h a l f b a k e r yMy hatstand runneth over
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[edited: changed from Oil Only and added second system
of air to air]
A vortex can be induced to be stable i.e. in air guns,
where a vortex current can travel many meters.
If we cause vortex currents in opposing directions,
perhaps
even one vortex current inside the other, we may
construct
a low cost countercurrent heat exchanger.
Probably cheaper than a regular car radiator we would be
replacing systems that cool the oil through pipes.
// [Edit: Remarked out:] This is wrong as spidermother
noticed: Our
system would use oil only - so that there is no need to
separate the liquids.
This could work for any two "fluids" oil, air, water or
even coolants changing phase.
In order to overcome the mixing, dissolving and
evaporation of one flow into the other
[edit: Originally I wrote: could probably be solved (in
next halfbidea.]
can be solved by a second system. For example: In a
water to air system, the hot water vortices pass heat to
the cool air vortices but also evaporating some of the
water into the air. This air is kept in a closed cycle, but
in a second air to air counter exchange system passes
the heat to ambient air with a minimal transfer of water
vapor. A final dryer could be added at the exit of the
heated ambient air, to drain excess vapor and retain it
within the system.
something like this
http://en.wikipedia...e_Ranque-Hilsch.png
[j paul, Jul 14 2011]
Vortex Tube
http://en.wikipedia.org/wiki/Vortex_tube
not the same thing but simular [duroncrush, Jul 22 2011]
[link]
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>something like this [vortex tube link by Jean
Paul] |
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Er. No.
The [[vortex tube]] has a single input and double
output and works at high pressures only. |
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I'm talking about something SIMILAR to what is
shown INSIDE the vortex tube, but has two
input sources: One input for the hot flow
direction (to be
cooled), the other input for the cold flow (to be
heated). |
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This would work without the need for high
pressures (a simple aquarium pump at typically 2
PSI (0.136 atm) and 70 Lph would be enough to run
a good heat exchange system like this). |
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And vortex tubes work (as far as I know) only with
gases and not liquids, while I'm talking primarily
about liquids, although it would work with a gas
too, as proven by the vortex tube. |
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There will surely be some mixing, right? So this would be for situations where that doesn't matter too much. Is that what you are thinking? |
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I don't understand how a countercurrent heat exchanger helps when you have a single fluid, though. You need to exchange heat between the oil and the water in a conventional cooling system, because they must be kept strictly apart, but if you only have oil, why not just circulate the hot oil directly through the radiator and back to the engine? |
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This might be more useful, for instance, in ventilating a building, where an imperfect heat exchanger is better than nothing, and a small amount of mixing is not a big problem. |
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Sorry
I got the image of two vortices passing each other and jumped to the wrong conclusion.
what fluids?
if the more dense one is on e out side it might work. |
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Countercurrent exchange causes an almost total
crossover of hot to cold and cold to hot. |
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I'm trying to eliminate the "radiator" - a device
where the hot fluid flows in tubules that allow the
fast transfer of heat to a cold source outside
these tubules. My radiator will have no tubules in
it. |
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Spidermother was correct in asking: If you have a
cold source of oil, just recycle it into the system.
She's correct. I was half-thinking. So lets discuss
an oil to air, or water to air exchange: |
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Instead of going through a radiator, we could have
the oil or water come down in pipes in a vortex
with air at ambient temperature (I'll soon discuss
that) coming up in a countercurrent vortex. The
problem of evaporation would have to be dealt
with. So oil to air is easier to deal with. I suppose
there wouldn't be much loss to evaporation. Am I
assuming correctly? |
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Anyway - the air in the system cannot be from the
environment, because then air with much of the
oil particles or evaporated water will be leaving
the system, something we don't want happening. |
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So the hot air will go through a second air-to-air
vortex system. The cooling vortex will be with
ambient air. The cooled vortex will retain most of
the original air. This will ensure that a minimum of
water/oil will be lost to the external environment,
while the heat is moved out. |
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This second air-to-air heat exchange could have a
dryer at the exit of the hot ambient air, with
silicon-gel... (Hey: That gives me a new idea: see
next week) or using thermal wheel. |
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I'm lost - how would 2 complicated vortex guns that don't exist cost less than simple tubes that do? |
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Not complicated at all. "Simple tubes" are quite
expensive as anyone who wishes to buy a car
radiator knows. |
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In large scale applications like industrial chillers, they
could be the most significantly costly component.
