• # Thread: measuring how much water is moved by an airlift?

1. ## measuring how much water is moved by an airlift?

Yeah...so don't cloud the water...just comment on my "idea." Don't reinvent my square wheel. Just tell me what you think i got wrong and right.
And this has been brewing in my head for years...how can I figure out what would be the best depth for an airlift where all the other parameters were the same (like air pump).
here is an idea.
I am going to use a standard 4 inch diameter PVC Pipe "lift" but you could model this for another "lift."

What is going to happen? lol. I really don't know... so sit down and think.... this ain't gonna be normal..not even for here.

So you keep the injection of air point at the same place in the 4 inch lift. Now you have a the 4 inch pipe alot longer than the expected sweet spot....
and you have to have a clear small diameter pipe 90 degree coupled into the bottom of the 4 inch airlift pipe. And the 4 inch airlift pipe is closed on the bottom, completely closed.
have I lost you yet....well i will...
now if you want to test the airlift efficiency at various depths...you simply fill the 4 inch lift to the depth you want to measure. Water goes back into the clear tube. Both the water levels are the same.... then turn on your air pump...what happens.
No really...what happens? Does the water lower in the small clear tube? does it not change? does the level of water in the clear tube raise?
But here is the kicker..the only genius part of this.... Say the airlift can raise the water in the 4 inch lift. That water comes from the small diameter pipe. If you have a .5 inch diameter clear tube as your reservoir. the water might drop 15-20 inches...or would it? Or would the volume of air bubbles in the 4 inch airlift displace the water so it went in to the clear tube? So either way you the small diameter tube could/maybe make it easy to see how much the airlift is lifting....maybe? And if it either raises or lowers the water the ability to find the sweet spot for the right depth could be as easy as filling the airlift to various depths, then turning on the air pump, and then measuring how much water moved.... IF IT MOVES AT ALL.
yeah, they legalized medical marijuana in Florida. What's your point?

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Okay I think I understand your question and setup design...

The 4" riser tube and the small clear tube would always have the same water level when the air pump was turned off, because both pipes would have the same density of water and the same atmospheric pressure pushing down on it.

When you turned on the air pump, you would be injecting air into the 4" pipe and creating a water/air mixture that would have a lower density than the pure water in the clear tube. The water in the clear tube would be pushed into the 4" riser tube until the pressure at the injection depth of the two pipes were equal. That means the clear small diameter pipe would have a lower water elevation than the 4" air/water mixture, but no water would exit the 4" riser tube.

Your testing setup would be perfect for comparing different air injection methods inside the same riser tube. The greater the elevation change in the small clear tubing (from static to dynamic) would show a greater density difference of the water/air mixture, and in theory that water/air mixture would produce the greatest amount of water output in an airlift.

That is a great idea, but there are people who will not agree with my hypothesis.

EDIT: A Better title for your thread would be "Measuring the Density Difference Inside an Airlift Riser Tube"
Last edited by Zac Penn; 11-04-2018 at 03:17 PM.

3. Originally Posted by Zac Penn
A Better title for your thread would be "Measuring the Density Difference Inside an Airlift Riser Tube"
Ideally you want the air-water mixture that lifts the most water -- so maximum volume of water for least volume of air.

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I don't think you can measure water moved but maybe for a known submersion and measured air flow the max pressure differential could be determined for a specific diffuser type. A more efficient diffuser will raise the water higher using the same amount of air? Large bubbles might produce a lot of surging that might not translate to increased flow? A loop setup with some resistance where actual flow could be measured would be more useful.

Luke,
Is this crude diagram simular to your idea?
Last edited by BWG; 11-04-2018 at 08:39 PM.

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BWG,
I feel like our two drawings would come up with the same conclusions however the tube with the most water movement would be reversed.

In your drawing the reservoir of pure water would only slightly lower when the air is introduced, and the water/air mixture would rise to maximum level.
In My drawing the reservoir of pure water would move substantially lower when the air is introduced, and the water/air mixture would rise only a little bit.

Well, now that I am re-reading that I see that the submergence depth would change significantly in my example when the air was introduced, so with the change in submergence the overall differential pressure would not be the same in both setups. Your drawing would yield more accurate test results due to the larger reservoir of pure water pushing into the riser tube, thus keeping the submergence depth more stable between static and dynamic.

