If you buy repurposed heatsinks with some being anodised and some not, it is a natural thought to paint them all black, both for aesthetic reasons and supposed radiation.
Is a non anodised heatsink better left silver or will painting it black help with radiation ?
Is a non anodised heatsink better left silver or will painting it black help with radiation ?
mm I guess not...
Dark is better for irradiate but anodized. I see special paints for use in engines or exhaust systems but they are for not rust or protect the pieces. Most equipment are silver.
Dark is better for irradiate but anodized. I see special paints for use in engines or exhaust systems but they are for not rust or protect the pieces. Most equipment are silver.
I would advise to not paint. Several years ago (many more than I'll admit 😀) I was wondering the same thing. I had four large natural aluminum heat sinks that I wanted to use for a small class A amp kit I bought. Because they were going to form the sides of the amp case and be visible, I decided to paint them black with some satin black spray paint from the local hardware store. Well, as it turns out, it's damned hard to get spray paint to go between the fins consistently and ended up with an ugly mess. I'm usually pretty good with spray paint, but this was impossible; trying to get the spray in between the fins inevitably ended up in runs and drips and swear words. 😱
Beyond that horror, ordinary spray paint will probably thermally insulate the heat sinks and counter-act any additional heat dissipation that results from painting the surface black.
Anodizing is really the best way to go here.
Mike
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Not to paint!
New colour by anodizing two pieces can be interesting.
In my town I get professional service who can anodize aluminium for me in the factory.
Other Diyers make anodize at home, but You need be confident to work
in security conditions with corrosive chemicals and electricity.
Need protective glasses and rubber gloves
Take care!
DIY multi color anodizing of aluminum with Tifoo anodising kit
How To Anodize Aluminum Best regards 🙂
New colour by anodizing two pieces can be interesting.
In my town I get professional service who can anodize aluminium for me in the factory.
Other Diyers make anodize at home, but You need be confident to work
in security conditions with corrosive chemicals and electricity.
Need protective glasses and rubber gloves
Take care!
DIY multi color anodizing of aluminum with Tifoo anodising kit
How To Anodize Aluminum Best regards 🙂
Have a look round for some local anodising companies and give them a ring. the last place I used I wanted 2 large aluminium (12" dia) brake disc bells hard anodizing and a set of 4 M22ish nuts and bolts blasting and plating with zinc and black. I think they charged me about £20 (cash) for the job, it really wasn't expensive and the quality was fine.
You may find someone local to do you a decent job for sensible money.
You may find someone local to do you a decent job for sensible money.
Heatsinks work more by convection than radiation so colour isn't such a large issue as surface area, orientation of fins and good air flow
even with the insulation qualities of paint a painted heat sink will still radiate more heat than the same sink in bare metal. Your most efficient option however is going to be an anodized heat sink.
Black is better any day of the week but paint layer must be thin and matte black, not shiny.
The big thermal resistance barrier is not through the paint layer itself but between solid surface and air.
The big thermal resistance barrier is not through the paint layer itself but between solid surface and air.
As a practicing professional materials engineer, let me weigh in.
From a purely thermal point of view, best option is to apply a thin coat of a matte black paint. Stay away from glossy finishes.
Heatsinks are overwhelmingly convective as far as heat transfer goes, so it won’t make a big difference, but a matte black paint will have a much higher emissivity than the “silver” aluminum for radiative transfer. A thin coat of paint will only create a negligible effect in terms of insulating against conductive heat transfer.
Cheers,
Terry
From a purely thermal point of view, best option is to apply a thin coat of a matte black paint. Stay away from glossy finishes.
Heatsinks are overwhelmingly convective as far as heat transfer goes, so it won’t make a big difference, but a matte black paint will have a much higher emissivity than the “silver” aluminum for radiative transfer. A thin coat of paint will only create a negligible effect in terms of insulating against conductive heat transfer.
Cheers,
Terry
Under natural convection conditions, the performance of a heatsink with a black surface will be 6% to 8% better than that with a plain or bright surface. However, this differential disappears under forced air conditions.
source:
http://robots.freehostia.com/Heatsinks/Heatsinks.html
or:
https://www.mouser.com/pdfDocs/Ohmite_Heatsink_Guide.pdf
Scott has right:
Heatsinks work more by convection than radiation so colour isn't such a large issue as surface area, orientation of fins and good air flow
source:
http://robots.freehostia.com/Heatsinks/Heatsinks.html
or:
https://www.mouser.com/pdfDocs/Ohmite_Heatsink_Guide.pdf
Scott has right:
Heatsinks work more by convection than radiation so colour isn't such a large issue as surface area, orientation of fins and good air flow
Black body emits into a vaccum about 5.76W @ 100K per meter square. Having heatsink @ 330K it will change to 690 W. Be aware that finning does not help. Assuming two sides of 4" high 19" unit to be a total heatsink projection area we'll get 0.1 m^2 thus 69W. Emissivity of an anodized aluminum is quite good.
Nonsense. Paint the heat sinks .. thinly tho.. with flat black paint.
Ideally with parts still as rough textured castings
Heat dissipates faster as result, researched, documented and proven.. decades ago.
This from a misspent youth fielding Yamaha TZ Racers for the Yama factory.
Lotsa testings by industrious Yama Engineers revealed that the thin black paint was best for purpose.
IE; keeping reciprocating parts running at ~11,000 rpms with a Heat critical 0.008 " running clearance ..from seizing solid.. at 180 mph.
Myopic beliefs aside, this was a serious issue, long ago dealt with.
As for the critical temps of a couple of $$ Output device.. Really ??
Ideally with parts still as rough textured castings
Heat dissipates faster as result, researched, documented and proven.. decades ago.
This from a misspent youth fielding Yamaha TZ Racers for the Yama factory.
Lotsa testings by industrious Yama Engineers revealed that the thin black paint was best for purpose.
IE; keeping reciprocating parts running at ~11,000 rpms with a Heat critical 0.008 " running clearance ..from seizing solid.. at 180 mph.
Myopic beliefs aside, this was a serious issue, long ago dealt with.
As for the critical temps of a couple of $$ Output device.. Really ??
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It's true, that paint is an insulator. Electrical insulator!
I've had success mounting parts straight to the painted surface. In other words, no mica, just grease. One mans "loss", another's gain.
Providing the aluminum was prepped smooth and the active device has no particular burrs or sharpies. So far just TO-247 parts.
I've gone so far as the contemplate taping off natural aluminum just for the area where the mosfets are going to be mounted!
I've had success mounting parts straight to the painted surface. In other words, no mica, just grease. One mans "loss", another's gain.
Providing the aluminum was prepped smooth and the active device has no particular burrs or sharpies. So far just TO-247 parts.
I've gone so far as the contemplate taping off natural aluminum just for the area where the mosfets are going to be mounted!
How to anodize without battery acid.
Acid vs non-acid process results look the same in photo.
Anodizing and dyeing aluminum without battery acid... - Observations
Acid vs non-acid process results look the same in photo.
Anodizing and dyeing aluminum without battery acid... - Observations
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