Henri Coanda and his Effect on Compressed Air

Henri defined the Coanda Effect – the tendency of a jet of fluid emerging from an orifice to follow an adjacent flat or curved surface and to entrain fluid from the surroundings so that a region of lower pressure develops.

Compressed air flows through the inlet (1) to the Full Flow (left) or Standard (right) Air Knife, into the internal plenum. It then discharges through a thin gap (2), adhering to the Coanda profile (3) which directs it down the face of the Air Knife. The precision engineered & finished surfaces optimize entrainment of air (4) from the surrounding environment.

Henri-Marie Coanda (1885-1972) discovered the Coanda Effect in1930. He observed that a stream of air (fluid) emerging from a nozzle tends to follow a nearby curved surface, if the curvature of the surface or angle the surface makes with the stream is not too sharp. For example, if a stream of fluid is flowing along a solid surface which is curved slightly from the stream, the fluid will tend to follow the surface.

A number EXAIR products are designed to utilize the Coanda Effect and aid their performance. In some products, the Coanda Effect aids to create an amplification area where additional ambient air is drawn into the total airflow to increase total volume of air upon a target. This creates a more efficient and effective product. Also, since not as much compressed air is required, the noise levels decrease for products like EXAIR’s air knives, air nozzles, air jets and air amplifiers. EXAIR has been successful with positive impact for compressed air energy savings and noise reductions helping us meet or exceed OSHA Standard 29 CFR-1910.95 9(a) Maximum Allowable Noise Exposure.

Please contact EXAIR with regards to our Intelligent Compressed Air Products. We can help you with your next cooling, blow-off, drying or any compressed air needs.

Eric Kuhnash
Application Engineer
Email: erickuhnash@exair.com
Twitter: @EXAIR_EK

1- Spoon Coanda image- https://creativecommons.org/licenses/by-sa/2.5/deed.en

Process Cooling Utilizing Vortex Tube Technology

Vortex Tube Theory

What is a Vortex Tube? How long have they been around? How do they work? Vortex Tubes have been around since 1928 with what may seem as an accidental existence by the developer George Ranque. George accidentally discovered the phenomenon while studying physics at Ecole Polytechnique in Paris France. Ranque was performing an experiment on a vortex-based pump to vacuum up iron fillings; during the experiment he noticed that warm air was being expelled out of one side and cold air out of the other when he inserted a cone into one end of the vortex. In 1931 Ranque filed for a patent for the vortex tube and two years later presented a paper on it.

George’s vortex tube was all but lost and forgot about until 1947 when the German physicist Rudolph Hilsch published a paper on the device. This paper became widely read and exposed the vortex tube to the industrial manufacturing environment. This paper revived what was thought to be lost and led the vortex tube into what we see today.

As to how they work, these are a phenomenon of physics and the theoretical math behind them has yet to be proven and set in stone. But the basics are this, high pressure compressed air (typically 100 PSIG) is fed into a chamber which contains a generator. The generator takes that high pressure air and spins it at a very high rate of speed. As the air spins it starts to heat up on the inner walls of the vortex tube as it moves towards the control valve. A part of that hot air exits at that valve. The rest of the air which has now slowed down is forced back up the tube through the center of the first high speed air stream. The middle stream of slower air gives up energy in the form of heat to the outer faster moving air. And because of this the inner stream exits the opposite end as extremely cold air! (Check out image below for a visual representation)    

How a Vortex Tube Works

Now the question is how can this technology be integrated into a production process? See below for applications.

Cold Air Gun Application

A few months ago, a high-performance knitted products manufacturer called. They operate 128 Spindle motors on circular sock machines (CSM) that require couplings. These couplings use hi-speed, hi-temperature bearings that have been failing regularly and prior to the predicted run life. This was resulting in loss of production while the circular sock machines are down and the bearings are replaced. Additional costs associated with refurbishing the failed bearing include labor and new bearings. The average cost of a failed circular sock machines bearing including lost production was around $1925.00 and on average they were seeing 180 premature failures each year.

My recommendation was using a Cold Gun with the dual outlets to spread the cooling around the bearing. They had tried fans and electric blowers and they noticed no benefits. However, when they placed the 3925 on the largest trouble maker that was burning bearings at the highest rate, they noticed a prolonged lifetime of over 260%!!!

The enhanced run life of the circular sock machines was noticed immediately as the non-cooled circular sock machine bearings continued to fail at a much higher rate when compared to the positions with the Cold Air Guns installed.

Based on the average cost of a failed circular sock machine bearings including lost production ($1925.00) and an average of (180) premature failures each year, their estimated annual savings using the Cold Gun is $346,500.00 on just the 12 high fail rate machines they have put these on to date. They are expecting to place a Cold Gun on every circular sock machine within 5 years focusing on the high fail rate machines first. 

