Minor update to correct something I said earlier that was inaccurate...I don't know what I was smoking when I first tested out peltiers stacked (one pelt on top of the other).
A few recent tests I ran gave me a very nice improvement in coldside temperature with a two-pelt stack, basically a little better than increasing the voltage running through the standard non-stacked pelts by 1V, with the improvement starting to degrade around 4V. I suspect that this degradation was due in large part to the crappiness of the heatsink setup (coolant temperature rose by a little less than 2 degrees C for every 1V increase in voltage, which I didn't see with a non-stacked assembly). I suspect that if one were to make a nice custom waterblock and use a decent radiator/fan setup, the performance enhancement of using stacked peltiers in a chiller (at these low voltages) would be worth consideration.
As it stands with my setup, the power drawn by 24 pelts at 2V would not be that much better than 12 pelts at 3V, and the setup would not be able to handle an increased heatload as well. So stacking peltiers is out. Again, I'll note that if one were designing a chiller system from the ground up, stacking the peltiers would definately be worth looking at.
Anybody know of kryotherm-ish software that can calculate with peltiers in a stacked configuration? As it stands, I've gotta run two copies of kryotherm, and play balance-the-numbers until the coldside temp of the top set = ambient T of the bottom set, watts of bottom set + heatload = heatload of top set, etc. Rather tedious.
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