# Peltier Design

## Main Question or Discussion Point

I'm planning to work on a water cooling device for physiotherapy using a peltier.

For this, I should be able to cool 500 g of water at a temperature of 35°C to 18° C.

This gives me a heat load of 315 Watts if I take time to be 3 mins.

Is it possible for a peltier to work against such a heat load? Where can I get graphs of heat load and DTmax, Vmax, Imax?

Thanks!

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berkeman
Mentor
I'm planning to work on a water cooling device for physiotherapy using a peltier.

For this, I should be able to cool 500 g of water at a temperature of 35°C to 18° C.

This gives me a heat load of 315 Watts if I take time to be 3 mins.

Is it possible for a peltier to work against such a heat load? Where can I get graphs of heat load and DTmax, Vmax, Imax?

Thanks!
I haven't used them before, but a quick Google search seems to show units like what you want. Here is a commercial link from the top of the search:

It claims to be a 400W unit that is 5cm X 5cm. Wow, I didn't know they could be that powerful in such a small package! (maybe I'm misinterpreting the specs, though)

http://images.villageorigin.com/001540-017/001.jpg?s=600 [Broken]

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I think you will need a real datasheet to really figure out your answer. The 400W is the applied power to the Peltier. This is not to say it can transfer 400W of Heat - these tend to be relatively inefficient so much of the 400W will actually be given off as excess (waste) heat.

OmCheeto
Gold Member
I think you will need a real datasheet to really figure out your answer. The 400W is the applied power to the Peltier. This is not to say it can transfer 400W of Heat - these tend to be relatively inefficient so much of the 400W will actually be given off as excess (waste) heat.
Drats! I didn't include the mass of the heat sinks from my experiments.....

I did the exact same experiment a few weeks ago when I purchased the exact same device. Ouch!
I just did a slightly more controlled experiment with some heat sinks and insulation.
After applying ~60 joules over 10 seconds to the device, I measured the following values:

Tcold dropped 2 °C
Thot jumped 14 °C

The temperatures then of course over time equalized

But it is obvious that a massive heat sink is required on the Thot side to make the device operate as advertised.

Peltier devices should not be operated naked, as they will quickly exceed their rated temperatures ( 138 °C for the TEC1-12706 ).
Data down the drain. :grumpy:

And looking at this post now, it appears I was a bit sloppy. I think it should have read; "After applying ~60 joules/second for 10 seconds to the device", as it was a 60 watt device.

hmmm....

Assuming the hot and cold thermal sink masses were identical and in 1 ounce increments and made of 99.999% silver, how many silver coins were used in the above experiment, assuming Temp0 was 20°C?
Ignore the heat capacity of the peltier device.

Heat capacity of silver: 0.240 Joule/gram°C
28.35 grams/ounce

I would do the math, but I've a friend in from Florida and am scheduled to meet her in [STRIKE]an hour[/STRIKE] 25 minutes.

ps. It's possible that the original experiment had only one silver coin on the cold side of the device and several silver coins on the hot side. So don't shoot me if this doesn't work out.

pps. I was going to do this experiment at the river last year as rivers are great heat sinks and threw my peltier device in my tool bag, ended up not doing the experiment, only to forget the little bugger was in there until 8 months later when I cleaned out my tool bag and found it totally smashed to pieces.

What precautions should I take when I use a peltier?

Last thing I'd like to see is the entire system blowing up.