Can a siphon be used to generate more power than a conventional penstock?

Discussion in 'General Science & Technology' started by GoTesla, Oct 10, 2020.

  1. GoTesla Registered Member

    Messages:
    8
    How do I insert an image? Can it be done from my computer or does it have to be from an internet site?
     
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. exchemist Valued Senior Member

    Messages:
    9,862
    The formula for kinetic energy is mv²/2, yes.

    But kinetic energy, to the extent it gets involved in this problem, is just an intermediate form of energy between gravitational potential energy and electrical energy. I think it is a mistake to get into that, because you will end up doing lots of calculations about velocity of water under various scenarios, that have no bearing on the overall energy transfer.

    Fundamentally, the energy conversion is from gravitational potential, of the mass of water at the top, into electricity, as a result of the mechanical (F x d) work done by the mass of water as it falls. F is worked out from F=ma, a being in this case g, the acceleration due to gravity. So if the head is h, the work done is mgh. The power output is therefore mgh/t. m/t is the mass flow rate (kg/sec).

    You can have either a fat pipe in which the water moves slowly, or a thin pipe in which it moves quickly, but that does not matter. Even in a Pelton turbine, the pipe feeding it is full of relatively slow-moving water under pressure, which is only converted into kinetic energy at the last moment by a high pressure nozzle, just before it hits the turbine blades.

    You will have to explain what Viktor Schauberger's jet is. I've looked him up and see he is described as a pseudoscientist, so it may be that it does not do what he thought it did.

    Please Register or Log in to view the hidden image!

     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. exchemist Valued Senior Member

    Messages:
    9,862
    I think an image created in a document can be copied and pasted into a post, but I admit the diagrams I have done this with are ones I have found pre-drawn on the web somewhere.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. GoTesla Registered Member

    Messages:
    8
  8. exchemist Valued Senior Member

    Messages:
    9,862
    Haha, yes, a crank website.

    Actually, reading this, Herbrand did not do any work on Schauberger's invention. What he did was compare the electrical output of two conventional turbines and got what he thought were anomalous results.

    The person who wrote this seems to believe in something called "living" energy of flowing water, as if the kinetic energy of water in a river is not merely due to a reduction in its gravitational potential energy (GPE), which of course it is: the steeper the slope, the faster the current.

    There is also some nonsense about the temperature of water in a vortex falling, as if, to counter the obvious objection about kinetic energy being due to fall in GPE, this supposedly extra energy comes instead from conversion of heat into kinetic energy. This is just bogus, I'm afraid. With a gas, expansion causes temperature to drop (e.g. how a fridge works). But a liquid is practically incompressible so this sort of thing does not occur.

    There are signs of mathematical illiteracy, too. For instance, the writer seems to think the fact that kinetic energy increases with the square of velocity mean that there is an "exponential" increase. He or she needs to learn that x² =/= eˣ !

    Please Register or Log in to view the hidden image!



    The point is that the kinetic energy in flowing water comes from GPE, or else from some other energy input. There is no free lunch. So you cannot, as he foolishly imagines, simply increase the velocity as much as you like, and get more and more power out as a result.

    (By the way, I should in fairness tell you that when I saw your name had "Tesla" in it, I immediately expected some sort of crank physics would be involved. But at least this one is not about magnets, which is something.

    Please Register or Log in to view the hidden image!

    )
     
  9. GoTesla Registered Member

    Messages:
    8
    The site may be crank, but I wouldn’t knock Schauberger'swork, he clearly knew more about water and it’s attributes than most people alive in his lifetime. He proved the experts wrong on a number of occasions. One such occasionwas whenSchauberger approached the University of Stuttgart to investigate his invention Helicoid Pipes:

    https://issuu.com/egelygyorgy/docs/the-energy-evolution---viktor-schauberger/232

    Professor Popel of Stuttgart University didn’t even want to give him the time of day.

    He expressed the view that the crucial areas of technology were founded on the legitimacy of classical mechanics and hence the laws governing the flow of liquids and gases should also be dealt with from this point of view.

    He could therefore state at the outset that Schauberger’s desired investigation of such pipes, would achieve no useful results for technology.

    If you read through the document, there is table in there, if I read it correctly, shows friction in the copper Helicoid pipe dropping to zero at one point! How?

    Here are two further studies of his work from the University of Queensland in Australia.

    The first however seems to prove that his turbine design I suggested could be used, becomes unstable at high speed, yet Viktor did build and use it himself! Don’t understand, is the problem the University hit down to gyroscopic effect? https://espace.library.uq.edu.au/view/UQ:300139

    The second study however, 7 years later, came up with something different and had this to say:

    A field that warrants further research is the effect of boundary layers on rotating objects, as the centripetal effect of the body on the flow causes the boundary layer to drop in pressure as rotation rate increases, contrary to typical flat plate solutions.

    To be honest, I’m not sure what that means, but seems to suggest something is happening that wasn’t predicted! https://espace.library.uq.edu.au/view/UQ:347551

    Don't mention the magnets, I haven't got to them yet! LOL
     
  10. exchemist Valued Senior Member

    Messages:
    9,862
    I don't like the look of the first link you supplied. I'm not going there.

    But anyway, this thread was about a siphon in a hydroelectric power station and that has now been dealt with.

    If you want to start another, on one of Schauberger's inventions, you could always do that.
     

Share This Page