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  #1  
Old 02-17-2011, 11:37 AM
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Lightbulb Water Column - air pressure

Water Column

We are trying to calculate OWC (oscillating water column)
we have a vertical pipe 2 meter diameter in a wave pool.
Every 5 seconds the water level rises 1 meter and descending again.
We would like to utilize this "water piston" to create pressurized air .
1 . what should be the air pipe exit diameter (on the top of the pipe) to create 10 bars air presssure?
2. Rising of the water column takes no more then 1 second (fast burst), is this enough time to pressurize the air volume (3.14 cubic meters) into said pressure?
3. Will the same pressured air flow remain after running in a 100 meters air pipe?
Thanks in advanced.
sol
sgilboa@seanergy.co.il
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  #2  
Old 02-17-2011, 12:22 PM
JohnS JohnS is offline
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Default Re: Water Column - air pressure

Quote:
Originally Posted by Unregistered View Post
Water Column

We are trying to calculate OWC (oscillating water column)
we have a vertical pipe 2 meter diameter in a wave pool.
Every 5 seconds the water level rises 1 meter and descending again.
We would like to utilize this "water piston" to create pressurized air .
1 . what should be the air pipe exit diameter (on the top of the pipe) to create 10 bars air presssure?
2. Rising of the water column takes no more then 1 second (fast burst), is this enough time to pressurize the air volume (3.14 cubic meters) into said pressure?
3. Will the same pressured air flow remain after running in a 100 meters air pipe?
Thanks in advanced.
sol
sgilboa@seanergy.co.il
You might get some effect from the oscillation, but I don't think this is going to work. Consider it quasi-statically first. At the quiesent water level, assume the pipe has been vented and is at atmospheric pressure, so water level is the same inside. If an over pressure of about 0.1 bar were created inside, the water level would be pushed down about 1 m. (10 m of water is 0.98 bar, but I've rounded to 1 bar for this discussion). Alternatively, if the external water level rises 1 m, the internal water level would rise 1 m ONLY if the pipe were vented to atmosphere, and depending on total internal volume of the air space, there will be an overpressure of less than 0.1 bar and a rise of less than 1 m.

If the total pipe volume is large, compared to the swept volume of a 1 m rise, then the rise will approach 1 m and the pressure will be very small. Alternatively, if the initial air volume is very small, there will be essentially no rise, but a 0.1 bar overpressure.

If you could create a 10 bar pressure from this setup, you could have a perpetual motion machine of the first kind; however, they never work out.
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Old 02-19-2011, 11:45 AM
tlrd tlrd is offline
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Default Re: Water Column - air pressure

Dear John,
This is a brilliant analysis, chapeau...
But I would like to discuss it with you and to clarify it - since we really don't want to kill the idea. We are even willing to build a small prototype - if you will agree to our assumptions and help with damnations required for the prototype.

As you know wave Oscillating Water Column (OWC) are working. Here is a sample link:

youtube.com/watch?v=gcStpg3i5V8&feature=related[/url]

So defiantly there is a huge pressure created (to turn the turbines) - We are not interested in electricity but using the air pressure created to pump fresh irrigation water from a spring reservoir on shore to an upper irrigation channel .

The off the shelf pump we have in mind needs only 8 bar pressure. If we can create this pressure from the waves it will save us lot of hassle... (no access to electricity) .

I hope this clarify my original request.

Thank so much
Sol
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Old 05-25-2011, 03:12 AM
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Default Re: Water Column - air pressure

but what if you had a column of water that was replenished by its own circulation? ie under high air pressure within a sealed system. Would water not discharge at a fixed pressure from this column via a turbine[s] back into the system through gravity?
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Old 05-26-2011, 12:18 PM
danielvulrich danielvulrich is offline
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Default Re: Water Column - air pressure

not sure if such a variant is possible
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