try setting your reference temperature to the mean of your expected temperatures.

In a closed system, Tref shouldn't change your final solution (although higher buoyancy forces can cause stability issues). In an open system, Tref can be the ambient temperature, but you need to be careful not to induce false flows with very large body forces.

The density is always an issue in fluent i usually use zero density or the density of the lighter phase (latter is suggested for multiphase flows)
Zaktatir is offline   Reply With Quote

Old   December 13, 2013, 04:14
Default
  #3
Member
 
Tom Marquardt
Join Date: May 2013
Posts: 33
Rep Power: 4
TomM is on a distinguished road
Hey,

thanks for your respond! I think I got your point but what does

Try setting your reference temperature to the mean of your expected temperatures

exactly mean? The initial temperature of the PCM is 295,13 K, the melting starts at 307K and the highest temperature possible will be the one of the Hot fluid stream melting the material with 325K.

If I get you right, 325K would be the temperature to go, is this correct?

Thanks!
TomM is offline   Reply With Quote

Old   December 13, 2013, 07:09
Default
  #4
Senior Member
 
Join Date: Jan 2010
Location: Germany
Posts: 268
Rep Power: 8
Zaktatir is on a distinguished road
That will be my start point!
Zaktatir is offline   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
Calculation of the Governing Equations Mihail CFX 7 September 7, 2014 06:27
whats the cause of error? immortality OpenFOAM Running, Solving & CFD 11 April 22, 2014 12:32
is internalField(U) equivalent to zeroGradient? immortality OpenFOAM Running, Solving & CFD 7 March 29, 2013 02:27
Static Temperature / Opening Temperature JulianP CFX 6 March 23, 2013 17:03
operation temperature skikay Main CFD Forum 0 September 7, 2012 01:29


All times are GMT -4. The time now is 23:20.