On 10/14/14, 6:13 AM, Chuck Harris wrote:
Uhmm? How does that differ from any heat pump, such as say, a freon
cycle refrigerator?
The COP for thermoelectric coolers (heat moved vs power consumed),
particularly at large delta T, is fairly poor, compared to heat pumps.
A heat pump might take 1 watt to move 5 watts, while a TEC might take 5
watts to move 1 watt.
The biggest problem with Peltier coolers is they have a very low
thermal resistance shunt (all of the thermocouple junctions) between
the hot side and the cool side. If you turn them off, the hot and
cool side will equilibrate almost instantly.
TECs are great for rapid adjustments of small delta T.
Not very efficient!
You can, however, make large stacks of Peltier coolers, hot to cool,
and cool them down to liquid air temperatures. This is done on
very low noise LNA's.
I've seen stacks of 5 TECs that look like a ziggurat for this kind of
purpose.
There's a problem with trading off the "incremental power" as you go
warmer (e.g. the tip of the pile sucks out 0.1 W and dissipates 1W, then
the next sucks up 1W and dissipates 10W, then the next unit has to
absorb 10W and dissipate 100W, etc.
-Chuck Harris
Chris Albertson wrote:
The worst thing about those small refrigerators is that were NEVER
designed
to cool objects that PRODUCE heat. A wine bottle does not burn any
electrical power. If you place even the smallest heat producing
electrical device inside the cooler it is going to have to pump out
whatever heat is being generating just to keep equal temperature with the
room's ambient temperature.
So you place some small device that uses 500ma at 12V and you have a 6W
heater. It will requires more than 6W of cooling power just to keep
even.
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