Science > Physics > energy derived from differential specific gravities?
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Science > Physics |
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"" |
| Date: |
26 Sep 2005 03:03:55 AM |
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energy derived from differential specific gravities? |
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
It comprises two identical vertical pipes capped at the bottom, both
having a gate valve near the bottom which allows the lowest portion to
be sealed off from the upper portion.
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around.
I forgot to mention that in both pipes, that upper portion contains a
little paddlewheel which connects ot an electricity generator just
outside the pipe. There's also a certain clever arrangement of baffles
below the paddlewheel.
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
By the way, I also want to calculate the speed with which the oil
rises, given its specific gravity. I know the quantity of
gravitational deceleration acting on it, but I don't know how to
calculate the upward force. Ignore all second order effects.
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| User: "Robert Morein" |
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| Title: Re: energy derived from differential specific gravities? |
01 Oct 2005 09:59:02 AM |
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<dances_with_barkadas@yahoo.com> wrote in message
news:1127721835.760675.136810@g47g2000cwa.googlegroups.com...
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
This example actually does not contain a Maxwell's Demon. It is, as is
always the case, a flawed attempt to exhibit perpetual motion. In this case,
as with many others, the flaw is that the system is not closed.
Here on Earth, we have many sources of potential energy. Every apple in a
tree has gravitational potential energy. It is pointless to try to trace
back, billions of years, to show how the apple got eight feet up in a tree.
To avoid that, the test of a perpetual motion system is performed with
careful establishment that the system is closed. In other words, it is
contained entirely within a sealed box, perhaps with one outlet which is to
be used for the presumed energy transfer.
You had some liquid which was so many feet off the ground. You pour it into
a hole in the ground, thus releasing potential energy, by converting it into
kinetic energy. If you did not use the kinetic energy at that point, it is
lost, by conversion into some less easily usable form of energy, such as
heat that diffuses through the Earth.
In one case, however, you contrived the pouring process, to make a sort of a
spring, ie., another potential energy situation, by pouring in a lighter
fluid, on top of which you put a heavier fluid. Just as with a coiled
spring, there is a trigger that will allow the heavier fluid to displace the
lighter one. At that point, you could capture some of the kinetic energy,
just as you could have with the minature waterfall that occurred when you
poured the fluids in.
This is a pretty dull example of perpetual motion "fraud."
Interesting ones are welcome.
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| User: "Brian Whatcott" |
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| Title: Re: energy derived from differential specific gravities? |
01 Oct 2005 07:57:52 PM |
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On Sat, 1 Oct 2005 10:59:02 -0400, "Robert Morein"
<nowhere@nowhere.com> wrote:
<dances_with_barkadas@yahoo.com> wrote in message
news:1127721835.760675.136810@g47g2000cwa.googlegroups.com...
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
This example actually does not contain a Maxwell's Demon. It is, as is
always the case, a flawed attempt to exhibit perpetual motion. In this case,
as with many others, the flaw is that the system is not closed.
There IS a maxwell's demon type heater/cooler available commercially.
Supply compressed air. amd it blows hot air out of one t pipe end, and
cold air out of the other. It's noisy and somewhat inefficient, but
the hot air is hot, and the cold air is cold - there can be a 150 degC
differential between the two flows.
Brian Whatcott
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| User: "tadchem" |
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| Title: Re: energy derived from differential specific gravities? |
01 Oct 2005 08:47:56 PM |
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"Brian Whatcott" <betwys1@sbcglobal.net> wrote in message
news:u2cuj1puv43pig00fgbub3reef518l9tni@4ax.com...
<snip>
There IS a maxwell's demon type heater/cooler available commercially.
Supply compressed air. amd it blows hot air out of one t pipe end, and
cold air out of the other. It's noisy and somewhat inefficient, but
the hot air is hot, and the cold air is cold - there can be a 150 degC
differential between the two flows.
It is named the "Hilsch Vortex" or "Hilsch Tube."
I have actually used one (as a pedagogical device) when I was a research
chemist at the Amarillo helium plant. Very low efficiency, but undeniably
effective. Frosts up quickly on a humid day.
http://www.visi.com/~darus/hilsch/
Tom Davidson
Richmond, VA
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| User: "daestrom" |
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| Title: Re: energy derived from differential specific gravities? |
02 Oct 2005 06:39:36 AM |
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"tadchem" <tadchemNOSPAM@comcast.net> wrote in message
news:jo-dnXxPgvPZoaLeRVn-sg@comcast.com...
