Using thermoelectric coolers

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I see you guys trying to come up with weird ways to cool these chips (like oil encased chips :rolleyes: ). And I was cruising around at Fry's the other day and saw these things. Thermoelectric coolers, act like a refrigerator getting cold on one side and hot on the other.

An externally hosted image should be here but it was not working when we last tested it.


{From All-Electronics web site}

1.18" (30 mm) square X 0.15". These incredible miniature solid state heat pumps raise or lower temperature in a small area almost instantly. Utilizing the Peltier effect these modules perform the same cooling or heating functions as freon based refrigerators but they do it with no moving parts, and are very reliable. Current applied to the device will produce heat on one side and cold on the other side, up to 68 C difference between the two sides. Modules can be mounted in parallel to increase the heat transfer effect or can be stacked to achieve high differential temperatures. Operate on 3-12 Vdc. Requires a heat sink to prevent overheating.


$17.00 each

Looking at the package at Fry's it looked like they required some current though, as they said Imax was like 2 or 3 amps.

Also another thing that may be of interest for water cooling. Fuel rails seem to look like good canidates for this stuff.

Here you can see how the fuel would travel through rail. Now you could seal the holes on an OEM one like this...or fashion it some way so that chip sits over the injector hole and make direct contact with the water (insulated chips here :att'n: ). If your gonna look at OEM...look at the inline 4 cylinders...they usually have this kind of fuel rail setup...Honda Civics from the 90's have a real good shape, with plenty of flat mounting area.

An externally hosted image should be here but it was not working when we last tested it.


You can also buy Fuel rail as unmachine stock that is just the basic shape plus the internal passage. No injector holes. Which you can then mount the chip on the flat top part.

An externally hosted image should be here but it was not working when we last tested it.


You can usually buy this stuff for like $10-$20 a foot from performance shops...hot rod/dragster shops more specifiecally. Then you can let the water do its convection magic.
 
Right, a Peltier cooler makes one side slightly cooler, but it makes the other side a lot hotter. All it does is increase your cooling headache. The only use for them is if you simply cannot move heat out of the transistor fast enough, but for some reason you are able to cool the peltier sufficiently.
 
Peltiers are really only useful if you want to get an IC below room temp.... and when you do, you need to start thinking about condensation problems.

Ive used these a lot before on cooling CPUs... i cant see how they could be applied to cooling amp ICs... ??

Although, it would be interesting to see if a cold amp IC sounds better.
 
Peltiers seem to be something of a black art and are not as simple to implement as people may think - "just whack a peltier on it and it'll stay cool", being the common misconseption.

Thermo-electric "heat pumps" are exactly that, they move heat from one side of the device to the other, but are not 100% efficient (as nothing can be) so create some heat themselves and this has to be accounted for when heatsinking the devices.

Typically the devices are used to cool computer chips in specialist applications, but have filtered down to the mainstream markets (albeit the computer modding market) and full peltier kits can be found that almost always are used in conjunction with forced water cooling.

The peltier is used as an interface between the chip and the water block which has water forced (by pump) through a closed system including a radiator and fan.

Try your local specialist computer shop for more on peltiers and water cooling and also check out the overclocking sites on the web.

Also you might want to look at phase change cooling (although it's really practical for audio) - literally using a fridge compressor to cool things down!

One guy even used liquid nitrogen to cool his PC! - check out "Mission Submersible" on Over Clocking Tools .

I hope this all helps?
 
annex666 said:
Thermo-electric "heat pumps" are exactly that, they move heat from one side of the device to the other, but are not 100% efficient (as nothing can be) so create some heat themselves and this has to be accounted for when heatsinking the devices.

Infact most are around 50% efficient.
If you have a 20W peltier, it means you need 20W of power to run it. Itll move 1/2 of that amount of heat, so 10W.
So... your pulling 10W of heat from the amp IC, then you have 20W on top of that of the heat the peltier makes itself making 30W you then need to remove from the hot side of the peltier.
It can be done with heatsinks... but water cooling is best to remove the heat quickly.
 
I have tried peltier junctions on some apps (not GC) and i have not really been satisfied,with the added heat generated by the peltier it made very large heat sinks necessary.It was also required to have its own seperate P/S as the current draw was not really linear.
A peltier can however lower the temp on the cool side up to 40 deg F lower than ambient.
ron
 
here's a thought: if you were willing to waste 20W on a peltier, you might as well instead use 12 80mm fans. the combined CFM of which would be something ridiculous like 500CFM and still 12 fans would consume WAY less then 20W!!! (well not really, about 14.4W but still)

blasting 500CFM of air over any heatsink should be sufficient cooling

goodo
iR
 
I still believe that the most efficent form of cooling a chip is convection.The chip with thermal grease bolted with nylon screws to a small plate of copper which in turn is solderd to several copper pipes setting vertically and have adequate air flow would provide more than adequate cooling.
ron
 
I still believe that the most efficent form of cooling a chip is convection.The chip with thermal grease bolted with nylon screws to a small plate of copper which in turn is solderd to several copper pipes setting vertically and have adequate air flow would provide more than adequate cooling.

Ron, this is just a theory but I wonder if the Helmholtz resonance effect would apply here with the copper pipes?

Sad I haven't got anything better to think about really! :confused:
 
Ok , quick pass at the calculator, a open tube is not a classic helmholtz resonator, it would resonate at around .5 x L(length of the pipe) wavelength and at odd harmonics of that wavelength to a lesser degree. However if the tube is IN the case and just open at the top and the bottom and the case is built with the inside dim. to the golden ratio (eliminate standing waves) and dampened with something like my old standby "silicone", there would be little if any resonance.I think it worth a try and i am going to incorporate it in my next cab design.Then i can build in the trick motrized pots also.
ron
 
Sorry guys , my mind is working (can ya hear the gears clash and smell the smoke?).OK on the tubes if total resonance is to be spread over a wide BW then use something in the order of a Karlson slot?Just take a dremel and cut a slot on each tube on the side opp the chip 2/3 L of the tube.A thin slot will not affect the heat wave transfer to any great degree.
ron
 
Ron, at least we are still thinking! ;)

I agree about putting heatsinks into the case for best results. A case with a hole in the top and bottom will make a nice convector and surrounding the heatsink with the case will, as you point out, protect it from a lot of airborne vibration.

I was reading about the Karlson speakers last week and if I ever see some decent sized tubes lying around will give them a try!
 
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