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Sanity check, please. Low energy-demand "lift pump" for water?

J

John P Bengi

Jan 1, 1970
0
Good point. The pressure at the bottom of the lift tube will be the same no
matter how you pump it up in one transaction. The bubble pump would have to
compressd the bubbles to hundreds of PSI to overcome the water pressure and
the garden hose would still burst.
 
D

Don Bruder

Jan 1, 1970
0
John P Bengi said:
Good point. The pressure at the bottom of the lift tube will be the same no
matter how you pump it up in one transaction. The bubble pump would have to
compressd the bubbles to hundreds of PSI to overcome the water pressure and
the garden hose would still burst.

Erm...

Am I missing something, or don't the bubbles float up the tube?

At the beginning, I see a ten foot tube with 3 feet of water in it.

As things get rolling, it's a 10 foot tube with 3 feet of mixed water
and bubbles, with the bubbles rising. As they near the top of the tube,
they expand somewhat (lower pressure due to less water above) and push a
bit of water up. Now there are 3.01 feet of water in teh tube, and more
bubbles coming from below. And the process continues, with each bubble
raising the height of the column some minute amount until finally, at
10.something feet, the mixed water/bubble column begins to spill out of
the tube.

No pressure, no bursting, just bubbles floating to the top of a column
of water, and drawing a bit of that water with them - Regardless of
whether the tube is ten feet or 100 feet.

Or have I missed something fundamental here?
 
J

John P Bengi

Jan 1, 1970
0
Nope. It's just that 3 feet of water has a certain pressure that has to be
overcome to get the bubbles into the tube and the air has to be compressed
to the same pressure to do this.

The bubbles will either just float to the tube of the tube and have no water
lift or not rise at all because of the water weight. I doubt you can have
both. The column of water above the bottom remains constant and will not
change pressure at the bottom of the column.
 
W

William P. N. Smith

Jan 1, 1970
0
Sure they do. There are examples of air lift
pumps delivering heads of 300 feet or more.
http://www.redrok.com/water.htm#pumps

Ah, I stand corrected. As long as the pressure depth of the "s"
(intake) is greater than the weight of the water/air collumn in P+H I
guess it would work. Learn something new every day, thanks!

As long as compressed air is free, I guess you can make it work,
though I don't see anything at AirLiftTech except for a brief mention
of "submergence ratio", and some "###" symbols on their brochure.

Nice toys, but a bit over the OP's price point. 8*)
 
W

William P. N. Smith

Jan 1, 1970
0
How much pressure will an aquarium pump produce?

I just bought
http://petco.com/product_info.asp?sku=4679826075&dept_id=-2 which
claims to do 96", and certainly does better for aerating our shallow
well than the pump it replaces. Of course, it's most of the OP's
entire budget... 8*}

I'd still think that if you have the energy to spin an air compressor
you're better off spinning a positive displacement water pump...
 
J

John P Bengi

Jan 1, 1970
0
Are you actually sure this works?

Sounds pretty neat but doesn't the air pump have to cycle on and off? The
air pressure would not go down because of the increased pressure/depth but
once the air starts lifting the head of water the pressure would not allow
more water into the mixing chamber.

This would be similar in concept to a clotheline system with a bucket of
water being lifted to the top one bucket at a time. Dump one at the top and
then send the next. The sytem potential is not used but the load is small at
any given moment.


I can be pretty sure this would only work for a vertical water tube. An
angular pipe would allow the water/air to pass each other I would think.

Duane C. Johnson said:
Hi John;

Not necessarily. The bubble bump tubing above the water
surface consists of a percentage of water and the rest
is air.

Lets say the air pump pressure is 5psi. This can push
air to a depth of about 12' in the source impoundment.
If the exit tube is 100' above the impoundment there
will be about 12' of water and 88' of air. Off course
this is broken up in short pieces. Also, there is some
friction so the water length will practically be a bit
less than 12'.

This ratio of water to air acts something like an
impedance transformation. This is not all that dissimilar
to the impedance transformation in the ram pump. See:
http://www.redrok.com/water.htm#pumps

Technically the maximum pressure in the tube is defined
by how much water is in the tube. This is only a
percentage of pressure that would occur if the delivery
tube was filled with water.

Neat huh!!!

