[time-nuts] Wine cooler as temperature chamber

[Jim Lux]

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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