This type of equipment can cost hundreds of
thousands of dollars for hospitals or other large
buildings. |
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I really like this idea, and the more general idea of
using vortices to carry one body of fluid within
another body of the same fluid. I just love vortices -
they are beautiful. |
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I have to say I don't hate this, but you are going to get some mixing. Thus it's only going to be appropriate for things where mixing is undesirable but not catastrophic, and even then probably require multi-stage systems as mentioned. |
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There remains the question of can you generate appropriate vortices without a very high pressure or flow rate that makes this prohibitively expensive/difficult. |
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I'm lost as to where you're going to get significant heat transfer without convective mixing. |
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Really interesting concept, but I don't think we have yet found an application where this could work. Very half-baked+ |
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I think I agree with [Rayford] depending on the definition of "significant". Although there will be heat transfer faster than diffusion due to molecular collision, the mixing at the edge of the vortex might make that effect insignificant. |
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I also worry about that throughput. I think ring vortices travel slower than the air in ductwork. In addition, there would need to be separation between vortices, so the heat exchanger will have to be much wider than a standard heat exchanger with the same capacity. |
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// significant heat transfer without convective
mixing// |
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In a closed-tube system, there's no mixing, and
heat is transferred through the tube walls (which,
admittedly, are usually copper or the like). In this
case, there's direct contact between a doughnut-
shaped vortex of cold water and the surrounding
body of hot water. |
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I also see lots of difficulties with this, but I still
love the idea of using vortex rings to carry one
liquid through another, miscible liquid. |
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With tubes present, the radiator acts as a thermal capacitor, albeit one with some resistance, capturing the heat and allowing radiation and convection to do their jobs. |
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Note that the Ranque-Hilsch vortex doesn't seem to transfer much heat from the warmer outer ring at the entrance to the cooler inner one escaping the tube. |
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If you have vastly different fluid densities, you'll end up with vastly different specific heats per volume of fluid, resulting in poor heat transfer efficiencies due to limitations on the side of the less dense fluid. |
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[Rayford] The transfer is the other way. It actually transfers heat from the cold air to the hot air, which is why you get hot and cold streams. Admittedly, I'm not sure the physiscs are clearly understood as to why this happens, but some of the theories do not depend on mixing. If it is possible to construct one that runs dissimilar materials, it might help explain the effect. |
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//With tubes present, the radiator acts as a thermal
capacitor,// |
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I don't think that's significant, unless the radiator is
only acting for very short periods. In continuous
operation, the thermal capacity of the metalwork
isn't relevant. |
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Thanks Max! Its great having someone on my side. |
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I originally was not thinking of the vortex tube but
before talking about how it wont work - take a
look at the currently single link (which is NOT my
idea, but has two vortices one inside the other in
opposite directions - and obviously there IS a total
transfer of heat from very cold at one end to
extremely hot at the other. |
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Granted this is achieved at high pressure, but has
anyone tried the heat exchange concept with low
pressure? You say it won't work. I say it probably
will. |
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[Pashute] The vortex gun/cooler requires the high pressure to generate the vortex. This also provides the energy to perform the anti-entropic separating of hot and cold air. Since you are trying to transfer heat from a hot to cold medium, that energy should not be required, but you are still going to have to generate the vortices, which will require energy from somewhere. |
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you should have deleted the link if it is getting in the way!
I would not have minded, it was only posted because I thought it might help. |
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j paul, it helps! I'm saying that although its not my
idea it does prove my point. |
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MechE I agree, I just think its worth checking how
much energy is needed for vortices, and I suspect
that not too much. |
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