Forced cooling without fans

Description

This is well known, that hot air is less dense than cold air, which makes it float up. Hot air can even make people into air (think balloons). Yet, I don't think I've seen many solutions that use this for cooling.

On the photo is a little project of mine. I have had an LED, a heatsink and a power supply. After putting them together, I found myself in a situation that LED overheats. I didn't have other heatsink at hand, so, after a bit of thinking, I came up with this.

I cut a plastic bottle to serve a chimney. Warped it in toilet paper to keep the air in the chimney from cooling (this will improve chimney's suction). Problem solved.

No fans. No extra power needed to make it work. No noise. Awesome! It's been working for two summers already.

Details

According to some old data I posted back in july 2013, when I was installing it, the temperature of the LED test point is 110 degrees with no chimney, and 80 degrees after the chimney was added.

Right now, I did a similar test with thermal imager.

Without a chimney, within 30 minutes the temperature of heatsink reaches 121°C. With the chimney on, the temperature after 30 minutes is 94 °C. Still getting this near-30°C-drop, but substantially higher absolute values (it seems there was something wrong with thermocouple-soldering way I did it previously. Or is it just dust?)

The drop may not sound like being much, but it can make a hell of a difference for LED lifetime.

If you are wondering, wtf is on the right side of the photo. It is.. no.. it was a halogen lamp that I used before this LED light. Until it blew up like a bomb, throwing red-hot pieces of quartz all over the place. Guys, don't use halogen lamps without shields. No, really.

Components

1 × heatsink that is a bit too small

1 × plastic bottle

1 × some toilet paper

1 × some sticky tape to hold stuff together

Discussions

Yann Guidon / YGDES wrote 08/24/2015 at 22:34

Hi !

The passive cooling sytem is excellent :-) I've used it for a sophisticated project in 2012 and it was the only solution. It works great but the higher the chimney, the better efficiency. So I've used very long aluminium tubes (3m tall) and it saved the day !
The bottom however was another story, it took 10 prototypes to get right...
https://www.facebook.com/media/set/?set=a.257975450964048.59940.101308076630787

Are you sure? yes | no

DeepSOIC wrote 08/25/2015 at 09:57

Cool to know this is used already.

3 meters high... quite a lot! It's not always that you can put some 3 meters of

vertical pipe ;)

10 prototypes... that's a lot. I would have given up probably.

Are you sure? yes | no

Yann Guidon / YGDES wrote 08/25/2015 at 10:08

3m because the higher, the better ! peak power for the cooled part is 2Ax24V and that's a lot of heat...
And there was no possibility to give up.
The result is seen in the french airport Charles de Gaulle
https://www.facebook.com/media/set/?set=a.256170667811193.59421.101308076630787
If you get to see them, think about the tiny chimnies inside the main rod :-)

Are you sure? yes | no

DeepSOIC wrote 08/25/2015 at 10:31

Leds are cool =)

If I ever get to complete my LED spectrum analyzer project, I'm going to put that here, on hakaday. I have already made the LED part of the project, which is now hanging above my bench lighting it (with an arduino that merely sends all the drivers a command to light up full). The part I still haven't done is programming some FPGA to get it alive.

No chimney cooling there =)

Are you sure? yes | no

Yann Guidon / YGDES wrote 08/25/2015 at 10:34

Keep us informed ! :-)

Are you sure? yes | no

Eric Hertz wrote 03/28/2016 at 09:23

Funny in this era of energy-efficiency-everything, the solution to cooling a computer CPU is to add a fan (or cooling a building uses A/C?) yet this ancient technology would do it without adding any energy-usage. Had no idea height and insulation had such an impact on functionality. Makes sense. Learn something new every day!

Are you sure? yes | no

DeepSOIC wrote 03/28/2016 at 10:11

I guess the reason is - practicality. Attaching a chimney to CPU is not very easy, and it will probably have to stick up through the case quite significantly, making it very inconvenient. (I just imagined a chimney that goes from my PC up through the roof, and ends with a nice rain-stopping cap =).

As for air conditioning - how is it supposed to work? The air inside buildings is probably not much hotter or colder than outside... Otherwise, just opening windows should do the trick.

Are you sure? yes | no

Eric Hertz wrote 03/28/2016 at 10:57

I dunno, you're the genius that knows this stuff, it's news to me! But, was thinking more about these gigantic buildings that have windows that don't open... But, yeah, maybe not so logical.

I dig the imagery of a CPU-chimney sticking through the roof. Awesome!

Are you sure? yes | no

Forced cooling without fans

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