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Re: Dippy bird

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  • Sam
    ... water ... energy, ... temperature, so ... hot ... (e.g., ... evaporate ... heat ... spontaneously. ... Phil, If I put a dippy bird in glass container and
    Message 1 of 10 , May 30, 2003
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      COMMENT BELOW:

      --- In AMBIENTENERGY@yahoogroups.com, "Phil Karn" <anonanon7@y...>
      wrote:
      > --- In AMBIENTENERGY@y..., "marvinjasoncarter"
      > <marvinjasoncarter@y...> wrote:
      > > Mr. Phil,
      > >
      > > I've been thinking about your statement which says "when the
      water
      > > runs out, the bird stops even though there is plenty of heat left
      > in
      > > the atmosphere." I have heard this said before and don't
      > understand
      > > what it proves.
      >
      > It proves a great deal.
      >
      > First, let's look at the laws of thermodynamics. The first law says
      > that energy is conserved. (Actually, it's the sum of mass plus
      energy,
      > but that Einsteinean detail is not important here.)
      >
      > The second law says that in any spontaneous process, the entropy of
      > a closed system must always increase.
      >
      > "Entropy" has units of heat energy divided by absolute
      temperature, so
      > when heat flows from a hot source into a cold sink it increases the
      > sink's entropy by more than it decreases the source's entropy.
      > Therefore the second law permits heat to flow spontaneously from a
      hot
      > object to a cold object until the two objects are at the same
      > temperature. Then the heat flow must stop.
      >
      > Any real system, such as an engine, must obey both laws of
      > thermodynamics at all times.
      >
      > The second law explains why it is not possible to build an engine
      > whose sole function is to convert heat from a single reservoir
      (e.g.,
      > the atmosphere) into useful work.
      >
      > The toy bird does indeed convert heat from the atmosphere into (a
      > small amount) of useful work, BUT THAT IS NOT ITS ONLY RESULT -- it
      > also evaporates water. And it just so happens that when you
      evaporate
      > water, you increase its entropy. A lot. So much so that its entropy
      > can increase even when its temperature decreases; that's how "swamp
      > coolers" can work.
      >
      > The dippy bird increases the entropy of the water it evaporates by
      > more than it decreases the entropy of the atmosphere by removing
      heat
      > from it. This satisfies the second law, so it can run
      spontaneously.
      >
      > But without liquid water to evaporate, the bird no longer has
      > something whose entropy can be increased. So it stops running. To
      > continue running it would have to decrease the total entropy of the
      > universe, and that's directly forbidden by the second law.
      >
      > Phil

      Phil,

      If I put a dippy bird in glass container and put him in water up
      to his ankles and sealed the glass container would he ever run out
      of water? IF so, where does the water go?

      Inquiring minds just gotta know...
      SD
    • Phil Karn
      ... Sorry it took so long to respond, I just noticed your note yesterday. The answer is very simple. When the humidity of the space above the water gets high
      Message 2 of 10 , Aug 4, 2003
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        Sam wrote:

        > If I put a dippy bird in glass container and put him in water up
        > to his ankles and sealed the glass container would he ever run out
        > of water? IF so, where does the water go?
        >
        > Inquiring minds just gotta know...

        Sorry it took so long to respond, I just noticed your note yesterday.

        The answer is very simple. When the humidity of the space above the
        water gets high enough, additional water will be unable to evaporate
        from the bird's beak and it will stop dipping.

        Phil
      • Phil Karn
        ... This might work, provided that the water vapor in the closed container could radiate enough heat out through the glass to keep it at a temperature below
        Message 3 of 10 , Aug 6, 2003
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          Sam wrote:

          > OK, so now I put a strong magnifying glass aimed at the birds beak
          > when he is at his "standing" position that he holds for a few
          > seconds to help dry up his beak some there...
          >
          > Would this speed up the normal process in any way?
          > SO, what you are saying is there is no way to produce a micro
          > climate that a poor little dippy bird would thrive in?

          This might work, provided that the water vapor in the closed container
          could radiate enough heat out through the glass to keep it at a
          temperature below that produced on the bird's beak by the sunlight. Then
          you'd have a heat engine working between the sun on the hot side and the
          earth's ambient temperature on the cold side. But if you didn't let the
          solar heat escape, then the bird would stop working when the temperature
          of the water vapor reaches that of the hot spot produced by the
          sunlight. Eventually, of course, it would also stop working when the
          whole thing melts and vaporizes.

          Phil
        • Phil Karn
          Sam, my email to you is bouncing with an unknown user error from mindlink. You re using address dabbs@mindspring.com. Phil
          Message 4 of 10 , Aug 6, 2003
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            Sam, my email to you is bouncing with an "unknown user" error from
            mindlink. You're using address dabbs@....

            Phil
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