Air pump lift hieght calculation.

Stuart Chignell

I had a look at the tornado and its flow seemed a bit low at 1.4m of head.(plus friction loss which will be reduced by sweeps instead of elbows (thanks guys)). The pump I had been about to order is the Laguna 11000 which is producing around 9100L/hr at 1.5m.

Cant remember who it was but simply telling me a propeller pump would be a good idea dosn't help me very much. I have found an axial flow/ properller pump that I will buy at some stage for my next system but it is a little oversized at 18L/s @3m of head for my current system.

PS :bigsmurf:

include only because my wife wanted me to. Colured text also due to unfortunate female influence.

Outbackozzie

whats the umm...watts on the laguna?

mylesau

hygicell wrote:

this is the second personal attack I have to counter on this thread, while I have always stayed civil and still am.

Are you serious - personal attack - bit of a stretch!

I'm done doing this :banghead:

. Frank look back through this thread and see if you can identify where you provided any facts or figures relating to efficiency of airlift pumps, seriously I can't find any. I won't touch any of your other comments.

I spent some time today reviewing Reinemann's PhD theses along with a few others and related papers. The research certainly supports the previous quote.

A freely available paper that clearly shows 50 - 60% efficiencies with Airlift pumps (note that this papers purpose was not to finding the most efficient Airlift pump) - Performance of Air-Lift Pump

Probably a bit technical, but if you find the definition for np - efficiency of the actual pump - but note that nt is the overall efficiency - but is only different by the efficiency of the compressor (i.e. ~ same as considering the efficiency of a centrifuge pump at the drive shaft rather than at the electric motor [typically about 85% efficient]) - putting it simply its close to actual efficiency depending on the air compressor used...

The key figure is Figure 9 - note efficiency is not expressed as a percentage (i.e. 0 - 1 not 0 - 100).

I have seen more efficient graphs in other papers for various variables related to head/submergence/orifice size/shape etc............

Conclusive enough for me.

mylesau

Stuart, I reckon your on the right track with the Laguna - when I was selecting a pump it was between a Laguna, an Oase and the Jebao (Tornado - JPP). It really came down to price and Watts / lph for me. I'm working with a very low head so it worked out well for me to buy 2 or 3 little Jebao's to do the same job as the larger Laguna or Oase with the obvious advantage of backups. I only bought one of the Jebao's initially to see how it went - no issues yet and it pumps what's on the box and draws the stated wattage.

So I'd suggest a comparison of the Laguna, Oase and Jebao for the head and flow that you want...see which one is more efficient

that should give you your answer, but you will no doubt want to consider price as well - the Oase are more expensive, but have a 5 year warranty, Laguna mid price with 3 year warranty.

mylesau

Ahh, that should have been Fig 8 not Figure 9 as the key figure to look at..........

Sleepe

Myles

On of my reasons for disagreeing with efficiencies of airlift pumps is the compressor. With a submerged centrifugal or axial pump the pressure is equal on both sides ie inlet and outlet. Motor speed/torque and design of the impeller/propellor determine the efficiency. Watts remain constant (I accept there may be minor fluctuations).
A compressor being external has a pressure difference between the inlet and outlet. Inlet is at atmospheric outlet is at the depth of the water ie about 1.4 psi at 1 meter. Unlike water air is compressible and so on the compression stroke generates heat, this is an energy expenditure for our purpose being wasted. No matter what air pump is being used I do not think this can change.

hygicell

Quite the paper you mention, Miles: very impressive, thanks.

It leads me to offer you and others my sincere apologies:
I have mis phrased my statement:

Instead of 'airlift pumps are energy inefficient"
(That was indeed simplistic as I am now aware of)
it is a bit more complicated than that.

My statement should have read:

Quote:

"The combination of a blower and one or several airlift pumps for pumping fluids is a very complex matter.
To calculate the energy efficiency of such a setup one will have to take into account at least four different parts, which each are influencing the energy efficiency of the whole setup.
For this discussion we must take into account:
1. energy efficiency of the motor
2. energy efficiency of the blower
3. energy efficiency of the air pump(s) connected to this blower
4. piping and appendages friction losses

for the simplicity of this discussion, we will assume other unmentioned factors as negligible.
for further simplicity of this discussion, we will assume piping and appendages as well dimensioned and their friction losses as negligible.

rests the three main points:
1. energy efficiency of the electric motor
this is dependent on the criteria for which this motor was designed: Voltage, Amps, RPM, Torque, etc...
The right combination of these criteria in all best proportions can lead to a motor energy efficiency expectancy of maximum 85 % .
for the simplicity of this discussion, let's assume the efficiency of this motor to be 85%.
Staying well aware that there is only a very limited margin for deviating from each of these best criteria and that considerable efficiency losses are inevitably to be expected from any deviation would reduce this efficiency more realisticly to 65 % or much less.

