One could refrigerate a jug of water for a few days
then use it as a heat sink for the copper tube.
That'd be inefficient but it might be cheaper
because it would eliminate the trip to the store
for bags of ice.
I like it.
Who needs a store? I make my own ice in a little stand-up freezer. In
the summer, when I'm fishing, I make about 10 to 20 pounds of it every
couple of days.
It's a lot cheaper than running a compressor at the low efficiencies
of a Hilsch tube...or buying ice.
Nifty! And probably a *lot* more energy efficient than the Peltier.
So, locate a square 10 gallon bucket, submerge coil, fill with water
and place it in the freezer. Figure out a pump to keep the drip leg
dry and Bob's your Uncle.
Yeah. Mine's a little bigger -- around 4 ft^3 -- but that one should
do it. BTW, mine has run without a hitch for 32 years. Sears.
Probably. (Remind me to tell you about the piece of research
equipment, using semiconductor Peltier chips, that I built for Japan's
MITI back in the '80s. Bridgeport, South Bend lathe, and ancient
Walker Turner drill press, and the thing went to Japan's research
agency for OTEC. <g>)
I'd be wary of doing it that way. The coil would develop a blanket of
water around it and the conductivity from the ice would be
If it's enough chilling, great. Otherwise, I'd break the ice into
chunks and toss them in the bucket.
You were going to tell me about the time you created a
Peltier-based test jig destined for Japan's Ministry
of International Trade and Industry to be used in Ocean
Thermal Energy Conversion research back in the 80's.
You used a Bridgy, a SB lathe and an ancient Walker
Turner drill press. Is that right?
--Winston <--After the tsunami, they didn't need
to hide it under Yucca Mountain.
Okay, a long tail...
I left AM to pursue a juicy contract with MITI (Japan's Ministry of
International Trade and Industry), to produce reports on new materials
applications. One of their big energy projects was OTEC (Ocean-Thermal
Energy Conversion). I wrote a paper on corrosion-resistant materials
for that project and then, in discussions with them, they expressed an
interest in the new semiconductor thermoelectric cells, as possible
candidates for electricity generation from
low-temperature-differential, high-volume seawater. They actually use
the Seebeck effect, but Peltier and Seebeck are like yin and yang.
Anyway, they said they wanted some of the new cells from a company in
Trenton, NJ, to test and evaluate. I drove down and bought a few dozen
for them. When I delivered them they said they wanted to get started
quickly because they had contracted with a company in Japan to build a
refrigerator-size test module and it would take a couple of months to
get it, and then another month to run tests.
I had a design in my head for a four-cell test unit that I could make
in one weekend. They said it wasn't enough cells. So I explained that
you could change cells in it in less than five minutes, and they could
easily test 20 cells in a day. They they could run some statistics,
figure the variance and standard deviations from a few day's worth of
testing, and have the results they wanted. So they threw some money at
me and said go ahead.
It was really simple. I took two 6-inch squares of 5/8" aluminum
tooling plate (2024 -- it was all I had) and cut a serpentine groove
in one side of each plate with a 1/2" end mill (mill -- I had to use a
friend's Bridgeport). Then I turned some custom barb fittings from
brass (turn). I drilled holes to clamp the two plates together,
leaving room for the Seebeck cells, and then drilled and tapped holes
for the barb fittings (drill). There were two barb fittings on each
plate, at opposite ends of the serpentine groove. Through one plate
you ran cold water. Through the other, warm water.
I placed four cells between the plates, smeared them with conductive
silicone grease, and clamped them together. Then I hooked aquarium
hose to the barb fittings. One pair of leads from each cell projected
out of the space between the plates. Ta-dah. About five hours of work,
You could measure the volume of water and the in-and-out temperatures
from each plate, and the electrical output of each cell. You can see
the implications -- a simple way to measure energy in/energy out at
different absolute temperatures and temperature differentials (there
was lots of insulation on the whole thing, in use) and to test the
output variance among cells. Very, very simple.
