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THe Ranque_Hilsch vortex can separate hot from cold air without any moving parts.
I know that this concept has been visited before, but this incredible marvel needs to be revisited (redux) and more fully examined.
If compressed air at room temperature is forced into a vortex tube, air as hot
as 200C will emerge from one arm and as cold as -50C from the other. Tubes can be placed in series, by the way.
I suggest that we mount them on top of lorries, with a cowling that forces air into them.
The cold air could be channeled into the back of the freezer truck, or into the cab on a hot day. The hot air could be released straight up, thus, not allowing hail to form, and saving literally millions of Pounds in hail damage.
One of many many links.
http://www.southstr...vtmatl/rhvtinfo.htm
[r_kreher, Jun 01 2008]
A recent thesis written on the device.
http://alexandria.t...xtra2/200513271.pdf
[daseva, Jun 02 2008]
Vortex tubes are inefficient coolers
http://en.wikipedia...tex_tube#Efficiency
[david_scothern, Jun 03 2008]
No Military Applications???
http://www.spartanb...rt-tank-Final!!.jpg
Britain's RAF Armored Brigadoon 405 [r_kreher, Jun 03 2008]
Wind Powered Fridge
Wind_20Powered_20Fr...o_20moving_20parts)
Prior funnel art, also bogus. [csea, Jun 04 2008]
Exair
http://www.exair.co...s+and+Spot+Cooling/
One example of Commercially available vortex tubes [csea, Jun 04 2008]
Amateur Scientist article on Vortex Tubes
http://www.visi.com/~darus/hilsch/
DIY project [csea, Jun 04 2008]
[link]
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If this is more efficient that a compressor, why are they not used more? |
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I have a doubt or two about the hail repelling aspects but the idea is too cool. |
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an anno has gone missing. if i deleted it, it was quite by accident. If you did, then hopefully you are editing it. |
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if you have a vortex, won't hot air, which weighs less, accumulate at the center ? |
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According to the first link, temperature
differences for a single-stage vortex
are much less than the 250°C you cite
(unless I mis-read). Also, efficiencies
are very low, meaning that there'll be a
strong tradeoff between the energy (as
increased aerodynamic drag) needed to
operate the vortex and the
cooling/heating effect it has. You may
be better off with a conventional heat
pump.... |
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...but I love the idea of the R-H vortex. |
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I am surprised that this device isn't getting more attention. I know that Engineers Without Borders are trying to develop it to take refrigeraton to the sub-Sahara. It apparently works, and as stated, can be set up in series. |
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Maybe one day the military will find a need for it. |
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Um... Friends, Romans and Countrymen. This vortex IS a good idea, and may well have ramifications of significant import for all of humanity. And I get a half a bun??? I was clicking on the "Random" button and saw where Bread and Butter Vendor got 48 + signs. wassssssssap? |
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I don't understand how it works, so to me it reads "given magic, we can do this". Why the focus on "compressed air" ? Wouldn't "air at a sufficient velocity" do ? and would the energy required to compress (or speed up) the air be less than that required by more normal refrigeration methods. |
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Also note that those ones with all the +'s have (usually) been around for a few years. |
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For this to be a good idea, the vortex must be more efficient than a heat pump that could equally be used to cool the truck - or more correctly, have a better whole-life energy cost including manufacture (which will probably benefit the simpler, no-moving-parts vortex). I don't think these devices are known for their efficiency, but rather their simplicity. Good things if you have a lot of free compressed air, bad if you're having to drive them with energy from your engine. |
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//If this is more efficient that a compressor// |
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It is very inefficient, and so won't be replacing conventional refrigerant / compressor based means of cooling. |
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It does have applications were the low efficiency is of no consequence. The compressor (which gets pretty hot) can be placed far away from the vortex and its output cooled, for instance. |
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Liquified air. Is that cold enough?? |
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"Chaining vortex tubes together, such that the cold outlet of one leads to the inlet of another could in principle at least reduce the temperature of the working gas to the point where it would liquefy. Part of my work has analysed the likely behaviour of several possible such 'cascades' for the liquefaction of air. " |
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Indeed, these devices are commonly used for cryogenic applications (in cascade). |
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The problem is that they either require a compression unit (which will cost lots of energy), or an intake of such large surface area as to cause much resistance against powering the vehicle forward (presumably forcing all the high velocity air into a nozzle via a large conical section), thereby also requiring lots of power. Either way, slapping one of these things on a car has considerable drawbacks, though it would be cool to have. |
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The giant cone on top could double as an uber frightening horn [+]. |
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I'm neutral on this one. I once did some research online about using a hilsch to cool a car's intake temp. I concluded it would be impractical because the pressures required for any reasonable amount of air would be very high. Plus, I'm not sure how much you touched on this but there is always a fraction of how much air goes to which side. For instance if the hot side gets the majority, it will be midly warm but with greater volume, and the cold side will be extremely cold but with very low volume. |
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But it is a neat idea nonetheless. |
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what am i missing? Here is a device with no moving parts, that can reach literally cryogenic temperatures. why is there all this negativity? not as efficient as a heat pump? are you kidding? |
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The "pressure" problem seems far from insurmountable. |
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care to cool a desert tank? Bring refrigeration to the Sahara? save petrol? |
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<Points at blackboard on which are written the Laws of Thermodynamics> |
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[kreher], the point is that all the energy required to run the thing is derived from the high pressure (high potential energy) at the inlet. Achieving this pressure is your main concern. And if you read my link, you'll see that a common inlet pressure is 7 times greater than the outlet. That's 90 psi, sir. Which is a daunting number if you sit to think about it. |
