Airlift Pump, 4.5 Inches Submergence Pumping to 66 Inches. Why is it Working?

If the fraction of liquid in the upbound froth weighs less than the 100% liquid in an equal area of submergence conditions, then it works. In this example, (4.5/66) x 100 ≈ 6.8%

But it usually does not work. Usually, this amount of submergence would bring the water to 3 to 4 ft (if that) and then the water just gurgles, slips down the sides of the tube, reforms a plug, goes up a bit gurgles, repeats and waste the energy. (in that case, no new water enters the airlift and even though the air passes through, the thing is effectively blocked as a water pump). I have always recommended 12 to 18 inches of submergence to the windowfarmers. This morning it was down to 3 inches submergence and still getting up there. (I am not planning to use this for anything just surprised that it can happen at all). Maybe the sip people could use it. They leave standing water at the bottom of their plants in big pots to rot the roots. Just kidding. That's just my opinion. With this they could start seeds in the same pots because there can be moist soil up top too. Leave it on 15 minutes a day and at 2ft pumping height, it would be pumping lots more water and certainly enough to keep seeds moist in a big pot.

What are you using to supply the air?

It sounds like a small aquarium air pump (bubbler). If this is correct, can you provide the electrical rating of the air pump (volts,amps,watts)?

Thanks

It is 3.5 watts 120 volts. I don't know how much air it supplies. Typically with the small ones, I think it is 1 to 4 litres per minute at 1 to 3 psi (Depending on the model). In this case, it reliably supplies 2 little airlifters that are over 100 ft away from the pump. Probably now, they need to be on once a week and in summer perhaps 3 or 4 times a day. It is on a timer. (With 8 to 15 inches submergence it pumps plenty of water).

I usually don't measure everything because it is participatory. (I want other people to join in and try it). Long term, it would be nice if it works off tiny compressors working from wind or water power or solar panels. I have found really cheap irrigation tubing that could carry the air. Theory is that if the system is cheap enough, you can use it in out of the way places and it is not worth stealing.

It is the one foot of coiled tube that stops the blowback. For the air to back flow it must push that foot of water out, thus raising the level in the bucket, with only an inch of tube, the amount is negligible. It doesn't matter if the tube is coiled or straight.

The main thing though, is the size of the bubbles relative to the tube diameter, if they are big enough, the water cannot fall around the bubble. Using an airstone inside a one inch diameter riser (under gravel filter) barely raises the level, it works because the top is below the water level,

Yeah, I agree about the tube at the bottom. And once the water starts moving forward, even though it is moving extremely slow at this height, it has momentum to keep a supply of water into the airlift. But size of bubbles related to the size of tubing is more complex because water flows down the sides of the tubes, through the air bubbles all the time. For me, one interesting thing is that some of the energy goes to the water that is being pumped up the tube but some of the energy is sent to the other side of the air inlet (and converted to forward momentum) in that 1 ft of tubing. Maybe if it was 4 ft, there would be more energy sent to that side and it would (eventually) go faster? But there would be an awful lot of friction loss in 4 ft of thin tubing. Perhaps if it was 3 ft of wider tubing away from the airlift and the last ft skinny tubing, it would store up more momentum? Don't know, still don't understand it. I added a longer length of airline tubing last night and submergence went to under 3 inches. (Pumping to about 67 inches high) . It is all a bit of a surprise to me.

Welcome to the forum Joanna, and interesting to hear of your experience with your little ones. I am not sure how it relates to Airlift pump. Could you explain further, or did you post in the wrong place? Regards

cnc Jim

You didn't say what the diameter of the air lift pipe is but I suspect that it is small enough that when you get the water up to the top it fills the pipe and if that pipe then runs down hill it will draw a vacuum against the vertical pipe and help pull the water up.

Nope, it pumped to 67 inches vertically with no downhill section. No vacuum involved either. I haven't even set things up well. I never got that lift over submergence ratio before. (Over 20 to 1). There is no point being a sleuth and figuring out what I did "wrong" without watching the video. I did something right but I just don't know what. 3 inches submergence simply should not work to that height. But it did for a couple of days. Sometimes it is hard to get 8 inches submergence to work to that height! But 3 inches wasn't just working, it was working very well. Need to find out why.

1↑. There is also the possibility of "slugs" of air carrying a film of water upward.

Yes that seems to be the case. I changed around the tubing today and I CANNOT get that "film" condition back! Maybe it requires a certain exact surface tension? Today even 8 or 9 inches submergence was proving iffy! Also, tubing, seems like 1/4 inch or 3/16 are close to the "perfect" size for this effect. However in cross sectional area 3/16 is just over half of 1/4 so there is probably room for testing another tubing size in between ( if it exists). I

I don't need that super low submergence for what I do but I get easily sidetracked. It is quite the puzzle! I looked at the airlift for maybe an hour today and even though it looks like a simple process a host of things are going on. For instance the water speed going up the tube. It isn't constant. When it speeds up, the slugs lose lots of water to the sidewalls. When it slows down, water gets pushed out of the tube back into the bucket. (wasting energy). One thing to improve it is to even out that speed.

If someone can figure out what caused the "perfect film or slug" at low submergence and how to replicate it, it is probably really useful to someone. Brian

I think you are mostly right. It needs a clean setup now. In a shed where I can vary everything and measure the changes. I think the inertia of the entry water once it gets moving in the small diameter small entry tube is critical too. In the broader sense, I guess this does not matter, it is just a problem that bugs me. Thanks for taking the time to look at it.

Brian

Anyway, I formalized the method somewhat and it is now working for some people in Denmark, France and the USA in the windowfarms community. (And working really well too). Which is not bad for 4 months after noticing the effect! Here is a windowfarms thread where it is confirmed and approved. http://our.windowfarms.org/2013/05/24/the-nuts-and-bolts/ There is also another person who has adapted my pallet garden method (which uses this airlift pump) to her design. Barbara Tien in California. I am now using a 4.5 watt bubble pump and it supplies a little fish pond and 9 of these things (all at the same time) 8 run pallet gardens and 1 is testing a "water wheel" feature that I am testing for my wife's pond. I havn't got the water wheel quite right yet but it has been turning for about 3 days now. Brian