What’s So Great About Air Entrainment?

Air entrainment is the phenomenon that occurs when air (or any gas) under pressure is released from a device in such a way that a low pressure is generated in the immediate area of the air (or gas) discharge.  Air (or gas) from the surrounding environment is then pulled (or entrained) into the discharged air stream, increasing its volumetric flow rate.  EXAIR Corporation has been engineering & manufacturing compressed air products to take maximum advantage of this phenomena since 1983…and we’ve gotten better & better at it over the past 36 years.

Obviously, the first thing that’s so great about air entrainment is…free air flow.  Every cubic foot that’s entrained means that’s a cubic foot that your compressor didn’t have to spend energy compressing.  Considering the EXAIR Super Air Knife’s entrainment ratio of 40:1, that makes for a VERY efficient use of your compressed air.

Another thing that’s so great about air entrainment is…it’s quiet.  As you can see from the graphic at the top of this blog, the Super Air Knife entrains air (the lighter, curved blue arrows) into the primary compressed air stream (the darker, straight blue arrows) from above and below.  The outer layers of the total developed flow are lower in velocity, and serve as a sound-attenuating boundary layer.  The sound level of a Super Air Knife (any length…here’s why) is only 69dBA.  That means if you’re talking with someone and a Super Air Knife is running right next to you, you can still use your “inside voice” and continue your conversation, unaffected by the sound of the air flow.

I always thought it would be helpful to have more than just a graphic with blue arrows to show the effect & magnitude of air entrainment.  A while back, I accidentally stumbled across a stunning visual depiction of just that, using a Super Air Knife.  I had the pleasure of talking with a caller about how effective a Super Air Knife might be in blowing light gauge paperboard pieces.  So I set one up in the EXAIR Demo Room, blowing straight upwards, and tossed paper plates into the air flow.  It worked just as expected, until one of the paper plates got a little closer to the Super Air Knife than I had planned:

As you can see, the tremendous amount of air flow being entrained…from both sides…was sufficient to pull in lightweight objects and ‘stick’ them to the surface that the entrained air was being drawn past.  While it doesn’t empirically prove the 40:1 ratio, it indisputably demonstrates that an awful lot of air is moving there.

If you’re looking for a quiet, efficient, and OSHA compliant solution for cleaning, blow off, drying, cooling…anything you need an even, consistent curtain of air flow for – look no further than the EXAIR Super Air Knife.  If you’d like to discuss a particular application and/or product selection, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Coandă Profiles

Here at EXAIR, Coandă is a household name that can be heard on any given day multiple times throughout the day. The Coandă effect is fairly easy to visualize with a ligthweight ball and some high velocity airflow. Take the video below for example. This 2″ Super Air Amplifier on a stand powered at 40 psig at the inlet easily lifts this hollow plastic ball and then suspends the ball due to the Coandă effect.

If you were able to see the airflow, you would see it impacting the surface of the sphere at all different points then following the profile of the sphere until it colides with itself and is forced to separate off the surface. The turbulent flow on the top is creating a downward pressure as well. The science behind this was all found and showcased by Henri Coandă. He showcased this with a propulsion device which used a domed hood with airflow to follow the curvature of the dome then exit off the sharp edge or where the separate air streams began to recombine causing a turbulent / low pressure area depending on the angle.

This stream of air following a surface begins to pull in all surrounding and impacted air molecules from around the stream which is called entrainment. This is a key factor for EXAIR products and one reason the Coandă profiles are a key characteristic to obtaining the peak performance and efficiency out of a compressed air product.

As the high velocity air stream exits the EXAIR model 1100 Super Air Nozzle the ambient air is entrained around the fins and angled surfaces of the nozzle.

Many EXAIR products utilize the Coandă principle to improve their efficiencies and performance. Below you can see the EXAIR product families containing Coandă profiles within their design which increases the ambient air entrainment resulting in an amplified air blowoff.

Super Air Wipes, Super Air Knives, Super Air Nozzles and Super Air Amplifiers use the Coanda principle to become some of the most efficient compressed air blowoff products available.

If you would like to discuss how the Coandă profile and EXAIR Intelligent Compressed Air Products® can help your process, please give us a call.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

What’s So “Super” About The Super Air Amplifier?

EXAIR Intelligent Compressed Air Products such as (left to right) the Air Wipe, Super Air Knife, Super Air Nozzle, and Air Amplifier are engineered to entrain enormous amounts of free air from the surrounding environment.

“Free air” from the surrounding environment?  You might think it’s too good to be true, and if you think you’re getting something for nothing, you’re right.  If you consider, though, that it’s oftentimes preferable to work smarter, not harder, then the use of engineered compressed air products is too good NOT to be true.  Case in point: the Super Air Amplifier.

The Coanda Effect is the “work smarter, not harder” part of the Super Air Amplifier

Simple and low cost, (hey, “engineered” doesn’t necessarily mean “complex and expensive”) the EXAIR Super Air Amplifier uses a small amount of compressed air to generate a tremendous amount of air flow through entrainment.  How much do they pull in?  Depending on the model, they entrain air at rates of 12:1 (for the 3/4″ Model 120020) to 25:1 (4″ & 8″ Models 120024 & 120028, respectively.)  The larger diameters mean there’s more cross sectional area to entrain air, so there is indeed efficiency to scale, size-wise.  There are a couple of great visuals in this video, if you want to see the entrainment in action (1:50) or the difference that the entrainment makes (1:30):

 

Where can you use a Super Air Amplifier?  The easy answer is, anyplace you want a consistent, reliable air flow.  The pressure supply can be regulated from a “blast to a breeze,” depending on the needs of your application.  The patented shim can be replaced for even higher performance, while maintaining the efficiency that makes it so valuable.  The balanced flow makes for incredibly quiet operation…no more noisy fans, blowers, or open-end compressed air pipes.  The body (3/4″ to 4″ sizes) is cast with a 2-hole flange for ease of installation.

When can you use a Super Air Amplifier?  Another easy answer: anytime you want.  If you need a continuous air flow, there are no moving parts to wear or electrical components to burn out.  Supply them clean, dry air, and they’ll run darn near indefinitely, maintenance free.

Alternately, if you need intermittent air flow, starting & stopping operation is as simple as opening & closing a valve in the compressed air supply line.  They produce rated flow immediately, and cut it off just as fast.

Some of the more popular applications are ventilation/exhaust, cooling, drying, cleaning, and dust collection.  There are five distinct models to choose from, and they’re all in stock.  We’re also happy to discuss special requirements that might lead to a custom product too.  Our Application Engineers work with Design & Production all the time to meet specific needs of particular situations.

If you’d like to find out more about letting the Super Air Amplifier, or any of EXAIR’s Intelligent Compressed Air Products work smarter for you, give me a call.

Russ Bowman
Application Engineer
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