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... (pressure in a car tire is ~ 40psi, won't be able to pump this with my little arms)... |
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see? This is why I was going on about a massive cone on top of your lorry. |
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90 psi... wait a minute, i can do this in my head. that's 6.3 Kg/cm2. (pause) (crickets chirping) (pause) I'm waiting for a stronger argument. |
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//(pause) (crickets chirping) (pause)// The thoughts of a *ranque* amateur. |
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You are waiting for a stronger argument, I am waiting for a stronger truck! |
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I remember my grandfather extolling the virtues of *his* compressed air vehicle engine. Basically a remodelled pnuematic drill. My arguments, at the tender age of eight and now some frundrgen years later, still hold true. Compressed air is expensive energy. No matter how you produce it. There are applications for vortex tube cooling/heating where compressed air is a "by-product" or would otherwise have been wasted. There are arguments for low maintenance, low mechanical strain. But you won't find these on top of a refrigerated truck. Bugs, for a start. |
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Moreover, the effeciency (cooling/heating ability) drops precipitously with pressure decrease. i.e. a non-linear drop in temp diff vs pressure drop. Will try and link to study. It is not a fact of low pressure=small temp difference, but we can "daisy-chain". |
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90 psi? That's a little more than six times atmospheric pressure. |
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Supposing we need a cooler on a vehicle, the best way to do it is the way with the greatest efficiency. Don't confuse output temperature with efficiency - a vortex tube system will indeed reach a very low temperature, but as [acurafan07] says will only produce a very small volume of air at that temperature, while dumping a lot of heat from the other output. |
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Vortex generators are not known for their efficiency (see link to Wikipedia), therefore this is not a suitable replacement for conventional heat pumps, because removing your air conditioning and replacing it with an equivalent vortex generator would increase your fuel consumption. |
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Unless, that is, you're measuring the merit of the device on some criterion other than fuel consumption. In some countries, mechanical simplicity would outweigh fuel economy (old Land Rovers and Toyota Land Cruisers go forever). |
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I may be wrong but i suspect that no matter how agressive your cone there is no way that it will produce 90psi at even 100 mph. This is more than six atmospheres of pressure. Additionally I can think of few operations where low efficiency is not a problem (military applications?). Neat, but not really something that will really work. If you want a huge source of waste energy look to the tailpipe. |
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// No Military Applications//
No military applications? Isn't that what they said about the 50 calibre machine gun? |
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Always with the funnels. Bernoulli must be rolling in his grave. |
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A truck at 100mph will give around 1.19kPa, or around 0.2psi. |
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Bad science. However, MFD removed to show as an example for others. |
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Just for kicks, about how fast would it have to go to generate the needed 90psi? |
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well, what i have learned from this exercise is that a funnel concept may not be the answer at all. What would i need to get to 90 psi? I think that would depend on the intake device. BTW several of my students are now very interested in this vortex. We will most likely build one next year. Thanks for all your input. I really enjoy this. |
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I haven't seen one of these things in action, ever, and all my knowledge of them comes from a 1970s issue of Popular Science (back before it started to suck). Back then, PS had one note that I could easily comprehend: it made one helluva lot of noise. |
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Now, my heat pump makes enough noise as it is. If this thing generates the kind of screech that I expect a high-velocity stream of air must, I don't want to supplant my tried-and-true technology, with its low-frequency, easily ignored rumble. |
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I'm glad to see your enthusiasm for the concept has not been dampened due to the hard reality of funnel failure! |
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See [link] for C. L. Stong's Amateur Scientist book ca. 1960. I built one in the early '70s along the lines of this model, and it worked fairly well. I compressed air to run it by using a pair of tanks, connected by valves, and filling one tank with water from the garden hose (at about 80 psi) so that the displaced air filled the second tank, closed the valve, drained the first tank, and repeated until I had about 2 l. of compressed air. Eventually, I got a schrader valve, and could fill the tank at the local gas station (but only to about 40 psi.) |
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You might be able to build a windmill-powered compressor to provide the compressed air, however, realize that the energy to drive the compressor basically comes at the expense of fuel economy. Hugely inefficient, but possibly fun, and educational. |
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/Just for kicks, about how fast would it have to go to generate the needed 90psi?/ |
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All things being equal*, about 1000m/s, or 3600km/h, or 2200mph. |
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*This is Mach 3 at sea level. The funnel physics do change above Mach 1, so it's not really a valid calculation. The fact remains however, that a truck will be of insufficient speed. |
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where did you get these figures? I think these measurements would come from holding a manometer out the window, without any intake device at all. I am sure that if you had any kind of well-designed intake device at all, you could easily exponentially magnify these results. |
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// you could easily exponentially magnify these results // |
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Good idea. If the facts don't fit the theoy, change the facts .... |
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This is SSSSOOOOOO doable!! You guys just wait till I Get my tabletop cold-fusion air compressor patented... (and yes, i will consider investors) |
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The vortex thingie would play a weak fiddle to your fusion device. |
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