vulture
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Improvised Airconditioning
It's very hot here in Belgium at the moment, ofcourse it's only that hot when I have exams, go figure.
Anyway, I was thinking of airconditioners and thought about improvising something with labequipment, more for fun than anything else.
So I figured, what if I put some water in my large dessicator, connect the vacuum pump and constantly evacuate it to about 100mbar. A fan would blow
the room air over the dessicator and the "exhaust" from the vacuum pump would simply be vented to the outside, properly sealed ofcourse.
I'm foreseeing a few major problems:
- 100mbar is not enough to make water boil at room temperature (30C now)
- the heatconductivity of thick dessicator glass is rather poor
Let's see if anyone else has some bright ideas for a poor mans airconditioning (no cryogenics or liquid propane stuff etc)...
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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12AX7
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Water is a crap-ass refrigerant, because it boils at such a low pressure, and tends to freeze at exactly useful temperatures.
Best way to improvise a refrigerator is to take apart a 'fridge and rebuild it. 
I'm guessing it's also nicely humid (about like Wisconsin in summer, although pleasantly not today  ), so a swamp cooler won't interest you...
Tim
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Mr. Wizard
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I have a couple of 'swamp coolers' (evaporative coolers) on my home. Water is pumped over three or four open pads with holes .5 to 2.0 mm in it. A 1/3
to 3/4 horsepower motor drives a belt driven squirrel cage, to move 5000 cubic feet of air per minute. The temperature outside is 94F (34.4C) and it
is 73F (22.8C) inside. I live in the desert south west of the US, and the units are very practical for all but a month of very humid weather. As 12AXT
noted, they are not comfortable when the humidity gets above 20%. A quick test with a wet bulb thermometer would tell you what you could achieve.
They are very economical, and in dry heat I have regularly seen 74F (23.3C) inside while it was 104F (40C) outside. Just about any idea involving
boiling refrigerants will quickly empty your wallet. Even the commercial units I have on my house , which are quite efficient, cost a fortune to run,
even at $0.10 /KWHr. The units are rated 3.5 and 3.25 'tons',an antiquated term, which means they can equal the cooling of that many tons of ice per
day.
Often much comfort is given by a common ceiling or desk fan. Unless the humidity level is 100% you will realize some cooling. Has anyone heard of
water misters? They hook up to a regular water line and use only a few liters of water per hour to create a fog like mist, suitable for cooling
outdoor areas. I was going to build a multi stage evaporative cooler , where one stage pre-cooled the air going in to the next stage, but I realized
the relative humidity levels would quickly rise as the air was cooled and would not yield much additional cooling.
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Magpie
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I agree that evaporative coolers ("swamp coolers") can be very economical and useful where the relative humidity is low enough. I lived in the
southwest US for a while where they were used effectively.
I now also live in a Western desert area but due to crop irrigation the humidity stays at about 40% RH all year. I don't have a swamp cooler but my
neighbor does. It seems to do the job quite well for him even at 40% RH.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Mr. Wizard
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Increased RH does make the home less comfortable. I agree the coolers will still work at even 40% RH but the comfort level will be much less, as your
clothes start sticking to your body, door frames start to swell from the moisture and potato chips get limp.
What sort of RH are we talking about in Belgium today?
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franklyn
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Quick and Dirty
| Quote: | Originally posted by vulture
Let's see if anyone else has some bright ideas for a poor mans airconditioning |
To chill , while working in the suffocating heat produced by
industrial vacuum ovens used for curing dielectric resin in
potted core inductive devices, the foreman rigged a copper coil
immersed in an alchohol bath containing dry ice. One end was
connected to the central compressed air supply and the other had
a bleed valve to allow a jet of freezing air out.
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Rosco Bodine
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If you can get an old large diameter parabolic satellite dish and drive mount , perhaps you could cover the dish
with reflective mylar and use it as a heliostat solar collector on a rooftop , with an ammonia cycle boiler coil at the focal point of the dish where
the feed horn would usually mount . You would need a good sized reservoir for storing the charged refrigerant between cycles . Since the
refrigeration system has no moving parts it would last practically forever .....and since it is solar powered it would have no operating cost . A
small solar panel and battery could supply all the electricity for the dish aiming motors and for the small fan motor on the evaporator . Most of the
system could probably be
assembled from scrounged parts cannibalized from
junked equipment at a scrap yard .
http://www.nh3tech.org/absorption.html
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unionised
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So far as I can judge you could still use a swamp cooler sort of thing (the efficiency would suck; here in the North of the UK it's 15c outside anyway
so it wouldn't matter; but it's also 75RH).
Dribble water over a cloth wrapped round a big metal pipe, put it outside and set a fan to blow air over it. This should cool the pipe. Get another
fan to blow air through the pipe into your house.
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Pommie
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A more chemical based system could use lithium chloride.
Heres a paper on it.
Mike.
Attachment: LiCl solar cooling paper.pdf (409kB)
This file has been downloaded 1440 times
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gsd
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Why not use the Ranque-Hilsch vortex tube extensively discussed in this forum and so beautifully condensed in a practicable format by tecnotacho at
his website:
http://www.tecnotacho.com/projeto1.htm
with the necessary modifications to adapt it to cool the air ?
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franklyn
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Here is another approach _
http://www.solarmirror.com/fom/fom-serve/bags/solar-icemaker...
.
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Pyridinium
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If your building were well insulated and you had a few hundred kilos of ammonium nitrate and some water, you could make the place nice and cool... ah,
well, nevermind. A couple hundred kilos of NH4NO3 might give the wrong impression these days.
I think KSCN gives a pretty cold solution as well. Again, you'd need quite a bit of it. Then you could evaporate the solution out in the sun, bring
the crystals inside, and do it over again :-D
You could always rig up a giant Peltier cooler, with the hot side facing outside your building... and running at a huge electricity cost, of course.
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DerAlte
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Here we rarely have temps above 100F But I'd much rather be in Tucson. We commonly have 95F but also 70% RH. That feel's like Death Valley at
midafternoon on a hot day - a heat index of 122F. For 4 months per annum, too. Pray for rain! It can then drop as low at 78F with 100% RH.
Regards,
DerAlte
[Edited on 7-7-2007 by DerAlte]
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Texium
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19-11-2023 at 12:05 |
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