Rudolf Hilsch, Shining a Light on the Vortex Tube

The Vortex Tube is also known as the Ranque – Hilsch tube is a device that takes a single source of compressed gas and splits it into two streams a hot and a cold. The Vortex Tube was invented in 1933 by French physicist Georges J. Ranque, however his findings never really went main stream until Physicist Rudolf Hilsch improved the design and published a widely read paper in 1947 on the device, which he called a Wirbelrohr. (Original publication in German can be found here.)

The Original drawing from Rudolf Hilsche’s 1947 Publication.

Compressed air is supplied into the tube where it passes through a set of nozzles that are tangent to the internal counter-bore. The design of the nozzles force the air to spin in a vortex motion at speeds up to 1,000,000 RPM. The spinning air turns 90° where a valve at one end allows some warmed air to escape. What does not escape, heads back down the tube in the inner stream where it loses heat and exhausts through the other end as cold air.

How a Vortex Tube Works

Both streams rotate in the same direction and at the same angular velocity. Due to the principle of conservation of angular momentum, the rotational speed of the inner vortex should increase. However, that’s not the case with the Vortex Tube. The best way to illustrate this is in Olympic Figure Skating. As the skater is wider, the spinning motion is much slower. As she decreases her overall radius, the velocity picks up dramatically and she spins much quicker. In a Vortex Tube, the speed of the inner vortex remains the same as it has lost angular momentum. The energy that is lost in this process is given off in the form of heat that has exhausted from the hot side of the tube. This loss of heat allows the inner vortex to be cooled, where it can be ducted and applied for a variety of industrial applications.

This Vortex Tube theory is utilized in basic Vortex Tubes, along with a variety of other products that have additional features specific for your application. EXAIR’s line of Cabinet CoolersCold GunsAdjustable Spot CoolersMini Coolers, and Vortex Tubes all operate off of this same principle.

If you’re fascinated by this product and want to give it a try, EXAIR offers an unconditional 30-day guarantee. We have them all in stock and ready to ship as well, same day with an order received by 2:00 ET. Feel free to get in contact with us if you’d like to discuss how a vortex-based product could help you in your processes.

Jordan Shouse
Application Engineer

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Rudolf Hilsche’s Publication Drawing provided by Die Zeitschrift für Naturforschung

(Photo Link https://zfn.mpdl.mpg.de/data/1/ZfN-1946-1-0208.pdf )

Heavy Duty Line Vacs: Made for Abrasive Materials and/or Higher Throughput

The Heavy Duty Line Vacs are made from a hardened alloy steel for abrasion resistance.  The generators inside these Line Vacs are more powerful than the standard models; so, that they can also convey heavier materials at higher conveyance rates.  They can reach rates as high as 40 lbs./min. (18.2Kg/min) of material.  With the hardened alloy construction, they are great for sand blasting applications, ceramic, glass, garnet, tumbling media and steel shot.  They are manufactured with inlet and outlet connections for ship-on hoses or threaded pipes.  EXAIR stocks the Heavy Duty Line Vacs in the range from ¾” (19mm) to 3” (76mm) for both hose and NPT connections.  These Line Vacs are our most powerful design with great wear resistance.

2″ Heavy Duty Line Vac (left;) the 3″ model (right.)

The table below gives a quick comparison of the EXAIR Light Duty Line VacStandard Line Vac & the Heavy Duty Line Vac models.  The test shows the 2″ size in each model conveying Rock Salt over two different horizontal distances.  As expected the Heavy Duty Line Vac conveys more material in less time!

Heavy Duty Line Vac Distance

The performance of the Heavy Duty Line Vac’s is nothing short of amazing!  With vacuum ratings between -144 to -20 inches of water column, it is more than likely there is a Heavy Duty Line Vac model that will suit your application.

HD Line Vac Performance

Models range from 3/4″ OD to 3″ OD either in smooth bore or NPT threaded models for the ultimate in versatility.  The table below shows the different Heavy Duty Line Vac Models and their respective recommended kit, which includes a pressure regulator for fine tuning performance, filter separator to keep the compressed air supply clean and a mounting bracket.

HD Line Vac Offerings

If you would like to discuss the Heavy Duty Line Vac or any of our quiet and efficient compressed air devices, I would enjoy hearing from you…give me a call.

Jordan Shouse
Application Engineer

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Compressed Air Dryers : What are they Good For?

Absolutely Nothing….. err ALOT! They are really good for a lot! Specifically removing moisture/condensate from compressed air.

In almost every operation, clean, dry compressed air will result in lower operating costs. The purpose of compressed air dryers is to overcome the dew point of your compressed air by removing water from it. Compressed air can contain humidity, and in the right environments it can reach the dew point temperature and condense into a damaging liquid. This liquid can be problematic, as it can contaminate your products or equipment, causing frozen pipes, and possibly leading to corrosion and other issues.

Now that we know how important they are how do you know which one is right for you?

