Why are top grade heatsinks never BLACK?

[ed^chigliak]

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

Yup... the Alpha PAL 8045 was indeed black. Did I paint the inside of my case matt black... nope.

I don't think it makes any difference. Radiant heat travels in straight lines and is absorbed by the nearest surface and the amount of cooling depends on the 'viewable' surface area and the delta T between surfaces. Since most of surfaces face each other the radiant heat will just radiate to the next fin or prong on the heatsink which will be at the same temperature so there is no delta T and negligible radiant effect. What your case 'sees' of the heatsink is the only radiant transfer but the viewable surface area is small because the heatsink is designed to maximise convective surface area. A radiant heatsink would be a matt black globe as big as possible and your case walls would have to be black and at a much lower temperature.

[krazy_olie]

*Looks at 486 Heatsink*

Yup Black.

[Butcher]

Heatsinks are black because it's easy to anodise aluminium heatsinks black. You have to anodize them anyway, and the layer of dye makes little difference to convective performance and can help radiation. You'll notice only Alu heatsinks are ever black and are anodized never painted. All copper sinks are shiny.

[joshwa]

Well, I've started the test: 8.25pm Silver heatsink on and AMD Athlon XP1700 (1466mhz) running SETI/BOINC 100% pic:



Update 8.55pm: CPU Temp 43C, Case 22C, Northbridge 32C. Time to spray...

I cleaned it in very hot water with a brush to get rid of all the dust stuck in it, then I dried it with a hairdryer - silver heatsink clean:



then I sprayed it (with a fairly thin coat), and made sure not to spray the bottom, and then dried it with a hairdryer again:



Time to put it back in the system...

[joshwa]

The results are in: after 30 minutes: CPU: 42C, Case: 23C, Northbridge: 32C - so far from conclusive, and the difference in CPU temp could be due to me re-applying the thermal paste and cleaning out all the junk from in between the fins... but it could be something to do with the fact that it's now black and looks COOL

[Zak33]

go Josh..go

[joshwa]

I guess with a hotter system, where a CPUs up to the 60s (C) it could make a bigger difference?

[Dougal]

Yeah, the black is just soo Cool that heat wants to get away.

[Zak33]

I have a feeling t would be best on a passive system from what everyone is saying....

I'm reallly not sure it acts as an insulant, making it harder for the copper to lose heat tho.

I reckon its fr the best though

[Zak33]

doesn't everone find it intriguing that most vid cards use black heatsinks tho...

except the big ones with fancy "buy me" heatsinks....all vanilla ones with vanila heatsinks use black!


I'm ognna edit the title to something relevent! as Trig said

[Butcher]

Mine has a rather plain looking silver heatsink actually. My old absolutely plain 9800 pro has a silver sink too.