Multiple peltier setup?

[SpaceRangerJoe]

ok, so i understand how a peltier works. one side gets real cold, the other side real hot, yada yada yada. but what i never understood, was why you would put one peltier on top of another. ok, so you cool one peltier with another. but you still have the same amount of heat to remove from the second peltier by water cooling, or whatever means you use. it just doesnt make sense to me. im obviously missing something, cause this apparently works. i read some guy oc'ed to 2.8 gigs or something outrageous using 4 pelts. can someone explain this to me?

[Bender]

A single peltier can create a 70 degree temp difference from ambient. If you stack peltier on top of peltier you can have more than a 70 degree difference. If the peltiers are side by side you won't get any greater temp difference but they will be able to handle more of a load.

[docJ]

I have worked with TECs for many years, a few years back I made a multistaged system that went down to -80 C, but it would only pump a few watts at that delta T.

[Wonko The Sane]

he was probably not stacking them. in a 2 pelt system, for example, the pelt on the cpu needs to deal with the heat from the cpu, but the pelt above it needs to deal with the heat from the cpu plus the heat of the other pelt.

[trey_w]

if you stack pelts, and and as you go you get smaller and smaller, jsut enough to cool the other pelt but create less heat as you go up

at the end(top) you would have a very small pelt, producing little heat

is this how stacking would work?

[docJ]

Yep, thats pretty close to how it works. Each new stage must be able to pump the heat from the stage before it, which is the heat pumped + the heat generated by that stage. Not always the best way to do it, but can be made very small or for special app's.

[Wonko The Sane]

no, the pelts would have to get bigger going up (away from cpu). for example if your cpu puts off 50W, and you put a 100 watt pelt on it, you would need a pelt of at least 150w on top of the 100w one (cpu+first pelt).

[docJ]

I guess I didnt say it clearly. We said the same thing just different ways. Stage 2 must be able to pump all the heat from stage 1, which is the heat pumped by 1 + the heat generated by 1 (stage 1 is on what you are cooling). Yes you can use a higher power TEC on the next stage, but it is also possiable to change the voltage to each to work in a different spot on the pumping curve and match things that way. A bit harder but doable.