Duane

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D

daestrom

Jan 1, 1970
0
John P Bengi said:
Are you actually sure this works?

Sounds pretty neat but doesn't the air pump have to cycle on and off? The
air pressure would not go down because of the increased pressure/depth but
once the air starts lifting the head of water the pressure would not allow
more water into the mixing chamber.

No, the air pressure just has to be high enough to go down into the water
and through the wall into the main tube. No more. And the air flow is
continuous.

One of the things though about this kind of pump is that it only works with
narrow lift tubes. If the lift tube is very wide, then the air bubbles
'slip' past the water more and more. Too much 'slippage' (in hydrodynamics,
we call it an excess 'drift velocity') and the water just splashes around
slightly above the water surface without getting 'lifted'. But with narrow
tubes, the surface tension of the water will keep 'slugs' of water trapped
between successive bubbles and is lifted.

There is a limit of course as to just how high the water can be lifted. But
more submergence of the lower end, and adjusting the air flow can get some
pretty impressive results.
I can be pretty sure this would only work for a vertical water tube. An
angular pipe would allow the water/air to pass each other I would think.

This gets back into the issue of just how wide the tube is. As I mentioned,
it is surface tension that 'traps' a slug in between bubbles. So a wide
tube will allow the 'slug' to break apart and fall through the bubble below
it. Because of the needs of surface tension, you can't pump soapy water
either (you just get lots of suds).

daestrom
 
M

Mike Swift

Jan 1, 1970
0
harry k said:
Same here but he is tring to do it on zip for money. I have my doubts
about the bubbler too and one of them is the point about the sloped
pipe vs vertical.

Also wondered about the re-charge problem. Will just inserting an air
fitting into the side of the pipe do it? Will it re-charge?.

As for pressure required: No, it will not need 'hundreds of pounds'.
All it needs max is a few pounds over the static pressure of the water
head. Say he has 200 ft lift, then only 50 psi should do it if it will
work at all.

Another approach would be a sealed tank at the bottom with the delivery
out at the bottom, air in at top and blow the whole contents up at one
shot. Would have to be cyclical but a 50 gal barrel ought to hold
pressure enough.

Harry K

Harry K


I have seen a bubble pump used in a well system with a damaged casing.
Only a 3/4" pipe would pass the damaged spot. A well company said it
would take about $15,000 to drill a new well to get any water. My
neighbor rigged a 3/4" pipe with a air fitting about 1 foot above the
lower end. The other end of the pipe was put in the top of a water
storage tank. An air, water mixture would dump into the tank. The
compressor was run with a 1/4 hp motor. This well was about 100 feet
deep with water at about 50 feet. As a bonus all of the air mixed with
the water caused the iron in the water to oxidize and settle in the tank
leaving better water than when he had the submersible pump in the well.

Mike
 
W

William P. N. Smith

Jan 1, 1970
0
harry k said:
I must be missing something. Given (say) a 200 ft vertical tube, the
pressure will be about 90 psi at the bottom.

No, the pressure is only the static weight of the water/air mixture in
the tube, which is less than the static pressure of the tube when full
of water.
 
W

William P. N. Smith

Jan 1, 1970
0
harry k said:
Which is true after the bubble lift is operating but doesn't it need
the 90 psi to begin operating? After all the first bubble up the tube
has to lift the entire colume of water.

No, it starts out empty. IIRC the pump only has to provide enough
pressure to overcome the pressure depth at the bubble injector.
 
E

Ecnerwal

Jan 1, 1970
0
harry k said:
Seems contrary to logic. Surely it needs enough pressure to lift all
the water/bubble slugs above it? Somehow that doesn't seem right
either as any pressure above the pressure depth would just blow out the
bottom of the tube, easiest route. Ouch, my head hurts.

Harry K

Get an air supply, some tubing, and a bucket of water. Far more
educational than contemplating newsgroup postings...you can see for
yourself, rather than have to figure out which argument "makes sense" or
matches your preconceived logic. Experiment!
 
A

Anthony Matonak

Jan 1, 1970
0
William said:
No, it starts out empty. IIRC the pump only has to provide enough
pressure to overcome the pressure depth at the bubble injector.

I suppose for higher lifts that one could add a little foaming agent
(soap?) to the water. Add a little screen of some kind at the top
end to pop the bubbles. Assuming you don't mind a little soap in the
water at the end.

