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Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462
Posted: 11:17pm 11 Jun 2012
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I have question about Thermoelectric Cooler
Found one on E-Bay
(Not sure if I should include page address as after so many days link will not work anyway)
My questions are:
1. Is it OK just to touch it to metal surface or thermal paste is a must
(suspect paste is essential)
2. Where would be the best place to get paste, and is it OK to buy some more or it ages quickly and I should have enough paste just for this job?)
3. Can I just connect it to 12V battery, or some other components are necessary to limit current?
Edited by Georgen 2012-06-13George
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 04:07am 12 Jun 2012
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1. Yes, I used the white paste that's sold for semiconductor heatsinks.
2. Any place that sells semiconductors usually has the paste
3. Yes, but its a better idea to use some thermostatic control.
These devices have a limit of the temperature difference between the cool & hot side.
I take it you know how to use these Peltier devices? One side gets hot as the other gets cool, so you need a BIG heatsink to carry that heat away. Use the biggest one you can lay your hands on. Also, the cool side is best located inside a well insulated box with the heatsink (plus fan) on the outside.
Be *very* careful with the attached leads, their bonding to the Peltier junction is not very strong mechanically. I actually managed to break a lead off (quite easy ) and carefully soldered it back but that process shorted a few junctions out.Klaus
Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462
Posted: 07:34pm 12 Jun 2012
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Thank you for info.
Looks that thermostat might be necessary
Will have to read bit more about > Peltier devices < as so far I did not find exact information on what is the maximum and minimum temperature device can safely produce.
I found so far, is to have heat sink to remove heat as device will cook itself.
No problem here, but what if you want to boil something?
From what I can see it is rather to warm up something, with preferred application as cooler.
George
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 04:29am 13 Jun 2012
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Its not a question of max or min temperature but rather of the max temperature *difference* between the hot & cold sides.
From dim memory recesses a figure of 40 deg C comes to mind, read up more about that.
What that means in practice is: if you built a cooler box and use it on a hot summer day, assuming the box is perfectly insulated, you're struggling to get the beer inside the box nice and cool .
With regards to boiling things, instead of removing heat from the hot side you have to keep the other plate surface cold - might be tricky - when you consider the max temperature difference and the max overall operating temperature of the Peltier junctions.
FYI, I used the device on a scientific research project where the aim was to condense moisture out of warm exhaled air passing through a hose. Chilling a small alu block with the air passing through it and a water drain worked perfectly .
It may also be useful to spot cool some semiconductor chip if power wasting is no problem. Its pretty useless (read inefficient) as a food cooler or warmer. Klaus
Georgen Guru Joined: 13/09/2011 Location: AustraliaPosts: 462
Posted: 02:06pm 13 Jun 2012
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If the difference of 40 degrees has to be maintained, then anything more than keeping something warm is out of question.
As you say, device was developed for spot cooling purpose.
But if Sun energy is for free, we can do all sorts of inefficient things without hefty energy price.
George
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:11pm 13 Jun 2012
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If you want to boil something, use a resistive heating element, it will be far more efficient.
Why ?
Because with a Peltier cell you will lose a lot of heat to the cold side through the actual Peltier cell itself.
A simple resistive water heater will be cheaper, a lot more efficient, and much more reliable.
For cooling, the heatsink needs to be kept cold.
For best results use water cooling with a high flow rate. A massive heat sink and powerful fan can be almost as good.
If your heat sink feels even slightly warm to the touch, the cooling capacity will be a big disappointment.
What you are cooling needs to be very well insulated.
The developed cooling power is really quite small for the watts you need to pour into it.
So don't expect very low temperatures.
The lowest temperature I have ever measured with really radical insulation and heat sinking was around -20C
And it took a very long time to struggle down to that temperature.
That 40C differential cooling figure previously mentioned sounds about right.
That would be when the heat leakage back through the Peltier cell equals the heat pumping capacity.
And it is as low as you can go with zero additional heat load.
Notice. New forum software under development. It's going to miss a few functions and look a bit ugly for a while, but I'm working on it full time now as the old forum was too unstable. Couple days, all good. If you notice any issues, please contact me.
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) and carefully soldered it back but that process shorted a few junctions out.
.
.