If you think you have an application that would benefit from Vortex tube technology, give us a call! We have a team of application Engineers in from 7AM-4PM EST M-F! Or shoot us an email to techelp@exair.com and one of those Engineers will reach out to you!

Jordan Shouse
Application Engineer

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Cold Gun Aircoolant Systems Eliminate Mist & Breathing Problems In Machine Shops

Some machine tool operations require flood coolant. Not only does the liquid remove heat of friction from the tool and the work piece, it also provides lubrication that the cutting of some materials require. For other machining operations, mist coolant removes heat, provides a measure of lubricity, and minimizes (to a degree) the volume of liquid used in a flood coolant application.

This high speed photograph illustrates how flood coolant gets atomized by a machine cutting tool.

Whether you flood or mist liquid right onto a tool cutting metal, some of it’s going airborne. CNC machines are oftentimes equipped with collection systems for coolant mist, and it’s not unusual to see ambient mist collectors installed in machine shops to take care of the mist that escapes individual machines.

These mist collectors play an essential role in these facilities, as there are considerable health risks associated with exposure to these fluids, both oil- and water-based. In the U.S., the National Institutes of Health (NIH) compiles & analyzes risks associated with skin contact & inhalation of metalworking fluids. The National Institute for Occupational Safety and Health (NIOSH) has comprehensive recommendations of limitations on exposure to them. In England, the Health & Safety Executive agency likewise published a document geared toward helping machine shops and their employees work safely with them.

Speaking of NIOSH, they strategize a Hierarchy of Controls that can be applied to most any industrial process:

Elimination of the hazard isn’t always possible, but when it is, it’s the most effective option.

While mist collectors (Engineering Controls) are reasonably effective (and essential in the large number of applications where metalworking fluids are necessary), there are still a fair amount of applications where liquid coolant CAN be eliminated. For those applications, consider the EXAIR Cold Gun Aircoolant Systems.

Cold Guns not only eliminate messy and potentially hazardous liquid coolants, but also have been proven to improve cutting tool life.

Using Vortex Tube technology, EXAIR Cold Guns generate cold air flow from a supply of compressed air, instantly & on demand, with no moving parts to wear or electrical components to burn out. They’re safe, quiet, effective, and install in minutes, using a built-in bar magnet and 1/4 NPT compressed air connection.

Both Standard & High Power Systems come with Filter Separators, and are available with Single or Dual Point Hose Kits.

We know we can’t replace liquid coolant in every machining application, but if you’d like to explore elimination of it in your processes, give me a call.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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EXAIR Cold Gun Prevents Melting of Chocolate During Filling

With Valentine’s Day coming up in the U.S. many of us will be buying chocolates for our significant other. My wife (somehow) doesn’t particularly care for chocolate, so I buy some for her anyway knowing that it will sit around until I eat it. I think most of us would agree that chocolate is even more delicious when melted and drizzled all over the top of just about anything. But, melted chocolate isn’t always a good thing.

I recently worked with a company that manufactures chocolate products. They came out with a new line of small candies and were encountering an issue during packaging. In their process, the chocolates are formed, cooled, and packaged for resale. During the packaging process they were experiencing a problem that caused the chocolates to melt. The bags are heat-sealed along the sides and bottom. This heat was transferring from the bag to the chocolates and causing them to melt. Rather than having a finished package of individual candies, they were melting together to form one large lump. Not exactly what they are hoping to deliver to their consumers.

 

Video of the bag filling process

Fortunately, EXAIR offers a range of different products that are suitable for cooling. For this application, they utilized a Model 5330 High Power Dual Outlet Cold Gun. With the fan-type nozzle installed, they were able to cool both sides of the package immediately after sealing and just before filling the bags with chocolates.

EXAIR’s Cold Gun was a Product of the Year finalist in 2007. Using only a source of compressed air, the Cold Gun and High-Power Cold Gun produces a stream of clean, cold air 50° (28°C) below your compressed air supply temperature. The Cold Gun is very quiet at only 70dBA and has no moving parts to wear out. Just supply it with clean, dry compressed air and its maintenance free! It’s available as both a standard and High-Power option, providing 2x the cooling power. Each style is available with either a single or dual cold outlet flow.

The Cold Gun is pre-set to an 80% Cold Fraction. In other words, 80% of the compressed air supplied to it will exhaust from the cold end of the tube, 20% from the hot end. This prevents the Cold Gun from freezing up during use and optimizes the gun’s cooling capacity. The Cold Gun is an ideal alternative to messy and expensive coolant mist systems. It eliminates the cost of purchase and disposal of cutting fluids as well as worker related health problems from breathing airborne coolant or slipping on wet floors. Replacing a coolant-based system also eliminates the need for secondary cleaning operations after milling or drilling.

If you have an application that you believe would be better served by the use of an EXAIR Cold Gun, give us a call.

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD