Well I'm probably going to be ordering some heatsinks that are not anodized. Now, having read some stuff, I've read that anodized heatsinks, because of their color (i think that's what i read) have better emmisivity (higher) and therefore have an improved rating.
Would the same be true for powder coating a heatsink? Like a black powder coat? Or would the powder coat actually trap the heat within the heatsink itself, since its an additional layer of 'paint' on the heatsink?
Would the same be true for powder coating a heatsink? Like a black powder coat? Or would the powder coat actually trap the heat within the heatsink itself, since its an additional layer of 'paint' on the heatsink?
Haha, there we go... 
From http://mitglied.lycos.de/Promitheus/heatsinks.htm
"If the surface temperature is kept low, for example by forced ventilation, radiation transfer is negligible because the heat is constantly being transported away. The anodized layer is more likely to have an adverse effect on transfer resistance because it has a thermal insulating effect. In cases forced ventilation is installed, especially when it has a string air flow, an untreated or chromated heatsink is most suitable."
/Hugo
From http://mitglied.lycos.de/Promitheus/heatsinks.htm
"If the surface temperature is kept low, for example by forced ventilation, radiation transfer is negligible because the heat is constantly being transported away. The anodized layer is more likely to have an adverse effect on transfer resistance because it has a thermal insulating effect. In cases forced ventilation is installed, especially when it has a string air flow, an untreated or chromated heatsink is most suitable."
/Hugo
Color does matter. Make it black, somehow.
The explaination I got was, "the same principle that makes a black object absorb heat is the same principle that allows it to give up heat."
I remember seeing (although I can not site where) that flat black paint is just as good as anodize.
The subject was covered in a thread called:
Chrome Heat Sinks
Do a diyaudio.com search
Good news: Painting can be done in your garage with common materials, anodize cannot.
The explaination I got was, "the same principle that makes a black object absorb heat is the same principle that allows it to give up heat."
I remember seeing (although I can not site where) that flat black paint is just as good as anodize.
The subject was covered in a thread called:
Chrome Heat Sinks
Do a diyaudio.com search
Good news: Painting can be done in your garage with common materials, anodize cannot.
well i found the chrome thread, and read it
it answers my question as far as whether to make it black or not - black is better, even mr. pass says so
but i'm still curious as to whether the paint used for powder coating will isolate the heatsink from air and hinder the heat exchange LOTS
btw, this is important, as the heatsink will most likely (if i get it) be used for an aleph .. and we all know they run hot enough for this to matter
it answers my question as far as whether to make it black or not - black is better, even mr. pass says so
but i'm still curious as to whether the paint used for powder coating will isolate the heatsink from air and hinder the heat exchange LOTS
btw, this is important, as the heatsink will most likely (if i get it) be used for an aleph .. and we all know they run hot enough for this to matter
good info you guys posted despite it allbut what kind of paint?
if i were going to paint a heatsink, i think i would look for furnace/oven/fireplace paint.
whatever you use should not be insulative and should enhance heat conduction (and thereby enhance radiation -> convection). by that criterion it seems any plastic-based paint would not be a Good Thing.
if i were going to paint a heatsink, i think i would look for furnace/oven/fireplace paint.
whatever you use should not be insulative and should enhance heat conduction (and thereby enhance radiation -> convection). by that criterion it seems any plastic-based paint would not be a Good Thing.
Me too don`t really know if paint has considerable negative effect on heat transfer capabilities but if I follow my gut feeling I`d say it does.
As I see it, any kind of paint is nothing else than a plastic coating - and You wouldn`t want to pack Your heatsinks in plastics (although when it`s very thin) - would You?
If at all painting, make the coat as thin as possible and I`d spare out the areas where the transistors are mounted.
AFAIK powder coating is nice stuff. Only with forced liquid (air/water/oil) cooling will you loose W/°C across the paint. For convection, where cooling from liquid (air) is low, radiation will make more difference, and as such increasing the emissivity will benifeit it.
Anodizing is very nice because saphire (aluminum oxide) is conductive, and the coating is also very thin (a few thou's).
Tim
Anodizing is very nice because saphire (aluminum oxide) is conductive, and the coating is also very thin (a few thou's).
Tim
yeah, anodizing is the preferred method, but its too expensive for me
as i said, i've someone locally that can do powder coating
the other option, although i don't know how i'd go about doing it, is oil based paint ..
looking over elliot's (sound.westhost.com) heatsink calculator, it says black oil paint (or something along the lines .. enamel?) is the best in emissivity ..
but PC would be the easiest for me
still looking for a close-to definitive answer whether the paint from PC traps the heat inside or not
and if it does trap the heat, whether the fact its black color makes up for the trapped heat?
i'd have no problem if the heatsink efficiency stayed the same, i'm not doing this to improve (the heatsinks are about 0.08-0.09 as it is) ..
as i said, i've someone locally that can do powder coating
the other option, although i don't know how i'd go about doing it, is oil based paint ..
looking over elliot's (sound.westhost.com) heatsink calculator, it says black oil paint (or something along the lines .. enamel?) is the best in emissivity ..
but PC would be the easiest for me
still looking for a close-to definitive answer whether the paint from PC traps the heat inside or not
and if it does trap the heat, whether the fact its black color makes up for the trapped heat?
i'd have no problem if the heatsink efficiency stayed the same, i'm not doing this to improve (the heatsinks are about 0.08-0.09 as it is) ..
Aud_Mot said:
Oh yes it can, and if its for a small heatsink, rather than a Pass monster, it is very simple to do
http://easyweb.easynet.co.uk/~chrish/t-anodis.htm
ummm, remind me why?
(now as a lead-in, I will have to say that most of my experience w/ powdercoat comes from auto applications)
most powder coats that I am aware of are in essence thermal insulators. why would you want to put a significant thermal barrier around your heatsink?
looks are one thing, but I don't thing powder coating is the right answer for this issue.
-bill
(now as a lead-in, I will have to say that most of my experience w/ powdercoat comes from auto applications)
most powder coats that I am aware of are in essence thermal insulators. why would you want to put a significant thermal barrier around your heatsink?
looks are one thing, but I don't thing powder coating is the right answer for this issue.
-bill
I have to just chip in my 2 cents here, but I have to back up what wrankin said, that the poweder coat or paint will act like an insulating blancket around the heatsink and push up it's thermal resistance a lot more than you could ever improve the dissipation via radiation by paiting it black.
So, if you do want to colour the heatsinks I would advise in getting them anodized as this will have a much smaller effect on than than any paint treatment would.
So, if you do want to colour the heatsinks I would advise in getting them anodized as this will have a much smaller effect on than than any paint treatment would.
Paint.
I would like to suggest that you use a mixture of 'blackboard paint' ( matt black finish) and shiny paint. I think enamel type paints are best thought they take a long time to dry. In addition you thin down the paint with a solvent to a point where it still holds to the aluminum reliably. Adding thick vicous paint will produce a thick layer and hinder heat transfer.
The mixed paint produces a semi matt finish which looks good even though it is still dull. I have brush painted many heat sinks but spray painting is more uniform and quicker. I use only one coat of paint.
Cheers.
I would like to suggest that you use a mixture of 'blackboard paint' ( matt black finish) and shiny paint. I think enamel type paints are best thought they take a long time to dry. In addition you thin down the paint with a solvent to a point where it still holds to the aluminum reliably. Adding thick vicous paint will produce a thick layer and hinder heat transfer.
The mixed paint produces a semi matt finish which looks good even though it is still dull. I have brush painted many heat sinks but spray painting is more uniform and quicker. I use only one coat of paint.
Cheers.
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