Nano Airlift Pump? How High Can it Pump?

There are large-scale instances of this same basic concept. If the proportion of injected air either 1) fills spaces between the water plugs/slugs, or 2) creates a foam such that the total weight of water in the up column is less than the head of "solid" water in the down column (or submerged depth), then water can be moved to a substantial height above the down column (or submerged depth).

This scheme is the basis of thermosiphon circulation, and has also been used for fish pumps. The higher you go, the less proportion of water must be maintained in the up column. I don't know if there is any absolute limit, but the "balancing act" gets more critical the higher you try to go.

Flooded refrigeration evaporators, vertical reboilers, etc., operate on this principle. There is (or was) a "Cricket" solar heating system that was somewhat like this. I think the main trick is to ensure that the upgoing column constantly maintains air spaces between the water plugs/slugs, or enough air bubbles in the rising foam, to keep the water from coalescing and falling back down. In the video, the small tubing helps to maintain the proportion of air spaces to water plugs/slugs. The water flow, being intermittent, is relatively small.

A coffee percolator (remember those?) is the same sort of deal.

(What was that "didgeridoo" pipe with the occasional holes in the side?)

Thanks Tornado,

I forgot to put a link in my first post. It is to a site that describes the different flow patterns in pipes. It had short paragraph descriptions, pictures, charts, math and little videos that you can click on that help explain what is going one.

http://www.thermopedia.com/toc/chapt_g/GAS-LIQUID_FLOW.html

Anyway, I know research of these types of flows is ongoing. And there are still some areas that are not fully understood. Perhaps nobody bothers to research airlift in tiny tubes? Certainly there are no easily readable figures available! For me, figures for the pumping rates in plain English would be very useful.

I imagine that all sorts of things will change the rate. Even some soap would change the rate of pumping! I made a pump a few months ago. It had a little t joint, a coil of tubing above the t-joint and sugary water with yeast in it was producing CO2 that was driving the pumping (plug flow). It was doing great until a little yeast bubbled over into the water being pumped. Then there was no plug flow anymore! And nothing pumped.

I am not capable of doing the math for the nano airlift pump. And I don't know how to program a calculator to do it. Anyone want to use the formula from the link to see how high the 1/4 inch tube can pump water (in theory) under the conditions I laid out? Just ball park figures. (While we await practical results).

Thanks

Brian

I know some people in the windowfarms project are playing with the nano pump idea too but sometimes it is months before things happen.

In the picture the relation ship of "24" max" and "how many feet" is a density ratio of the columns.

So the higher you want to lift, either have more air in the rising column (less water) or more than 24".

This "more than 24" is because the aerated section below static head (water level in the bottle) adds to lift by the water pressure in the fall line.

Or actually - it's not that complicated math.

Also why the 'convention' is to look for 'deep submersion' of the aeration point.

However - you can best this 'design' by changing that 'T' connection to be like a venturi arrangement. not because of 'additional 'thrust', but; a) so the bubble can fully fill the tube earlier - as opposed to turning the corner, then 'streaming' before it properly expands. b) so the air momentum is not 'competing' with the static head.

I.e. swap the water and air lines in the diagram

As for 'additives' - the last thing you want is a 'wetting agent' - as this effects 'meniscus effect' which is what helps keep the 'slug' from leaking past the bubble

Ideally you want to set a consistent ratio of bubble to length of slug.

So most of your thought should be toward how to best 'design the T' as a controlled injector.

Using 34point5's dimensions, the air blower's output pressure needs to exceed 24" water column. The required air flow (cfm) will depend on how much water is to be moved, the air/water ratio (which correlates to the ratio of column heights), and the pipe size(s).

In the model I made the pressure enough to push air 1 meter down under water.

This is typical of the type of aquarium air bubble pump that I have. The idea of the model was to get lots of people involved especially those in windowfarms (who use aquarium pumps all the time for airlift).

The problem is that the shift from plug flow to bubble flow to wispy annular completely changes the volumes of water moved per volume of air injected. (You cannot simply use brute force and maintain the same efficiency). For instance, you can sometimes reduce the air input and have more water pumped. (because of a change from churn flow to plug flow).

I am sorry that I offended people by calling it a "design". It was just to keep people doing the experiment on a similar track.

Anyway that is the deal. How high can you pump using those guidelines?

Enough air pressure to push air 1 meter under water and 2 ft of submergence. (use a venturi if you like) and using 1/4 inch tubing or 3/16 inch tubing for the long airlift pipe? We know it is more than 13 ft. How much more? I had about 1.4 liters per minute of air flow but I guess that depends on your bubbler.

Thanks, Brian

The powers that be at work probably would not let me set up some experiments, but I have an air-bubbler (champagne) fish thawing system with a blower good for 30" or so water column and 60 cfm, and oodles of water. With two valves, two flow meters, and a selection of pipe sizes, one could find out quite a bit.

