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

Radiation through: glass – air cavity – glass

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   October 25, 2005, 12:30
Default Radiation through: glass – air cavity – glass
  #1
Yingchun
Guest
 
Posts: n/a
Hello all,

Here I am again to ask something about radiation using cfx5.7.1. Now I need to consider incident solar radiation effects to a double skin façade system, the physical sequences would be: Solar radiant flux (W/m^2) from solar generator is striking on an external glazing (glass with thickness 12mm) then to an air cavity, then through an internal glazing (double glazing â€" glass(6mm)+airgap(12mm)+glass(Low E, 6mm)), and then to an internal controlled environment. I have generated the solid (material glass plate) and fluid zones (air) and now I have the following questions.

1. Can I set an isotropic radiation flux on the surface of the external glass as a source (the side facing the solar generator)? If this is the case, this surface has to be a wall boundary condition, but the thermal radiation option there shows 'opaque', it seems I still need to provide a temperature (or a heat flux) and an emissivity for the boundary. The surface is not 'opaque' anymore, but I don't have other choice.

2. 'Monte Carlo' model is selected as the thermal radiation model option, should I use 'gray' or 'multiband' model for both solid zones and fluid zones? Is the scattering model necessary for this case? The radiation properties for the 'glass plate', how do I define the 'Absorption coefficient' and 'scattering coefficient'?

Any suggestions would be highly appreciated (many thanks to the previous comments from Opaque. Sorry, Opague, this time I asked more)

Regards, Yingchun

  Reply With Quote

Old   October 26, 2005, 08:24
Default Re: Radiation through: glass – air cavity – gl
  #2
Yingchun
Guest
 
Posts: n/a
Any comments here? eagerly waiting responses from you experts.

regards, yingchun
  Reply With Quote

Old   October 26, 2005, 10:28
Default Re: Radiation through: glass – air cavity – gl
  #3
opaque
Guest
 
Posts: n/a
Dear Yingchun,

Have you had a look at the Heating and Ventilation tutorial? There is an example showing where to setup the solar radiation condition. The example uses directed (collimated) radiation..

CFX does not support semi-transparent external boundaries, but you add these external radiation influences via sources. They can also be a function as frequency/wavelength as well.

When setting up an external directed radiation source, be careful with the External Refractive Index setting. If you do not set it, the rays is taken without refraction through the first boundary of the solid.. Set/Unset it and you will be able to see what I mean..

Again regarding modelling, it is up to you what you want to do.. In general, radiation solar calculations are done with two bands. More bands usually do not bring additional bang for the buck..

Regarding Gray, and Multiband models. CFX does not support mixing the models across a domain interface, that is, if one side is Gray, the other side must be the same as well. Otherwise, you will get an strange error message..

Properties are set in the same spot for fluids and solids: materials tab.

Good luck, Opaque
  Reply With Quote

Old   October 26, 2005, 10:48
Default Re: Radiation through: glass – air cavity – gl
  #4
Yingchun
Guest
 
Posts: n/a
Thank you, Opaque, i am afraid I didn't find the 'heating and ventilation tutorial', would you please let me know where i can find it? I use the command line 'cfx5help' and i can access all the tutorials listed there, but it seems the tutorial you mentioned is not there.

Thank you for your help again

Regards, yingchun
  Reply With Quote

Old   October 26, 2005, 11:05
Default Re: Radiation through: glass – air cavity – gl
  #5
opaque
Guest
 
Posts: n/a
It is called Air Conditioning Simulation, or tutorial 17 in ANSYS CFX 10.0.. It may be a different number in 5.7.1

Look for the Window boundary section..

Opaque..
  Reply With Quote

Old   October 26, 2005, 11:12
Default Re: Radiation through: glass – air cavity – gl
  #6
Yingchun
Guest
 
Posts: n/a
Hi Opaque, Thank you for your information. Just found it, actually, the same number. wasn't aware this is the title. I've also read some informaiton - cfx5 best practices guide for HVAC - which gives some suggestions on how cfx deals with direct solar radiation.

You are really helpful, thank you very much (no further question for now)

Regards yingchun
  Reply With Quote

Old   February 27, 2012, 16:14
Default Thermal radiation through single and double glass using ansys-fluent
  #7
New Member
 
ADETOLA
Join Date: Oct 2011
Posts: 6
Rep Power: 15
BIMSON2K is on a distinguished road
Pls,does anyone have an idea of how to go about modelling solar thermal radiation through air-glass-air and air-glass-air-glass-air.

I have just started using e ansys fluent software but things seems not to be going of fine.


Pls help
BIMSON2K is offline   Reply With Quote

Old   February 27, 2012, 17:46
Default
  #8
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,862
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
There are tutorials on this in the CFX documentation. But if you are using Fluent you are on the wrong forum - this is the CFX forum.
ghorrocks is offline   Reply With Quote

Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
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 Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
radiation through glass amrjoao FLUENT 0 July 19, 2011 11:18
air bubble is disappear increasing time using vof xujjun CFX 9 June 9, 2009 08:59
surface to s. radiation in air above transp. fluid dace CFX 1 March 3, 2009 08:35
Cavity air flow with radiation – result variable Yingchun CFX 1 November 25, 2005 12:13
radiation problem for square cavity using fluent john Main CFD Forum 0 September 30, 2005 08:40


All times are GMT -4. The time now is 18:19.