Paddywhacker - 14-3-2009 at 21:11
Has anybody made an ice bath cooled by Peltier devices, or seen plans for such a project?
I am wondering how low a temperature you could be expected to produce, and whether it would be worthwhile building such a thing.
kclo4 - 14-3-2009 at 21:59
I know they are only 5-10% efficient and can produce ice. What is the lowest temperature reference you can find for them?
Mr. Wizard - 14-3-2009 at 22:19
I posted something about them at this :
http://www.sciencemadness.org/talk/viewthread.php?tid=10192&...
I have a picture and a link there. I still haven't tried it out yet.
indigofuzzy - 15-3-2009 at 00:15
You're going to need one heck of a heat sing on the hot side of the thermocouples. I'd recommend forced water cooling.
Paddywhacker - 15-3-2009 at 12:57
Yeah, I figured to use a heatsink and fan from an old computer CPU.
Water cooling would indeed be better, but more fiddly to implement.... maybe two baths mounted together with the Peltier sandwiched between.
NeutralIon - 15-3-2009 at 13:34
Typically a Peltier junction can achieve a Delta-T of 40 to 50°C under no-load conditions. By that I mean the thing being cooled is not releasing
energy (heat) and there are no sneak path for heat to flow to the coolee. Need very good insulation (vacuum would be nice).
The heat sink on the hot side of the junction must be able to hold its temperature while dissipating the power from the Peltier. And make sure that
heat does not flow back to the coolee.
So if you use a large block of ice for the heatsink you might get to -40°.
not_important - 15-3-2009 at 23:57
A cpu heatsink & fan is way to little if you're trying to cool much sample at all.
Contrabasso - 17-3-2009 at 11:57
Peltier devices do work! BUT need to be within close limits as they actually have little thermal power -heat moving capacity.
With the cost of devices and the PSU you may be better off finding a beer cooler, setting the thermostat to it's lowest setting and recirculating
either brine or auto antifreeze. You should be able to move liquid at -10 with a beer cooler, you will never get -10 with a single peltier chip.
Peltier chips can be stacked to get bigger temp diferentials or heat flow. BUT all at great cost!