2. energy efficiency of the blower
this is dependent on the criteria for which this blower was designed: Flow, Pressure, air temperature, moisture, etc...
The right combination of these criteria in all best proportions can lead to a blower energy efficiency expectancy of maximum 85 %.
for the simplicity of this discussion, let's assume the efficiency of this blower to be 85%
Being well aware that there is only a very limited margin for deviating from each of these best criteria and that considerable efficiency losses are inevitably to be expected would reduce this efficiency more realisticly to 65 % or much less.

3. energy efficiency of the airlift pump
is, (according to the paper provided by Miles) dependent on at least the following decisive criteria : Pipe diameter, pipe length, head, submergence ratio, required flow, required pressure, air injection method and bubble size. Other criteria could be air temperature and moisture, etc... (not limited to this list).
The right combination of these criteria in all best proportions can lead to an airlift pump energy efficiency expectancy of maximum 85 %.
for the simplicity of this discussion, let's assume the efficiency of this airlift pump to be 70% .
Being well aware that there is only a very limited margin for deviating from each of these best criteria and that considerable efficiency losses are inevitably to be expected.(more realisticly 35 % or less)

Conclusion: airlift pump setups could, in the best circumstances, lead to an energy efficiency of 85% * 85 % * 70 % = 51%
(A more realistic approach would make that: 65% * 65 % * 35 % = 15 %).

Even that would be assuming that it is possible for a layman (or even for an engineer) to perfectly adjust and coordinate motor choice, blower choice, number of airlift pumps in the circuit, pipe diameter, pipe length, head, submergence ratio, required flow, required pressure, air injection method and bubble size (all these for each airlift pump) for both optimal conditions and realistic approach.

I admit that this is a better phrasing of my statement
I also admit that this is a theoretical approach.

But so is the paper you mention, Miles
and this is explicitly acknowledged by the writers all through the paper, in the conclusions, in the discussion printed at the end of the paper and in the last sentence of the author's closure, the very last sentence of the paper:
(3) A test on the designed pump has not been done particularly.

As for not providing any facts or figures relating to efficiency of airlift pumps, I have not checked whether I have actually done so or not.
What I have done and stated is to check my theory on every single paper encountered on airlift pumps that allowed me to do so by providing the flow and the head of each pump together with the energy input.

Each and every one has confirmed my suspicions.

Unfortunately I have not kept track of these calculations. I never thought I would be challenged. I wrongly assumed that you would consider me as trustworthy.
As I consider you to be.

But I am ready to do them again for every possible paper that you might provide and put the results in an Excel sheet for future reference.

Friendly greetings

Frank

mylesau

Sleepe wrote:

On of my reasons for disagreeing with efficiencies of airlift pumps is the compressor. With a submerged centrifugal or axial pump the pressure is equal on both sides ie inlet and outlet. Motor speed/torque and design of the impeller/propellor determine the efficiency. Watts remain constant (I accept there may be minor fluctuations).
A compressor being external has a pressure difference between the inlet and outlet. Inlet is at atmospheric outlet is at the depth of the water ie about 1.4 psi at 1 meter. Unlike water air is compressible and so on the compression stroke generates heat, this is an energy expenditure for our purpose being wasted. No matter what air pump is being used I do not think this can change.

Not sure I see your point - if you use an electric motor to turn a centrifugal or axial pump some heat/noise is generated as well. So it simply comes down to the efficiency of the electric motor (could be something else) turning the centrifugal or axial pump and the air compressor (could be an electric motor and blower, diaphragm, axial piston, or other) pumping air at relatively low pressure.

I don't know much (anything) about the efficiencies of air compressors, but a quick google indicates at least a 50% energy efficiency for a typical air compressor - an airlift pump doesn't need anything like those pressures so I can only guess that the efficiency is well above 50%? Could be wrong though.

But even at 50%, if the airlift is running at 60% efficiency, that makes 30% efficiency over all - if we look at some of the previously listed efficiencies of the centrifugal pumps in use for AP (21%) (even though they are not being used for identical purposes), is it not conceivable that the airlift may be more efficient in certain applications? This is certainly what researchers working in the field with knowledge that far exceed mine suggest.

Side note, but I thought interesting, and not quite what I expected - stumbled across this link in my travels and thought it would be worth while looking at the efficiency of this monster propeller pump:

High-flow, low-head pumps provide safe passage for pacific salmon

I was very disappointed - %42 - 'after thousands of hours of CFD modelling and scale model testing, a new pump design was created'.

Sleepe

Get a a bike tire pump, stick a finger over the outlet (after pulling the handle back) now pump. Now imagine your muscles are the electric motor (get warm) end of the pump (gets warm).
Take a fan on the end of a rod, stick it in water and twist, what gets warm?

mylesau

Not convinced

I think its more like fitting a longer tube to the end of the bike pump and sticking it in the water and pumping - not nearly as much resistance as sticking your finger over the end and little heat would be generated provided you don't restrict the flow with small diameter tubing

But I do take your point - I have no clue what the difference in efficiencies are, but suggest at the low pressures used, they won't be worlds apart.

