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Archimedes pump

  1. Sep 26, 2014 #1
    Hello;

    I have been toying with the idea of creating an Archimedes pump using PVC and 6 inch drainage pipe. The idea is that by using tubing coiled around a PVC core, and rotating it using torque on PVC collars, as long as the pump is angled correctly, and friction is sufficiently low (the collars would ride on stainless-steel rollers), the physics of the matter would point to a kind of anti-gravity effect; where the water is moved upward by continually changing the inclined plane upon which it rests.

    The inertia of the water at rest gives way as the cavity holding it lowers, yet the water moves upward through the spiraling effect!

    There's no water loss as the water is held in a tube, and not between a screw and a channel, as in typical materials-handling and sewage-moving Archimedes pumps; the big boys of the pump business. These are usually open on the top, anyway, and so not really pumps in the strictest sense of the word, but really augers.

    I want to pit a tubular Archimedes pump against a typical pressure-head pump. Of course, to get readings that would show the Archimedes pump to be an energy-efficiency winner (of course, there's still the matter of capacity to consider, since the pump can only spin so fast without the water adhering to the sides of the pump through centrifugal force), I would need a long enough run to put the pressure pump at a disadvantage through having to lift the entire column of water with each gallon inputted.

    Am I wasting my time? Please tell me if my anti-gravity statement is the result of a mirage, or something in physics that I cannot see?
     
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  3. Sep 26, 2014 #2

    phinds

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    I'm not following you but if you are talking about something that basically gives free energy, then it is a Perpetual Motion Machine and is banned on this site.
     
  4. Sep 26, 2014 #3

    Q_Goest

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    I think you're just referring to a conventional pump like this one:

    archimedes_screw.gif

    As opposed to the Archamedes screw concept:

    Archimedes_screw.JPG
     
  5. Sep 28, 2014 #4
    Is that really you, sitting on the edge of a cliff? Wow!

    Yes, the picture of the conventional pump is correct. If no pressure is applied to the crank, and water can flow in at the top, it will turn like an engine.

    I'm not talking perpetual motion; just conservation of energy. My idea is for something that can be run by solar power, and just runs and runs, all day every day, in sunshine-belt areas. It lifts water thirty or forty feet to a retention basin, and then the water may be used to irrigate terrace gardens, or pressurized by filling a standpipe, or let back into the pump at night to drive a pump at a lower level, or some-such work.

    The difference is materials; we now have the materials for making such a pump in sufficient quantities and cheap enough to make the idea feasible. Gas (or diesel), and new pressure pumps are very expensive, and expensive to maintain, while they will require the plastic used to make the Archimedes screw pump, anyway, to distribute the water. As for the nomenclature, I think you will find both pumps are called "Archimedes" pumps and work on the same principle, but that shouldn't get in the way of my proposal.
     
  6. Sep 28, 2014 #5

    Q_Goest

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    I got the picture off the net. I think it's somewhere on the Appalachian Trail but not sure.

    I guess I'm still not following you. There are water pumps driven by solar power. Pumps can even be driven by flowing water. The energy available from water flowing from one height to another is dictated by Bernoulli's equation. The amount of energy required to raise water from one level (A) to another (B) is equal to the amount of energy gained from lowering the same amount of water between those two levels. But there's always some frictional forces that also have to be overcome so the amount of energy put in to raise water from A to B is always slightly greater than the energy that can be extracted from lowering the same amount of water the same height.

    Perhaps your question is whether or not one of the Archimedes screw type pumps is more efficient than something like a centrifugal pump. That I don't know. A centrifugal pump can be very efficient. There's a huge variety of pump types on the market and the Archimedes screw types are also found in industry, so clearly there's an application for them. What you'll find is that various pump designs lend themselves to certain applications. For example, reciprocating machines often find a niche in applications that require very high pressure but at relatively low flow. Those machines can have a very high efficiency but they are typically more expensive than a multi-stage centrifugal type. An Archimedes screw might be more competitive with centrifugal machines for very low pressure applications. The type of pump is dictated by the economics of capital cost, energy cost and maintenance cost.
     
  7. Sep 29, 2014 #6
    If you look at the center of gravity for each pocket of captured water, you will find that it is off center from the shaft. The eccentricity will cause a torque to the shaft that must be overcome just to hold the pipe screw stationary. As soon as you turn the crank to raise the pockets of water, you exert increased torque on the shaft. Now with the water moving upward, you are performing work which requires an energy supply to perform it. Since the water is in a tube, it will have a friction component to it as it slides along, thus increasing your energy requirement. So ultimately, you don't have the situation you thought you would in your problem statement.
     
  8. Sep 29, 2014 #7
    Thank you both! This is great thinking; much better than what I could find on an Engineers' forum under Ag Engineering. Oh, well; the best minds will be taken by the hardest subjects, and really I only just started Math for Math Majors and Engineers before quitting college. I almost side-swiped my my math professor's car with my pickup truck, and that was a shakeup, as well.

    The computer has made me more confident, but in my day there was no Windows, and the paper printout was expensive and slow. Just a few results were printed for every three feet of paper used, so "results paper" filled big boxes. IBM main frames were the only machines that compared with a typical desktop or laptop on the market, today, and that's what we were given to work with.

