What Is A Coanda Profile?

The big thing that sets engineered products like EXAIR Intelligent Compressed Air Products apart from other devices is the engineering that goes into their design.  Several principles of fluidics are key to those designs:

The one I wanted to discuss today, though, is the Coanda Effect, what it means for our engineered compressed air products, and what they can do for you:

The Coanda effect is named after Henri Coandă, who was the first to use the phenomenon in a practical application…in his case, aircraft design.  He described it as “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.”  Put simply, if fluid flows past a solid object, it keeps flowing along that surface (even through curves or bends) and pulls surrounding fluid into its flow.  Here’s a demonstration, using an EXAIR Super Air Amplifier and a plastic ball:

What’s interesting here is that the Super Air Amplifier is not only DEMONSTRATING the Coanda effect, it’s also USING it:

Air Amplifiers use the Coanda Effect to generate high flow with low consumption.

EXAIR Standard and Full Flow Air Knives also have Coanda profiles that the primary (compressed air) flow follows, and uses, to entrain “free” air from the surrounding environment:

Compressed air flows through the inlet (1) to the Standard 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.

EXAIR Air Wipes can be thought of as “circular Air Knives” – instead of a Coanda profile along the length of an Air Knife, an Air Wipe’s Coanda profile is on the ring of the Air Wipe, which entrains surrounding air into a 360° ring of converging air flow:

Air Wipe – How it works

So that’s the science incorporated in the design of our products.  But what does it mean to the user?

  • Efficiency.  Pulling in a tremendous amount of “free” air from the surrounding environment means minimal consumption of compressed air, while still getting a hard hitting, high velocity air flow.
  • Sound reduction.  This air entrainment also creates a boundary layer in the air flow, resulting in a much quieter air flow than you get from a simple open-end blow off.

EXAIR Corporation is committed to helping you get the most out of your compressed air system, and thanks to Mr. Coandă, that includes reducing your compressed air consumption and noise levels.  If you’d like to find out more, give me a call.

Russ Bowman, CCASS

 

 

 

Application Engineer
EXAIR Corporation
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Daniel Bernoulli, Entraining EXAIR Products

Daniel Bernoulli was born February 8, 1700 in Groningen in the Netherlands and was the son of Johann Bernoulli an early developer of calculus. It is believed that Daniel did not have a good relationship with his father. This mainly stemmed from the both of them entering the same scientific contest at the University of Paris. The two tied and his father Johann took exception to being compared to his son as “equal” and could not accept the shame and banned Daniel from his home. Daniel tried to reconcile their difference but his father carried this grudge to his death.

Earlier in Daniels life his father convinced Daniel to study business as there was no income incentive to study mathematics but against his will Daniel did choose the study of business. His father then convinced Daniel to study medicine but Daniel still wanted to study mathematics and agreed to study medicine under the condition that his dad teach him mathematics privately. Daniel completed his bachelors degree at the age of 15 and his masters degree when he was 17. Daniel then went on to study medicine and received his PhD in anatomy and botany from the Universities of Basel, Heidelberg and Strasbourg.

Daniel Bernoulli was very accomplished but mostly known for Bernoulli’s principle. Bernoulli’s principle is the relationship between fluid speed and pressure. An increase in the speed of a fluid will occur simultaneously with a decrease in the fluid’s pressure or potential energy. The Venturi effect, published in 1797 by Giovanni Venturi, applies Bernoulli’s principle to a fluid that flows through a tube with a constriction in it. The Venturi tube provides a handy method for mixing fluids or gases, and is popular in carburetors and atomizers, which use the low pressure region generated at the constriction to pull the liquid into the gas flow. It also offers a particularly clear example of the Bernoulli principle.

For example, above is how a Super Air Wipe works. Compressed air flows through an inlet (1) of the Air Wipe into an annular chamber (2). It is then throttled through a small ring nozzle (3) at high velocity. This primary airstream adheres to the Coanda profile (4), which directs it down the angled surface of the Air Wipe. A low pressure area is created at the center (5) inducing a high volume flow of surrounding air into the primary airstream. As the airflow leaves the Air Wipe, it creates a conical 360° ring of air that attaches itself to the surface of the material running through it (6), uniformly wiping the entire surface with the high velocity airflow.

EXAIR incorporates the Bernoulli Principle with our engineered products which entrain air such as our Super Air Knives, Super Air Wipes, Air Amplifiers and Static Eliminating products to name a few. We have several Applications Engineers that will appreciate your call to discuss our products. If you have an application or question please call 800.903.9247 or visit us on our website www,EXAIR,com and let us help you.

