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Air Compressor/Vacuum Pump Answered

I have a theory: You have your supply of compressed air. You connect that by hose to one branch of a y-connector. The other branch is connected to a hose that goes into some sort of fluid that you want to move from one vessel to another. The trunk of the y is your exhaust (in theory). So now I give, say, 15 psi out of my air supply and that shoud drag my fluid out of its vessel through the y connector to the destination of my choosing. Would that work?

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user

. Pneumatic positive-displacement pump. The drive end works just like a steam engine 'cept it uses compressed air. Compressor side is similar to a car engine. 85% certain.

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NachoMahma (author)NachoMahma2008-08-10

. Compressor is probably more like a two-cycle engine.

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PKM (author)2008-08-09

This is possible, but the air needs be at high pressure and exit into an area of low pressure relative to the supply (preferably atmospheric pressure).

There is an experiment you can do to demonstrate this. Cut most of the way through a plastic drinking straw and bend it at 90 degrees to open up the cut. Hold it so it looks like an upside-down L, dip the bottom end in a container of water, and blow hard through the other end- water should be sucked up the vertical part and spray out of the cut. As Kiteman pointed out, because of the difference in density you have to have a large flow of air to pump liquids, but it is possible.

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bumpus (author)2008-08-08

It would be the other way around. If you pump water out of something with a y-connector, with one nozzle linking to a supply of air, and the other to water, and the final where everything gets dumped out, you create a vacuum, the water pulls the air out of the one nozzle. (diagram if I didn't explain well..) The blue is water The red is air The purple is a mixture of air and water Inside the circle is where your vacuum is, pulling air in. I hope that helps...

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Kiteman (author)bumpus2008-08-08

Never mind a diagram, I have a photo! Look what I just found in my shed! I had to take the photo at an odd angle to see past the glares (I've turned the photo on its side to make the pump right-way-up), but this is a venturi pump. Water flows in the ribbed tube at the top (ribbed to keep a rubber tube in place), and squirts through the narrow nozzle in the middle. This jet squirts into the small cup opposite, and out a hole in the cup to the outside world. The jet (from nozzle to cup) reduces the pressure inside the main body of the pump, so air is drawn in through the arm on the side.

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bumpus (author)Kiteman2008-08-08

Yes! Thats exactly what it is, in our science class rooms, all the faucets have these type of connecters. Not like the photo, but same principle.

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Kiteman (author)bumpus2008-08-08

The glass ones are fragile. You tend to see them in stainless steel now, because they're tougher, and you can unscrew the ends to clean them out after some incompetent child lets more than air get sucked up the side-arm.

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flagrantfouler (author)Kiteman2008-08-08

So I can use liquid to move air but not the reverse?

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Kiteman (author)flagrantfouler2008-08-09

You can use any quickly-moving fluid to move any other fluid, but there's the matter of mass - light things aren't so good at moving heavy things.

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user

. It will work the other way (that's how some spray paint guns work)), but it usually takes a lot of air to move a little liquid.

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NachoMahma (author)NachoMahma2008-08-08

. BTW, aspirators usually take a lot of water to move a little air.

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Kiteman (author)2008-08-08

Yes.

Well, actually, no. It's slightly more complex than that, but a moving fluid will generate a drop in pressure.

School science labs connect small devices called venturi pumps to taps - the water flows in and through a narrow constriction. This creates a pressure-drop, which draws air in through a side-arm.

They can be glass or steel.

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flagrantfouler (author)2008-08-08

Oh, let's put a check valve on the branch connected to our fluid so that it will only flow out of the vessel and towards the exhaust, which is the trunk of the y.

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