On Thu, 16 Oct 2008 22:26:10 -0700, Richard Clark
wrote:
Well, it's been a coon's age since I've seen vacuum cleaners that
would let me attach to their exhaust - so that's out.
The problem with vacuum cleaners is that they all suck. I have an
ancient Electrolux and a Shop Vac that both have usable exhaust ports.
I also have a Hoover upright and a Hoover cannister in the office that
do not. Y'er right that it's a vanishing breed.
However, you re-read what I scribbled, you might notice that I
suggested that one use the air compressor to pressurize the 3/4" PVC
pipe. That's because the average vacuum cleaner can barely generate
more than a few PSI. They also leak badly. If you're trying to lift
a column of sand or demonstrate backpressure, it's much easier with a
proper air compressor.
As for driving compressed air into a short (or open). I've done that,
but not for sand excavation.
I have. The clumsy backhoe operator (me) once dropped a load of dirt
on top of the steel 3" conduit end during construction. I'm also the
idiot that forgot to shove a protective rag into the conduit end. I
spent the next two days trying to figure out how to get the dirt out
of the pipe. I eventually fabricated a cylinder shaped rubber plug
with an eyebolt down the center, dumped some water into the conduit,
and dragged the plug through the pipe with a winch. It took about 5
passes for the water to come out clear. I then pumped out the
remaining water, dragged a sponge through the pipe a few dozen times,
and then let evaporation do the final cleanup. Compressed air was
attempted just for fun, but it was obvious that it wasn't going to
lift the dirt out of the pipe.
Rather, I've used what was commercially
called the "vortex effect" which separates the two air current flows
you allude to above to create a hot stream and a chilled stream of
air. (Elevated or depressed from the average of the inlet
temperature.) I used this for cooling electronics in a paper mill.
Not particularly efficient, but compressed air was available, and the
VorTec nozzle was a quick and easy solution to their NEMA enclosures.
See:
http://www.vortec.com/support_casestudies.php
or
https://secure.vortec.com/store_prod...tID=9&prodID=6
Nice. I built several out of the original Amateur Scientist book
(which I still have on my bookshelf) in the early 1960's. It worked
amazingly well. Much later, I built one out of PVC pipe, which
melted. Now I know why they're made out of metal. Never mind the
inefficiency. It's the noise they make that drives me nuts. At one
point, we had 4 of them in series, with 4 assorted air compressors
pumping about 4 SCFM into each, and got it down to about -100C. We
started with a group of about 10 lab students, and ended up with a
crowd of about 100 nosey students wondering why someone was trying to
operate a jet engine on campus.
This, and some of my fluidic applications constitute a specialized
niche in alternative logic systems. Notably, they all work off
principles of reflected power that demonstrate palpable examples.
I'll pass. I don't believe in logic any more. Everything can be
explained in terms of politics, psychology, and conspriacies. Logic
is obsolete.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060
http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558