Heatsinks by the foot, cheap FYI

[Windcrest77]

Heatsinks bought by the foot very reasonable prices. Put a TCG profile blade in your miter saw to cut them to your desired final length.

Heatsinks | Speciality Shapes | Orange Aluminum

 

[Mark Tillotson]

Orange county, not orange metal, note!


Actually not being anodized means they won't radiate heat, just conduct it into the air, so not the most efficient(*) - which is why they are cheaper. But painting will fix the emissivity cheaply.


(*) with a fan that's not an issue, but fans make noise...

 

[garrbage]

Actually not being anodized means they won't radiate heat, just conduct it into the air, so not the most efficient(*) - which is why they are cheaper. But painting will fix the emissivity cheaply

Anodizing as a process have nothing to do with ability to radiate heat. Anodizing and black is a different story . I encourage you to calculate how much energy dissipates of aluminium heatsink through radiation and throughnatural convection at normal conditions with T+30K (50C OK to touch but uncomfortable to hold longer than a minute or two). It is negligible. At higher (much higher) temperatures plates are turned
Painting heatsinks..... unless one is using anodizing dyes or extremely thin layer of paint it makes dissipation by convection more difficult hence rendering heatsink less efficient. So, paint very thin or don't pain at all

 

[Mark Tillotson]

Anodizing as a process have nothing to do with ability to radiate heat.

Wrong, bare aluminium has very low emissivity and anodized has very high emissivity at far-IR (I have a heat camera, I know this), since the oxide layer is opaque in far-IR (most substances are in fact).

Anodizing and black is a different story

Actually they do the same job of changing the metal's emissivity from about 0.0 to about 1.0 - basically all anodizing looks black to predator vision!

I encourage you to calculate how much energy dissipates of aluminium heatsink through radiation and throughnatural convection at normal conditions with T+30K (50C OK to touch but uncomfortable to hold longer than a minute or two). It is negligible.

30C difference indoors will be about 200W/m^2, which is small, but not negligible, it all helps. Its more important when using an enclosure as the heatsink, as fins make a big difference to convection but not to radiation.

At higher (much higher) temperatures plates are turned
Painting heatsinks..... unless one is using anodizing dyes or extremely thin layer of paint it makes dissipation by convection more difficult hence rendering heatsink less efficient. So, paint very thin or don't pain at all

Definitely, spray paints are very thin - powder-coating would be a mistake!

 

[Windcrest77]

So a chunk of of this aluminum material can be made an even better heatsink by anodizing it at home? I intuitively would not have guessed that! Intuition tells you you are adding an insulating layer, who'd have thought not!

Battery acid and lye (100% sodium hydroxide) are available just about anywhere and very cheap. Sulfuric acid from the auto parts store is 37% acid, and 100% lye is available as drain cleaner from any store. Anodizing seems like a pretty simple process at home if you're careful. Hot plate, a pot, oven thermometer, distilled water, water, buckets, anode lead, some lead roof flashing, a car battery charger with a 2A limiter setting and the aforementioned chemicals used in their recommended dilutions. And optionally some clothing dye.

Out of all the videos I've watched to anodize, I like this guys the best, very straightforward and clear. He uses two lead plate anodes to spread out the electrolysis processing.

YouTube

 

[garrbage]

Wrong, bare aluminium has very low emissivity and anodized has very high emissivity at far-IR (I have a heat camera, I know this), since the oxide layer is opaque in far-IR (most substances are in fact)

Thanks for sharing.
Do you have explanation why after anodizing existing (definitely not anodized) heatsink, resulting temperature indistinguishable from before? As far as I recall a bit below 50C measuring accuracy as usual +/- 0.1C, experiment accuracy 1.0%-1.5% was working at huge power plant automation lab at the moment have some free time to spare on various experiments .
Also I see it all over industrial designs, large and small not anodized aluminium heatsinks, old CRT monitors, motor drivers, invertors, all over the place.

So a chunk of of this aluminum material can be made an even better heatsink by anodizing it at home?

Not really, but prettier definitely unless you running something way past 150 centigrade
Anodizing.... did he mentioned that you need to keep the solution cold? Preferably about 10-12 degrees centigrade to get thicker and stronger film

 

[PRR]

> explanation why after anodizing existing (definitely not anodized) heatsink, resulting temperature indistinguishable from before?

Despite what the "Paint It Black" fans tell you, for items at near-touchable temperatures in fairly-free air, air convection far exceeds radiation.

Radiation goes as third(?) power of temperature. Up or down. Up around red hot radiation tends to dominate; but falls off very quickly at cooler temperatures.

Same applies to building heating "radiators". Steam, hot air, or fins you can touch. Painting them black or aluminum makes imperturbable difference. Thin pain or thick paint makes almost no difference, because any paint conducts heat far better than convective air.

As you say, up past 150 deg C radiation may show. But we don't run Silicon hot enough to be 150 on the fins, and we don't heat our homes with >150C "radiators" (convectors) because it would burn the baby. (Electric fins inside housings may run >100C, but the housing catches the small radiation and turns it to convection.)

 

[garrbage]

> explanation why after anodizing existing (definitely not anodized) heatsink, resulting temperature indistinguishable from before?

Despite what the "Paint It Black" fans tell you, for items at near-touchable temperatures in fairly-free air, air convection far exceeds radiation.

Radiation goes as third(?) power of temperature. Up or down. Up around red hot radiation tends to dominate; but falls off very quickly at cooler temperatures.

Same applies to building heating "radiators". Steam, hot air, or fins you can touch. Painting them black or aluminum makes imperturbable difference. Thin pain or thick paint makes almost no difference, because any paint conducts heat far better than convective air.

As you say, up past 150 deg C radiation may show. But we don't run Silicon hot enough to be 150 on the fins, and we don't heat our homes with >150C "radiators" (convectors) because it would burn the baby. (Electric fins inside housings may run >100C, but the housing catches the small radiation and turns it to convection.)

Thank you, that is exactly what science tells us and facts support.
Despite what the "Anodize It" fans tell you