Tag: rudolf hilsch

The Legend of Rudolf Hilsch

Published on by jasonkirbyLeave a comment

It is thought that Georges Ranque, a French inventor, inadvertently discovered a key principle while developing early prototypes during the German occupation of France. These prototypes later attracted the interest of Rudolf Hilsch, a German physicist who was working on low-temperature refrigeration systems for military applications. Although Hilsch improved upon Ranque’s original design, he found that it did not surpass conventional refrigeration methods in achieving lower temperatures. Ultimately, the device became known as the Hilsch tube.

The Hilsch tube was constructed using a pair of modified nuts along with several other components. The horizontal section of the T-shaped fitting contains a specially machined element that fits tightly within the arm, featuring a spiral cross-section on the inside that differs from its external shape. At the spiral’s “step,” a small opening connects to the T’s leg, allowing air to enter through the leg and exit via this opening, creating a spiraling flow. The “hot” pipe measures approximately 14 inches in length with a half-inch internal diameter, and its far end is fitted with a stopcock to control the system’s pressure. In contrast, the “cold” pipe is about four inches long, also with a half-inch internal diameter, and its end that connects to the spiral piece includes a washer with a central hole of roughly a quarter of an inch in diameter. Various washers with different hole sizes can be utilized to adjust the system’s performance.

EXAIR’s Vortex Tube operates by channeling compressed air into a tube where it flows through nozzles positioned tangentially to an internal counter-bore. This innovative nozzle design induces the air to rotate in a vortex at speeds reaching up to 1,000,000 RPM. As the air spins, it makes a 90° turn, allowing a valve at one end to release some of the heated air. The remaining air continues down the tube, losing heat in the process, and ultimately exits through the opposite end as cold air.

Both streams in a Vortex Tube rotate in the same direction and at the same angular velocity, which would typically suggest that the rotational speed of the inner vortex should increase due to the conservation of angular momentum. However, this is not observed in practice. A useful analogy can be drawn from Olympic Figure Skating: when a skater extends her arms, her spinning slows down, but as she pulls them in, her rotational speed increases significantly. In the case of the Vortex Tube, the inner vortex maintains a constant speed because it has lost angular momentum. This loss manifests as heat, which is expelled from the hot side of the tube. Consequently, the inner vortex cools down, allowing the cooled air to be channeled for various industrial applications.

How the EXAIR Cabinet Cooler System Works

The theory behind the Vortex Tube is applied to standard Vortex Tubes and a range of other products designed with specific features tailored to your needs. EXAIR offers a variety of solutions, including Cabinet Coolers, Cold Guns, Adjustable Spot Coolers, Mini Coolers, and Vortex Tubes, all of which function based on this fundamental principle.

If you have questions about Rudolf Hilsch, or anything regarding EXAIR and our products, please do not hesitate to reach out.

Jason Kirby
Application Engineer
Email: jasonkirby@exair.com
Twitter: @EXAIR_jk

Rudolf Hilsch and How the Ranque-Hilsch Vortex Tube Came To Be

Published on by Jordan T ShouseLeave a comment

The exact beginnings of the device remain unclear. It is believed that a French inventor, Georges Ranque, stumbled upon the principle and abandoned some initial prototypes in the wake of the German Army during France’s occupation. These prototypes caught the attention of Rudolf Hilsch, a German physicist engaged in developing low-temperature refrigeration systems for the war effort. Hilsch enhanced the original design but discovered that it did not outperform traditional refrigeration techniques in reaching relatively low temperatures. Eventually, the device became recognized as the Hilsch tube.

The Original drawing from Rudolf Hilsche’s 1947 Publication.

The Hilsch tube was assembled using a pair of modified nuts along with various other components. The horizontal section of the T-shaped fitting features a uniquely machined element that fits snugly within the arm. This element has a spiral cross-section on the inside, contrasting with its outer shape. At the “step” of the spiral, there is a small opening that connects to the T’s leg. When air enters through the leg, it exits through this opening and spirals around the one-turn design. The “hot” pipe measured approximately 14 inches in length and had a half-inch internal diameter. Its far end is equipped with a stopcock to regulate the system’s pressure. Meanwhile, the “cold” pipe is about four inches long, also with a half-inch internal diameter. The end that connects to the spiral piece has a washer with a central hole of around a quarter of an inch in diameter. Additionally, washers with varying hole sizes can be used to fine-tune the system.

With EXAIR’s vortex tube, 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 forces 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 into 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 with 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 been 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 Coolers, Cold Guns, Adjustable Spot Coolers, Mini Coolers, and Vortex Tubes all operate off of this same principle.

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EXAIR HazLoc Cabinet Cooler Systems provide safe and reliable

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, the 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

Send me an Email
Find us on the Web 
Like us on Facebook
Twitter: @EXAIR_JS

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 )

Rudolf Hilsch, Shining a Light on the Vortex Tube

Published on by Jordan T ShouseLeave a comment

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 Coolers, Cold Guns, Adjustable Spot Coolers, Mini Coolers, and Vortex Tubes all operate off of this same principle.

EXAIR HazLoc Cabinet Cooler Systems provide safe and reliable heat protection in classified environments

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

Send me an Email
Find us on the Web 
Like us on Facebook
Twitter: @EXAIR_JS

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 )

People of Interest: Rudolf Hilsch

Published on by John BallLeave a comment

Vortex Tubes

The EXAIR Vortex Tubes use compressed air to generate a cold air stream at one end and a hot air stream at the other end.  The history behind this phenomenon is rooted in the Ranque-Hilsch tube.

In 1931, a French physicist, Georges Ranque, tried to use a cyclone vortex to separate iron filings from the air.  He noticed that when he capped one end with a slight opening, the air would become very warm.  Being disappointed with the design flaw, he shelved his patented idea for several years.  In 1946, Rudolf Hilsch picked up this idea from Georges Ranque and refined the design.  This product has now become known as the Vortex Tube.  In this blog, I will cover Rudolf Hilsch as a person of interest.

Rudolf Hilsch was born in December 18th, 1903 in Hamburg, Germany and died on May26th, 1972.  In 1927, Rudolf received his doctorate at the age of 24.  In 1938, he worked with a colleague, Robert Pohl, to create one of the first working semiconductor amplifier.   From 1941 to 1953, Hilsch became a professor of physics at Erlangen, and in 1947, he published his paper on the Ranque-Hilsch tube which he called the “Wirbelrohr”, or whirl pipe.  This publication became well known and was the start of the Vortex Tube.

To expand a bit more into his publication, the design for spinning the air at a high rate of speed can produce a separation of temperatures.  It starts with a generator to help facilitate a vortex action.  As the vortex travels toward one end, a portion of that air will travel back through the center toward the opposite end.  (Reference picture below).  As these two vortices interact, conservation of momentum forces the inner vortex to give off energy in a form of heat to the outer vortex.  This separation of temperatures will give you a hot air stream and a cold air stream.  This type of device can do this without any moving parts or refrigerant.  You just have to supply a compressed gas.

To continue on with his career, in 1953, he became a full member of the Bavarian Academy of Sciences.  Also, at that same time, he started teaching physics at the Physics Institute of the Georg August University of Göttingen well into the 1960s.

EXAIR manufactures Vortex Tubes that utilizes this phenomenon with compressed air.  We stock units with cooling capacities up to 10,200 BTU/hr and can reach temperatures from -50oF to +260oF (-46oC to +127oC).  So, thank you Mr. Ranque and Mr. Hilsch for creating a product to generate hot and cold air in a single unit.  If you would like to discuss any applications where cooling or heating is needed, you can talk with one of our Application Engineers.  We will be happy to help.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb