Why are top grade heatsinks never BLACK?

[Zak33]

Matt Black?

It radiates heat the best....much better that shiny silver and gold.

So why aren't heatsinks black?

[Lee H]

..because blacks classed as boring so they tart them up with neon colours, huge glowing fans and then sell them with the "ooooh factor"

Saying that if they anodised the cooler i.e copper to give it a black coating this might affect the thermal co-effiency more and not make them as good at cooling as a plain metal heatsink.

Then again it might be down to costs of making. Anodising takes time, chemicals and electricity so this would then push the end price up - Something you consumers DO NOT like.

My advice - buy a black marker

[Michael]

Doesn't black only absorb heat energy from light? No difference in the dark?

I could be completely wrong though, didn't exactly do well in Science at school.

[chriswood_7]

Yeah its also a very good heat emitter... but I dont think colour effects conduction or convection, its only when light (radiation) is concerned.

Chris

[TeePee]

Do heatsinks disipate much heat by radiation? Or do they lose more heat through conduction to the air? Surely it's better for the bare metal to be exposed to the air to conduct heat to it, rather than being insulated by a layer of paint...

[YorkieBen]

racism?

[chriswood_7]

racism?

Hehe

[Dorza]

My heatsink is matt black. Might be old now but it still cools a barton 3000 down nicely.

[subucni]

I may be wrong (been years since i was in a class room) but my take on it is like michael, it's energy from light, in which case surely you would want a white heat sink to give off energy into the atmosphere more efficiently just like a radiator (hence the reason they are white) because you'd want to get the heat away from the heatsink to cool it, where as a black one just absorbs the energy from the light as it doesn't reflect it, so it would be worse and just get hotter.

But the bigger answer is probably more to do with conduction, convection and radiation, if you were to coat the heatsink it would likely have an adverse affect on the conduction properties of the heatsink that outway the convection/radiation benefits of giving the heatsink a coloured coating. and thats just probably why they don't bother doing it.


bres



:edit: seems like i was beaten to it while typing, damn you all. haha

:edit: My bad, i knew i was going wrong somewhere, cheers Kalniel

[kalniel]

Hehe I'm with the conduction/convection crowd White radiators are much less effective than black or whatever ones, but in a lot of cases you actually want to regulate the heat loss even from radiators as the returning water will require less heating.

The aim with computer heatsinks is to transfer heat to air (or water), ie conduct. Which is why you want good airflow. Conducting materials oddly seem to often be coloured in ways that reduce their radiation - think of artic silver or ceramic (white) heat paste. Convection is more about the movement of air that best presents cooler air to the heatsink. Radiating something in an unbounded environment (eg space) is sometimes a good idea (especially where conduction and convection don't work, like space ), but inside a metal box.. not so (would just radiate back to the components )

[BenW]

Because you have to add something to the metal to make it black which makes it less pure and more expensive to manufacture

[kempez]

So what we're saying is that Silver/gold is like the perfect balance between heat absorbtion and reflection

Or am I crazy

[herulach]

So what we're saying is that Silver/gold is like the perfect balance between heat absorbtion and reflection

Or am I crazy

No, just that silver or gold is what colour metals are, and painting them black would slightly increase heat loss by radiation, but probably dramatically reduce convection losses, which are the big ones

[ajones]

Can we call you crazy just for the hell of it?

[Jonny M]

Tell that to the Thermoengine

[kempez]

Can we call you crazy just for the hell of it?

Yeah most people do generally