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

1. If that is the case then the only way to do it would be to start with both pipes at the same height, and filled to the top.

then to find the sweet spot we would have to have the injection port on a piece of pipe and lower it to the various depths. And before doing so we would have to refill the apparatus

2. BWG
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For any bubbles to appear in pipe B air pipe A will be void of water.

3. Originally Posted by BWG
For any bubbles to appear in pipe B air pipe A will be void of water.
You are missing the third pipe.
Pipe A in your drawing is NOT the air pipe. It is just a clear tube filled with water.
Pipe B is the airlift riser tube that has a cap at the bottom and Pipe A TEEs into the bottom of Pipe B.
Pipe C is the air pipe that injects air into Pipe B to create the air/water mixture.

Luke I really don't know what will happen exactly with different sized pipes with regards to how much the water levels will change. However, I believe that Pipe B would be higher than Pipe A, and that Pipe A will be at a lower level than it was before the air was injected because some of that water would enter Pipe B.

4. LOL...I'll bet they stay the same, and therefore I have not found an easy way to determine the comparative efficiency...well i have...by putting the air diffuser on a pipe and having both pipes full of water to the top and then turning on the air and see how much water is blown out the top of the airlift. You'd only have to turn off the air, lower the pipe to the new trial depth, and refill the two pipes and then turn the air back on for each depth....
yeah that would work...
we were wrong about it pulling water from the small pipe unless the water in the airlift pipe actually goes somewhere. The water pressure in bot pipe would remain the same...ahhhh? I think?

5. Originally Posted by lukef
LOL...I'll bet they stay the same, and therefore I have not found an easy way to determine the comparative efficiency...well i have...by putting the air diffuser on a pipe and having both pipes full of water to the top and then turning on the air and see how much water is blown out the top of the airlift. You'd only have to turn off the air, lower the pipe to the new trial depth, and refill the two pipes and then turn the air back on for each depth....
yeah that would work...
we were wrong about it pulling water from the small pipe unless the water in the airlift pipe actually goes somewhere. The water pressure in bot pipe would remain the same...ahhhh? I think?

Based on the statement in red...
You would need to install a ball valve between the small reservoir pipe and the large airlift pipe, and close the ball valve after the large pipe stops blowing water out the top. Then you can stop the air and see how low the water level is in the large pipe compared to the trapped water in the small pipe.

Based on the statement in blue...
For all I know you may be correct. At first the water in the small pipe will try to enter the large pipe and push the air/water mixture out of the pipe, but since it can't go anywhere the pressures would equalize and bring the water level in the small pipe back to the starting point. Or maybe not??? HAHAHAHA You seem to have some free time available, so build a test rig and let us know what happens

6. BWG
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My guess the air diffuser creates a pressure point that exerts in all directions. The water in A raises slightly and the the air/water mix in B goes higher because the rising bubbles are displacing water.

Second prediction is the apparatus is of little value for testing airlifts. A test loop with resistance to simulate filtration would be more useful. Resistance that would force 3 to 4 inches differential between the water in and out of the airlift. Flow measuring on the water return.
Last edited by BWG; 1 Week Ago at 03:13 PM.

7. I am so ashamed for actually doing it ....

Oh I forgot to insert the pictures of the test rig...
Last edited by Zac Penn; 1 Week Ago at 01:18 PM.

8. Just to clarify my above comment about being ashamed...
The test did exactly what i expected to, so I am ashamed for doubting myself

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Zac,

It is easy to speculate, but it is another thing entirely to actually expend energy to test out an idea or prove a concept (as you have done here). You have nothing to be ashamed of. Thank you for going to the effort of demonstrating this effect for the benefit of those of us involved in this discussion.

Paul

10. I have no idea what the hell you guys are talking about when it comes to these airlift discussions, but I totally agree that it is a great idea to experiment with different theories . You never know unless you try...

11. well ****..OK OK OK? Now zac do this....will ya huh huh huh...... filll the airlift tube to the top. have the airstone submerged right below the surface, the clear tube will be just as full. Now turn on the air.... and see how much water is forced out the top, wait till the water level levels off drop it a couple of inches wait...drop it again...wait..drop it wait.....
It will give you an idea about the force generated by the air in the lift tube.... at some point the water will quit lowering in the clear tube..that would be the sweet spot...sorta. maybe..no wait? what?

12. and thanks

13. Originally Posted by lukef
well ****..OK OK OK? Now zac do this....will ya huh huh huh...... filll the airlift tube to the top. have the airstone submerged right below the surface, the clear tube will be just as full. Now turn on the air.... and see how much water is forced out the top, wait till the water level levels off drop it a couple of inches wait...drop it again...wait..drop it wait.....
It will give you an idea about the force generated by the air in the lift tube.... at some point the water will quit lowering in the clear tube..that would be the sweet spot...sorta. maybe..no wait? what?