I wish there was a way to design this kind of testing rig so that many different riser tube configurations could be tested without much changing to the rig. Unfortunately, each riser tube tested would have to some kind of side view modification so we can see where the air/water mixture maxed out in the tube.

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Luke,
I have been thinking about your idea, and I think it is an excellent one, except a slight variation is popping into my head.....

A limitation of your design is that the 4” airlift tube is built into the system, and changes are to the 4” tube (to test different injections, etc) are going to be involved. And what about different sizes of riser tubes (e.g. 3”, 2”, etc.)?

Consider this modification to your proposal: use a larger receptacle to hold the water (I am thinking large “Rubbermaid” trash can) and use an inexpensive Uni-seal to still attach a junction, elbow, and a length of vertical clear pipe — just as you suggest. Now, simply place the “test-subject” airlift riser tube into the larger reservoir, with the caveat that — this is important — the vertical extension of the airlift riser tube is far higher than the maximal lifting (just as in your proposal) such that there will only be lifting within the airlift riser tube, but no flow out of that riser. The amount of lifting of water above the static water level in the reservoir will result in a proportional decrease in water within the reservoir — which presumably could be visualized as a decrease in water level on the clear sight tube.

The drawback of using something with as much volume as a big trash receptacle is that there might not be much draw-down of water level to visualize......but I am gravitating towards cheap ideas. Probably the best possible option would be a length of pipe for the reservoir which is just large enough in diameter to accommodate any size of airlift one might want to test (along with injection manifold, etc). Probably, a length of 6” or 8” diameter pipe as the reversion would be optimal, but that can get expensive.

Do you follow what I am suggesting!

7. Originally Posted by bigbrudda84
Ideally you want the air-water mixture that lifts the most water -- so maximum volume of water for least volume of air.
NO! that is not what I want...I want to talk abut THIS not THAT. I asked for psters t nt "muddy the water by talking abut anything else. Period....though you can see how this would help figure that out.

8. Originally Posted by Zac Penn
Okay I think I understand your question and setup design...

The 4" riser tube and the small clear tube would always have the same water level when the air pump was turned off, because both pipes would have the same density of water and the same atmospheric pressure pushing down on it.

When you turned on the air pump, you would be injecting air into the 4" pipe and creating a water/air mixture that would have a lower density than the pure water in the clear tube. The water in the clear tube would be pushed into the 4" riser tube until the pressure at the injection depth of the two pipes were equal. That means the clear small diameter pipe would have a lower water elevation than the 4" air/water mixture, but no water would exit the 4" riser tube.

Your testing setup would be perfect for comparing different air injection methods inside the same riser tube. The greater the elevation change in the small clear tubing (from static to dynamic) would show a greater density difference of the water/air mixture, and in theory that water/air mixture would produce the greatest amount of water output in an airlift.

That is a great idea, but there are people who will not agree with my hypothesis.

EDIT: A Better title for your thread would be "Measuring the Density Difference Inside an Airlift Riser Tube"
zac...we are not going to discuss what the title should be? are we?
But back to my idea.... yes you got it...and you fleshed it out.... but one thing needs to be clarified...the greater the difference in diameter between the two pipes holding the water the easier it will be to see in the smaller clear pipe, correct?

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If the air pipe is small and the air pressure enough to over come the water height and flow air into the large pipe it will always empty of water 100%. With this setup it's not possible to test open end diffuser types such as a pressure chamber.

Still think a test loop setup with resistance simular to filtration is the way to go.

10. Originally Posted by BWG
I don't think you can measure water moved but maybe for a known submersion and measured air flow the max pressure differential could be determined for a specific diffuser type. A more efficient diffuser will raise the water higher using the same amount of air? Large bubbles might produce a lot of surging that might not translate to increased flow? A loop setup with some resistance where actual flow could be measured would be more useful.

