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Sterling Vortex Pressure-Gain Tube

Ranque-Hilsch Vortex Tube used in reverse
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I remember early on in my time here, I stumbled upon an idea that just so happened to get me into mechanical engineering as a hobby. It called for the use of a Ranque-Hilsch Vortex tube- A neat little geometric marvel that somewhat embodies the concept of "Maxwell's Demon". Compressed air enters in through tangential port(s) within a section of tubing. Most of the flow will travel up the tube and out the "hot" end; the enlarged exhaust outlet with a conic section blocking the very center and allowing only the outer wall of flow out. Conversely, there is a small diameter hole on the other end of the tube, closest to where the tangential linlet ports are located. This very small hole in the center is called the "cold" end.

Whether through acoustic streaming or otherwise (the mechanism is still today not fully understood), somehow this system splits a compressed gas or gasses into very hot and very cold; from an inlet of, say, 70 degree F air at 80psi, one might obtain 200 degree F air out the hot end and -10F out the cold; the geometry effectively separates out the faster moving molecules while transferring maximal amount of energy to them out of the system; leaving a low pressure core of extremely dense, very low energy gas.

That's all well and good, but it does require a source of compressed air; in essence it trades pressure for temperature separation as both hot and cold outlets are only around @ ~9psi with an input of 80psi.

If one were to theorize that whatever means of temperature separation could be utilized in reverse, my idea is for two low pressure turbochargers, one intercooled one not, forcing their air in through the respective cold and hot side while imparting solid body rotation, and yielding very high pressure air out of the tangential ports at an average of the two temps; essentially using the temperature difference through working mechanism of vortices to amplify the pressure.

acurafan07, Jun 09 2013

Vortex Tube http://en.wikipedia.org/wiki/Vortex_tube
[acurafan07, Jun 09 2013]

Wirbelrohr http://amasci.com/amateur/wirbel.html
Little bit more technical than wikipedia [acurafan07, Jun 14 2013]

[link]






       I have toyed with that for sure- I guess the biggest drawback I see is the cold side port; even if the tangential inlet air is pressurized along with the vacuum of the hot side, Id think the orifice necessary to blockhotter air would be decently restrictive with that kind of flow. But, no way of being sure. Still have yet to tinker with a vortex tube in person.   

       The reason I picture this idea working out well in my head is because I'm envisioning the vortices combining in what would be the inlet cross-section of a normal VT, and the temperature difference causing a lot of expansion of the inner intercooled air vortex once it meets the hotter outer vortex; thus converting a lot of rotational momentum into additional pressure. If 100psi= 9psi at -8F @ 150cfm, 9psi at 180F @ 350cfm, is it not reasonable to think that the reverse would be feasible?   

       Realistically, we can't have much lower than ambient for the cold side; however even if the "hot" air, non-intercooled, is at ~250F and the two combine to form a flow of Xpsi air at 220F and 500cfm- it can be further aftercooled back to around ambient; retaining much of say ~50psi
acurafan07, Jun 09 2013
  

       So an antivortex? I have never heard of this property of vortices. It is very neat. But compressed gas already drops in temperature on losing its compression. Enthalpy, I think? I wonder how much colder the cold side is than the gas would be anyway or becoming depressurized.
bungston, Jun 09 2013
  

       If we don't really know why it works in the first direction, how we gonna know what to do in the second direction? (Or the third?)   

       However, I think it is fair to summise that one effect of a vortex is density separation, and another could be compression (at the outside) and rarification (at the inside) with corresponding differences in temperature.   

       If this is so, then how would a difference in temperature cause an increase in pressure?
Ling, Jun 10 2013
  

       All Parts are there, some preliminary experiment is certainly possible. A search of the literature might find it has been done.   

       The thermodynamic law about things going from order to disorder would vote against an efficient mechanism, but you might get some effect. Try it and see. Shop air and a water bath of filled with ice might get you started. Add the turbo later.
popbottle, Jun 10 2013
  

       //If this is so, then how would a difference in temperature cause an increase in pressure?//   

       Is that not the mechanism of Tornadogenesis?
acurafan07, Jun 10 2013
  

       Cool idea and an original take [acurafan07]. It seems to me that whatever centrifugal forces coming into play to concentrate heat energy into the outer layer of air wouldn't work the opposite way if the flow was reversed. The vortex would still be a vortex possibly rotating clockwise rather than anti-clockwise but wouldn't distribute heat energy back into the centre. This is interesting enough that an empirical test would be the way to go.   

       Does anyone know if the same effect happens with high pressure water and the relative volumes of hot and cold output? It might be a novel way to create hot water for showers and cold water for drinking in extreme, remote environments where you have access to a high pressure pump but nothing more.
AusCan531, Jun 10 2013
  

       Thanks [Aus] very glad you find it so.   

       Oh wait- Maybe the cold air should enter through the hot side then. I knew something was a little off there.   

       Even so, while the heat would not distribute outward, wouldn't the lack there-of within the center layer? As they would both seek equilibrium (remember, acoustical streaming or what not).   

       They've proven for almost certain that the "vortex separation" in which the two oppositely rotating vortices yield the highest temperature separation with minimum flow boundary layer interaction is caused by an ultrasonic frequency range; the german term for vortex tube is "wirbelrohr" or roaring whistle; referencing as the English translation doesn't the loud whistling sound inherent with the device.   

       I'd say my greatest curiosity relating to vortex tubes would be to integrate a broadband ultrasonic generator + piezo crystals and precisely amplify the frequency range. Also, some studies reference using a straight-through nozzle ejection gas or fluid through the blunt noze of the hot end cone allows for higher cold end extraction (essentially acting as a center-motive venturi)- coupling a frequency resonator along with an ultrasonic water nozzle in the hot cone- that could be very interesting but doesn't constitute an idea here just yet...quarterbaked?
acurafan07, Jun 11 2013
  

       I spent a few weeks breathing from the cold end of a vortex tube. Maybe that's why I don't understand anything on this page.
baconbrain, Jun 12 2013
  

       Upon further consideration, I doubt water would behave the same as air due to its lack of compressibility. Shame.
AusCan531, Jun 13 2013
  
      
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