That's the story. They loved it. And they decided not to invest in
Oh, I forgot the Plexiglass covers. The grooves were on the outside of
the sandwich, and I covered them with 1/8" Plexi. That way you could
see if a bubble was trapped in there that would screw up the output
readings from one cell.
I guess your clamping pattern assured that every cell
had an equal share of hot and cold sink coupling.
That apparently is really difficult to do.
One of our own disassembled a shorted PWM control for an RC application
and found that say 30% of his SMT MOSFETs barely made contact
with the heat sink. (You could really see the problem by inspecting
the 'sil pad' that was wedged between the heatsink and devices.
Some FETS made quite a deep impression and some were not apparent
Sounds like Science, too. One could bolt on thermocouples for instance.
Ouch! That's like deciding not to buy a car because all
you could test were Yugos. :)
I love the TE concept but despair over their inefficiency.
I suspect that Stirling motors would work the best in
this application, no? ('Sounds like a great purpose
for 'flare gas' at last.)
That'd be a way to create a solar heat collector, too.
I expect the plexi would have to be replaced with another
aluminum sheet, though.
It was an even pattern, and any difference would be apparent at the
plates' edges, but it also counted on the grease. In any case, it
worked. We moved one set of cells all around on the plates and the
results were pretty consistent.
I attached 1N914 diodes for my own initial tests. They're very linear
for temperature when back-biased within a certain voltage range --
MUCH better than thermistors. But the leads have to be short. Amplify
the results with a 714 op amp and drive a small meter. +/- 1 deg. F
over quite a long range.
That was in 1981, remember. d8-)
I don't remember the values. I have a couple of them that I scrounged
from an old camping cooler. It killed the battery in my van one night
and I took it apart for revenge.
They'd likely be the most efficient energy coverter at those
temperatures. But you're dealing with very small temp. differentials.
It would take a *lot* of Stirlings to generate useful power.
These chips had flat-finished ceramic wafers on both sides.
I really don't remember. I had used the same system years earlier for
a temperature-tire gauge for SCCA races. Those little things respond
in less than 2 seconds.
They were out at sea. The OTEC plants generally are old ships anchored
in warm water, over fairly deep waters that are much cooler at the
depths. I haven't heard anything about them for 20 years. The whole
thing probably was a dud.
Speaking of Stirlings, have you heard anything about that
multiple-Stirling solar array that PG&E was building a couple of years
ago? I would have thought something would be reported about it by now.
I hadn't heard a thing, until you mentioned it just now.
Hmmm. That doesn't sound good.
Oh, well, we're going to have all the oil we could possibly want,
after the Republicans win the White House. And gas will be $2.50 a
gallon! Free, if you show your Tea Party ID card!
They'll probably drill in my back yard. I wonder who owns the mineral
Yeah, I took all the shelves out of the freezer in my shop fridge and put a
great big tub under the little ice maker in there. It holds 30-40 pounds of
ice if I remember to turn the tub around so the other side fills. In the
summer when I am fishing a lot that is never a problem. LOL.
I would consider using the freezer part of the fridge to pre-cool a coil of
air, but its on the other side of the shop. I actually considered putting
my CNC computers inside a little apartment fridge in the shop. Maybe now is
the time to get a second shop fridge. LOL.
The problem is, for instance, aluminum melts at approximately 1220 deg F and cooling your air supply down by a paltry 60 or so degrees will have a neglible efferct on total heat transfer at best--at worst, no effect or perhaps it could even be negative.
You've intentionally reduced total mass air flow to the part itself by throwing away the heated portion--air which is in all probablilty is say 150 deg F or so--IOW, no where near the temp where there is a significant danger of any cutting tools clogging up and that sort of thing....air which all by itself (though hot to the touch) would be perfectly adequate where the goal is keep the part / chips / temp at some temperature well below the danger zone....
When it comes down to it, despite the claims of the various vendors, I really do have serious doubts that any more heat is carried away from the workpiece by using the cold air out of a vortex tube than would be carried away by simply using the same amout of total of mass air flow that would have been output into a standard air nozzle at room temp directly from the compressor instead.
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