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when i was a kid i loved swimming. i even got some cool
trophys and medals. during training sessions our teacher
taught us ways to glide through water with minimal
effort,
especially during long distance when conservation of
energy is important.
anyhow i digress.most deep sea animals glide
by
catching
currents if they go any distance, for short bursts of
speed
the employ their fins. so what is my idea. simply put it is
an engine that consists of a metal ring with coolant
inside.
the coolant gets cold enough to freeze water around it
which is already sub zero. these rings break off and fall
behind in the chosen direction (directed by a small but
powerful rotor). when small but numerous chunks of ice
break off, the energy of the ice floating to the top acts
sort of like an underwater jet engine. anyway the coolant
would be cooled by something like a nuclear or a special
HTE device. this energy is used to cool the coolant and
freeze water around the metal ring.
unfortunately the environment impact of the device
might
not be so friendly it can probably be engineered to be
more
friendly.
Slush Puppy
http://www.slushpup....za/SlushFlash.html
A South African thing [codrakon, Aug 20 2009]
Enthalpy of Fusion
http://en.wikipedia.../Enthalpy_of_fusion
how and why liquid solid transitions occur with temperature change [codrakon, Aug 20 2009]
[link]
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Shift keys broken [codrakon]? |
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no i cut off my pinky fingers using a saw at one of my
previous jobs. by accident. |
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It'd be hard to cut both pinkies off, unless it was in
seperate accidents. Which would be rather odd. Two
pinky castrations? Odd, but doable. |
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ever tried pushing aluminium plates through a worn
band saw? one finger is enough. now the other one
just thinks its off. |
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You should've told him you were paralyzed and typing this with a pencil in your teeth. |
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now lets talk about the idea? |
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//the ice floating to the top acts sort of like an underwater jet engine// |
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You lost me here. As ice builds up it will become slightly more and more bouyant. As it breaks away the sub will become less bouyant and sink, how does this translate into thrust? |
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(Tell me to shut up if I'm wrong here...) I see it as two separate concepts:
1: Engine system freezes water to use as reaction mass for propulsion. It would be easier to push against the ice (solid, use toothed wheels or something) than water (liquid, flows away from the pushing system).
2: Ice floats. As the chunk of ice leaves the engine, it floats up to the surface, A sloped plate at the rear of the engine could translate some of the 'up' into 'along'. Also, I don't think the submarine will get lighter or heavier (assuming an approximately continuous process) as the water will expand as it freezes (constant mass, not constant volume).
I suspect a long, gradual freezing process inside a tube (rather than the outside ring as above) would be best. |
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I'm also confused about how this provides propulsion, but I think a peltier device would work better than refrigeration in this application. I'm sure a sub's nuclear reactor could generate enough electricity to power a big one. |
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[neutrinos] this is exactly the idea i was thinking
about. the plate converting up to along would
actually be a longish tube where the ice displaces
water as it floats to the surface, creating some
kind of flow of water, and perhaps enough force
to propel the submarine forward. |
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the whole purpose of this design is to provide a
means of propulsion that uses minimal amounts of
energy, perhaps for pushing something like a
supersub (post by moonguy) very long distances
and use small amounts of energy doing so. |
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since the temperature of water past down further
than fifty meters is usually between 0-3 degrees
centigrade, hopefully cooling the water into ice
will actually be fairly easy. oh God why did i not
study mechanical engineering. stupid computer
engineering totally sux. |
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i was giving this idea some thought earlier and
concluded that this giant submerged ice machine
could only move at very slow speeds. |
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however maybe someone with the expertise
perhaps calculate for a 20 ton submersible,
assuming the angle of the ice tube is at 30 degrees
angle to the body and is lets say 30 meters long, 0
degrees ambient temperature at 100 meters
submerged, with no currents; how fast could this
vehicle go if 1 cubic meter of ice was produced
every 5 seconds? then how much energy would be
required by normal propulsion methods, as
opposed to how much energy would be required
to produce the said volume of ice. also assume the
vehicle travels for 10 kilometres (if it moves at all). |
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//since the [...] water [...] is usually between 0-3 degrees [...], hopefully cooling the water into ice will actually be fairly easy.// |
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Well, just remove the same amount of heat it would take to warm the same water to 86 deg. C. Ding! finished. Except... what you gonna do with all the waste heat? Can't vent it, the ice won't form; can't keep it, the sub will melt... |
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[lurch] - the same as is done on any other submarine. I don't know what is done, but it's an existing problem, so I guess it has an existing solution.
Possible uses: Heating interior (occupants, etc), heating (a little bit) the sloping rear 'propulsion plate', run a Stirling engine to recover some electrical energy. |
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//the same as is done on any other submarine.// What is done with //any other submarine// is that the excess heat is dumped into the surrounding water. Which is not a problem, since they aren't trying to freeze that surrounding water. That is, it's not a problem as long as you don't need to worry about being spotted by unfriendly thermal-imaging satellite eyes... then it's minimize, move, and stay deep. |
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[lurch] please explain why it takes the same
amount
of energy to freeze 1 cubic meter of saline water
under 100 meters of pressure and at 0 degrees
already compared with heating
that volume of water to 86C. i am sorry i am not
sufficiently educated in chemistry. |
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the excess heat could be used to heat a fin of the
vessel and create some lift. the vessel would be
forced downward on one side and upwards on the
other, assuming neutral buoyancy. |
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Wouldn't heating the water make it less dense, and hence make the sub less floaty? |
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//please explain why...// first, I gotta apologise for getting the number wrong - it's just slightly shy of 80, not 86. But, anyway... when you take water and warm it up, the only difference is the molecules are moving slightly faster. Cool it down, they go slightly slower. Cool it down enough, the molecules start to stick to each other to make ice crystals. |
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Now, remember, temperature is a measure of the average speed, or kinetic energy, in the molecules. But a water molecule that's free to dance around would have to give up a whole bunch of kinetic energy to become a stuck part of an ice crystal. So that's what it does - one molecule sticks, hands off its extra energy to the other molecules - they now go slightly faster, the stuck one is much slower, the average stays the same. (But it can't keep happening, because the unstuck molecules are going too fast to stick.) |
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Looked at on a macro scale, you're cooling down a tub of water, and you can extract heat all the way down to where it's at 0 deg. C. Then you extract some more heat. Measure the temperature again. It's still 0 deg. But, you notice a chunk of ice floating in the tub. |
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Extract more heat. Still 0 deg. Bigger chunk of ice. |
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Eventually the whole tub is a solid block of ice. There's no water molecules left to make the transition from liquid to solid state, so now when you extract heat, the temperature starts to go down again. |
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Anyway, look up "heat of fusion" or "enthalpy of fusion". Have pencil & paper by you. |
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It's going to take a lot of energy to run a cooler to locally freeze water around an immersed object. Ice cubes last awhile because of this. |
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