Originally Posted by Mootsfox
Burn, if you need a really dry room, you can also turn up the AC and wait until it starts putting out extremely dry 60F air.
TECs can stand a lot of heat, especially if they are not connected to anything. You can just run a hair dryer or heat shrink gun on it until it is good and toasty, which will drive out any moisture. Let it cool down a bit before sealing it though, don't want to cook your sealant.
Some rough guidelines on performance and efficiency for TECs. First, the cooling power is related to the TEC current and the Th, nothing else. The voltage is just to achieve a current. Because TECs are semiconductors and develop a reverse EMF in addition to the purely resistive component, the current you get for a given voltage depends on a lot of things - the hot side temp and Qc affect it the most.
The highest CoP for dT under 20C is achieved at around 25% of Imax. But Qc drops a lot, so you need more and bigger TECs to get the same cooling power. You also can't develop much dT.
At 25% Imax, you can get a CoP over 2.5 at 10C dT - so for example, at 10W in you move 25W. But Qc is only 30% of Qcmax for the 10C dT curve.
At 20C dT drops CoP to 1.4, and Qc is only 25% of Qcmax. That's probably past the point of diminishing returns for most uses.
Going up just a bit to 35% of Imax gives what I think is the sweet spot - decent efficiency with reasonable cooling power. At 35% Imax, you still get a CoP of 2.0 at 10C dT, and Qc is up to 45% of Qcmax.
20C dT drops CoP to 1.2, and Qc is 40% of Qcmax. That's more reasonable.
Even at 30C dT, you get .7 CoP, and Qc is 30% of the 30C dT curve Qc max. So you can get some decent cooling without the big heat load.
Going to any current much above 50% Imax gives pretty rotten efficiency. At 75% of Imax, even the 10C dT curve is below .8 CoP, and the 30C curve is below .5. You put in twice as much power as the heat moved. Going all the way to Imax puts the 10C curve below .5 and the 30C curve below .3 - that's pretty ugly territory.
What that says is you want the biggest TEC you can get that will physically fit in your application, and undervolt it to get to the cooling you need. That reduces waste heat and cuts your electric bill.Edited by Uncle Jimbo - 5/25/08 at 12:02am