Sprayed Heatsinks

matt09

Member
2006-08-06 1:38 pm
I have some black anodized heatsinks which have got a bit scuffed.
The simplest remedy seems to be to spray them with matt black paint.
(I don't have facilities or time to re-anodize them myself)

Can people confirm if spraying an entire heat sink with spray paint will only make negligible difference, or will it make more difference than expected and something to be avoided?

It's standard matt spray paint but I was wondering if even a thin layer over the ENTIRE area would have a bigger effect than expected since it is an insulating layer. The alternative is to just colour over the scuffed bit with black marker pen but the black wont quite match.

Thanks
 
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Ian Finch

Member
Paid Member
2010-04-11 4:22 am
Coffs Harbour, NSW
For completeness, you need to be specific about the type of paint used. Most paint, particularly water-based paints, are quite thick because they're for brush or roller application and form a significant insulating layer when dry.

Solvent based spray paints applied in a fine mist just sufficient to evenly colour the surface, can be very thin - almost as thin as marker pen ink which would be closer to ideal and make little difference to the cooling rate if it didn't rub off so easily. Matting agents in the paint tend to thicken and weaken the layer so a satin finish may be a good compromise.

If you know someone who builds models, has an airbrush etc, this is the ideal tool and permits a wide range of paints to be thinned and used without the need to buy overpriced cans of automotive touch-up spray or other standard DIY paints that may only form a weak paint layer. The cans also just hang around, rusting away when you've finished with your project.
 
Proven! decades ago that a thin spray of Flat black paint on ali finned castings improved cooling on Aircooled Race engines by ~10/15% over unpainted ones.
These engines being valued at Many Multiple times times that of some Dorky electronic bits.
Just saying :)
Note that Watercooling increased Heat removal/dispersion.. raised Power outputs by another 15% over aircooled types though ;)
Which is Why few aircoolers exist these days.. outside of Yardening equipment and Mopeds
.
 
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infinia

Member
2005-05-15 9:51 am
SoCal
Proven! decades ago that a thin spray of Flat black paint on ali finned castings improved cooling on Aircooled Race engines by ~10/15% over unpainted ones.
These engines being valued at Many Multiple times times that of some Dorky electronic bits.
Just saying :)

yeah but the air cooled cylinder castings run waaay hotter than SS heatsinks so you cant throw those eff. gains numbers around. I think all this emissivity data comes because of the space program not some dorky grease monkeys. I'm sure the cheapest satellite cost more to put into orbit than any race car.
 
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wwenze

Member
2008-03-07 12:46 pm
You're not going to spray the entire heatsink with paint anyway right? How are you able to reach in between the fins? At least anodizing can reach between the fins.

If it is just one fin out of 50 that will be modified, it won't matter regardless of how much science is discussed.
 
the outside edges are probably the areas needing a black touch up.
Try spraying so that these EDGES get a black coat. The faces of the fins will hopefully receive almost no paint coating and thus retain their existing emissivity.

But definately use only VERY thin paint coating.

I saw a figure for relative emissivity vs conduction heat transfer for solid state style passive heatsinks. It stated only 8% was due to emissivity. If you lost half of that 8% due to a too thick coating over all of the fins, you still have 96% of the original.