Build - Ranque-Hilsch Vortex Tube

[Feb. 4, 2017]

This is a placeholder page for a future build. Pending an actual build, references will be collected on this page.

Note: Although this is often called a Hilsch tube, the original invention was by by French physicist Georges J. Ranque while German scientist Rudolf Hilsch improved the original design; therefor it seems more proper to call the devise a Ranque-Hilsch Vortex Tube, or more commonly, just vortex tube.

SAFETY WARNING:

Do not underestimate the potential dangers of working with compressed air. Metal components under pressure can come apart frighteningly fast, and can cause severe injury. Wear eye protection at all times, and stand clear of potential debris paths. Do NOT try to hand-hold your vortex tube when operating. See the link below for some real world stores on the dangers of compressed air:

http://www.hobby-machinist.com/threads/respect-compressed-air.56183/

Nomenclature

There are a number of variables which can effect the efficiency of the vortex tube. For the purposes of discussion, the following conventions will be used:

d_c = inside diameter of cold orifice

D = inside diameter of hot tube

L = effective length of the vortex tube hot pipe from inlet to the plug

L₂ = effective length of the vortex tube cold pipe from inlet to end

n = number of vortex "nozzles"

R = radius of the vortex tube

Here is a simple spreadsheet for calculating important build dimensions for a given tube internal diameter : Vortex Tube Dimensions

Build #1 - Simple, Low Cost Vortex Tube

[Feb. 19, 2017]

My plan is build a number of vortex tubes, starting with a very simple tube and progressing to a more sophisticated build with replaceable parts. This first build is intended to be a "proof of concept" just to make a working (although not very efficient) vortex tube. This tube is made with mostly off-the-shelf parts, so anyone should be able to make one. I used a lathe and mill to build the tube (because I have them!), but it could also be built with basic workshop tools.

It works! While the performance is modest, I was actually able to get some hot/cold differences in operation. The best performance was at the start, before my air compressor reserve was depleted; I also measured with compression coming just from the compressor running. If I had access to a more powerful compressor, I think I would have gotten better performance (see the photos below for the specifications for my compressor).

Ambient temperature = 19.9 degrees C. The chart below shows the temperature differences I was able to attain (all temperatures in degrees C):

I turned a plastic plug on the lathe, and drilled a 5/32" diameter hole for the vortex jet. The plug was held in place in the tube with a brass pin (ground flush with the outside of the tube). The tube was inserted in the copper tee and held in place with medium strength thread-locker. Note the blue line on the tee to mark the position of the vortex orifice. I used thread-locker to fasten all tubing connections (except the end cap), both to avoid heating (and melting the plastic plug), and also so I could disassemble later if necessary.

For the cold orifice, I used a steel washer from my junk box; I was lucky enough to have one which had the dimensions I needed, but common washer could be used and turned or ground to fit. Instead of a valve I used a copper end cap with drilled holes (4 x 1/8" diameter holes); the vortex tube requires some restriction of flow on the hot end to work properly.

References

• The working principle of a Ranque-Hilsch Vortex Tube By Yunpeng Xue
  • I have listed the above first as it is the best document I have found on the topic. Excellent discussion of practical issues with good illustrations.
  • An Investigation Of The Effect Of The Hot End Plugs On TheEfficiency Of The Ranque-Hilsch Vortex Tube
  • The end plug can be optimized for heating or cooling.
• C. L. Stong, The Amateur Scientist, London: Heinemann Educational Books Ltd, 1962, Chapter IX, Section 4, The "Hilsch" Vortex Tube, p514-519
  • Suggests the following (but see next reference which recommends L=9.3D):
    • L = 32D
    • L₂ = L/3.5
  • The Effect Of L/DRatio On The Temperature Separation In The CounterflowVortex Tube
  • The optimal L/D ratio is found to be 9.3 (optimized for heating)
• Influence Of The Vortex Angle On The Efficiency Of The Ranque-Hilsch Vortex
  • No real improvement from changing the vortex angle.
• Maxwell’s Demon in the Ranque-Hilsch Vortex Tube : Technical article which includes some interesting schematics.
• New Design of Ranque–Hilsch Vortex Tube: Helical Multi-Intake Vortex Generator [abstract ony]
  • Recommends n=4 and d_c/D = 0.5
• Performance Improvement of Ranque - Hilsch Vortex Tube by Using Conical Hot Tube : This is primarily a technical paper, but it does include some practical advice for a build.
  • Suggests an internal conical angle of 2.5 degrees on the hot tube improves efficiency.
  • Performance Improvement of Ranque-Hilsch Vortex Tube by Varying Inside Surface Roughness of Hot Tube
  • Includes dimensions for the experimental vortex tube.
  • Performance Study OfA Modified Ranque-Hilsch Vortex Tube
  • The design of the vortex chamber is studied.
• Popular Science, May 1947, p. 144, Maxwell's Demon Comes to Life : Interesting article, but with very limited build information.
• Popular Science, Nov. 1947, p. 190, Homemade "Maxwell's Demon" Blows Hot and Cold : A rather crude build which appears to have poor performance; I include this as a design to be avoided.
• Popular Science, Oct. 1976, p. 123, Vortex Tubes Blow Hot and Cold : Includes interesting cutaway of commercial vortex tube, as well as some performance data.
• Vertical Integration with a Vortex Tube
  • Freshman engineering project with extensive drawings.
• Wikipedia article : Vortex Tube
• Patents (U.S.)
  • 1,952,281 (original US patent by Ranque) : Method and apparatus for obtaining from alpha fluid under pressure two currents of fluids at different temperatures
  • US3173273 A : Vortex Tube (1965); improvements by Charles D. Fulton.
    • Includes good drawings and lengthy discussion of design principles.