"Brian Whatcott" <betwys1@sbcglobal.net> wrote in message
news:u2cuj1puv43pig00fgbub3reef518l9tni@4ax.com...
<snip>
There IS a maxwell's demon type heater/cooler available commercially.
Supply compressed air. amd it blows hot air out of one t pipe end, and
cold air out of the other. It's noisy and somewhat inefficient, but
the hot air is hot, and the cold air is cold - there can be a 150 degC
differential between the two flows.
It is named the "Hilsch Vortex" or "Hilsch Tube."
I have actually used one (as a pedagogical device) when I was a research
chemist at the Amarillo helium plant. Very low efficiency, but undeniably
effective. Frosts up quickly on a humid day.
http://www.visi.com/~darus/hilsch/
Yep. We used them in the Navy as part of damage control. They fit in the
back of a steam suit for entering spaces filled with live steam after a
steam-line break. Supply the suit with compressed air, and the guy inside
is nice and cool. One poor sailor made the mistake of tucking the 'hot end'
of the tube inside his suit (supposed to be left hanging out at the waist).
Burned his leg when he brushed up against it, that's how hot the 'hot end'
got.
daestrom
Tom Davidson
Richmond, VA
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
04 Oct 2005 04:15:34 AM |
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Robert Morein wrote:
This example actually does not contain a Maxwell's Demon.
no one, least of all I the original poster, said it did. I said that
Maxy built something on the side. In our imagination. Got an issue
with thought experiments?
It is, as is
always the case, a flawed attempt to exhibit perpetual motion.
No, it was a **question** about where the energy came from. I never
asserted or implied that there was perpetual motion.
This is a pretty dull example of perpetual motion "fraud."
Interesting ones are welcome.
No, it was a **question** that arose from looking at an actual
engineered pipeline, and thinking about what goes on inside it.
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| User: "Robert Morein" |
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| Title: Re: energy derived from differential specific gravities? |
04 Oct 2005 10:46:37 PM |
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<dances_with_barkadas@yahoo.com> wrote in message
news:1128417334.237433.296800@f14g2000cwb.googlegroups.com...
Robert Morein wrote:
This example actually does not contain a Maxwell's Demon.
no one, least of all I the original poster, said it did. I said that
Maxy built something on the side. In our imagination. Got an issue
with thought experiments?
It is, as is
always the case, a flawed attempt to exhibit perpetual motion.
No, it was a **question** about where the energy came from. I never
asserted or implied that there was perpetual motion.
OK, OK, OK.
Peace.
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| User: "tadchem" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 04:50:45 AM |
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<dances_with_barkadas@yahoo.com> wrote in message
news:1127721835.760675.136810@g47g2000cwa.googlegroups.com...
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
Is he in the Union?
It comprises two identical vertical pipes capped at the bottom, both
having a gate valve near the bottom which allows the lowest portion to
be sealed off from the upper portion.
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around.
I forgot to mention that in both pipes, that upper portion contains a
little paddlewheel which connects ot an electricity generator just
outside the pipe. There's also a certain clever arrangement of baffles
below the paddlewheel.
Three months later, we open both gate valves.
Why so patient? Are *you* in the Union?
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
....Work you did against gravity when you first lifted the water and the oil
into the pipe
By the way, I also want to calculate the speed with which the oil
rises, given its specific gravity.
You'll need to know a lot more.
What is the viscosity of the oil and of the water, the temperature of the
system, the surface energy of the oil/water interface, the diameter of the
gate valve, and so on...?
For example, below 0° C the water won't flow unless you have several hundred
feet of it (a glacier), and then only very slowly.
Best set up the experiment and *measure* it.
I know the quantity of
gravitational deceleration acting on it, but I don't know how to
calculate the upward force. Ignore all second order effects.
See Archimedes about that one. He is the Principle authority on buoyancy.
Tom Davidson
Richmond, VA
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 05:00:12 AM |
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How about a big pipe created going out into space? It removes all the
pollution of the Earth, it pumps it right on out there. What principle
does it use for power?????
The venturi effect.
Thank you. No applause, uh save it for the end.
