Henri Coanda: Founder of The Coanda Effect (1886-1972)

EXAIR uses the Coanda effect in many of our products. Henri Coanda is an important figure in the world of fluid dynamics and aerodynamics.

Henri Coanda was a prominent Romanian Inventor and aerodynamics pioneer is known for the creation of the Coanda-1910 experimental plane as well as discovering the Coanda effect. On June 7, 1886 Henri was born in Bucharest Romania to General Constantin Coanda and Aida Danet. In 1899 Henri’s father who desired him to have a military career had him transfer to a Military High School for additional years of schooling, where he graduated with the rank of Sergeant Major. Continuing his studies, he went on to technical school back in Bucharest for Artillery, Military, and Naval Engineering. In 1904 he was sent to an artillery regiment in Germany where he would enroll in Technische Hochshule. Henri did not give up on studying and in 1907 went to Montefiore Institute in Liege, Belgium, where he met Gianni Caproni.

In 1910 Henri and Gianni began a partnership to construct an experimental aircraft which was later called the Coanda-1910. The Coanda-1910 was unlike any other aircraft of its time as it had no propeller; instead it sported an oddly shaped front end with built-in rotary blades arranged in a swirl pattern. These blades were driven by an internal turbine screw that would suck air in through the turbine while exhausting the gases out of the rear, propelling the plane forward. This initial jet engine was quite impressive for the time, but sadly nobody believed it would ever fly and is believed that it never did achieve flight. Coanda is not credited with the invention of the jet engine, but his technology spurred the future of aviation into the future.

During World War 2 Henri spent his time developing the turbo-propeller drive system from his 1910 Biplane. After World War 2 had ended Henri began furthering his research on the Coanda Effect which would become the basis for several investigations into entrained and augmented flow of fluids. Later on in 1969 Henri would spend the last of his days in Romania serving as Director of the Institute for Scientific and Technical Creation. Coanda died on November 25, 1972 in his home town of Bucharest.

Here at EXAIR we have taken Henri Coanda’s, Coanda Effect and applied it to a number of our products to help amplify total airflow and save on compressed air.  The most notable product lines are our Air Amplifiers, Air Nozzles, and Air Knives – which are some of the most efficient products of their kind. These products can help lower your compressed air demand. 

If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Calculating CFM of Air Needed for Cooling

It’s easy to know that EXAIR’s vortex tubes can be used to cool down parts and other items, but did you know that our air knifes can be used to cool down these same things? It’s the same process that we do every day to cool down hot food by blowing on it. Every molecule and atom can carry a set amount of energy which is denoted by physical property called Specific Heat (Cp); this value is the ration of energy usually in Joules divided by the mass multiplied by the temperature (J/g°C). Knowing this value for one can calculate the amount of air required to cool down the object.

Starting out you should note a few standard values for this rough calculation; these values are the specific heat of Air and the specific heat of the material. Using these values and the basic heat equation we can figure out what the amount of energy is required to cool. The specific heat for dry air at sea level is going to be 1.05 J/g*C which is a good starting point for a rough calculation; as for the specific heat of the material will vary depending on the material used and the composition of the material.

Heat Flow Equation
Using the standard heat equation above add in your variables for the item that needs to be cooled down. In the example I will be using a steel bar that is 25 kg in mass rate and cooling it down from 149 °C to 107 °C. We know that the specific heat of steel is 0.466 J/g°C therefore we have everything needed to calculate out the heat load using air temperature of 22 °C.
Calculating Joules/min
Using the heat rate, we can convert the value into watts of energy by multiplying the value by 0.0167 watts/(J/min) which gives us 16,537.18 watts. Furthermore, we can then convert our watts into Btu/hr which is a standard value used for cooling applications. Watts are converted into Btu/hr by multiplying by 3.41 Btu/hr/watt, giving us 56,391.77 Btu/hr.
Converting Joules to Btu/hr
Once you have Btu/hr you can plug the information into a re-arranged Cooling power formula to get the amount of CFM of air required for cooling.
Calculating CFM
As you can see in order to cool down this steel bar you only need to 343 CFM of air at 72°F. This can be done very easily and efficiently by using one of EXAIR’s Air Amplifiers or Air Knife. Sometimes you don’t need to use a vortex tube to cool down an object; sometimes simply blowing on it is good enough and its pretty simple to calculate out which product would fit your application the best.

