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Thread: Simple Airlift Pump Equations??

  1. #1
    Associate Engineer
    Join Date
    Mar 2017

    Bang Head Simple Airlift Pump Equations??

    Hi all,

    I am on a mechanical engineering foundation degree course, and have been tasked to give a 30 min presentation on air lift pumps.

    Now we are only on our second week of hydraulics, so the various papers I have come across online are way over the top of my head.

    My instructor/lecturer has promised there are some simplified 'rule of thumb' type equations or guideline out there but I haven't been able to find anything.

    My question is, can anyone provide any stripped back equations that don't go too deep into the theory, like a basic comparison between eduction pipe depth, air pressure induced, flow rate etc.

    Many thanks in advance, any help for the newbie greatly appreciated!

  2. #2
    Principle Engineer
    Join Date
    May 2015
    Consider the air bubble/water as a mixture and calculate the density for said mixture. Your mixture is less dense than water so it will want to rise. If it was a piece of wood as long as your pipe, how high would the end be above the surface for an equivalent average density?

    At a lower height your pump will flow.

    Air density will change with depth so pick an average depth for the pipe.

    Know the flow rate of air at discharge? The volume of the pipe? How high the lift?
    Calculate how much volume in the pipe is taken up by the air and assume the rest is water. If you can find an efficiency rating for this kind of pump you could multiply that in for improved accuracy.

    Put up Mr. Bernoulli’s equation and point out the rho x g x height part as being the thing you are emphasizing.

    Another part of the Bernoulli equation will equate flow volume to pressure but this might not amount to much in a pump open to atmosphere. But at least mention it once in your presentation.

    Not near 30 minutes worth but if you can rig up something operated by a tire pump you might be able to wear out the Instructor in about the same time it takes to explain what is here.

    Also, since the rules of the forum indicate that you shouldn’t post homework, if this helps, you owe us all a beer.

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