Eric Kuhnash
Application Engineer
E-mail: EricKuhnash@exair.com
Twitter: @EXAIR_EK

Gen4 Super Ion Air Wipe Eliminates Static on Bottling Line

Just recently I worked with our Distributor in Argentina on an application for a manufacturer of bottled water. Once the bottles are filled, a protective security seal is placed along the top of the bottle. This serves two purposes, it prevents any form of tampering as well as keeps the cap of the bottle clean throughout the rest of the manufacturing process. Since most people drink directly from the bottle, this area needs to remain clean and not be exposed to contamination later on in the process.

Their problem was that static was building up on this plastic which caused an improper seal on the cap of the bottle. Further down the processing line, the bottles can be exposed to water that contaminates the bottles. They had to implement an inspection process as it was not acceptable to allow any contaminated bottles to leave the plant. Without a solution, they were losing time due to the necessary inspection as bottles were being rejected at a rate of almost 30%.

IMG_2625

The recommended solution was to install a Model 8164 4″ Gen4 Super Ion Air Wipe just prior to the point in the process where the seal was applied. The plastic material passed through the center of the Super Ion Air Wipe which neutralized the static charge on the material. Without a charge, the seal was applied correctly and they were able to eliminate the need of a manual inspection. After installation, the reject rate dropped to 0%!!

The Gen4 Super Ion Air Wipe provides a uniform 360° ionized airstream and is available in both 2” and 4” ID sizes. Its clam-shell design makes it easy to clamp around a part for neutralizing static electricity and contaminants. The high volume, high velocity airflow attaches itself to the surface and wipes it down with static eliminating ions. The airflow stays attached to the surface and is effective up to 15’ away from where it’s mounted. It’s lightweight and easy to mount using the ¼-20 tapped holes on the back or can also be held into place with just rigid pipe.

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As the temperatures begin to decline, so does the humidity in the air. Drier air results in an increase in static problems. Get ahead of it this year and check out EXAIR’s wide line of various Static Elimination products, all available to ship same-day from stock!

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

Super Air Wipe Vs. Block Type Air Wipe

Air Wipes, which provide 360 degree blowoff, are typically used to remove heat, liquid, debris or static from wire, cable, pipe, tube, or extrusions.

We had a customer that was using a block type Air Wipe from a competitor to remove water from an extrusion.  These air wipes are built using a plastic material, typically with some additional ceramic insert to resist abrasion of the wire, the halves are hinged with air holes drilled into each half which carries air through the block and on to the wire. They were using these block air wipes on several lines. The interesting point of this blog is that it required 5 block type air wipes to equal the results of 1 EXAIR Super Air Wipe.

Since EXAIR’s Super Air Wipe equaled the performance of 5 of the competitors it consumed less air was less expensive and produced less noise.  Also in space sensitive applications the EXAIR Super Air Wipe is much thinner than the block type.  To highlight this the Super Air Wipe is 1.13″ thick on all 11 models that range from 3/8″ to 11″ throat diameter.   The performance of the block air wipe can only be changed by altering the inlet air pressure while the EXAIR Super Air Wipe can also be changed by adusting the inlet air pressure OR by adding an additional shim the force can be nearly doubled!

Many of these block type air wipes use a series of holes to direct the compressed air supply at an angle over the material that needs to be cleaned off.  EXAIR’s Super Air Wipe being an engineered compressed air product use’s fluid dynamic’s to create more force as demonstrated below. The air from EXAIR’s Super Air Wipes is a continuous 360 degrees, without the gaps a series of holes creates.

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How The Air Wipe Works

Compressed air flows through the inlet (1) of the Air Wipe into the annular chamber (2).  It is then throttled through a small ring nozzle (3) at high velocity.  This primary airstream adheres to the Coanda profile (4), which directs down the angled surface of the Air Wipe.  A low pressure is created at the center (5) inducing a high volume flow of surrounding air into the primary airstream.  As the airflow leaves the wipe, it creates a conical 360° ring of air that attaches itself to the surface of the material running through it (6) uniformly wiping the entire surface with the high velocity airflow.

Block type air wipes are generally available in standard sizes up to 7″ in diameter while EXAIR’s Super Air Wipes are available in stock diameters up to 11″ and we also offer custom sizes to suit many other applications.

If you have any items that need to have a 360 degree blowing pattern, I would enjoy hearing from you…give me a call.

Steve Harrison
Application Engineer
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