Maybe a silly heatsink idea...

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In reading this forum I've seen a lot of threads on heatsinks and heat dissipation. The only options I've seen for increasing dissipation are adding fans or water cooling. I also noticed some posts regarding the use of fans at a greatly reduced rpm just to increase the air flow without the noise. Water cooling has its own obvious problems.

Back in the original Macintosh days overheating was a problem since the Mac didn't have any fans and everything was in one case. The cheap and easy solution at the time was to basically stick a funnel over the vent holes at the top to increase the velocity of the heated air which in turn would increase the air flow inside the case.

Is there a reason an approach like this couldn't be used to increase the air flow over the fins of a heatsink too?
mrothacher said:
A few years ago, a guy from Cleveland made amplifier chassis that were shaped like miniature nuclear power plants. he claimed it was a much more efficient shape for cooling, probably for the same reasons cited by WindChill. If I can find a picture, I'll post it. You've gotta see these!
That sounds cool. ;)

Boron control rod attenuators. And since I live just outside Houston I think I can dump just about anything I want into the air around here as long as it doesn't come from a car. ;)
Creative Heatsinks

You guys have me thinking.....

I have some 2 in. or so aluminum tubing that would look great. A series of stacks.

The question is, can anyone offer some guidelines about fastening several heatsink members together with a chunk of aluminum bar? I'm sure that the contact area is important, and I take it that it works, but I'm uncertain how to estimate or evaluate the inefficiencies that would occur due to the thermal resistance that arises at the point where two things are bolted together.


Secondly, I know that heatsinks get less efficient the taller they get, since the differential temperature between the sink and the air passing by is reduced as the heated air passes the higher parts of the heatsink. I saw a tech note at one of the suppliers' websites that helps you evaluate this effect, but I don't remember where. Anybody know where that is, or can you give a formula or rule of thumb?
Im not sure I see the funnel increasing air flow. If it works like a venturi: the pressure drops, the velocity increases and there is heating through friction, a net loss in the enrgy that is causing the air to rise. I think chimneys are intended to get the stuff above structures and into the air currents and maybe to increase velocities so that the stuff is ejected well above the stack?
The only way I can see a venturi helping is if air current reaches a point of turbulence at the heat sink.
An interesting passive method of increasing diffusion in a convective system is to construct a countercurrent exchange arrangement where the cool air runs with the incresing heat gradient. This way the temp difference between the two mediums is on average maximized. You see this type of system throughout living sytems: for getting maximum gas exchange in the gills of fish and lungs of air breathers as well as maximum heat retention or loss in the blood vessels of appendiges.
I think an analogous situation would be be a vertical heat sink with transistors mounted at the top and convective heat flow rising or blowing from the bottom. this way the temp difference (diffusion potential) is on averge greatest.
hey all,
i've been checking out this thread and have two cents' worth to contribute. my aleph 5 uses the class A case designed by "lottus blossum" that uses alternating blocks and fins bolted together. for spacers between the fins, i used 1/2" channel aluminum oriented such that the "bottom" of the channel is towards one fin and the open side is towards another fin. this allows me to make it really tight, and results in a chimney effect. it feels almost like a fan is blowing when held above the amp. i didn't do any calc's but thought that the channel would increase surface area and aid in evacuating the hot air. however, maybe this is all hot air.
I've noticed skived heatsinks conduct heat better, at least in my computer heatsinks.

To make a skived heatsink a shaving blade is scraped across the top of a block of metal, raising a fin. The fins are slightly rough, which increases the surface area available for heat conduction.

Any hands for peltier cooling?
with peltier you would have to have even bigger sinks because there would be power dissipated by transistors + power dissipated by peltier (another 100 watts or more), the only thing that you would benefit is the longer life of the fets, because they would be running cooler.
When did everything go so horribly wrong? ;)

Actually that's all pretty funny. The underutilization of "brocolli technology" should be corrected immediately.

Anyway, seriously, all I was originally trying to do was offer a possible mechanism to get a little more air flow over the heatsinks passively. It wasn't intended to provide maximum efficiency or even a great improvement. Just a little more air...
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