Tag: exair vortex coolers

Which Vortex Tube is Right for You?

Published on by Al WooffittLeave a comment

EXAIR’s Vortex Tubes are a great product for many cooling applications. When supplied with a clean and moisture-free source of compressed air, they will generate two streams of airflow, one hot and one cold. They are a low-cost and reliable solution, capable of producing temperatures ranging from -50°F to +260°F. We have flow rates from 1scfm to 150scfm, producing refrigeration over 10,000btu/hr.

With this wide range of performance possible, it may be a bit daunting trying to select the right model of Vortex Tube. In this blog I am going to explain the differences between the two different series that we offer: 32XX and 34XX, and why you would want to choose one over the other.

The difference between the two model types comes down to the Cold Fraction, which is determined by where the Control Valve is positioned. When you open the Control Valve (by turning it counterclockwise, as shown by the blue arrow in the photo to the right), it decreases the Cold Fraction, which leads to a reduced flow and a significant drop in temperature in the cold air discharge. Conversely, closing the Control Valve (by turning it clockwise, indicated by the red arrow) boosts the cold air flow, but causes a smaller temperature drop. This ability to adjust is crucial for the Vortex Tube’s flexibility.

You can set the Cold Fraction as low as 20%, which means that a small portion (20% to be precise) of the supply air is sent to the cold end, resulting in a significant temperature drop. On the flip side, you can crank it up to 80%, meaning that most of the supply air heads to the cold end, but the temperature drop won’t be as drastic. Our 34XX Series Vortex Tubes are designed for Cold Fractions between 20-50%, while the 32XX Series caters to 50-80% Cold Fractions.

So how do you select the right model for you? To determine this, you need to know what temperature and flow will best serve your application. For most situations, the ~20°F produced by an 80% cold fraction is sufficiently cold. At this cold fraction, you will get the most flow (80% of the inlet supplied). Applications like welding or brazing benefit from higher flows. When your starting temperature is hundreds of degrees Fahrenheit, there is little difference in blowing -20°F air vs +20°F. What you need is more volume to strip away the heat as quickly as possible. In this instance, a 32XX series is the way to go.

If you need lower flow, or to achieve extremely cold temperatures, then the 34XX series would be the best choice. A chocolate maker took advantage of the lower flow rates offered by this type of Vortex Tube as they didn’t want the airflow to disturb the surface of the chocolate as it cooled, affecting the finish. The greater temperature drop allowed for rapid cooling without reducing quality.

Whatever your cooling application, our Vortex Tubes will likely be able to help. If you would like to discuss it, please give us a call!

Al Wooffitt
Application Engineer

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

Vortex Tube Theory

Published on by Russ BowmanLeave a comment

Vortex Tube theory is one of the more interesting accidental inventions of the 20th Century…splitting a flow of air into two streams: one hot, and one cold.  Georges Ranque happened upon the phenomenon in the 1930s. He patented it in 1933, but it wasn’t commercially viable at the time. In the 1940s, it caught the interest of German physicist Rudolph Hilsch, who “tweaked” Ranque’s design and published a widely read paper on it in 1947. Over the next few decades, the use of compressed air became more prevalent in a wide range of industries, eventually becoming the “4th utility” that it’s known as today. With that increase in use came improvements in air compressor design & function – improvements that finally bestowed long-awaited commercial viability on the Vortex Tube.

From Ranque’s curious observation of a previously unknown physical phenomenon, to mass production & worldwide use, the Vortex Tube is truly a marvel of 20th Century technological advances.

So, how does it work? Ranque’s patent and Hilsch’s paper both detail what it is and what it does, but to this day, nobody’s been able to offer any 100% scientific proof as to HOW it does what it does. The commonly accepted explanation involves a proven scientific principle called conservation of angular momentum. That’s a mouthful, so let’s break it down:

Momentum is a physical property of matter, defined by its mass and velocity…and it depends on both. Something with more mass will have more momentum than something with less mass, if their velocities are the same. And something moving at a higher velocity will have more momentum than something that’s moving slower, as long as their masses are the same. Unless otherwise specified, “momentum” is usually considered to be linear – the matter is moving in one direction.

Angular momentum is also defined by mass and velocity, but its value is also affected by rotational inertia, which is determined by the distribution of its mass around the center point of its rotation. If an object moving at a certain velocity is forced closer to its rotational center point, it has to speed up to maintain (or conserve) angular momentum. Physics really, really, (really) wants to make that happen, according to the laws of conservation of matter & energy. And physics ALWAYS obeys the law…which forces us to as well.

Consider figure skaters doing those dizzying moves where they spin on the ice on one skate. If the skater spins with their arms straight out and then brings their arms in, close to their body, they begin to spin faster. The skater’s mass doesn’t change, but their mass distribution around the rotational center point does…so physics gets its way by increasing the velocity. Therefore, energy (angular momentum, in this case) is conserved. It’s impressive how easy some of them make it look:

In a Vortex Tube, the airflow is discharged tangentially into the tube, making it spin inside the inner wall of the tube at a specific velocity. When it reaches the end of the tube, it’s forced to change directions and continue spinning inside that outer spinning flow, but in the opposite direction. Unlike our figure skater in the example above, though, its velocity doesn’t change. Something has to, though, because physics ALWAYS gets its way. Since the energy of its angular momentum HAS to be conserved, that energy gets converted into heat, which transfers from the outer spinning flow and exits the vortex tube’s “hot” end. When it does so, the temperature of the remaining, inner spinning air flow goes down.

Just a few examples of how EXAIR Vortex Tubes are used in industry.

That’s our story, anyway, and we’re sticking to it. In any case, it works, and it works quite well. If you’d like to find out more, give me a call.

Russ Bowman, CCASS

Application Engineer
Visit us on the Web
Follow me on Twitter
Like us on Facebook

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.

Image
Image

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 )

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 Application Engineer

BrianFarno@EXAIR.com
@EXAIR_BF