If you have any questions about compressed air systems or want more information on any EXAIR’s of our products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Usefulness of a Coanda Profile

How did a past inventor help generate efficient compressed air products for EXAIR?  In the early 20th century, Henri Coanda who was a Romanian aeronautical engineer that built an experimental Coanda-1910 airplane.  There are some debates if the airplane actually flew, but he invented a curved surface for a wing to generate a Coanda effect. The Coanda effect is the “tendency of a fluid jet to stay attached to a convex surface”1.   Thus, a moving stream of fluid will follow the curvature of the surface rather than continuing to travel in a straight line.  The Wright Brothers who flew the first airplane in the state where EXAIR is located, Ohio, used the Coanda effect to create lift.  With a curved profile, the air will adhere to the surface, causing a low pressure which makes the airplane fly.

Standard Air Knife

Super Air Amplifier with shims

EXAIR uses this Coanda profile to make some of our Intelligent Compressed Air Products™.   Like the airplane wing, our curved surface will also create a low pressure.  How does this help?  Well, high pressure will always travel to low pressure.  Instead of lift, we use the low air pressure to entrain ambient air.  This ratio is what we call the amplification ratio.  The higher the amplification ratio, the higher the efficiency for a blowing device. Two main compressed air products that EXAIR manufactures use this type of profile; Air Knives and Air Amplifiers.  I will cover both below.

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.

The Air Knives that use the Coanda profile blows air along the length of the knife at a 90o angle from the exit.  We offer two types; the Standard Air Knife and the Full Flow Air Knife.  The Standard Air Knives are made in Aluminum or Stainless Steel with blowing widths up to 48” (1219mm).  The inlet ports are at each end; so, the overall length is 1” (25mm) longer.  The Full Flow Air Knives have the port or ports on the back.  The air blows out the entire length of the air knife.  The maximum length is 36” (914mm).

Both types of air knives use the Coanda profile to generate a low pressure as the air exits the gap and “hugs” the curve (reference photo above).  This low pressure draws ambient air into the air stream at a 30:1 amplification ratio for both the Standard Air Knife and Full Flow Air Knife.  So, for every one part of compressed air, we entrain 30 parts of ambient air.  Besides efficiency, it also adds mass to the air stream for a hard-hitting force.  With this engineered profile, the air stream is laminar which gives a consistent force across the entire length and reduces noise levels.  Not only will they save you money,  but they are also OSHA safe.

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

The Air Amplifiers use the Coanda profile in a circular form to pull in dramatic amounts of free surrounding air.  The Coanda effect is able to generate a low pressure to blow air for cooling, cleaning or removing smoke and debris efficiently and quietly.  The Air Knives above blow a flat stream of air while the Air Amplifiers will blow a conical air stream.  They can reach amplification ratios up to 25:1. The Super Air Amplifiers use a patented shim to increase efficiency.

Unlike fans, they blow a laminar air stream for quick cooling.  They do not have any moving parts or motors to wear, so they are very quiet.  EXAIR manufactures five different sizes from ¾” (19mm) to 8” (203mm).  The Adjustable Air Amplifiers have a plug that can be adjusted to control the blowing force from a breeze to a blast.  For cleaning surfaces, this is a nice feature to “dial” in to exactly what you need.  We also manufacture five different sizes in aluminum and stainless steel ranging from ¾” (19mm) to 4” (102mm).  Both Air Amplifiers can be attached to ducts to remove debris, heat or smoke from the area.

Utilizing the Coanda effect allows for massive compressed air savings. Whether it is a flat or round air stream, EXAIR can do this with high amplification ratios.  If you would like to discuss further how our Air Knives or Air Amplifiers can help you in your applications, please contact us. An Application Engineer will be happy to help you.  History has shown us a way to increase efficiency when using compressed air.  And you can take advantage of it with the Coanda profile.  Thank you Mr. Henri Coanda.

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


1note – Wikipedia – Coanda effect

Products Built to Last and Maintenance Free

As an avid outdoors man, I have learned a lot about myself during these days of quarantine and social distancing; mainly I don’t quarantine very well. With all the climbing gyms closed, traveling strongly discouraged, and social distancing in place my  lifestyle has been brought to a grinding halt much like many of us. opening up, which will be good for all of us. 

So, in place I have taken upon myself to learn a new hobby that I can do solo and safely. In the past weeks I have spent learning about mountain biking and all that comes with it. This includes the maintenance required to work on a bike, specifically the front derailleur which controls the front major gear changes (and gets damaged if crashed). Realigning the front derailleur is one of the hardest fixes that one can do on a bike as it has three different adjustments that need to be made at the same time. Thus, I embarked on a week long project of learning how to make the adjustment and man was it frustrating.

