Cooling the Parhelia

[tutkija]

Originally posted by Dr Mordrid
Physics 101:

It's called the "black body" effect. Heat is absorbed, and re-radiated, more efficiently by a black object. This is why they paint auto radiators and transmission coolers black. This effect is only negated at very high temperatures.

Wilhelm Wien (U. of W¨¹rzburg) won the 1911 Nobel Prize for Physics for his 1893 theoretical paper on black body radiation and discription of what became known as "Wiens displacement law";

Lambda= C3/T

where

C3 = 2.898 x 10-3 mK
Lambda = wavelength in microns

Wein's displacement law tells us that as a body gets hotter the wavelength at which its maximum spectral exitance occurs gets smaller.

Dr. Mordrid

This is true. The "black body" is physical term for ideally absorbing/radiating body. in the real world we could use term "grey body", whitch has ideally propertys close to the "black body". The color of the object does not always tell the absorbtion/radiation properties of the object. For example grey paint reflects more radiation than white paint. This is due to the paint composition. By painting the metal object with some paint or other coating changes the absorbtion/radiation properties acconding to the coating properties.

[Greebe]

tutkija, we're talking emissitivity of a black body, not spray paint

[dslash]

Maybe they can use some Alpha heat sinks on Parheila-512 http://www.micforg.co.jp/
use S series(S1560+30mm Height),UBC series,or SB series will be cool...
S series

UBC series

SB series

[Tempest]

I don't know what the final Parhelia will look like or how it will be cooled, but this is what I want mine to look like
<img src="http://koti.mbnet.fi/~sampokoo/misc/heliabig.jpg">

[[GDI]Raptor]

How about one of those VapoChill to cool it down....

[Marshmallowman]

Physics 301
"black body" radiation is physics term, while most "balck bodies" used in experiments are black, some are actually different colours, its all about the emissivity (not sure if that is the right term) of the body over its entire frequency range. (from radio waves to xrays and more)

a "black body" has a certain emission profile, the curve is somewhat shaped like a "beer gut", in that it increases smoothly then curves to drop sharply at its highest frequency(of emission)

oh..and a "black body" radiator can glow different colors...

PS apologies for the analogies

[tutkija]

Originally posted by Greebe
tutkija, we're talking emissitivity of a black body, not spray paint

I understand that and i know difference between black body and body coated with "black paint". Comments like
"This is why they paint auto radiators and transmission coolers black. " suggest that painting object with black paint will always change properties towards black body.

[Dr Mordrid]

You are saying that an objects color and coatings don't affects its thermal characteristics?

Better re-think that. Also: not all color coatings are paint...even though paints DO have an effect.

Dr. Mordrid

[Greebe]

tutkija, using any old off the shelf spray paint will in 99% of the time degrade performance instead of improving it. What's needed is either an metal impregnated (typically Aluminum) flat black paint or one specially formulated with Silica/Silicone to the like that NASA uses.

So to conclude that radiators use (common, off the shelf) spray painted black and thus moves it toward a true black body is an incorrect assuption on your part.

It works like this (color, not paint)

White, (silvered) slowest to absorb, slowest to release thermal energy.

Black (flat black) fastest to absorb, fastest to release thermal energy

Grey (or green) is middle of the field on both counts.

We're only stating this all for the record to ensure readers who don't know are informed of the facts correctly.