On 10/13/14, 4:17 PM, ed breya wrote:
I have this nice little thermoelectric "12-bottle" wine cooler (about
one cubic foot inside) that I've fixed twice already, and it just
crapped out again. It's always the same thing - bad caps in the
switching power supply - they're just too small to take the necessary
ripple current. So, I could replace them again and be good for a couple
of more years, cram bigger caps in there and maybe have a permanent fix,
or decommission it from beverage service and convert it to a chiller
cabinet for the lab.
I'm wondering if anyone has experimented with these things to see how
low in temperature they can go. In normal service, the minimum setpoint
is 50 deg F, so not all that cold, but I'm sure it can do better than
that with a good supply and running full blast. There's about one inch
of insulation on all sides, and the door is double-layered glass.
There's a circulator fan on each side of the TEC.
The TEC probably has a maximum delta T of about 30-40F.
They are usually about 10% efficient, so for every watt you suck out,
you need to dissipate 11 watts from the hot side.
MELCOR (now part of Laird)
has all the ap notes you might need.
I would put in a bigger supply and new control system, but it wouldn't
be worth it if it can't chill much better than original. I don't know
yet if the TEC is accessible for possibly upping the size and rating.
I have experimented with R-12 type mini-friges for this purpose - they
can typically reach minus 40 deg running continuously, but will be
oil-starved at the high vacuum, low flow conditions there, so may not
last long compared to normal service. They're kind of awkward and ugly
too - the best would be a nice small, glass-doored wine chiller, with a
normal refrigeration system built in, but maybe a TEC type would be OK
for some uses.
Ed
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