    "The eccentricity will cause a torque to the shaft that must be overcome just to hold the pipe screw stationary."

    That about says it; I knew it would run the machine in reverse, but didn't think of it as an energy requirement, as well. I guess I'd better turn elsewhere for my contribution to irrigation, though the fact that an Archimedes pump will pump water at minimal speeds and therefore minimal energy input, means that it could be used in situations where energy is limited to non-internal combustion engines, like windmills at low wind speeds and solar energy during the winter months. Coupled with drip-irrigation, it still might be a great alternative in dry, rugged, mountainous areas where water may be captured from distant winter snow-pack melt and mountain thunderstorms.

    Just starting grape vines or olive trees on a mountain side using drip irrigation opens up a potentially huge source of revenue, even in North America. Geez! Wine sells for you-know-what a bottle, and olives produce the healthiest vegetable oil on the planet. Both, once established, reach deep in the ground for water, the length of a grape vine's roots being proportional to its climbing ability. Olives are extremely drought resistant, and originally grew in dry and hot mountains, the Atlas mountains. If you could cheaply "walk" the water up the mountain side in steps consisting of Archimedes pumps coupled with solar panels, for even just a few hundred feet, you might have the makings of a very profitable crop. "Religious agriculturalists," that is, farmers who will do anything as long as profitable farming is the end product, will see the sense I am making and invest.

    Even disregarding the friction component, and water may be compared with some of the lighter oils in both its cohesiveness and lubricating qualities (correct me if I'm wrong), I must find a way that is dirt cheap to make my test; and emphasize slow speeds, low energy costs and the use of alternative, "no petro" sources of energy as the selling points of a successful demonstration.

    Sounds like something for a younger man with land and time to spare.

    Thank you both for answering.
     
  9. Oct 3, 2014 #8

    rbelli1

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    You could also put a crank on top and you will be able to operate it in a "no power" situation too.

    BoB
     
  10. Oct 3, 2014 #9
    Yes, and that would give the operator great arm strength. However, I was really looking at a way to frame the Archimedes pump so that a big wheel, like a bicycle wheel or bigger, could be placed around it at about five feet above the ground, and this would be turned by a belt coming off of a very small pulley.

    The pulley would turn a hundred times or so for each time the big wheel turned, and thus an electric motor could be used to turn the Archimedes pump even if it was twenty-five feet long. The motor would be powered by solar cells. The idea must be "costed out." Then, the setup must be compared with a typical gas-powered pressure-pump.

    People always think of Archimedes pumps as screws laying inside channels, and that setup is not very efficient where pumping water is concerned, but a tube wound around a PVC core is one-hundred percent efficient less the friction of the assembly where it turns on it's bed of rollers. The technology to make a tubular pump cheaply is new, but now is abundant and found everywhere. That is the black plastic corrugated drain pipe found in almost every Home Depot, or similar store. This can be wound around a semi-rigid PVC pipe, and the result supported by a frame made of dimensional lumber. The cost is probably about the same as a pump and gas motor, but the savings may be very great in the long run. Lifting water is a lot of work, no matter how you look at it. Water is heavy, 8.3 pounds per gallon. If you can reduce the cost of this essential work by half, or even a third, you're looking at tens of thousands of dollars savings per crop acre each year in arid areas.

    Thanks for the input,

    Jagtig
     
  11. Oct 9, 2014 #10
    Hello, again;

    I thought some more, and figured that the amount of water on the low side of the central axis could be very small, given that pump is made from round tubing and the bend, or curve, of the tubing is symmetrical around a rigid round part, or the PVC central pipe. I don't see where distorting a round makes it any less "centerable," or centered, relative to a rigid core.

    That might mean that the amount of energy needed to hold it at rest or lift the water in a tubular Archimedes pump is commensurately small. Therefore, the greatest part of the energy applied to the pump is to overcome friction between pump barrel and the frame that holds it at the angle it operates at and to keep changing the angle at which the water rests, causing it to spill to a higher level through being redirected by the shape of the tubular container of the pump.

    However, whatever the case, the energy needed to hold the pump at rest, overcome this force, or produced by the pump when it is rotating in reverse, is only as great as the sum of the weight of the water off, or below, axis, in every chamber formed by the spiral of tubing. At 8.35 pounds per gallon, that would be a few hundred pounds over a practical length, such as of fifty feet. That's a considerable weight, but I don't think it exists, because if it did we would have heard about it by now, possibly in connection with the pumps used in sewage treatment plants, and other places where pistons and gears just don't work. Now, these materials-movers and sewage-treatment plant pumps are big, big machines, and such a force would be considerable, to say the least.

    Now, if the symmetry of the design is such that there is no such imbalance, then we must assume that pump is turning in reverse because it has been started in that direction and the net inertia of all the water in all the chambers flowing in the direction opposite to which the pump is turning is the motor, or driving, factor, while the lowest chamber releases the water in a propulsive, or jet-like, way, from greater to lower pressure. As the pump fills from the top, the process is continued; but fluid inertia, not weight is the driving factor.

    Fun thinking with you.
     
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