Radiation surface area for fins

[MechMick1]

Hi,

I am currently trying to simulate heat loss from a complex geometry using FEA.

I have an object similar to a pipe with radial fins and I am trying to allow for heat loss from this body due to radiation.

Should the surface area used for radiation heat loss be the entire body surface? Even the surfaces of the fins which face each other? Or should these surfaces of the fins be excluded and only surfaces perpendicular be included?

My impression is that the surface of the fins facing each other will not contribute efficiently to radiation heat loss to the environment, and should not be included.

Any help would be greatly appreciated.

Thanks,
Mick.

 

[IRstuff]

Do a search for "view factor" which accounts for the occlusion of the field of view of the fin by another fin. The efficiency is lowered, but it could still be significant.

TTFN
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[chicopee]

How much surface temperature do the fins have and what is the ambient?

 

[racookpe1978]

You will actually be losing some fin radiation "ability" due to the view factor mentioned above, but unless you are radiating heat into a vacuum, the extra fin area will likely be far more important in increasing your cooling losses into the air flowing past.

To be most accurate, remember the temperature across the fin as well. The tips will be substantially cooler than the roots, and, since radiation is T^4 ... even "a little bit cooler" can be a substantial problem.

 

[MechMick1]

Hi,

Thank you for the replies. The 'view factor' was the term I was looking for.

The fins are not actually for heat dissipation, they are just part of an existing geometry I am trying to analyse, so I am not trying to optimise the performance, just understand how I should simulate it.

Thanks again for all the help,
Mick.