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To paint or not to paint - Heatsink Question
To paint or not to paint - Heatsink Question
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Old 9th October 2018, 01:38 PM   #11
Soundhappy is offline Soundhappy  France
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ShopBuilt - How to Anodize Aluminum!

Quality work
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Old 9th October 2018, 02:07 PM   #12
oreo382 is offline oreo382  Canada
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Paint is better,just don't paint the area where the transistor/mosfet is mounted.
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Old 9th October 2018, 02:20 PM   #13
metalman is offline metalman  Canada
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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.

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Terry
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Old 9th October 2018, 02:21 PM   #14
rookakoma is offline rookakoma  Hungary
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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/Ohmit...sink_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
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Old 9th October 2018, 02:58 PM   #15
alexberg is offline alexberg
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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.
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Old 9th October 2018, 08:42 PM   #16
Bare is offline Bare  Canada
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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 ??

Last edited by Bare; 9th October 2018 at 08:49 PM.
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Old 9th October 2018, 08:49 PM   #17
Btsd is offline Btsd  Australia
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I go with what look I want.
Bottom one (aleph J) black heatsinks with polished edges.
Second up (aleph mini) fully sandblasted heatsinks with polish edges.
Everything else I have built in the Aleph set is fully sandblasted.
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Old 9th October 2018, 09:28 PM   #18
res07njc is offline res07njc  United States
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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!
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Old 10th October 2018, 01:00 AM   #19
vdi_nenna is offline vdi_nenna  United States
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To paint or not to paint - Heatsink Question Send a message via Yahoo to vdi_nenna
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
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Old 10th October 2018, 10:12 AM   #20
KatieandDad is offline KatieandDad  United Kingdom
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Thank you guys. The heatsinks are already painted in matt black. I'll leave them alone.
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