Cold Fraction Explained

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

Getting Prepared for Static

Here at EXAIR we are finally starting to experience cooler weather. Over the coming weeks we will start to see the temperature steadily drop (with the occasional spike here and there just to make things difficult!). One thing that inevitably comes with cooler weather is static issues. Before we get to that point, it is always good to review what options we have to remove static. There are two primary ways to eliminate it — Active Static Elimination, and Passive Static Elimination. But which method is better? To answer this we need to know the difference between them:

Passive Static Elimination, as the name implies, gets rid of static passively. Typically, this solution comes in the form of a bare wire or some conductive material like copper, which helps create a path for the static charge to disperse. The benefit of this method is that once it’s set up, you can pretty much forget about it (well, sort of — we’ll touch on that later).

Passive Static Eliminating Bar

This kind of static elimination doesn’t require any power and has virtually no operating costs. However, the downside is that the conductive material has to maintain contact, often dragging along surfaces. This can cause the eliminators to wear out over time, meaning they will eventually need replacing (so you can’t completely forget about it). If your product is fragile, the contact from the eliminator might harm the surface. Plus, passive eliminators tend to gather dust and debris, which could end up on your product. Lastly, a passive eliminator struggles to maintain contact with objects of different shapes and complexities.

Active Static Elimination, like the Static Eliminators Product Line from EXAIR, provides several methods to effectively remove static from a surface without any physical contact with the product. This immediately addresses the drawbacks of the previously mentioned passive eliminators.

Gen4 Static Eliminators

If your product has an intricate design, the ionized airflow from many of our Gen4 products can be aimed to reach every part of it. Since there’s no direct contact, Active Static Elimination won’t harm your product’s surface. Plus, you won’t have to worry about contaminating the product because of this non-contact approach. In fact, our line of Static Eliminators that operate on compressed air is excellent at clearing away dust and debris from surfaces.

Lastly, our Active Static Elimination products are built to last and won’t degrade over time like Passive solutions do.

On top of these great benefits, EXAIR will honor a 30 day guarantee to test our products in your facility.  As well as honor a 5 year built to last warranty on compressed air products and a 1 year warranty on any electrical component.

If you have an issue with static that you would like to discuss, please give us a call.

Al Wooffitt
Application Engineer

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Banner Image by Ben Kerckx from Pixabay

Let’s Keep Things Clean: Advantages of the Flat Super Air Nozzle

Flat Super Air Nozzles have replaceable shims to vary performance.

A panel manufacturer was having some issues with black contamination affecting the powder coat paint.  They were using an overhead chain conveyor that would move the panels from the paint booth to the oven for curing.  At the end, the panel would be offloaded to a conveyor belt to move into storage for later assembly.  They were having quality issues with black specs that showed up on the gray paint.  They found out it was coming from the links from the overhead chain conveyor.  They contacted EXAIR to see if we had a solution for them. 

We reviewed the specifics of what was occurring in their application so I could understand better the nature of the problem. After evaluating a couple of options, I recommended two pieces of our model 1122, 2” Flat Super Air Nozzles.  This nozzle blows a 2” wide airstream with a powerful force to cover the width and depth of the chain links.  They were able to cut the flashing for the guard around the chain conveyor to blow the air.  One was located on the side of the conveyor, and the other was placed at the top of the conveyor.  The 2” Flat Super Air Nozzles were installed and oriented at a point along the travel, where there weren’t any panels on the hook supports.  This ensured that the debris was removed before the painting process began.  The issue was that debris mixed with the powder paint during application and then baked into the finish. The panels then had to be reworked or scrapped.  Once they installed the EXAIR Flat Nozzles, the quality improved immensely as they were able to remove the loose debris before raw panels were added to the conveyor.

To expand more on the EXAIR Flat Super Air Nozzles, they have a wide range of uses.  Their unique design utilizes a patented shim for improved efficiency, safety, and force range.   EXAIR has an easy way to change the shim to better suit different applications.  You can increase or decrease the force of the nozzle by just removing two screws and changing the thickness of the shim inside.  EXAIR offers a Shim Set to allow for adjustment to a range of forces to meet your needs and without overusing the compressed air.  Many times our Flat Nozzles are compared to plastic flat nozzles. Those nozzles do not have this capacity. They also tend to break when installed within harsh, abrasive or otherwise rough, industrial processes. 