- Don
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| User: "dave.harper" |
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| Title: Re: energy derived from differential specific gravities? |
29 Sep 2005 01:54:37 PM |
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wrote:
How about a big pipe created going out into space? It removes all the
pollution of the Earth, it pumps it right on out there. What principle
does it use for power?????
The venturi effect.
Well, I can't tell if you're kidding, but I'm going to assume you're
not.
The venturi effect requires a fluid velocity to create a pressure
difference. There's not really any real velocity with the situation
you describe. I think you mean just the basic air pressure difference
between the ground and space? If that was the case, why do you need a
tube at all? Why doesn't the air just rush out into space? Answer:
gravity. The air pressure on the earth's surface is due to gravity,
and air can't be sucked out into space because the energy required to
lift it is more than the energy you can get from the pressure
difference.
Dave
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| User: "Vaughn" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 05:10:10 AM |
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<dances_with_barkadas@yahoo.com> wrote in message
news:1127721835.760675.136810@g47g2000cwa.googlegroups.com...
1) There is no such thing as perpetual motion.
2) Crossposters suck.
Vaughn
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| User: "Autymn D. C." |
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| Title: Re: energy derived from differential specific gravities? |
27 Sep 2005 10:33:28 AM |
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Vaughn wrote:
1) There is no such thing as perpetual motion.
2) Crossposters suck.
wrong:
http://groups.google.com/group/sci.physics.electromag/msg/cc6de58454fa420c
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| User: "dave.harper" |
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| Title: Re: energy derived from differential specific gravities? |
28 Sep 2005 09:45:30 PM |
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Autymn D. C. wrote:
Vaughn wrote:
1) There is no such thing as perpetual motion.
2) Crossposters suck.
wrong:
http://groups.google.com/group/sci.physics.electromag/msg/cc6de58454fa420c
A "Coriolis motor"? Well, I hate to break it to you, but that's not
perpetual motion. It's just converting the rotational energy of the
earth into fluid energy. And the rotational energy of the earth is
limited. Even if the earth was a solid, perfect sphere of iron with no
internal rotational losses, the energy you're converting into fluid
energy with that motor would slow the earth's rotational energy as a
function of C*e^-r*t. Not only that, but your motor is converting the
earth's rotational energy at a horribly inefficient rate. If you want
to tap the earth's rotational energy, you'd be better off with a
rotating generator with its axis perpendicular to the earth's axis.
Dave
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| User: "Autymn D. C." |
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| Title: Re: energy derived from differential specific gravities? |
12 Oct 2005 06:54:38 AM |
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dave.harper wrote:
A "Coriolis motor"? Well, I hate to break it to you, but that's not
I said engine.
perpetual motion. It's just converting the rotational energy of the
earth into fluid energy. And the rotational energy of the earth is
limited. Even if the earth was a solid, perfect sphere of iron with no
internal rotational losses, the energy you're converting into fluid
energy with that motor would slow the earth's rotational energy as a
function of C*e^-r*t. Not only that, but your motor is converting the
Yes, it is PM, literally. Solve for zero energy. There is no
solution. You are confusing "perpetual motion" with "self-sustenance".
earth's rotational energy at a horribly inefficient rate. If you want
to tap the earth's rotational energy, you'd be better off with a
rotating generator with its axis perpendicular to the earth's axis.
It's not /that/ horrible. And how is one supposed to get a
differential acceleration if the generator is foroffkilter?
-Aut
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| User: "dave.harper" |
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| Title: Re: energy derived from differential specific gravities? |
13 Oct 2005 01:42:21 PM |
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Autymn D. C. wrote:
dave.harper wrote:
A "Coriolis motor"? Well, I hate to break it to you, but that's not
I said engine.
Well, here's a direct quote from the link: "The bad thing about my
Coriolis motor..." But that's a moot point.
"Engines" are generally defined as machines that convert heat energy
into work (i.e. heat engines), and your machine does not use heat.
Your device is really just an energy converter, since all it does is
convert the earth's rotational energy into another form.
Yes, it is PM, literally. Solve for zero energy. There is no
solution.
