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Maxwell's Demon via molecular reed valves can produce work?

  1. Oct 23, 2011 #1
    Well not literally The Maxwell's Demon...

    If a one-way reed valve can be brought down to size of only a few molecules, don't you think it could allow passage of a gas molecule across a barrier in one direction only?

    How I think it could work:

    -The small size (molecular) of the valve is critical to vastly reduce the probability of two gas molecules meeting at the valve at the same time from both sides of the barrier which will defeat the purpose the valve - a molecule coming in will also let molecule from other side out or prevent the valve from opening.

    -The one-way valve which may include a spring, must be lighter in weight than a single gas molecule. Either the valve must be made light or use a heavy gas or both. Example of gas that can be used is Tungsten or Sulfur Hexaflouride or the dangerous, Radon or Mercury Vapor.

    The reason for the valve having less weight is to prevent the gas in the intake side of the valve from being bounced back by the inertia of the valve.

    -The valves, probably millions/trillions of them could then surface an enclosing chamber. If this chamber is sealed, the pressure inside will keep increasing until the probability of both molecules from inside and outside arrives at the valve at the same time which either prevents the valve from opening or allows a molecule out after an arriving molecule comes in.

    -If the chamber can have a small a opening, a steady jet of gas is produced and work achieved, even in ambient (room) temperature.

    -Obviously, this chamber had to be enclose in a much larger and sealed gas chamber for safety purposes. Turbines and/or generators must be inside this sealed chamber.

    How it will not work:

    -Due to the molecular size of the valve, possibly only few atoms worth, will have elastic properties as well just like the gas molecules. A gas molecule forcing it open, will cause it to clap open and close indefinitely without loss of energy by heat/friction. The clapping action will allow gas molecules inside the chamber to escape.

    -I have no idea how to introduce friction/damping in the molecule valve so it won't clap. For best result, it must remain close once its returned to its resting position by the spring, until it's forced open by a gas molecule. Note that damping/friction is not really a significant loss in efficiency if the chamber can be thermally insulated. The action will heat the inside of the chamber which will return energy lost through damping back to the gas inside the chamber and ultimately, to the jet.

    -Has anyone made valves that small before or at least, lighter than the heaviest/densest known gas?

    What do you guys think?
  2. jcsd
  3. Dec 24, 2014 #2

    I independently had a similar thought today and after a bit of google-ing found your post. I think your idea is good, at least when we view gas as a bunch of molecules that have a position in space, some energy and inertia.

    The Ideal reed valve you propose is trying to achieve 100% movement in the pass direction and 0% movement in the block direction. This is of course most desirable, but also as you mentioned difficult to achieve on molecular level. However we don't need 100% efficiency for the concept to work.

    My thoughts revolved around a wave, but without any moving parts for simplicity. After all all we're trying to achieve is to increase the probability of gas molecules traveling in one direction vs in the other direction. If we're able to achieve 70/30 ratio (i.e. 70% chance of molecule passing in the pass direction and 30% in the block direction) than the number of gas molecules in same sized closed systems when the system reaches equilibrium should be 30% of molecules in the section facing the block-side of the valve and 70% in the section facing the pass section of the valve. This implies pressure difference that could be utilized to produce energy or for other applications.

    Design of such valve is possible. Tesla valve is a good example that achieves this on macro-scale and I don't see any reason why it wouldn't work on nano-scale. However maybe simpler designs would also be feasible. A simple 'funnel' hole should do the trick. From the block direction only molecules that hit the hole directly will pass through. However from the pass direction in addition to the direct hit's we also have a possibility of molecules bouncing off the walls of the funnel before hitting the hole and getting through. Therefore simple nano-size funnel already achieves the goal of having a difference in probability of passing in opposite direction therefore creating a valve like effect. Of course more refined designs could magnify the effect allowing us to achieve better probability difference.

    Other the production of energy which you mentions I see application of this in few other areas:
    - producing thrust: macro scale surface with large valve density would produce a constant flow of gas from one side to the other acting as a fan, this could be to move the molecules (application: air fan with no moving parts) or even the surface itself (application: propulsion system)
    - heating/cooling: the energy of the high pressure area would increase and as temperature is a measure of energy so would it's temperature (application: self heating and self cooling houses, refrigerators boxes with no moving parts etc.)

    OK - so that was a quick offloading of ideas floating around in my brain. They're not refined as I didn't really have much time to think them through well so any constructive (or destructive) criticism is more than welcome.

  4. Dec 24, 2014 #3


    Staff: Mentor

    Sorry. Discussions of perpetual motion machines are not permitted here. The ideas presented here are well known. You may want to research Smoluchowski's trap door or Feynman's ratchet.
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