black anodized heatsinks

[skaara]

I have the heatsinks for aleph 2 and I would ask you if its worth to anodize them to black (I can get them profesionally anodized, for a price of course) - is there significat benefit, will heatsink improve its k/w rating?

I posted pics of my heatsinks here:
http://diyaudio.com/forums/showthrea...&threadid=6018



Thank you,
Jure

[Roberto Amato]

Try this Excel sheet. Can give you a pretty good estimate of
unknown heatsinks data.

[haldor]

Black anodizing will help them radiate heat better, but that is not the primary cooling method for heat sinks. Moving air is what cools heat sinks and the color doesn't impact that at all unless you paint them which makes them work worse.

I would only anodize them for esthetic reasons or if it is very inexpensive. Pay attention to keeping the airflow unobstructed and you will do a lot more to increase their efficiency.

Phil

[Roberto Amato]

Well, if we trust that Excel sheet, actually the plain polished aluminium sink roughly has a C/W about twice of the same black
anodized. A great deal of heat goes away through radiation.

[hifiZen]

Yes, surface emissivity is a significant factor. Also, an anodize finish will harden the surface and help protect against scratches and dents... eg. it's a much more durable finish than bare aluminum. Not to mention the aesthetics...

[hifiZen]

If you're a little adventurous, you can anodize yourself without too much trouble. See here: http://www.focuser.com/atm/anodize/anodize.html. What isn't mentioned on this page any more is that you can use common RIT fabric dye (available at Safeway etc.) instead of expensive commercial anodizing dyes. Only black RIT dye will be inferior to the commercial stuff, but other colours should be just fine. RIT dye is cheap enough that you don't have to bother trying to keep and preserve the solution to get max mileage out of it.

[Klaus]

Hi,

what Alberto said (and gave as a calculation tool, thanks!) is totally right: by painting black the efficiency of the cooler will almost double!

At about 60°C in average (depending on the geometry) 30% of the heat are emitted by heat radiation, the rest of 70% by convection. And the emission-factor for this goes up from less than 0.1 to above 0.9. Factor 1 would be the ideal black radiator.

Also the conducted heat transport increases, because a part of this transport also is radiation. Of cause the main transport effect is convection – energy given directly from “metal-atom to air- molecule”.

So, silver coolers are almost nonsense, all effective coolers are black. Black is beautiful !

Regards

Klaus

[Roberto Amato]

Originally posted by Klaus
what Alberto said (and gave as a calculation tool...

Who's "Alberto"???

[skaara]

Could anyone please tell me how many A/h are needed for 1cm2 that I will be able to calculate the time needed for my heatsinks?

[hifiZen]

105mAh/in^2 is close (900A/min/ft^2)... so that's roughly 16.3mAh/cm^2. If you follow the directions on that website, you should leave an additional margin... maybe 20%, and of course the time will vary with the acid temperature - the cooler the better too. I haven't tried this before, so I'm just going on what I've read, but it doesn't look very hard to do if you're careful.