If one peltier can get things really cold, two should get things colder. Right? Well...
NOTE: You can click on the images to get (slightly) bigger versions.
I used two peltiers for this experiment, a 40mm and a 30mm. Well, the theory went that
simply putting the second peltier on the cold surface of the first would not give max results
since the overhang of the larger peltier wouldn't have much work to do. So, I grabbed an
aluminum block, 1 inch thick, and put it between the two peltiers. The larger pelter is
attached to the liquid cooler and the other to the bottom of the block. You can't see the
large peltier in the picture but everything else is pretty clear.
Since I was going for the gold, in temperature, I needed to eliminate the introduction of
heat from the environment. The best I could come up with was the foam you can see in the
picture. I've had good luck with it before so I wrapped the unit as best as I could. Since
I was running with ice water for some of the experiment I should have put foam on the top of
the liquid cooler and around the tubes but...
You can see from this graph that the heat produced + the heat pumped by the small peltier is more than the large peltier could handle. The liquid cooler seems to be able to take anything I throw at it! I ran the system without the small peltier on for most of the experiment. You can see where I turned it on for short periods of time. Check out these stats for single peltier operation.