On 2009-09-05, Ed Huntress wrote:
"DoN. Nichols" wrote in message
...
[ ... ]
What about a vortex cooler -- no moving parts (unless you count
the air). A bit noisy, however. :-)
[ ... ]
Those darned things still confuse me. I've never looked closely enough to
figure out how they really work, aside from the simple expansion of air and
its consequent absorption of heat. But there's more to it, I think.
Note that there are two ends to it, and cold air comes out one
end, and hot air out the other.
Essentially, compressed air is fed in tangentially around a
point just past the junction of a disk and a large diameter tube. In
the center of the disk is a smaller hole, going off to a tube in the
other direction. The larger tube has an obstruction at a distance so
the total area is similar to the smaller tube (and I think ideally the
larger tube has twice the area of the smaller tube).
The tangential feed causes the air to form a spinning disc at
that point. Hotter air has molecules in faster motion than colder air,
so the hotter molecules tend to (on average) collect around the OD of
the spinning disc of air, and the colder molecules migrate to the
center. Since there is only one direction the hotter molecules can go
(down the larger tube) and while there are two directions the colder air
can go, most of the hotter air from the compressor is going down the
larger tube, so the pressure is a bit higher there, and the colder air
mostly goes down the smaller diameter tube. (It might be possible to
make it more efficient by putting a blocking disc near the center on the
hot side so the colder air can't go that way readily.
I made one of these a long time ago, using mostly plumbing
fittings and a bit of turned and machined brass after seeing one in a
demo of the things one of the other labs in the area was developing.
(The air from the cold side was piped into the helmets of tank crew,
especially those who are trapped down inside the tank during normal
operation.)
Anyway, without knowing anything about their thermodynamic efficiency, yes,
they sure look appealing from a simplicity standpoint.
What I made was terribly inefficient -- it took a lot of
compressed air to get a reasonable separation between hot and cold
output -- but the hot side pipe was uncomfortable to hold, and the cold
side was quite pleasant in mid summer. I understand that the main
things against them are the noise output and the relatively poor
efficiency. But in a tank, there is energy to spare, and an already
noisy environment, so the cooling is quite welcome.
Enjoy,
DoN.
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