Anthony
 
D

Derek Broughton

Jan 1, 1970
0
To add another potential kink to this experiment, I see people assuming that
"a" bubble has to lift the water above it. Perhaps that would be true in a
high-lift application, but in aquarium filters it is very definitely _not_
true. The smaller the bubbles, the better your water flow (noting that, as
mentioned earlier, aquariums rarely raise the water more than a foot). I
think if you were going to try this you'd want to try varying the bubble
size.
 
J

John P Bengi

Jan 1, 1970
0
This doesn't work without the surface tension of the water, we are told.
Soap destroys the surface tension.
 
J

John P Bengi

Jan 1, 1970
0
The uptube must have some water in it or the bubble has nothing to float to
the top of.

Duane C. Johnson said:
Hi Harry;
The up tube is empty when you start!


Duane

--
Home of the $35 Solar Tracker Receiver
http://www.redrok.com/led3xassm.htm [*]
Powered by \ \ \ //|
Thermonuclear Solar Energy from the Sun / |
Energy (the SUN) \ \ \ / / |
Red Rock Energy \ \ / / |
Duane C. Johnson Designer \ \ / \ / |
1825 Florence St Heliostat,Control,& Mounts |
White Bear Lake, Minnesota === \ / \ |
USA 55110-3364 === \ |
(651)426-4766 use Courier New Font \ |
[email protected] (my email: address) \ |
http://www.redrok.com (Web site) ===
 
W

William P. N. Smith

Jan 1, 1970
0
harry k said:
either as any pressure above the pressure depth would just blow out the
bottom of the tube

That's why the bottom of the tube is some distance (20 feet?) below
the air injection point.
 
E

Ecnerwal

Jan 1, 1970
0
Derek Broughton said:
To add another potential kink to this experiment, I see people assuming that
"a" bubble has to lift the water above it. Perhaps that would be true in a
high-lift application, but in aquarium filters it is very definitely _not_
true. The smaller the bubbles, the better your water flow (noting that, as
mentioned earlier, aquariums rarely raise the water more than a foot). I
think if you were going to try this you'd want to try varying the bubble
size.

The typical aquarium air lift pump is moving large volume at low head;
Often only the dynamic head of the pumping (circulating water within the
tank). In that situation, large tube and small bubbles work well. For a
greater lift, I believe that you will find larger bubbles and smaller
tube work better. Experimenting is good.

As far as I know, there really no need or use to having much pump tube
below the air input point - the whole premise that this is based upon is
that bubbles travel up in water, and so long as that is true, injecting
bubbles at the bottom of the tube should be fine and is supported by
past experience - but experiment with that, too, if you feel any doubt
about it. Pointing the air tube up the pump tube does tend to help.

Note that I still don't think this will be an efficient way to do the
original job, since it will cost a great deal more power to run the
compressor than to simply pump the water.

And Willy - a 4 inch diameter trunk on a cherry tomato - wow!
 
D

Don Bruder

Jan 1, 1970
0
Ulysses said:
So, Don, did you ever get your garden watered? If so, how?

Still in the planning stages - IT won't be goin gin until next year, if
at all. IT's too late to get started and expect anything to happen this
year, but I'm toting buckets of horse-puckey up the hill to where I want
to put it in, so that I've got something that at least resembles "soil"
when the time comes.

Still plotting and planning on the exact how of getting water up there,
but it's looking like my only *PRACTICAL* option is to go with a
secondary pump down here at the house, and running PVC up the hill to
fill a reservoir at/above the garden site, then drip-watering using
gravity feed from there.
 
D

Don Bruder

Jan 1, 1970
0
Dean Hoffman said:
How about we check my sanity? Do you go downhill when you leave your
house? Would there be any way to let gravity do the work? One end of a
heavy rope fastened to a barrel or tank and the other end to your vehicle
bumper?

To make it worth the bother, such a container would likely outweigh my
car! :)

But it is an idea I've toyed with. Probably not practical for several
reasons - biggest being the lack of anything resembling a straight run
to take the car down without giving buildings, fences, and livestock a
terminal case of rope-burn as it goes by, closely followed by the cost
of a rope of sufficient capacity and length to do the deed.
 
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