[time-nuts] Cycling of Peltier junction

[J. Forster]

Peltier devices have been used as temperature control elements for
decades. I've never heard of fatigue failures, but, if I were designing a
chamber as you suggest, I'd try to keep the temperature differential
across the TE element under maybe 15 to 20F. The harder you push it, the
greater the stress.

Also, the heat pumping power falls dramatically as the delta-T increases
and it's a situation of rapidly deminishing returns.

I'd not worry much about ramping the drive.

FWIW,

-John

===============



> Does anybody know about using the same Peltier junction for both heating
> and cooling?
> I'm concerned about thermal/mechanical shock when changing the polarity
> back-n-forth between hot and cold.  Maybe there needs to be a controlled
> ramp, if so then how do I figure out the rate?
>
> Why:
> I'm in the process of building a small environmental chamber for my home
> lab. The volume is ~30 liter, target temp range of 0C to 60C.  For the
> cooling side I am using water circulation (radiator, pump, reservoir &
> water block) and Peltier junctions.  At first I was planning to have two
> separate systems, one for heating and one for cooling, but then I got to
> thinking that using just the water and Peltier could be used for both.  I
> will be using a PID for temp control, and two TEC1-12726 Peltier Qcmax(w)=
> ~240 $B"$(BT =0j
>
>
> Regards,
> Jerome
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