• Here is a link to the full explanation: https://rollitup.org/t/welcome-back-did-you-try-turning-it-off-and-on-again.1104810/

200 X Cree XP-G3 on one board

Levradus

Levradus

Well-Known Member
While im getting that huge heatsink after covered with anodized black manufacturer added number of its capable wattages as passive cooling..
But dont know any technical thing about it
 
Will-In-China

Will-In-China

Member
Shugglet said:
lol, okay. Any reasoning for being dubious? Or just for the sake of being.
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When light hits something thats black I agree it heats up faster than something thats white, this is radiation, what we are dealing with is convection, the cooling occurs when the air moves over the heatsink, the heatsink does heat the air pushing it up, but the light hitting the heatsink is not whats heating it up.

I think black is chosen just to hide the dirt and dust better or just because it looks cool, I'm not 100% sure but If air gave priority cooling to things that are black, I think we'd see allot more black things.

I guess as everything around the light is waterproof you could just tip over some rubbing alcohol and use a small bottle brush to get into the fins to make sure theres no mould lurking.
 
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Shugglet

Well-Known Member
Will-In-China said:
When light hits something thats black I agree it heats up faster than something thats white, this is radiation, what we are dealing with is convection, the cooling occurs when the air moves over the heatsink, the heatsink does heat the air pushing it up, but the light hitting the heatsink is not whats heating it up.

I think black is chosen just to hide the dirt and dust better or just because it looks cool, I'm not 100% sure but If air gave priority cooling to things that are black, I think we'd see allot more black things.
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We arent discussing convection, we are discussing radiation. Absorption and Emission are two sides of the same coin, so if its good at absorption it is also good at emission.
 
Will-In-China

Will-In-China

Member
Shugglet said:
We arent discussing convection, we are discussing radiation. Absorption and Emission are two sides of the same coin, so if its good at absorption it is also good at emission.
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So if I have one anodized black heatsink and one white one, both the same size and i heat them both equally with say a soldering iron (not with light) and you are saying that the black one will heat up and cool down quicker, do you think its measurable with like a red laser temp meter?
 
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Shugglet

Well-Known Member
Will-In-China said:
So if I have one anodized black heatsink and one white one, both the same size and i heat them both equally with say a soldering iron (not with light) and you are saying that the black one will heat up and cool down quicker, do you think its measurable with like a red laser temp meter?
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Conduction wold heat them equally fast, in theory though pretty sure the black should cool faster. No idea on rates.
 
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Shugglet

Well-Known Member
Will-In-China said:
I'm pretty sure they will cool at the same rate, next time I see a black and a white heat sink ill buy them and do the test, it should make a good you tube video
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Now thinking about it, the black heatsink in theory should heat more slowly than the white because it is radiating the incoming heat more efficiently to begin with.

Doing a simple search on google might save you the trouble but do what you want should be interesting.

Might I suggest doing the experiment in a vacuum though, in order to amplify the effects. After all, conduction and convection are by far the dominating sources of heat transfer in most heatsink applications and you dont want them skewing your results.

It should also be noted that the anodization is where the real gains come from in a passive cooling system, but if your going to anodize it, might as well make it black because it is the most efficient color to emit the heat.

Finding this information all took about ~5 minutes.
 
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