Vortex Tubes – The Basics, And Beyond

The Vortex Tube might be just about the most interesting compressed air device around.  They have no moving parts, and they don’t need any but a compressed air supply, which they ‘split’ into a hot air stream, and a cold air stream.

EXAIR Vortex Tubes come in three sizes – Small, Medium, and Large – and 24 distinct Models across those three sizes.  They’re all in stock, along with Hot & Cold Mufflers (for sound level reduction,) Automatic Drain Filter Separators (to keep the air supply clean & moisture free,) Oil Removal Filters (to coalesce any trace of oil from the air supply,) and Solenoid Valves & Thermostats (to automate operation.)

From left to right; a few value added accessories for your Vortex Tube: Hot Muffler, Cold Muffler, Automatic Drain Filter Separator, Oil Removal Filter, and Solenoid Valve/Thermostat Kit.

The Vortex Tube, right out of the box, is easily adaptable to a wide range of cooling (or heating) applications.  If your needs are specific, though, we can customize a Vortex Tube to meet them:

  • Material of construction: our stock Vortex Tubes are made of 303SS and are equipped with a plastic Generator and Buna o-ring.
    • For high temperature (>125F ambient) applications, we can install a brass Generator and Viton o-ring, suitable for ambient temperatures up to 200F.
    • If the environment is particularly aggressive, or if industry codes (I’m looking at you, food & pharma) call for it, we can also make them out of other materials.  We’ve, for instance, made them out of 316SS, complete with material certifications, when needed.
  • Flow & temperature: the Hot Valve can be opened or closed to dial in a particular Cold Fraction (that’s the percentage of the supply air which is directed to the cold end.)  If you know what flow rate and temperature you want, we can replace the Hot Valve with a non-adjustable plug, so your Vortex Tube’s cold flow is only dependent on the compressed air supply temperature and pressure.
  • Accessories: if you’re looking for features like a magnetic base, or a flexible cold air hose, you might consider an Adjustable Spot Cooler.  If you like the idea of tool-free change of air flow/temperature, that’s definitely the way to go.  If you want those other options, and don’t mind using a screwdriver to adjust the Cold Fraction, those other options are compatible with any Medium Vortex Tube.
Model 3925 Adjustable Spot Cooler

These are just a few of the most common possibilities for customizing a Vortex Tube.  If you have a spot cooling application you’d like to discuss, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Georges J Ranque: Father of the Vortex Tube

Georges J. Ranque is known as the inventor and father of the Ranque-Hilsch Vortex tube. The vortex tube is device that takes a compressed gas and generates hot and cold streams from a source of compressed gas. George accidentally discovered the phenomenon on accident while studying physics at Ecole Polytechnique in Paris France. Ranque was looking was performing an experiment on a vortex-based pump to vacuum up iron fittings; during the experiment he noticed that warm air was being expelled out of one side and cold air out of the other when he inserted a cone into one end of the vortex. In 1931 Ranque filed for a patent for the vortex tube and two years later presented a paper on it.

Georges vortex tube was all but lost and forgot about until 1945 when the German physicist Rudolph Hilsch published a paper on the device. This paper became widely read and exposed the vortex tube to the industrial manufacturing environment. This paper revived what was thought to be lost and led the vortex tube into what we see today.

How an EXAIR Vortex Tube operates

During World War 2 Georges Ranque started to develop different steels that would be used in military aviation efforts. He later went on to work at Aubert et Duval Steelworks as the Director of Metallurgical Laboratory. While at Duval he would continue to developing alloys for the aviation industry.

Interestingly, in 1972 he went on to publish a book on the search for the Philosophers Stone, a mythological chemical substance that Alchemist’s thought could be used to turn base metals into Gold. The following year in 1973 he passed away in his home just outside of Paris.

Here at EXAIR we have expanded the uses of Ranque’s original vortex tubes for various different cooling uses. The vortex tube can be found in our Cold Guns, Spot Coolers, and Cabinet Coolers. In many cases EXAIR’s spot coolers and cold guns have been used to replace coolant in simple milling and grinding applications. Also, EXAIR’s Cabinet Coolers have been keeping control cabinets from overheating for many decades. 

If you have any questions or want more information on how we use our vortex tubes to improve processes all over industry. Give us a call, we have a team of application engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Vortex Tube Cold Fractions Explained

Simply put, a Vortex Tube’s Cold Fraction is the percentage of its supply air that gets directed to the cold end. The rest of the supply air goes out the hot end. Here’s how it works:

The Control Valve is operated by a flat head screwdriver.

No matter what the Cold Fraction is set to, the air coming out the cold end will be lower in temperature, and the air exiting the hot end will be higher in temperature, than the compressed air supply.  The Cold Fraction is set by the position of the Control Valve.    Opening the Control Valve (turning counterclockwise, see blue arrow on photo to right) lowers the Cold Fraction, resulting in lower flow – and a large temperature drop – in the cold air discharge.  Closing the Control Valve (turning clockwise, see red arrow) increases the cold air flow, but results in a smaller temperature drop.  This adjustability is key to the Vortex Tube’s versatility.  Some applications call for higher flows; others call for very low temperatures…more on that in a minute, though.

The Cold Fraction can be set as low as 20% – meaning a small amount (20% to be exact) of the supply air is directed to the cold end, with a large temperature drop.  Conversely, you can set it as high as 80% – meaning most of the supply air goes to the cold end, but the temperature drop isn’t as high.  Our 3400 Series Vortex Tubes are for 20-50% Cold Fractions, and the 3200 Series are for 50-80% Cold Fractions.  Both extremes, and all points in between, are used, depending on the nature of the applications.  Here are some examples:

EXAIR 3400 Series Vortex Tubes, for air as low as -50°F.

A candy maker needed to cool chocolate that had been poured into small molds to make bite-sized, fun-shaped, confections.  Keeping the air flow low was critical…they wanted a nice, smooth surface, not rippled by a blast of air.  A pair of Model 3408 Small Vortex Tubes set to a 40% Cold Fraction produce a 3.2 SCFM cold flow (feels a lot like when you blow on a spoonful of hot soup to cool it down) that’s 110°F colder than the compressed air supply…or about -30°F.  It doesn’t disturb the surface, but cools & sets it in a hurry.  They could turn the Cold Fraction down all the way to 20%, for a cold flow of only 1.6 SCFM (just a whisper, really,) but with a 123°F temperature drop.

Welding and brazing are examples of applications where higher flows are advantageous.  The lower temperature drop doesn’t make all that much difference…turns out, when you’re blowing air onto metal that’s been recently melted, it doesn’t seem to matter much if the air is 20°F or -20°F, as long as there’s a LOT of it.  Our Medium Vortex Tubes are especially popular for this.  An ultrasonic weld that seals the end of a toothpaste tube, for example, is done with a Model 3215 set to an 80% Cold Fraction (12 SCFM of cold flow with a 54°F drop,) while brazing copper pipe fittings needs the higher flow of a Model 3230: the same 80% cold fraction makes 24 SCFM cold flow, with the same 54°F temperature drop.

Regardless of which model you choose, the temperature drop of the cold air flow is determined by only two factors: Cold Fraction setting, and compressed air supply pressure.  If you were wondering where I got all the figures above, they’re all from the Specification & Performance charts published in our catalog:

3200 Series are for max cooling (50-80% Cold Fractions;) 3400’s are for max cold temperature (20-50% Cold Fractions.)

Chocolate cooling in brown; welding/brazing in blue.

EXAIR Vortex Tubes & Spot Cooling Products are a quick & easy way to supply a reliable, controllable flow of cold air, on demand.  If you’d like to find out more, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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