It does have a solution:
E1 - integral[ Qc(t) dt ]0,t = E2
Where E1 is the rotational kinetic energy of the earth at t=0, E2 is
the rotational energy of the earth at t=t, and Qc(t) is the input
energy of your coverter as a function of time (which gets its energy
from the earth). However, Qc(t) = dE/dt, so you end up with a
differential equation with the general solution Ce^-rt, which is the
standard decay funtion.
Whatever equation you solved for is not taking into account the FINITE
kinetic energy of the earth's rotation. Start your converter, and
you'll bleed off the kinetic energy of the earth over
trillions/quadrillions of years (depending on the size of your
converter).
What equation are you using?
You are confusing "perpetual motion" with "self-sustenance".
I don't think you understand the true definition of "perpetual motion":
http://en.wikipedia.org/wiki/Perpetual_motion
"Perpetual motion refers to a condition in which work is done without
an energy source."
By this definition, your "converter" fails since it's getting its
energy from the earth (again, which is a finite source). If you
include the earth as part of your machine, it still fails this
definition since all you're relying on is an existing, FINITE energy
reservoir (i.e. earth).
Dave
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| User: "Autymn D. C." |
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| Title: Re: energy derived from differential specific gravities? |
20 Oct 2005 10:55:34 PM |
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dave.harper wrote:
Well, here's a direct quote from the link: "The bad thing about my
Coriolis motor..." But that's a moot point.
I said both, but was pointing out the engine part for this thread.
"Engines" are generally defined as machines that convert heat energy
into work (i.e. heat engines), and your machine does not use heat.
Your device is really just an energy converter, since all it does is
convert the earth's rotational energy into another form.
Engines take differences, such as from a couple, or otherwise convert
or transduce energies. Motors move from a single force or energy, like
a bike--being over 99% efficient. Then again, they can move from the
strongest of many forces. If the observer shares the engine's frame,
then it could be a motor.
Yes, it is PM, literally. Solve for zero energy. There is no
solution.
It does have a solution:
E1 - integral[ Qc(t) dt ]0,t = E2
Where E1 is the rotational kinetic energy of the earth at t=0, E2 is
the rotational energy of the earth at t=t, and Qc(t) is the input
energy of your coverter as a function of time (which gets its energy
from the earth). However, Qc(t) = dE/dt, so you end up with a
differential equation with the general solution Ce^-rt, which is the
standard decay funtion.
Whatever equation you solved for is not taking into account the FINITE
kinetic energy of the earth's rotation. Start your converter, and
you'll bleed off the kinetic energy of the earth over
trillions/quadrillions of years (depending on the size of your
converter).
What equation are you using?
Since the convertor runs off the very initial and iterative condition
of its source, it'll never reach zero.
You are confusing "perpetual motion" with "self-sustenance".
I don't think you understand the true definition of "perpetual motion":
http://en.wikipedia.org/wiki/Perpetual_motion
"Perpetual motion refers to a condition in which work is done without
an energy source."
By this definition, your "converter" fails since it's getting its
energy from the earth (again, which is a finite source). If you
include the earth as part of your machine, it still fails this
definition since all you're relying on is an existing, FINITE energy
reservoir (i.e. earth).
The definition is not true because it's not literal, and it makes a red
herring. Exponents try to rule it out by making it a paradox. Of
/course/ work is done /with/ an energy source, even in the case of
perpetual motion.
-Aut
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
24 Oct 2005 08:51:59 AM |
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Autymn D. C. wrote:
dave.harper wrote:
"Engines" are generally defined as machines that convert heat energy
into work (i.e. heat engines), and your machine does not use heat.
Your device is really just an energy converter, since all it does is
convert the earth's rotational energy into another form.
Engines take differences, such as from a couple, or otherwise convert
or transduce energies. Motors move from a single force or energy, like
a bike--being over 99% efficient.
I think you're confused. First of all, you've used both "motor" and
"engine" to describe your machine, yet provide two separate definitions
for each. Which is it? Secondly, engineers and scientists do not use
these definitions of engines and motors, so I think you'll find that
your the only one that believes your definitions. Lastly, where a
"difference" and a "single force/energy" differ is not a clear line to
begin with (i.e. is the motor operating of a voltage "source", or a
voltage "difference"?). This is really, however, a moot point since it
has no bearing on perpetual motion. I'm not sure why you tried to
point this out to begin with, especially considering you used both
words to describe your device.