If you are reading my apostrophes enclosing 'design' as me being offended - don't. I'm not at all.

Actually I think it's quite interesting - otherwise I wouldn't have posted.

Or be trying to explain how you can get the best lift.

That said; in the 'slug' video in your 2nd link - the small bubbles are 'air waste' in lift terms. They may reduce density in the column, but you would be better off having 'clean slugs' and that waste air in the lifting bubble.

My reasoning is height is going to be a function of leakage past the bubble.

Meaning a tube diameter of about two meniscus is potentially the best 'non-leakage'.

Though I've never measured it, or sat down and worked it out, I have observed that in about a 1/8" or 3.5 mm bore tube, any water will self bead into slugs - and is usually quite determined to remain so.

It may be well worth your while to explore this. You're going to need multiple tubes to get meaningful volume at the 'end application' anyway, so why not solve the height question then see how many your pump can run?

I just now looked at the http://www.thermopedia.com/toc/chapt_g/GAS-LIQUID_FLOW.html link. That would take a while to digest, but it looks as though it more than covers the experiments suggested in my earlier Post 6.

Agreed, as I have throughout with your comments.

So calling that 'well covered'

Were I going to 'enter the competition', which I'm not:

If - as I suspect - there is enough capillary attraction/meniscus 'strength' to suspend a small slug against gravity in a 3.5 mm tube - "how high" comes down to 'how long is the bubble'. Meaning 100's of feet would be possible.

Say the 3.5 mm bore holds the meniscus, then slug frequency is going to be determined by how small the slugs can be - (given the slugs have to add up to 24" of head, or the system will 'blow back")

Line loss will no doubt subtract from this 'max head' - as demonstrated - when the rig was slowed down, delivery was less effected [proportionally]

So what is wanted is a bubble of a determined length, injected (cleanly) at a frequency that sets desired slug length.

This 'switching' approach would naturally suit an air activated 'flip-flop', in the dual tube scenario, or a rotary valve in the multi-tube scenario.

Both could also meter the water (set slug length)

However the mass-flow is still going to be delivered Watts of pump into the standard formula for hydro/pumping [less losses].

Given the efficiency of compressing air is not great, and far less in those pumps - a small d.c. gear pump might be a better option if the power source is PV.

But, as conceived, it would quite suit 'bellows'.

Which can of course be done primitively via direct solar.

I tried something close to 3.5 mm tubing for my first attempt. It was sillicon rubber and it was a failurel. Silicon rubber is hydrophobic but the plugs seemed to "cling" to the insides of the pipe and it did not pump well at all. Extremly slow movement of plugs.

Even when I took the pump away and just let the water run down to the bottom, it was slow! So I think even the material that the tubing is made of matters. Maybe 3.5 mm pipe made of a different substance would work great?

Anyway thanks for discussing this.

It is curious that nobody knows the answer. Is guesswork acceptable?

I cannot think of a location where I would be allowed to try it. I thought that by now someone living in a high rise might have tried.

Anyways, maybe tomorrow or in a week or a month, someones curiosity will get the better of them.

Bye,

Brian.

Ok, "Bye" to you too Brian - & good luck

We all know the quotation marks were sarchasm right from the start, "right?".

"(I guess you read the venturi stuff somewhere?)".

I did not expect "curiosity" from you anyway. You don't have a "clue" what the answer is.

And you couldn't care less.

"Good for you" Thanks for your "input".

I'm not sure why you are so resentful of finding the right answer, and so determined to read in that which is not there - but rest assured, that is not my OT vote.

When you said Bye, I said Good Luck, that's what I meant.

With the same 24 inch submergence, a guy on instructables got 16 ft high.

I moved recently and took the roof off a shed and it gave me the chance to do the experiment again and "beat" the 16 ft height. I got 18 ft (because It is important to leave room for others the beat the result). There is some interest at http://our.windowfarms.org/ and people have use the results of the experiment to easily circulate water in 10 ft windows for their "windowfarms". The 18 ft experiment showed that my earlier rejection of the thin blue airline tubing might be in error. I initially had big problems getting water to run through new tubing for the 18 ft experiment too. New tubing seems to have some sort of coating that is strongly hydrophobic. So plugs of water will not flow back down the tube. Without flowback, the tube can get blocked with more height of water than the 24 inches pressure can push. It just sits there with nothing happening! I have always used old tubing before (flowback was never an issue) so it came as quite a surprise. (There might now be an advisory in windowfarms to clean or muddy up your new tubing before you use it). Some windowfarmers have converted from the original "needle valve" set up to T-Joint and for many the conversion has been successful.

I think that the experiment might mean that a kid with 20 dollars worth of tubing and a bellows might be able to pump water from a 20 ft deep borehole well to survive in drought conditions. Maybe even from a 40 ft deep borehole if more experiments are done.

http://www.youtube.com/watch?v=6_88_xUd5Zs

Brian