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Vortex Tube Operation

Fluid (air) that rotates around an axis (like a tornado) is called a vortex. A Vortex Tube (VT) also called a Ranque-Hilsch Tube or cooling tube creates cold air and hot air by forcing compressed air through a generation chamber which spins the air centrifugally along the inner walls of the Tube at a high rate of speed, over 1,000,000 RPM, toward the control valve. A percentage of the hot, high-speed air is permitted to exit at the control valve. The remainder of the (now slower) air stream is forced to counterflow up through the center of the high-speed air stream, giving up heat, through the center of the generation chamber finally exiting through the opposite end as extremely cold air. Vortex tubes generate temperatures down to 100°F below inlet air temperature.

The volume and temperature of cold air produced by a Vortex Tube are controlled by the valve in the hot air exhaust. This volume (Cold Fraction) is the percent of total input air released through the cold exhaust. For example, if the total volume of compressed air input is 15SCFM and the Cold Fraction is 70%, then 10.5 SCFM exits the cold end and 4.5 SCFM exits the hot end. A high Cold Fraction. (i.e., more than 50% or the input air exiting the cold air exhaust), produces the maximum efficiency -- the greatest BTUH output. This occurs at Cold Fractions of 60% to 70%, where the amount of air released at the cold exhaust and the temperature drop are optimized. Cooling machining operations, electronic controls, liquid baths, and workers will require high Cold Fractions for maximum refrigeration.

History

The Vortex tube or Ranque effect was discovered around 1930 by George Ranque. George Ranque, a French physics student, was experimenting with a vortex-type pump he had developed when he noticed warm air exhausting from one end, and cold air from the other. Ranque soon forgot about his pump and started a small firm to exploit the commercial potential for this strange device that produced hot and cold air with no moving parts. However, it soon failed and the vortex tube slipped into obscurity until 1945-1947 when Rudolph Hilsch, a German physicist, published a widely read scientific paper on the device which he called a Wirbelrohr.
Hilsch Vortex Tube Spiral Chamber Cutaway

The separation of gas mixtures, oxygen and nitrogen, carbon dioxide and helium, carbon dioxide and air with the vortex tube(VT) was reported in 1967 by Linderstrom-Lang and in 1977 by J. Marshall.
In 1979 steam was used as working medium by Takahama. In 1979, two-phase propane was used as the working medium by Collins.
In 1988 Balmer applied liquid water as the working medium. It was found that when the inlet Pressure is high, for instance 20-50 bar, the energy separation effect still exists. So it proves that the energy separation process exists in incompressible (liquids) vortex flow as well.
In 2004, natural gas was used as working medium and with the VT natural gas was liquified by Nikolay Poshernev.

Vortex Theories

1. While one airstream moves up the tube and the other down it, both rotate in the same direction at the same angular velocity. That is, a particle in the inner stream completes one rotation in the same amount of time as a particle in the outer stream. However, because of the principle of conservation of angular momentum (tendency of a rotating object to keep rotating at the same speed about the same axis of rotation), the rotational speed of the smaller vortex might be expected to increase. (The conservation principle is demonstrated by spinning skaters who can slow or speed up their spin by extending or drawing in their arms.) But in the vortex tube, the speed of the inner vortex remains the same. Angular momentum has been lost from the inner vortex. The energy that is lost shows up as heat in the outer vortex. Thus the outer vortex becomes warm, and the inner vortex is cooled.
2. Temperature is an average of how fast the particles are bumping into each other. Because it's an average, it means that air is composed of fast and slow (hot and cold) particles. A vortex tube merely separates the hot which goes to the peripheral of the spinning vortex and exhausts out the hot side and the cold air is diverted back through the center to exit the cold end.
3. Turbulent eddies (whirlpools) expanding and contracting are causing the heat transfer.
4. Adiabatic compression and adiabatic expansion is causing all the heat separation.
5. Acoustic streaming theory states there is a relationship between the acoustic resonance
frequencies and the forced vortex motion frequency. The energy separation inside the VT is due to the damping of the acoustic streaming along the axis of the tube towards the hot exhaust.
6. Secondary circulation states that some of the separation of heat is caused by a closed flow of medium inside the VT because studies show cumulative mass flow over the cross section of the vortex tube in the cold end direction, is larger than the cold exhaust flow.
All these theories focus on thermodynamics (compression and expansion), turbulent flow, viscous friction, internal heat transfer, acoustics and flow pattern.

Advantages over Traditional Refrigeration

* Maximum Ambient Temperature of 175°F verses 130°F for traditional
* No moving parts, high reliability
* Output easily controlled
* Constant temperature
* No electricity or RF interference
* Intrinsically safe
* No refrigerant or chemicals
* Effective spot cooling
* Low cost
* Compact, lightweight
* Can cool in dirty or contaminated area
* Instant cold air
* Adjustable temperature
* Produces cold air 100F° (55.6C°) below inlet air temperature
* Can produce air from -50F° (-46C°) to +260F° (+127C°)

Applications

Vortex Tubes have a very wide range of application for industrial spot cooling on machines, assembly lines and processes.

• Cool machining operations
• Set solders and adhesives
• Cool plastic injection molds
• Dry ink on labels and bottles
• Dehumidify gas samples
• Cool worker suits in extreme conditions
• Cool heat seal operations
• Thermal test sensors and choke units
• Cool cutter blades
• Temperature cycle parts
• Cool bore-scopes (while in a 1200F° boiler)
• Cool miner's suits
• Cooling glass
• Laboratory experiments