Thermal - Radiation ambiant temperature

[Nexxon]

Hi all,
I am currently working on the thermal assessment of a cubesat with Ansys 14. I want to simulate the radiative heat transfer inside the satellite (between the different components. For that I set a surface to surface radiation, input the emissivity etc...
My problem is: what is the ambient temperature? should I enter the temperature of space (~2.7 K) or the expected satellite's temperature (~200 K)? This makes a hudge difference in the results.
Thank you very much for your help!

 

[IRstuff]

?? Ambient temperature is a non sequitur. If there's essentially no air, there is essentially no ambient temperature. Moreover, if you are doing radiative transfer, why do you need ambient temperature?

The surface temperatures are, and should be, the net temperatures after accounting for radiative solar and earth load and radiative loss to space, coupled with the thermal load, both radiative and conductive, from the internal equipment and radiators and shields. This is not a casual calculation. The last time we had this done, it required quite a bit of expert knowledge.

TTFN
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[Nexxon]

Thank you IRstuff,
Ambiant temperature may be non sequiture, but it is a input parameter for the computation of the surface to surface radiation in ansys, I also don't understand why and that is why I am asking this question. Furthermore, simulations showed that this parameter has an influence on the results.
There is no air, that is right, but there is a temperature (~2.7 K).

To be clear, I am talking about the radiative heat transfer inside the satellite. The heat loads from the sun, albedo and earth IR have been calculated and are applied on the external surface of the satellite, as well as the satellite radiation to space. The heat generation due to the electronic components also. My problem is to define the radiation from one component of the satellite to another.

 

[IRstuff]

Then, that's not the ambient temperature, but the background temperature for space, which is, as measured by COBE (

http://en.wikipedia.org/wiki/Cosmic_Background_Explorer),

which is 2.7K.

The internal heat transfers should fall out of the calculation that you seem to already have.

Perhaps some diagrams of what you are trying to model is in order.

TTFN
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[flash3780]

This may help you with modeling surface-to-surface radiation via the radiosity method:

http://www.ansys.com/staticassets/A...article/AA-V1-I1-View-Factoring-Radiation.pdf

It's been a little while since I've done thermal modelling in Ansys, but here's a thread that I wrote about modelling radiation to ambient, which may also be helpful:

http://www.eng-tips.com/viewthread.cfm?qid=298500

I'm not sure that Workbench has quite provided all of the tools required to do a proper thermal model yet... although they're always adding functionality. You may have an easier time applying your thermal boundary conditions in ANSYS APDL.