That is very easy to do so I will play with it tomorrow. My guess is that the water in the clear tube will remain all the way at the top during this entire test, until the air flow is stopped. Then the water level in the riser tube will drop as well as the water level in the clear tube.

Now comes the fun part...
If I turned the air back on again without doing anything else the water level in the clear tube would remain the same, and the air/water mixture would rise BUT it would not go all the way to the top like it was before. The submergence will be different because the water level in the clear tube would have dropped.

At the beginning we had (pulling a number out of thin air) 36" of submergence in the clear tube, then when we turned off the air the water in the clear tube dropped to 30". Now we only have 30" submergence so the lifting capability of the airlift has been reduced for the second test.

Your test procedure would yield the same results as if I filled the riser tube to the top, dropped the air diffuser to the bottom and then turned on the air. When I turned off the air the water in the clear tube would end up being the same height as if I slowly dropped the air diffuser to the bottom and then turned off the air.

14. BWG
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The density of the water in B will change with air bubbles but the total weight of the air/water mix will not change (unless you have a way of weighing air). The level in A will only change from the pressure created from the air stone since the weight of the water mix in B remained constant. Looks like from the video the change in A was very slightly positive. Without water flow through the riser difficult to see value with the apparatus.
Last edited by BWG; 1 Week Ago at 08:51 PM.

15. Originally Posted by BWG
The density of the water in B will change with air bubbles but the total weight of the air/water mix will not change (unless you have a way of weighing air). The level in A will only change from the pressure created from the air stone since the weight of the water mix in B remained constant. Looks like from the video the change in A was very slightly positive. Without water flow through the riser difficult to see value with the apparatus.
I agree, not much value to this test that i can see so far. One thing that I need to point out with the video is that when i made the black marks on the tube and pipe, the test rig was empty. I then filled it with water and ran a test before shooting the video. After the initial test the water levels were slightly higher than the black marks because the air tubing and air diffuser had displaced water back into the pipe instead of being filled with water. That is what raised the water level above the mark.

16. BWG
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I think your old airlift setup would be better. Put a restriction on the measured return to produce 3 to 4 inches differential to simulate filtration resistance.

17. Originally Posted by Zac Penn
That is very easy to do so I will play with it tomorrow. My guess is that the water in the clear tube will remain all the way at the top during this entire test, until the air flow is stopped. Then the water level in the riser tube will drop as well as the water level in the clear tube.

Now comes the fun part...
If I turned the air back on again without doing anything else the water level in the clear tube would remain the same, and the air/water mixture would rise BUT it would not go all the way to the top like it was before. The submergence will be different because the water level in the clear tube would have dropped.

At the beginning we had (pulling a number out of thin air) 36" of submergence in the clear tube, then when we turned off the air the water in the clear tube dropped to 30". Now we only have 30" submergence so the lifting capability of the airlift has been reduced for the second test.

Your test procedure would yield the same results as if I filled the riser tube to the top, dropped the air diffuser to the bottom and then turned on the air. When I turned off the air the water in the clear tube would end up being the same height as if I slowly dropped the air diffuser to the bottom and then turned off the air.

UUUHHHHH, Can I go back and edit this so I am correct???

I spent 5 minutes testing this idea and sure enough I have a big old foot in my mouth about the water level in the clear tube. However, I was correct about the statement in red.

So here is what actually happened...
Filled the riser tube to the top which also filled the clear tube to the same level.
I turned on the air and slowly dropped the air stone into the riser tube.
Water slowly overflowed the riser tube and the water level in the clear tube started to drop as water overflowed the riser tube
(duh...That makes sense now because the clear tube is measuring the pressure of the water BELOW the air stone + the air water mixture above the air stone)
I lowered the air stone to the black mark on the air tubing and the water level in the clear tube settled, and the air/water mixture remained at the very top of the riser tube.

The final water level of the clear tube was about 1.25" higher than the test run, I made a video of yesterday, because the air/water mixture was higher than it was in that test. I marked that level on the clear tube, turned off the air pump and then filled the test rig back up to the top

I then turned the air pump back on, stepped back a few feet to keep dry, and then observed the new black mark on the clear tube. The riser tube overflowed until the mixture was settled at the top of the riser tube and the water level in the clear tube was at the same level as it was in the first test 5 minutes before.

So, I was wrong first but then redeemed myself by being correct on the second test.

Conclusion...
This test yielded exactly the same data as the test the day before. It only showed us the maximum lift capable given a specific submergence, air supply, air injector and riser tube combination.

18. Dang it Luke...I thought you had some kind of master plan that you needed testing before releasing more information to your loyal subjects? We can't let the conversation about airlifts die. I actually had a visitor to the warehouse this week that is interested in a 30K gallon pond powered by airlifts. If things go well, then we may have a fantastic airlift powered build in the near future. As long as the HOA approves the plans

19. I received a very interesting Private Message and I wanted to share what was said, but I assume this person wanted to remain anonymous so I will leave out their identity....