Luke,
Is this crude diagram simular to your idea?
I see where you went. BUT that is not where my mind is going...you see I was trying to get away from what you were suggesting. Think abut it..in a loop we have no static precise measurement. even if we raise the level of the pipe the air is being injected to to the point where it quits having water come over the top it is more of a WAG than a precise measurement. I was applying the principle behind the use of a pipette to measure very small volumes of liquid to this problem. If Zac is right then my usage of a thin diameter clear pipe may not work any better than a larger diameter pipe..if I understand him right...and he is right(?).
I was hoping the density of the water would drop the water in the small tube by an exponential rate of the small diameter of the clear tube to the large diameter of the airlift tube. If that works we can precisely measure the effectiveness of various configurations. With my main one being the depth/point at which the airlift is most effective with all other variables remaining constant...
So zac...do you think it will work because the airlift will "suck" an exponentially greater amount of water to fill the airlift.
But my reservation has not been resolved by your post.... if the column of water is "less dense" in the airlift but reaches a higher level, might the two columns even out? ya see that is why I had to give it to the rest of you.....
It could initially work and then even out to ZERO?

11. Originally Posted by Zac Penn
BWG,
I feel like our two drawings would come up with the same conclusions however the tube with the most water movement would be reversed.

In your drawing the reservoir of pure water would only slightly lower when the air is introduced, and the water/air mixture would rise to maximum level.
In My drawing the reservoir of pure water would move substantially lower when the air is introduced, and the water/air mixture would rise only a little bit.

Well, now that I am re-reading that I see that the submergence depth would change significantly in my example when the air was introduced, so with the change in submergence the overall differential pressure would not be the same in both setups. Your drawing would yield more accurate test results due to the larger reservoir of pure water pushing into the riser tube, thus keeping the submergence depth more stable between static and dynamic.

I wish there was a way to design this kind of testing rig so that many different riser tube configurations could be tested without much changing to the rig. Unfortunately, each riser tube tested would have to some kind of side view modification so we can see where the air/water mixture maxed out in the tube.
Ha you see this is getting muddied. you guys just can't stay in one box. OH well I started this so let me get muddy.
First NO Zac. His is NOT better. His might give you just another number, but it would be because he was trying to eliminate the difference in the two levels for a reason on HE feels is important to him. I can disregard that. I want to measure the power of the airlift to overcome exactly that. I do not need it to be unaffected by disparity in heights. The height is giving me exactly what I am measuring. What I need is to determine which depth is best...not a realtionship of volume vs energy or whatever tangent he is trying to go. his tangent is his own course.
What we/I am trying to pindown is what depth for air injection would be ideal for a given pump using the same ejection port/device/airstone/collar.
And I already solved your roadblock about needing all these differently made forms to measure the difference of force created at various depths if air injection.... and it is so simple....
you put the air injection site near or at the bottom of an 8 ft airlift tube... to test it the force created at 2ft you fill the airlift tube and small clear tube to a depth of two ft...you want to measure 2ft 1in? then turn it off and add an inch of water.... you see? nice huh?

12. I bet you make one of these zac.... lol... my best guess is to use a something 1/2inch or less for the clear tube.

13. Originally Posted by BWG
If the air pipe is small and the air pressure enough to over come the water height and flow air into the large pipe it will always empty of water 100%. With this setup it's not possible to test open end diffuser types such as a pressure chamber.

Still think a test loop setup with resistance simular to filtration is the way to go.
No it won't.
zac..you are just going to have to show us.

14. and this thing could still result in the water in the small clear tube not changing one iota..or even being raised instead of lowered
I just thought of it in my head....and I was wrong once before

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To get any air to flow from air pipe A into water pipe B the pressure would have to greater than the water level C. Putting air pressure on air pipe A greater than C pressure to create bubbly flow would empty air pipe A of water.

16. Originally Posted by BWG
To get any air to flow from air pipe A into water pipe B the pressure would have to greater than the water level C. Putting air pressure on air pipe A greater than C pressure to create bubbly flow would empty air pipe A of water.
we aren't doing that..sorry to confuse you

17. the air is
being released into pipe B....

18. Now will it raise the water level of pipe B and thereby pull water from pipe A to do so? If it does then the higher it raises the water the more water it will draw from pile A....
If it doesn't then it will still be interesting

19. but it could just bubble away and not have any affect..or it could reverse flow into pipe A.... I am leaning towards either it does not affect the level of the water in A, or it lowers the water level of A. I actually have more belief in it not doing anything to the level of water in A

20. and this thing could still result in the water in the small clear tube not changing one iota..or even being raised instead of lowered
I just thought of it in my head....and I was wrong once before
you see the level will be higher in B but the density will be lower...so the force may be equal in both pipes, and therefore the level of pipe A will remain constant

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