I can tell you that my air compressor runs a little warm (easily touched to sensitive skin), and my water pump is just noticably warm, but the air compressor is only air cooled, where the water pump is water cooled (though only through indirect contact via the casing)...air compressor is audible, but not loud, water pump is inaudible. And as I've said before, I achieved a better flow from 35 Watts input into the air compressor hooked up to the airlift pump than I did with 35 Watts into the electric motor driving the pump... Oh, and in case its of value, the air line I use is, I think, 10mm ID, standard air hose that is not noticably warm above the water line.

I'm hoping to try a large diameter airlift when I get a chance to see if the flow increases, and I'll try to revisit running two airlifts of the same air supply, as the research that I've read suggests that this will likely lead to improvements.

The number that I think is most relevant with airlift pumps is the air flow to water flow ratio. Many of the papers I've seen quote these numbers. Typically they range from about 1 to 2, but a paper I saw recently suggested that an airlift pump running at zero head height (i.e. at the surface), can achieve a value as low as 0.39. My best guess, not knowing for sure what my air compressor is delivering (50 - 70 lpm or less due to the depth) and the flow I'm getting, puts it close to 1 litre of air generating a flow of 1 litre of water. If I could improve this ratio down to 0.5, I'd be pumping somewhere in the region of 6,000 lph of water with only 35 Watts. I've yet to find a centrifugal pump that can come close to that...but they may very well exist?

DanDMan

hygicell wrote:

Browsing through their catalogue, I have found efficiencies varying from 40 to 80%.What is also shown is that if the motor is not used at it's designs best efficiency load, the motor efficiency drops down dramatically.

Just a note that I posted to the useful info section. These efficiencies can be corrected using capacitors. A blower motor for example can have its power draw cut by 60%! I was able to trim 15% of the amp draw off my well pump. Good stuff for what ever motor you use on what ever type of pump. Only works with AC motors though.

hygicell

Miles,
I like your perseverance
I really do

Airlift pumps could not have found a better defender :cheers:

It is good to question my statements
It can only shatter my conviction (in which case I will silently retire momentarily to a corner to shed some tears

)
Or consolidate it.

It is the inherent inefficiency of pumping gases that led me to believe that airlift pumps (oops, airlift pump setups)
even if well dimensioned (which the paper you have provided shows to be a real challenge)
must be less efficient than any other (well dimensioned) pumping system

The bike pump is a good example:
The pumping upstroke consists of two parts: a first part where you have to build up enough pressure to equalize the existing counter pressure
and a second part where you exceed the counter pressure.
Both are consuming energy.
you will concede that only the second part of the upstroke is efficient
Suppose you would limit yourself to the first part of the upstroke
Al the energy invested in the first part is wasted: you can pump for hours (days, years...) without a single bubble coming out of the pump
You are not sucking in any fresh air (or gas) on the backstroke, since the gas in the system will compress and expand with every up- and backstroke
you might argue that this costs very little energy, because the compression from the upstroke builds up potential energy and assists in the backstroke
That is true, but the friction of the pump has to be surmounted both on up and backstroke
and compressing air gives heat
that heat is lost to the ambient air
And you produce sound
and you produce wear
If you limit yourself to the first part all this energy is continually wasted
If you overcome the initial counter pressure, only that part is energy efficient (discounting the extra heat and sound losses)

hope this helps to understand

Frank

hygicell

Quote:

These efficiencies can be corrected using capacitors.

please explain
Would that also be valid for other pumps (i. piston, centrifugal...)

Frank

Chappo

This inneficiency can be reduced in any AC motor,,, basically on inductor ( coil) causes the sine waves of the current and voltage to get out of synconisation,, capacitors cause opposite movement of these waves ,, so get them back in sync.

Next .....

mylesau

Frank,

hygicell wrote:

Airlift pumps could not have found a better defender

This was not my aim, my aim was to prevent misinformation.

I've read scientific research that clearly proves your argument to be false. I am a scientist, and have confidence in science.

I'm not going to enter into a debate about the efficiencies of air compressors - without effort I have found suitable air compressors with efficiencies above 60%.

I feel that your argument has centered around using maximum efficiency figures for centrifugal pumps (in this I don't include propeller pumps - again just to be clear) which are not practical values at low head height and for the typical pumps that would be used in AP, and have attempted to compare these figures to lower efficiency figures of airlift pumps - this, in my opinion, is an unreasonable argument to make as the efficiency of airlift pumps tend to be higher at lower head height.

I believe you have misrepresented the research paper recently linked - your agument suggests that this paper is solely based on theoretical data - this is false - Fig. 2 shows the airlift pump used experimentally to obtain experimental data which is clearly shown in Fig 8 as small circles.

Frank, none of the above is meant as a personal attack, so please do not take it as such.

Postulate away, but I'm really not interested in arguing further - spend some money, purchase those airlift research papers, you'll then have more time to spend on AP. :wink:

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Air pump lift hieght calculation.

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