Chrome Heat Sinks

Hi!

The colour of a heatsink is more important the hotter it get, but in numbers in not sure about the difference. Compare a black car vs. a white in the sun! If you have convection cooling it's a minor importance but if radiation is the main cooling it's very important.

In your case I think it's no big deal of the colour of the heatsink.
 
Hi!

The chrome on the aluminium usually much more thick, and it is like a "cover" on it.

It is looking good, but the heat-dissipating efficiency will be less, for sure.

Please think, that you "cover" with a material your heatsinks. It is like you close it to some box.
I'm NOT recommend to do it, if the amps running with high wattage.
On higher heatsink temperature the chrome will be not nice after a time period.

BR,
 
Years ago Audio Amature (now AudioXpress) had an article on heatsink 101.

The relevent part: If your heatsink is not black anodized, and you cannot get it anodized, PAINT it black - the color makes a difference.

Mick Jagger sang it best: "I see a chrome heatsink and I want to paint it black."

(Sorry)

Aud_Mot
 
The surface is important when we talk radiation as I and the rest of us says but have also in mind that in case you didn't know: the heat conductivity is related to the electrical conductivity with one exception! Don't use stainless steel for example.

Today question is: What material conducts heat very well but is a bad electrical conductor, in fact an isolator? The answer is revealed thursday!
 
Black-Body Radiation

Why does a black heat sink radiate better?
A black object is merely absorbing all radiation in the optical spectrum, correct? While a white object is reflecting optical radiation. The reason a black car is hotter in the sunlight is because it is absorbing energy, and not reflecting it away like a white car will. This doesn't sound like a good trait of a heat sink. Some of you may be getting confused with black-body radiation, which has nothing to do with color. Black-body radiation is a misnomer which merely explains the radiation given off of an object as a result of its temperature, not its color!
It is true that a painted black heatsink will radiate, but a shiny metal heatsink will not only radiate but reflect, thus reducing it's overall temperature.

Check me on this one:
http://www.phys.virginia.edu/CLASSES/252/black_body_radiation.html
This was the first site that I found after an internet search.

Sorry to be preachy,
Dan
 
peranders said:
Today question is: What material conducts heat very well but is a bad electrical conductor, in fact an isolator? The answer is revealed thursday!

Have you ever thought about daimonds?

Yes, it's true. Daimonds are the BEST heat conductor. It's a typical crossword question but I haven't got it from a trustworthy source. Anyone who knows better?
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
No, a black body is the optimal radiating color.

The principle of reciprocity is at work here; the ability to
absorb photonic heat is the same as the ability to radiate.

The black heat sink will get hotter in the sun, but the chrome
heat sink will run hotter when transistors are mounted to it.

In any case, this is not the main mechanism for ordinary
amplifier heat sinks not running in a vacuum. If they were
underwater, it *really* wouldn't matter.
 
Nelson,
Sorry to be argumentative here, but this does not make sense to me. If a black car radiates heat just as much as it absorbs heat, then why is it hotter than a white car?

It seems to me that the car in the sun is an extreme case, though. One usually doesn't put his or her amp out in the sun. If one did, however, the black heatsink would definitely be hotter than a shiny one, much like the car example. But lets look at another extreme, two heatsinks, one black and one shiny, in complete darkness. What difference does the color make if there is no light to reflect off of the heatsinks. They would both have no color, except for their blackbody radiation (usually in the infrared). The equation for blackbody radiation is only dependent on temperature, and has nothing to do with paint. Hence, both heatsinks would give off the same amount of radiation.

So, what am I getting at?:

In bright light (sunlight) the black heatsink will be hotter.
In no light (darkness) both heatsinks would be the same temperature.

If you are right Nelson, then at some point in the middle (medium light) the black heatsink will have to radiate more heat than it absorbs, as opposed to the shiny one. What is the mechanism for this change? It does not seem clear to me.

I realize that radiative heat loss is not as productive as conductive heat loss and painting a heatsink black will not be too big of a problem. But, unless someone can explain it to me it seems to be worse (however slight) than a shiny heatsink.

I am shooting from my own intuition and a little bit of physics and I may be totally wrong. Can you spot an error or oversight in my logic?

-Dan
 
As usual, I'm on the run, so maybe I didn't catch the full drift, but Nelson is correct. Black both absorbs and radiates better.
Light and heat (i.e. infrared) are both part of the electromagnetic spectrum, they aren't separate things. Only the frequency changes.
Why is a black car hotter in the sun? Black absorbs more frequencies of light than white does; the albedo is lower. The light is absorbed and 'down-converted' into heat. White absorbs fewer frequencies (and less efficiently) and so receives less energy from the light. Bear in mind that cars aren't a good case, because you get greenhouse effects from all the glass, unpredictable ventillation depending on the surface area underneath (in the shade, that is), and so forth.
Anyway, put a black piece of metal in the sun and it will heat more quickly, but come dusk, it will also cool more quickly.

Grey
 
The black one is hotter, because it heats up more, but dissipates the same amount as the chrome car (ALMOST the same, just slightly more). Because almost all of the heat let off by the car isn't by radiation, but by convection. Radiation really doesn't account for much at all.

I'd think painting a heatsink black would hinder things, sure it would radiate more, but this doesn't account for much heat dissipation, but it would insulate the metal from the air, and well I doubt paint is a good heat conductor (maybe lead based paint? :))...