Types of compressed air Dryers

Refrigerant Dryer – the most commonly used type, the air is cooled in an air-to-refrigerant heat exchanger. (Here is a great blog deep diving on Refrigerant Dryers)
Regenerative-Desiccant Type – use a porous desiccant that adsorbs (adsorb means the moisture adheres to the desiccant, the desiccant does not change, and the moisture can then be driven off during a regeneration process). (Here is a great blog deep diving on Desiccant Dryers)
Deliquescent Type – use a hygroscopic desiccant medium that absorbs (as opposed to adsorbs) moisture. The desiccant is dissolved into the liquid that is drawn out. Desiccant is used up and needs to be replaced periodically. (Here is a great blog deep diving on Deliquescent Dryers)
Membrane Type– use special membranes that allow the water vapor to pass through faster than the dry air, reducing the amount of water vapor in the air stream. (Here is a great blog deep diving on Membrane Dryers)

The selection of an air dryer is done best by the professional who knows or learns the particular end uses, the amount of moisture which each use can tolerate and the amount of moisture which needs to be removed to achieve this level. Air, which may be considered dry for one application, may not be dry enough for another. Dryness is relative. Even the desert has moisture. There is always some moisture present in a compressed air system regardless of the degree of drying.

For compressed air, the best way to specify dryness is to cite a desired pressure dew point. Different types of dryers, therefore, are available with varying degrees of pressure dew point performance. To specify dew point lower than required for an application is not good engineering practice. (Naming a pressure dew point is how to state the degree of dryness wanted.) It may result in more costly equipment and greater operating expense.

If you have questions about compressed air systems and dryers or any of our 15 different Intelligent Compressed Air® Product lines, feel free to contact EXAIR, and I or any of our Application Engineers can help you determine the best solution.

Jordan Shouse
Application Engineer

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Gen4 Super Ion Air Knife Cleans Art!

I took a phone call recently from an artist who applies thin colored films to glass sheets. He then uses several panes of that colored glass to build beautiful simplistic art installations! They are so clean and clear every angle you look through you get a different color and view you wouldn’t expect. But he was having a problem, these sheets of glass were building a large static charge and making every bit of dust and dirt stick to the surface. They were spending countless hours painstakingly cleaning every panel of glass because one spec of dirt would ruin the end goal.

Colored Glass Walk Way

Originally they called in to look at the Super Air Knife, which is good to remove dirt, dust and debris – but does not eliminate static if that debris were to be held on to the glass with static. His idea was to poor water on the glass then use the Super Air Knife to blow the water off, messy but they were hoping to kill two birds with one stone. Getting rid of the static and cleaning the glass all at once. He was excited when I told him about out our GEN4 Super ION Air Knife! It would have the ability to neutralize the static charge and blow away any debris clinging to the surface.

The Gen4 Super Ion Air Knife floods an area or surface with static eliminating ions. With a uniform airflow across its length, misalignment to critical surfaces, like a web, is avoided.  The force can be adjusted from a light breeze, to a full out blast of air. The Gen4 Super Ion Air Knife is electrically powered, is shockless and has no moving parts.

How It Works

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How The Gen4 Super Ion Air Knife Works

In the diagram above, compressed air flows through an inlet (1) into the plenum chamber of the Gen4 Super Ion Air Knife. The flow is directed to a precise, slotted orifice. As the primary airflow exits, it creates a uniform sheet of air across the entire length, pulling in in surrounding air (2). An electrically powered Gen4 Ionizing Bar (3) fills the curtain of air with positive and negative charges. The air stream delivers the static eliminating ions to the product surface (4) where it instantly neutralizes static and cleans off dust and other particulates.

The Gen4 Super Ion Air Knives are powerful tools, and very quickly dissipates 5kV of static even at low compressed air supply pressures. At 5 PSIG, only 3.7 SCFM (0.3 BAR, only 105 SLPM) of compressed air per foot of length is required!!  Sound levels are also very low, resulting in quiet operation.

super ion air knife performance

Added Features –

  • Compressed Air Inlets are provided on each end and the bottom of the Super Air Knife
  • Thicker shims can be installed easily if more force is needed.
  • Emitter points are durable stainless steel
  • The high voltage cable is armored to resist cuts and abrasion, and has integral grounding.  Threaded bayonet connector is fully assembled and ready to use
  • Electromagnetically shield cable protects sensitive electronics
  • Gen4 Ionizing Bars and Power Supplies are UL Component Recognized to U.S and Canadian safety standards and are CE and RoHS compliant
  • Power Supplies are 115/230 VAC selectable and come with 2 or 4 outlets
  • Standard lengths from 3″ to 108″ (76mm to 2743mm) are offered, and custom lengths are available to meet your process needs

Successful applications include web cleaning, pre-paint dust removal, shrink wrapper machinery, printing equipment, package cleaning,and bag opening/filling operations.

If you have questions about Gen4 Super Ion Air Knives, other types of Static Elimination products,  or any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Jordan Shouse
Application Engineer

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Image courtesy of Jared Yeh Rainbow Panorama, Creative Commons License Attribution 2.0 Generic (CC BY 2.0)