Yes, it is PM, literally. Solve for zero energy. There is no
solution.
It does have a solution:
E1 - integral[ Qc(t) dt ]0,t = E2
Since the convertor runs off the very initial and iterative condition
of its source, it'll never reach zero.
By this definition, your converter is unnecessary. All you need is the
earth itself. The earth has a "very initial and iterative condition".
Why do you even need your machine?
I don't think you understand the true definition of "perpetual motion":
http://en.wikipedia.org/wiki/Perpetual_motion
"Perpetual motion refers to a condition in which work is done without
an energy source."
The definition is not true because it's not literal, and it makes a red
herring.
What you've just done is what we used to call "hitting the eject
button". You now claim that the mainstream definition of "perpetual
motion" is not true, and you've substituted your own definition to fit
your needs. Your machine does not fit the mainstream definition of
perpetual motion. Your machine is more aptly described as a "constant
energy decay" system. This is just like every other physical systems
in the entire universe. Welcome to the club.
Dave
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| User: "harry k" |
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| Title: Re: energy derived from differential specific gravities? |
27 Sep 2005 09:18:40 PM |
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Autymn D. C. wrote:
Vaughn wrote:
1) There is no such thing as perpetual motion.
2) Crossposters suck.
wrong:
http://groups.google.com/group/sci.physics.electromag/msg/cc6de58454fa420c
So I assume you are a ultra billionair by now? No? What a surprise.
Harry K
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| User: "daestrom" |
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| Title: Re: energy derived from differential specific gravities? |
27 Sep 2005 06:25:27 PM |
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<dances_with_barkadas@yahoo.com> wrote in message
news:1127721835.760675.136810@g47g2000cwa.googlegroups.com...
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
It comprises two identical vertical pipes capped at the bottom, both
having a gate valve near the bottom which allows the lowest portion to
be sealed off from the upper portion.
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around.
Being 'lighter than water' means it takes less energy to push it uphill.
But oil is often more viscous than water, meaning it takes more energy to
make it move through a pipe at all. Pumping *any* real liquid is a
combination of overcoming potential energy differences, changes in velocity,
and viscous friction.
I forgot to mention that in both pipes, that upper portion contains a
little paddlewheel which connects ot an electricity generator just
outside the pipe. There's also a certain clever arrangement of baffles
below the paddlewheel.
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
You could extract more energy from the first pipe if you didn't bother to
fill the space below the gate valve. You've put the same amount of energy
into the water above the gate valve in the first pipe as you have put into
the water above the gate valve in the second pipe.
But putting water below the gate valve in the first pipe has made it so you
can't recover any of the upper water's energy by merely opening the gate
valve. The energy isn't 'gone anywhere', you just have to change the system
in order to recover it (e.g. let the water out of the bottom chamber).
Putting oil below the gate valve in the second chamber has made it so at
least some of the upper water's energy is recoverable by opening just the
gate valve. Not as much as if the lower chamber were empty, but at least
some.
By the way, I also want to calculate the speed with which the oil
rises, given its specific gravity. I know the quantity of
gravitational deceleration acting on it, but I don't know how to
calculate the upward force. Ignore all second order effects.
The bouyant upward force is equal to the difference in density of the oil vs
water times the volume of oil (several ways to calculate the bouyant force
on the oil). But how fast this oil moves is a function of that force, the
viscosity of the oil (varies with temperature and oil properties), the
size/shape of any nozzle/baffles you have.
If the viscosity is relatively high, you can get into what's known as
Counter-Current Limiting Flow (CCLF). That's the phenomenon that limits how
fast an upturned bottle of water will drain out (flow through the neck
alternates between air bubble up, and water slug down). In your case it
could be 'oil slug up', followed by 'water slug down'. But this can be
avoided by the judicious placement of a separate 'up' flow path and 'down'
flow path.
daestrom
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
27 Sep 2005 07:58:18 PM |
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daestrom <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around.
Being 'lighter than water' means it takes less energy to push it uphill.
But oil is often more viscous than water, meaning it takes more energy to
make it move through a pipe at all...
He forgot to mention the pumping is very slow, with no viscosity loss.
Nick
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| User: "Lance" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 11:11:44 PM |
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thought carefully and wrote on 9/26/2005
1:03 AM:
Where did this energy come from?!?
