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Accelerated magnetic particles through pipe

  1. Oct 9, 2012 #1
    Well I was sitting and thinking and please confirm or dispute my claims.
    Let's imagine we have a copper or whatever material pipe lets say a plastic pipe with copper wire windings around it , through that pipe we blow let's say steam from a heat source that heats water to steam.
    Now is it possible to have some sort of microscopic magnetically charged particles added to the water so when it turns to steam it would blow through the pipe with high speed carrying all the tiny magnetic pieces with it and they would induce EM field in the windings which in turn would read as voltage from the ends of the windings.
    Would this work and it if would how efficient (approximately) would it be , Could it be more efficient than putting that steam into a turbine that would instead turn a generator that would get the same voltage... ? As much as I have heard that the (water-steam-turbine-generator) cycle has only about 30% of efficiency.

    Thanks.
     
  2. jcsd
  3. Oct 9, 2012 #2
    Well, first of all, there is no such thing as "magnetic charge;" anything magnetic always comes as a dipole: equal parts N and S.

    However, your question would make sense if the particles were electrically charged. If we had a gas of charged particles being blown through a solenoid, then yes, a current would be induced in the solenoid (provided the gas is not overall neutral--a current would only flow if there were more of one charge in the gas than the other). However in normal circumstances, it's very hard to create a charged gas, maintain it in the ionized state, and confine it to a small area like a pipe, since like charges repel eachother. So there really aren't any generators which use an effect like this.

    However, you might be interested to know that there are devices which work in reverse: instead of generating electrical energy by harnessing a flowing gas of charged particles, some devices use electrical energy to ionize and then accelerate the gas. One example was the old the Ionic Breeze brand of air purifiers (however the new ones actually do have fans). They didn't have fans and instead used precisely that kind of electromechanical effect to generate wind. (Air purifiers with fans have been found to be more effective at purifying air, so the fanless designs are more rare now.) A brand of air purifiers that still uses a fanless design is LightAir.
     
    Last edited: Oct 9, 2012
  4. Oct 9, 2012 #3
    Sounds like a reverse MHD. I actually made one of those (MHD) and tested it in artificial ocean water. It worked, but very inefficient, and what a stink. Japanese company made a boat like that too, 1200 HP and 15 Knots, chuckle.
    Check out "The Hunt for Red October." (movie)

    DC
     
    Last edited: Oct 9, 2012
  5. Oct 10, 2012 #4
    Ok I had some wrong words like the magnetic charge I just misspoken that one, but the main idea was something like this, if you would have a let's say plastic pipe with copper windings around it precisely wound and you would throw a let's say 5cm diameter magnet through that pipe the magnet going through the pipe would induce EM in the windings and hence electricity at the ends of the windings so far so right I guess?
    And if that is true then I thought that why wouldn't the same rule apply for a stream of much much smaller stream of little magnets like magnetic dust of some ferromagnet or whatever.
    The only problem I guess would be that the tiny little pieces while flowing would stick together with time and for something similar to a ball and the other fact is that you can't have any iron or metal parts in the system or they would stick to the walls?

    Ok please give some insight into what I just said.
    Thanks, have a nice day.

    And yes I have seen The Hunt for Red October.
    I live in the part of world which was once a part of the soviet union so I get to see some military stuff like nuclear missile launch silos and bunkers left over from that time, pretty interesting to visit such places.
     
  6. Oct 10, 2012 #5
    You can perfectly let vapour push a magnet directly and this will create some electrical power in the coil, sure. You will even get a very acceptable efficiency.

    It is not done because splitting the functions into a turbine and a generator is more efficient, and because parts rotating indefinitely are more convenient than single shots.

    Now, if you compare the magnet in pipe pushed by vapour with a turbine plus generator, the difference isn't huge! You have a shaft between the blade and the magnet...

    But this separation permits many refinements:
    - The magnet is cool
    - The coils see permanently many alternating magnets. COMPACT!
    - The turbine can have many stages, so vapour stays slow and loses little energy in sonic bangs
    - You can re-heat the vapour meanwhile
    - You can optimize both speeds at vapour and magnet to some factor

    So while a true magnet in a true coil is a decent converter, as opposed to MHD which is not, it is less good engineering than a turbine plus generator.

    Thermal power plants have an efficiency limited by Carnot's theorem (or by the second law of thermo). The limit is linked stiffly by the temperatures of the hot vapour and the condensed water; as a physical limit, it won't improve by engineering details. In fact, existing power plants a rather close to this limit, especially because big, immobile plants have heat exchangers to pre-heat the water and steam, and possibly to power a second thermal cycle (gas turbine followed by steam turbine).

    An other general notion in engineering: a single part should not be given several functions, because concentrating too many design constraints on one part makes it bad for everything.
     
  7. Oct 10, 2012 #6
    CM
    Actually your question was stated quite clearly in your first post.

    Specifically to your idea, all the small magnetic particles, if you could keep them separated, would, because of each having two poles, cancel out any usable magnetic field and no electrical current would be generated. (Jolb said it already above, in short form.)

    One other thing to keep in mind is that the generator in a power plant is very efficient, it is the turbine that is driving it, being a heat machine, that is the weak element.

    Also consider all the drag that would be generated by pumping any liquid through a pipe. The pump would have to be driven by a heat engine and you are right back were everyone has to start, but with an extra inefficient step added.

    Just for fun try coming up with a air compressor for a jet turbine that has no moving parts. That will give you a challenge. (Hint: ionization of air plus magnetic or electrical acceleration.)
     
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