Thanks for the testing. I am a newbie and found airlift is an interesting subject and been reading those posts in Koiphen. I have some thought on your test set up and latest idea from Luke...

Based on what I have read, with certain air pump and pipe diameter, there will be a certain depth that gives you the most flow. In this test, The “most flow” will results in the MOST amount of water overflow (water lost). With your current set up, the pipe MAY NOT be long enough to find that “sweet” depth? That’s why your first and second tests gave you the same water level on the clear tube (1st test with the air stone at the bottom, 2nd test with air stone drop slowly)?

If you make the tube longer, as you slowly drop down the air stone (deeper than your current pipe allows), the water may overflow more. If that occurs, the water level on the clear tube will be lower (make sure you re-mark it when you use a longer tube so that you have the same distance from the top to the mark). At some point, the water will stop overflow, that is the “sweet” deep that you look for.

Now, hopefully your pipe is long enough.. To confirm the “sweet” deep, you do the next test

You know the deep of the “sweet” spot on the previous test, let say it’s X ft.
1) Refill water in the pipe
2) Lower the air stone more, let say 5 or 8 inches deeper than the “sweet” deep, X ft in the previous test. (The expectation here is that because air stone is deeper, the back pressure is higher and results in less efficiency, and the water on the clear tube will be higher.. Or in other word, the total water overflow is less)
3) Turn on the air pump.. I think if you can kink the air tube and release the air slowly to avoid the turbulence, that may give us a more accurate result..
4) Observe the results to see where the water level in the clear tube is.. If it’s higher, which mean we lost less water, which mean less “flow”..

I think this is what Luke mean in his latest suggestion.. One think that he may not have thought of was the tube was NOT long enough….

Well, hopefully I make some sense here...

Reading through that idea the first time I didn't think it would yield the same results as they hypothesized but the second read-through makes me tend to agree. However, the thing we don't know for sure is whether or not the depth that produces the most water overflow would actually yield us the most total water flow when placed into service. That depth or "sweet spot" as they referred to it, would certainly achieve the greatest lift possible, but I am not certain as to whether it would provide the most flow.

This is how I see the experiment going...
Using the same exact setup as the previous test, but using a 10' long pipe.
Using the same air stone and air pump setup you would fill the pipe completely to the top and slowly drop down the air stone.
Obviously the deeper you drop the air stone, the greater submergence you will achieve, thus creating a larger pressure differential between the clear tubing and the riser tube with the air water mixture.
However, the deeper the air stone is dropped the more back-pressure that is exerted on the air pump, so the total air flow begins to drop.
At an unknown water depth the increasing submergence depth and the reducing air flow ratio will come to a point in which the air being supplied is not enough for the deeper submergence.
At this point the riser tube will stop overflowing and the water in the clear tube will start to rise, even when the air stone is lowered to a deeper elevation. That is due to the water/air mixture starting to become more dense which will push more water back into the clear tube, that was previously in the riser tube.
Once you see the riser tube stop overflowing then you mark that elevation on the clear tubing and you have your "Sweet Spot."

What value would we gain from this experiment????
I personally think this experiment is more about finding the sweet spot of the AIR PUMP instead of the sweet spot of the airlift. If the air pump could continue to produce the same amount of air at lower and lower depths then the riser tube would never stop overflowing into infinity. However, since the air flow is reduced as the diffuser is lowered into the riser tube you can compare different air pump manufacturers and see which one has a greater efficiency at lower submergences.

Thoughts?

20. Well....Poop!!!!

That test doesn't work out very well. I tried it with a 10' long piece of 4" pipe and things were going good until we started to get around 6 feet of submergence and 13" or so of lift. The air/water mixture turned into a foamy froth and would continue to overflow with the froth even without lowering the air stone anymore. That was giving us false water levels in the clear tube so i had to abandon that method.

I then switch over to specific submergences with the air off and the riser tube completely full. I would then turn on the air pump and wait for the actual mixture to stop overflowing and the froth to start emerging. I was hoping that would yield clear results but even when i dropped the air stone to 9.5' feet (roughly 20 LPM of air from the Hakko 40L) the lifting height just kept going up. That means a 10' pipe was not long enough to get to the point of diminishing returns or the "sweet spot". I don't have the time or supplies on hand to make it any taller today so this was a bust. Lift at the final test was around 21" before the froth was an obvious factor, and obviously the water flow produced was a zero.

So does that mean that with a
Submergence of 9.5', zero lift height, 23 watts and 20 LPM of air supply to a single airlift,
would produce more total water flow than
Submergence of 4', zero lift height, 30 watts and 40 LPM split evenly between two identical airlifts?

I seriously doubt it but that is just a hunch based on previous experience and thinking about the friction losses inside the single 4" riser tube with a massive amount of water flow VS the friction inside two 4" riser tubes with only moderate water flow. Maybe if the pipe was larger diameter that wouldn't be an issue but then you would still need to proportion the air in a larger tube so general flow vs friction ratios should be similar.

Too much brain power is needed and I am lacking it right now

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