You physics guys always crack us mechanical engineers up. Keep these
jokes coming.
Lance
*****
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| User: "harry k" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 08:18:25 AM |
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wrote:
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
Same place the energy comes from if you lift a weight tied to a rope
and let it drop. Result is a net loss in energy. You spend more
pumping the stuff than you get back from the generator.
Harry K
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| User: "PD" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 11:56:17 PM |
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wrote:
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
It comprises two identical vertical pipes capped at the bottom, both
having a gate valve near the bottom which allows the lowest portion to
be sealed off from the upper portion.
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around.
I forgot to mention that in both pipes, that upper portion contains a
little paddlewheel which connects ot an electricity generator just
outside the pipe. There's also a certain clever arrangement of baffles
below the paddlewheel.
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
By the way, I also want to calculate the speed with which the oil
rises, given its specific gravity. I know the quantity of
gravitational deceleration acting on it, but I don't know how to
calculate the upward force. Ignore all second order effects.
Let us imagine the same thing in a more colloquial fashion.
I have a glass of water and a glass of beer. As the bubbles form in the
glass of beer and rise to the surface, they pass through cleverly
designed baffles and turn a wheel and generate electricity.
Wait... Here's a better one.
I have a box of concrete and a box of cereal on a railroad car. As the
cereal in the box settles, it displaces air between the flakes, which
rises and, passing through cleverly designed baffles, turns a wheel and
generates electricity.
Where, oh where, does this energy come from?
PD
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
27 Sep 2005 03:08:51 AM |
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PD <TheDraperFamily@gmail.com> wrote:
dances_with_barkadas@yahoo.com wrote:
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around...
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
So far, it looks like everyone's missed the mystery--that the second pipe
releases more energy than the first...
Nick
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| User: "dave.harper" |
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| Title: Re: energy derived from differential specific gravities? |
28 Sep 2005 09:51:42 PM |
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wrote:
PD <TheDraperFamily@gmail.com> wrote:
dances_with_barkadas@yahoo.com wrote:
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around...
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
So far, it looks like everyone's missed the mystery--that the second pipe
releases more energy than the first...
The second pipe released energy because energy was stored in it to
begin with. When I lift a rock up above my head, that's potential
energy. When I lift water up to the top of the pipe, it's ALSO
potential energy. You can't ignore the energy you put into the system
to begin with (i.e. hauling water to the top of the pipe).
Dave
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
29 Sep 2005 02:18:32 AM |
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dave.harper <dave.harper@gmail.com> wrote:
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
So far, it looks like everyone's missed the mystery--that the second pipe
releases more energy than the first...
The second pipe released energy because energy was stored in it to
begin with...
But why did it release MORE than the first pipe,
even though the second pipe's initial pumping
required less energy than the first's?
Nick
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| User: "PD" |
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| Title: Re: energy derived from differential specific gravities? |
30 Sep 2005 08:40:40 AM |
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wrote:
dave.harper <dave.harper@gmail.com> wrote:
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
So far, it looks like everyone's missed the mystery--that the second pipe
releases more energy than the first...
The second pipe released energy because energy was stored in it to
begin with...
But why did it release MORE than the first pipe,
even though the second pipe's initial pumping
required less energy than the first's?
It doesn't. All you've done is contrive to extract a little of the
second's (smaller) total energy before releasing the rest. Just to make
it concrete, we'll toss in some numbers pulled out of a hat.
Pipe 1:
1. Insert 4.0 J of energy to fill pipe
2. Empty pipe and extract 4.0 J of energy
Pipe 2:
1. Insert 3.8 J of energy to fill pipe
2. Let water and oil trade places and extract 0.3 J of energy
3. Empty pipe and extract 3.5 J of energy
PD
Nick
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
29 Sep 2005 01:42:16 PM |
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wrote:
dave.harper <dave.harper@gmail.com> wrote:
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
So far, it looks like everyone's missed the mystery--that the second pipe
releases more energy than the first...
The second pipe released energy because energy was stored in it to
begin with...
But why did it release MORE than the first pipe,
even though the second pipe's initial pumping
required less energy than the first's?
It released MORE than the first, yes. But the first still has ALL the
energy you put into it. The second does not have all the energy you
put in it, since the denser water moved down to the bottom (lower
potential energy).
