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Anyone here know how a ranque hilsch vortex tube works?

  1. Apr 20, 2015 #1
    if you have a reference for someone with a semester of thermo (as opposed to a grad student with 3 semesters), a link would be appreciated .

    meanwhile, a quick question: temperature, as determined by one of its factors for gases, translational kinetic energy, follows a planck distribution. but with the way this separates hot and cool air, are the kinetic energy distributions of the separated air more or less constant ? i'm referring to the moment after they are separated.
     
  2. jcsd
  3. Apr 24, 2015 #2
    If you can believe this graduate engineering student who goes to Berkeley it looks like it is still a "hot topic of research".

    " 5 Summary

    It is nearly impossible to explain and predict the phenomenon inside the vortex tube. Kurosaka believed that acoustic streaming produces the total temperature separation within the vortex tube. However, he does not mention any energy conversion effects. Ahlborn, et al. concluded that the conversion of kinetic energy into heat explains the Ranque-Hilsch effect, but no explanation of vortex whistle or turbulence effects was made. Furthermore, numerical analyses are highly dependent on the turbulence model used to create simulations. Studies confirmed some of the earlier observations, but the numerical data still do not completely explain the temperature separation. This author believes that a combination of the many observations may be able to explain why the vortex tube induces a radial temperature separation. It may be concluded that acoustic streaming, energetics, turbulence effects, etc. are somehow connected with each other, but the missing links are yet to be found. The conclusions presented here have not been entirely refuted, but the single unifying theory that accounts for the Ranque-Hilsch effect is still a hot topic of research."

    From,

    http://www.me.berkeley.edu/~gtdevera/notes/vortextube.pdf [Broken]

    From,

    https://www.google.com/search?q=how...=Dd46VcasO-2xsASWi4DwBw&ved=0CAYQ_AUoAA&dpr=1
     
    Last edited by a moderator: May 7, 2017
  4. Apr 24, 2015 #3
    Also see,

    http://www.newmantools.com/vortex.htm#vortex

    From link,

    Operation
    Any fluid that flows and rotates about an axis such as a tornado, is called a vortex. A vortex tube creates a vortex and separates it into two air streams-one hot and one cold. Figure 1 shows how a vortex tube works. Compressed air enters a cylindrical generator which is proportionately larger than the hot (long) tube. The generator causes the air to spiral. The spiraling air is forced down the inner walls of the hot tube at speeds reaching 1,000,000 rpm. At the end of the hot tube, a small portion of this air exits through a needle valve as hot air. The remaining air is forced back through the center of the incoming air stream but at a slower speed. The heat in slower moving air is transferred to the faster moving incoming air. This super-cooled air flows through the center of the generator and exits through the cold air exhaust port.

    Temperature Separation Effects
    The Vortex Tube Creates two types of vortices: free and forced. In a free vortex (like a whirlpool) the angular velocity of a fluid particle increases as it moves toward the Center of the vortex-that is, the closer a particle of fluid is to the center of a vortex, the faster it rotates. In a forced vortex, the velocity is directly, proportional to the radius of the vortex-the closer the center, the slower the velocity.

    In a vortex tube, the outer (hot) air stream is a free vortex. The inner (cold) air stream is a forced vortex. The rotational movement of the forced vortex is controlled by the free vortex (hot air stream). The turbulence of both the hot and cold air streams cause the layers to be locked together in a single, rotational mass.

    The inner air stream flows through the hollow core of the outer air stream at a slower velocity than the outer air stream. Since the energy is proportional to the square of the velocity, the cold air stream loses its energy by heat transfer. This allows energy to flow from the inner air stream to the outer air stream as heat creating a cold inner air stream.

    Cold Fraction
    The percentage of total input air volume released through the cold air exhaust of a Vortex Tube is called the Cold Fraction. A valve located in the hot air exhaust of the Vortex Tube controls the Cold Fraction. For example, if the total compressed air input is 15 SCFM (424.5 SLPM) and the Cold Fraction is 70%, the amount of air exiting the cold end wilt be 10.5 SCFM (297.2 SLPM); 4.5 SCFM (127.4 SLPM) exits the hot end.

    Cold Fractions of 60-80% produce maximum efficiency-greatest power (BTUH) output- and are ideal for cooling machining operations, electrical controls and enclosures, liquid baths and workers. Low Cold Fractions (less than 50%) have reduced airflows and produce the lowest temperatures for cooling glass, laboratory experiments and for testing electronic components.
     
  5. Apr 25, 2015 #4
  6. Apr 25, 2015 #5
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