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Re: Dippy bird

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  • Phil Karn
    ... in ... understand ... of ... Good question. There s a *very big* difference between the toy bird and the steam locomotive. Unlike the toy bird, the steam
    Message 1 of 10 , Dec 3, 2002
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      --- 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.
      >
      > Would this not also be true of a steam Locomotive? If it were to
      > run out of water, it too would stop even though there were plenty
      of
      > heat left. Once and for all, what exactly does this prove?

      Good question. There's a *very big* difference between the toy bird
      and the steam locomotive. Unlike the toy bird, the steam locomotive is
      burning fuel that keeps a boiler at a temperature well above ambient.
      The steam from this boiler is used to do work against a piston, and is
      then released into the atmosphere.

      It would be theoretically possible to build a steam locomotive that,
      instead of releasing the spent steam into the atmosphere, condenses it
      back to liquid water that could be recycled back into the boiler. The
      condensor would be essentially a radiator that would absorb the waste
      heat from the steam and radiate it to the atmosphere.

      The problem is that such a radiator would be too big and bulky to be
      practical on a locomotive. But this is exactly how many large
      stationary power plants operate; that's why they have those big
      cooling towers and/or are located next to a river, lake or ocean. Such
      plants have considerably greater efficiency than gas turbine or
      internal combustion engines that simply vent their combustion products
      to the environment.

      You can close the loop with a condensor in such a steam plant because
      of the external source of energy that heats the boiler, and the fact
      that the spent steam is well above ambient temperature. Find a good
      way to pass that heat to the environment, and the water will condense
      on its own.

      But you can't do this with the toy bird because the water vapor is
      already at or below ambient temperature. It won't cool any further on
      its own, so it won't return on its own to the liquid state. So the
      liquid water becomes a consumable; when you use it up, the bird stops.

      Once again, we see that the second law must be obeyed.

      Phil
    • Phil Karn
      ... in ... understand ... 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
      Message 2 of 10 , Dec 3, 2002
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        --- 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
      • Sam
        ... water ... energy, ... temperature, so ... hot ... (e.g., ... evaporate ... heat ... spontaneously. ... Phil, If I put a dippy bird in glass container and
        Message 3 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 4 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 5 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 6 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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