If you have a “dirty” process, and you wish to blow it away in a safe and effective manner, EXAIR will have a nozzle for you.  We offer a variety of sizes, materials, and designs to best fit your application.  You can speak with an Application Engineer if you need more details.  The company above was glad that they did. 

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

Giovanni Battista Venturi: A Real Renaissance Man

Leonardo Da Vinci (1452-1519) was the quintessential Renaissance Man: artist, philosopher, scientist, mathematician, and an inventor ahead of his time. From the 15th to 18th Centuries, though, he was primarily known for his paintings. Then, in 1797, Giovanni Battista Venturi published his “Essai sur les ouvrages physico-mathématiques de Léonard de Vinci”, which brought to light Da Vinci’s immense volume of work in the scientific fields of fluid dynamics and aerodynamics. Curiously, he was only able to do this because of the access he gained to notebooks that had been looted by Napoleon’s troops during their occupation of Milan, Italy, and brought back to France.

To conclude that Venturi was just a writer, though, would be as bad as regrettable as calling Da Vinci just a painter. Born into a rich family in northern Italy, he was a star pupil at the Jesuit seminary in his hometown of Bibbiano. He was such a good student that in 1756 – at the age of ten – he started attending the seminary in Reggio Emilia, studying logic, metaphysics, and mathematics.

As a teenager, he enrolled in the university there, studying physics and biology before returning to the seminary, where he was ordained as a priest in 1769. He taught logic at the seminary for five years, and then went on to “the big city” of Modena to teach philosophy and geometry at the university there. He was 28 when he started there, and by age 30 he was teaching physics as well.

In addition to his service in the priesthood and at the university, he also held the office of official state engineer, mathematician, and auditor, appointed by the Duke of Modena. This meant he was responsible for the construction of bridges, draining of marsh land, and implementing regulations for the building of dams. And, in his spare time, it seems he also completed the town of Modena’s historical memoirs, a task that had been started by the town historian, but had remained dormant since his passing, some 56 years earlier.

All of this would have earned Venturi local, probably regional, and perhaps even national fame…especially the part about making Leonardo Da Vinci famous for more than just his art. But what really sealed his place in the annals of history was his discovery of a particular fluidic effect: namely, that a reduction in fluid pressure results when a fluid flows from one section of a pipe into a narrower section.

The Venturi effect, named after the real Renaissance man who discovered it, Giovanni Battista Venturi who published a paper on it in 1794.

Despite its discovery in the late 18th Century, it was not actually practically applied for almost 100 years, when an American hydraulic engineer named Clemens Herschel patented a water flow meter, in 1889. He named it the Venturi Meter, and they became prolific in water works around the turn of the century. Coincidentally, Mr. Herschel had a background in bridge building too.

Today, there are numerous machines that use the Venturi effect: fluid moving educator pumps, gas inspirators in grills, stoves, & Bunsen burners, paint atomizers, wine aerators, locomotive engine steam injectors, sandblasting nozzles, scuba diving regulators…and vacuum generators.

That last one is where EXAIR gets involved. We incorporate Venturis into our E-Vac Vacuum Generators, which are capable of vacuum levels up to 27″Hg. They’re used for material handling, pick & place systems, bag/package opening, label placement, vacuum forming, and workholding, just to name a few.

The wide throat diameter of the Adjustable E-Vac makes it suitable for applications where small amounts of particulate and/or liquid may be drawn through.

They’re also used in our Reversible Drum Vac and EasySwitch Wet-Dry Vac Systems. These are just two selections from our extensive line of compressed air operated Industrial Housekeeping Products.

EXAIR Reversible Drum Vacs (left) can fill a 55 gallon drum with water in 90 seconds, using a powerful Venturi. Our Chip Trapper Systems (middle) incorporate a Reversible Drum Vac to vacuum coolant from machine tool sumps for filtration. The EasySwitch Wet-Dry Vac uses a Venturi as well for dry and liquid cleanup applications.

Giovanni Battista Venturi retired in 1813, but continued writing a number of scientific and literary works, including a collection of Galileo’s manuscripts & letters. He died in 1822, at the age of 75.

Russ Bowman, CCASS

Application Engineer
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