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PostPosted: Fri May 10, 2002 6:29 am 
Heat transfer is conduction, convection and radiation?

Its all in the distance? Radiation is to the fourth power of distance? So the fins closer together will heat up the air more?

Convection is the least effective way of cooling or the reverse, heating air? It is mostly by displacement.

Conduction is direct heat transfer, by mechanical contact. How heat waves(long infrared wavelength or frequencies) travel is like elctrical current flow. Electrons pile up when they try to turn corners. Piling up electrons cause friction and create heat. This governs heatsink shape design? Use a collector of heat(to store the energy or heat), in the base of the heatsink as a researvoir and conducts into fins to be cooled.

Black body or paint assorbs more heat, metallic surface of fin reflects heat back to the black paint, but also rediates into the black paint.

So, we want to radiate heat from the metallic fins and let thin black paint assob it. Then we want the air heated by the black paint by radiation to be cooled by convection. Cool air replaces hot air by displacement.


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PostPosted: Mon May 13, 2002 1:37 am 
How much trouble is there to paint the heatsink?

Just sit the bare heatsink on lots of newspaper and use dull black(not glossy) automobile spray paint from 12" and have a thin coating. Dull black is theoretical infrared black body. Dull black paint filler is very fine carbon powder.

Quick drying paints will allow you to test the effect of black paint in a few minutes. Your motherboard sensors and your hand will give you the result.

If you want to try thicker paint, just spray some more. If you don't like it anymore, just use paint remover.

Have fun?


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PostPosted: Mon May 13, 2002 1:52 am 
Did you know I stole the paint idea from the Solar hot water heaters?

They flow water over black painted copper sheet, under sun light thru glass panel.


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PostPosted: Mon May 13, 2002 9:25 am 
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Joined: Thu Nov 08, 2001 1:01 am
Posts: 3987
:arrow: :idea: are the components from the sun that heat the black surfaces present inside of a cpu case (paint will prob act as an insulator, and impede convective transfer of heat?!?)? :?:


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PostPosted: Tue May 14, 2002 1:56 am 
It's really comparison of air over paint and water over paint? Air needs dull black where as water needs glossy black. Glossy black for water is because dull black paint will be washed away.

Many small aluminum featsinks were anodized black. But it is not effective because anodization is done by sulfuric acid then boiling water to create a thick saphire coating. The thickness of the coating is 1/4 of the black color wavelength. The anodized coating does not store heat.

Dull black paint with carbon powder will store heat then gets cooled down efficiently. Mechnical engineer's concept of heat transfer has to be supplemented by infrared wavelength transmission theories in physics or electronics to complete the rediation part of heat transfer. Absorption, reflection and transmission


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PostPosted: Wed May 15, 2002 12:45 am 
We welcome anyone to try some paint and report the censor readings, before and after?


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