Tag: venturi cooler

Cold Fraction Explained

Published on by jasonkirbyLeave a comment

EXAIR has published numerous articles detailing the functionality and applications of Vortex Tubes. This innovative technology, which produces cold air without the use of Freon or mechanical components, is rooted in physical principles and has been known by various names, such as the Ranque Tube, Ranque-Hilsch Tube, and Maxwell’s Demon. Today, it is commonly referred to as the Vortex Tube, capable of generating air temperatures as low as -50 °F (-46 °C) through the high-speed rotation of compressed air. In this article, I will discuss how to adjust the Vortex Tube to achieve varying temperatures and cooling effects, focusing on the concept of Cold Fraction.

The term “Cold Fraction” refers to the proportion of supply air allocated to the cold end of a system. A higher Cold Fraction indicates an increased flow and temperature of the cold air, while a lower Cold Fraction results in diminished cold air flow and temperature.

The performance chart below illustrates how the settings for “Pressure Supply” and “Cold Fraction %” influence the operation of Vortex Tubes. For instance, with an operating pressure of 100 PSIG and a cold fraction set at 20%, the cold side experiences a temperature drop of 123°F, while the hot side sees a rise of 26°F. Conversely, maintaining the same pressure of 100 PSIG but adjusting the cold fraction to 80% results in a 54°F decrease on the cold side and a significant 191°F increase on the hot side.

EXAIR Vortex Tube Performance Chart

In a convection or conduction air cooling application, two key factors must be considered: the air flow rate and the temperature difference between the cooling air and the heated component. It is advisable to begin with the maximum cold fraction; however, you may discover that a slightly reduced flow rate, along with the corresponding lower temperature, could better meet your requirements. The positive aspect of this adjustment is that it does not affect compressed air consumption, allowing you to enhance performance without incurring additional operational costs.

If you have any questions about Vortex Tubes, or anything regarding EXAIR and our products, please do not hesitate to reach out. We would love to hear from you!

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

Super Air Amplifier vs Fan

Published on by Al WooffittLeave a comment

One of the more common applications we work with is cooling. In most instances, the goal is to cool the part as quickly as possible. In order to cool faster, you would think that blowing the coldest air possible would be the best option. Our Vortex Tubes can produce air as cold as -50°F! However, in many instances, more effective cooling will be achieved through larger volumes of air. As long as the ambient air temperature is lower than the target temperature, larger volumes of ambient air will outperform a small volume.

Our Super Air Amplifier is a great option for producing large volumes of laminar (non-turbulent) airflow for minimal compressed air consumption. Using a Coanda profile along with a patented shim, compressed air exits the Amplifier in a manner that generates a low pressure zone, which helps pull in the surrounding ambient air. This creates an amplification ratio of up to 25 times! Due to the laminar output flow having the same speed and direction, it is very effective at removing heat from a target. It also helps keep noise levels down.

The most common, non-compressed air alternative to our Amplifiers is an electric fan. Fans utilize motors and blades to direct air towards their target. When air comes in from behind the fan, the blades push the air forward to the target. This action generates turbulent air flow, as well as a lot of noise. Due to the use of motors, there are parts that can wear out over time, leading to additional maintenance costs over the lifetime of the fan.

Ultimately, when it comes to cooling, what we care about most is how quickly a given solution will get the job done. Is a Super Air Amplifier going to cool faster than a fan? In the video below we put both options to the test. As you will see, the Super Air Amplifier is significantly faster:

If you have a cooling application that you would like to discuss, give us a call!

Al Wooffitt
Application Engineer

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Robert Boyle and Boyle’s Law

Published on by Al WooffittLeave a comment

We’ve written many blogs about our intelligent compressed air products; we have a lot of great products to talk about (our Vortex Tubes are my favorite). Occasionally, we like to talk about certain people of interest, or people that have had an impact on the compressed air industry. In this blog I am going to cover one of those people: Robert Boyle.

Born on January 25, 1627, at Lismore Castle in County Waterford, Ireland. He was an Anglo-Irish natural philosopher, chemist, and physicist, and he explored various other fields of study. In 1661, he published his book The Sceptical Chymist, which many regard as the cornerstone of modern chemistry.

Even though his main focus was chemistry, one of Boyle’s most notable scientific contributions is what we now call the first gas law, aptly named Boyle’s Law. Boyle’s Law explains how pressure and volume relate in a closed space when considering the mass of an ideal gas. Boyle, along with his assistant Robert Hooke, utilized a closed J-shaped tube and added mercury from the open end, which caused the air on the opposite side to compress due to the pressure. After conducting this experiment with various amounts of mercury, Boyle concluded that the pressure of a gas is inversely related to the volume it occupies.

Boyle used a ‘J’ Tube – Sealed on the Short End, and Open at the Long End

This relationship between pressure and volume is of obvious interest to us in the compressed air industry. Nitrogen, oxygen and hydrogen (the three primary components of air) are ideal gases, so are governed by this relationship. This means that if we reduce the volume of a given space, the air inside that space will increase in pressure. This principle plays a key role in various areas of air system design as well, including determining compressor output, reservoir storage, pneumatic cylinder efficiency, and more.

Sadly, on December 31, 1691, Robert Boyle passed away. However, the impact he made on fluid dynamics lives on to this day. At EXAIR we use the pressure and volume of compressed air for our products to make them quiet, safe and efficient. If you have questions about any of our quiet EXAIR Intelligent Compressed Air Products, feel free to contact EXAIR or any Application Engineer.

Al Wooffitt
Application Engineer

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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

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