It's like lifting two bowling balls up and putting one on a flat
surface, and the other ball on a slope. Let both go and the second
bowling ball releases energy, while the first does not. All you've
done is set up a situation where energy can be released with one ball,
but not with the other. Same with the pipes.
Dave
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| User: "Loren Amelang" |
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| Title: Re: energy derived from differential specific gravities? |
27 Sep 2005 12:44:25 PM |
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On 27 Sep 2005 04:08:51 -0400, wrote:
PD <TheDraperFamily@gmail.com> wrote:
dances_with_barkadas@yahoo.com wrote:
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around...
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
So far, it looks like everyone's missed the mystery--that the second pipe
releases more energy than the first...
No it doesn't. You are stopping the experiment too soon. It is true
that some energy will be released when the oil floats to the top. But
the experiment is not over until you release all of the fluid from
both pipes. Then you find that the second pipe with oil at the top
releases less energy than the one with water all the way to the top.
Loren
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| User: "" |
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| Title: Re: energy derived from differential specific gravities? |
27 Sep 2005 12:11:27 AM |
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Where do the glass of water and the box of concrete figure in anywhere?
Why not have an generator produce power for an electric motor, which
runs the generator, producing perpetual motion?
Or have a propeller on an air boat blow into a sail on it.
One county fair had an elaborate demo of perpetual motion, a vast array
of gears and wheels visible to the public. Behind the curtain was a
guy turning a crank.
The only thing that apparently is infinite is the human ability to
produce memes and debate them.
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| User: "Robert Morien" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 04:03:53 AM |
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In article <1127721835.760675.136810@g47g2000cwa.googlegroups.com>,
wrote:
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
It comprises two identical vertical pipes capped at the bottom, both
having a gate valve near the bottom which allows the lowest portion to
be sealed off from the upper portion.
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around.
I forgot to mention that in both pipes, that upper portion contains a
little paddlewheel which connects ot an electricity generator just
outside the pipe. There's also a certain clever arrangement of baffles
below the paddlewheel.
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
News will tell you. Just wait
By the way, I also want to calculate the speed with which the oil
rises, given its specific gravity. I know the quantity of
gravitational deceleration acting on it, but I don't know how to
calculate the upward force. Ignore all second order effects.
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| User: "Brian Whatcott" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 11:46:20 PM |
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On 26 Sep 2005 01:03:55 -0700, wrote:
Let us imagine that Maxwell's Demon has constructed an apparatus for
us.
It comprises two identical vertical pipes capped at the bottom, both
having a gate valve near the bottom which allows the lowest portion to
be sealed off from the upper portion.
We have these empty pipes, and in the first pipe, we spend an amount of
energy to pump water into both portions, then close the gate valve.
In the second pipe, we fill the bottom portion of the pipe with oil,
close the valve, then fill the rest of the pipe with water. Our total
pumping-energy was lower thatn with the first pipe, because oil is
lighter than water, takes less energy to push it around.
I forgot to mention that in both pipes, that upper portion contains a
little paddlewheel which connects ot an electricity generator just
outside the pipe. There's also a certain clever arrangement of baffles
below the paddlewheel.
Three months later, we open both gate valves.
In the first pipe, nothing moves.
In the second pipe, the water in the upper portion flows downward, the
oil in the lower portion floats upward. The baffles are cleverly placed
such that the paddlewheel turns, generating electricity.
Where did this energy come from?!?
By the way, I also want to calculate the speed with which the oil
rises, given its specific gravity. I know the quantity of
gravitational deceleration acting on it, but I don't know how to
calculate the upward force. Ignore all second order effects.
When you pump water up a pipe, you provide it with potential energy.
When it flows down again, it hands back that potential energy that
scales like m.g.h
What is the upward force on the blob of oil? The force is equal to the
weight of water that the oil displaces, less the weight of oil.
This is effectively, an upwards acting weight, called buoyant force.
However, the speed at which this oil blob moves is conditioned by the
resistance of the container, and the counterflow of the water.
Think of it reaching terminal velocity quite soon, like a parachute
jumper.
Brian Whatcott Altus, OK
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| User: "tadchem" |
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| Title: Re: energy derived from differential specific gravities? |
26 Sep 2005 03:53:06 PM |
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http://www.garrettspecialties.com/product_info.html/products_id/2537
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