Tag: cold air tubes

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

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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 )

Video Blog: The Effects of Back Pressure On A Vortex Tube

Published on by Brian FarnoLeave a comment

The video below is one that I have explained to customers countless times over my tenure here at EXAIR. Vortex Tubes are most efficient when discharging the cold and hot air streams into atmospheric conditions. This video is my attempt to showcase just how much it will affect your performance when a restriction on the discharge cannot be avoided.

If you would like to discuss Vortex Tubes and their feasibility in your application, feel free to contact an Application Engineer today!

Brian Farno, MBA – CCASS
National Business Development Manager

BrianFarno@EXAIR.com
@EXAIR_BF

Clerk Maxwell: The Man, the Myth, the Demon

Published on by jasonkirbyLeave a comment

Thermodynamics is a branch of physics that focuses on heat and energy. It studies how these forms of energy move and change within a system. An isolated system is a key concept in thermodynamics; it is a space that does not interact with anything outside of it. This means that no heat or energy can enter or leave a system. Understanding these principles helps scientists and engineers design better machines and improve energy efficiency.

The unique physical phenomenon of the Vortex Tube principle generates cold air instantly, and for as long – or short – a time as needed.

Maxwell’s demon is a thought experiment created by the mathematician James Clerk Maxwell. This imaginary being has the ability to see fast and slow-moving molecules in a gas. By sorting these molecules, the demon could supposedly create a situation where one side of the container is hot, and the other side is cold, without using energy. This idea challenges the second law of thermodynamics, which states that systems tend to move towards disorder. Maxwell’s demon shows that there are limits to our understanding of energy and order in the universe.

How a Vortex Tube Works

Maxwell’s demon is a molecule-sized trapdoor that separates a box of gas into two sides. The demon observes molecules and only allows fast-moving molecules to pass through to one side, and only slow-moving molecules to pass through to the other side. This would cause the temperature inside the container to increase without any work being applied, which would violate the second law of thermodynamics.

The cold air from the Vortex Tube (dark blue arrow) is aimed directly at the inlet plenum of the Air Amplifier. As it draws in environmental air (at ambient temperature, pale curved arrows), the Air Amplifier discharges cool air (light blue arrow) at the desired temperature.

The Vortex Tube by EXAIR is a product that demonstrates this theory to its fullest extent. Using an ordinary supply of compressed air as a power source, Vortex Tubes create two streams of air, one hot and one cold, with no moving parts. Vortex Tubes offer a temperature range between -50F to +260F, with flow rates ranging from 1 to 150 SCFM. EXIAR Vortex Tubes are constructed of stainless steel, which offers resistance to corrosion and oxidation, and will provide years of reliable, maintenance-free operation.

If you would like to discuss the Vortex Tube, please do not hesitate to contact an Application Engineer. We are always happy to help!

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

How Do I Change the Air Flow and Temperature of a Vortex Tube?

Published on by Russ BowmanLeave a comment

If you’re a regular reader of the EXAIR Blog, you likely know that you can get cold (and hot) air from a Vortex Tube. You probably also know that there are ways to get more or less flow, and higher or lower temperatures. Today, I wanted to write about vortex tube operation. First, let’s recall the basics:

The unique physical phenomenon of the Vortex Tube principle generates cold air instantly, and for as long – or short – a time as needed.

To change the cold (or hot) air flow AND temperature (you can’t do one without the other), all you have to do is manipulate the Control Valve, or Hot Valve, as it’s oftentimes referred to because of its location at the ‘Hot’ end of the Vortex Tube. Essentially, as you open it, more hot air exits, meaning there’s less air to go to the ‘Cold’ end. By increasing the ‘Hot’ flow, more kinetic energy (in the form of heat) is carried away. And, since more energy (heat) is given off, the energy (heat) in the cold flow decreases as well, so you get colder air…and less of it as the hot flow increases. We can use the data in EXAIR’s Vortex Tube Specification and Performance Tables to calculate the cold (and hot) flows and temperatures at different positions of the Hot Valve. Let’s say we have a Model 3210 Vortex Tube that uses 10 SCFM when supplied at 100psig:

Let’s assume the compressed air supply temperature is 70°F and the Hot Valve is open wide enough to allow 40% of the Model 3210’s 10 SCFM (or 4 SCFM) worth of compressed air consumption out. That means that 60% (or 6 SCFM) are going to go out of the cold end. We call this condition a 60% Cold Fraction:

And, at that 60% Cold Fraction, the cold air is going to be 86°F colder than the supply of 70°F, which means that the 6 SCFM of cold flow is going to be -16°F. If the Hot Valve is opened further, to allow 5 SCFM out the hot end (and hence the other 5 SCFM will go out the cold end), that 5 SCFM of cold flow will now be 100°F colder than the 70°F supply, or -30°F. That’s as low as you can go with a 3200 Series Vortex Tube…they have a Cold Fraction range of 50-80%.

Now let’s say you want even COLDER air. You can simply replace the generator (shown to the left) in the Model 3210 to make it a 3400 Series Vortex Tube. If you replace its 10-R Generator with a 10-C Generator, you’ll now have a Model 3410, and you’ll be able to adjust your Vortex Tube to the 20-50% Cold Fraction range. The difference between R and C-style generators is the center hole size. The hole sets up proper internal pressure conditions to work better in each temperature range. In short, the generator type optimizes the temperature drop for each working condition.

You’re still working with a compressed air consumption of 10 SCFM, so, while the air gets colder, the flow decreases. At a 30% Cold Fraction, for example, you’ll get -48°F air (70°F – 118°F), but only 3 SCFM (30% of 10 SCFM) of the total flow going in.

If you need a -48°F net air temperature, but cannot accommodate such a reduction in flow, using a generator with a higher consumption rating is how you get around such an issue. If you were to replace that 10-C Generator with a 30-C, now it is a Model 3430 with triple the original flow of model 3410. Readjustment of the hot valve would be necessary to get back to a 30% Cold Fraction. That means the air flow will be the same temperature (-48°F) but it’s going to be 9 SCFM (instead of 3 SCFM.)

All you need to change the Cold Fraction of an EXAIR Vortex Tube is a flat-head screwdriver. If it’s something you’re going to be doing more frequently, our Adjustable Spot Coolers have a Temperature Control Knob that works the Hot Valve and may be a better choice for an application.

This is from the Vortex Tubes and Spot Cooling Products section of Catalog 35. The first graphic at the beginning of this blog is what you’ll find on page 200. You’re welcome.

The Adjustable Spot Coolers also come with three different generators, so you can get the different flows at the same temperature, or vice versa, as described above. If you have an application requiring cold (or hot) air flow, on demand, you’re looking for an EXAIR Vortex Tube. For help picking the right one, give me a call.

Russ Bowman, CCASS

Application Engineer
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