Performing tricky maintenance can be one of the most frustrating and stress inducing things when all you really want is for something to work without any hassle. Whether its hours just trying to figure out what the issue is or actually fixing it, let’s be honest, it never goes as planned. The same can be said for maintenance on things such as compressors, cars, and production equipment. Here at EXAIR we strive to eliminate this frustration and hair pulling maintenance and replace it with maintenance free products.

EXAIR’s lines of compressed air products such as our Vortex Tubes, Super Air Amplifiers, and Super Air Knives have no moving parts. No moving parts means no wear down parts and no wear down parts means little to no maintenance. Besides the occasional air filter element change out or something getting lodged inside the product EXAIR’s compressed air products will run almost indefinitely as long as they are supplied with a source of compressed air, typically run through a standard 5 micron filter separator. 

Although you cannot really prevent dirt from collecting in a filter separator (that is, in fact what they are meant to do) you can prevent dirt, dust, and debris from getting into your products by using one of EXAIR’s Filter Separators. Filter Separators remove water condensate, dirt, dust, and debris from your compressed air line before it enters your compressed air product. This prevents the particles from disrupting small air outlets or lodging in the small pathways inside our compressed air products and keeps the product running like new.

All in all, maintenance is not fun to have to deal with and can be costly at times. By using EXAIR’s engineered compressed air products you can eliminate at least one thing to worry about on your list of maintenance that needs to be performed. With a little bit of preventive measures you can keep our products running like new for years and years.

If you have any questions or want more information on any EXAIR’s of our products, give us a call, we have a team of application engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Why Use EXAIR Super Air Knives: Return on Investment

Return on Investment, or ROI, is the ratio of profit over total investment.  Many people use it to check stocks, financial markets, capital equipment, etc.  It is a quantitative way in determining the validity for an investment or project.   You can use the ROI value to give a measurable rate in looking at your investment.  For a positive ROI value, the project will pay for itself in less than one year.  Any negative values would represent a high-risk investment.  In this blog, I will compare the ROI between an EXAIR Super Air Knife to a common drilled pipe.  Let’s start by looking at Equation 1 to calculate the Return on Investment:

Equation 1:  ROI = (Total annual savings – Total Project Cost) / Total Project Cost * 100

The Total Project Cost is the cost of the product with the labor to install.  In our example, we will use a 24” (610mm) wide blow-off device.  One device will be an inexpensive drilled pipe and the other will be a high-efficiency EXAIR Super Air Knife.  The drilled pipe had (48) 1/16” (1.6mm) diameter holes spaced ½” (13mm) apart.  EXAIR manufactures the model 110024 Super Air Knife with a .002” (.05mm) slot along the entire length.  Both have a blowing width of 24” to cover the conveyor.  The model 110024 has a retail price of $491.00 each.  The cost of the drilled pipe was around $50.00.  What a difference in price!  But, how could EXAIR remain a leader in this industry for over 35 years?

Let’s continue on with the Return on Investment.  The amount of time required to install the Super Air Knife across the conveyor only took a maintenance staff about one hour to mount.  The labor rate that I will use in this example is $75.00 per hour (you can change this to your current labor rate).  The labor cost to install the knife is $75.00.   The Total Project Cost can be calculated as follows: ($491 – $50) + $75.00 = $516.00.  The next part of the equation, Total annual savings, is a bit more in-depth, but the calculation is shown below.

Super Air Knife

EXAIR manufactures engineered products to be efficient and safe.  The Super Air Knife has a 40:1 amplification ratio which means that 40 parts of “free” ambient air is entrained for every 1 part of compressed air.  For comparison, the Super Air Knives are to compressed air systems as LED lightbulbs are to electricity.  In that same way, the drilled pipe would represent an incandescent lightbulb.  The reason for this analogy is because of the amount of energy that the EXAIR Super Air Knives can save.  While LED lightbulbs are a bit more expensive than the incandescent lightbulbs, the value for the Return on Investment is at a higher percentage, or in other words, a short payback period.  On the other hand, the drilled pipe is less expensive to make, but the overall cost for using it in your compressed air system is much higher.  I will explain how below.

To calculate the Total Annual Savings, we will use the same blow-off scenario as above.  The amount of compressed air used by the drilled pipe is around 174 SCFM (4,924 SLPM) at 60 PSIG (4.1 Bar).  The model 110024 Super Air Knife has an air consumption of 55.2 SCFM (1,563 SLPM) at 60 PSIG (4.1 Bar).  At an electrical rate of $0.08 per Kilowatt-hour, we can figure the cost to make compressed air.   Based on 4 SCFM per horsepower of air compressor, the electrical cost is $0.25 per 1000 standard cubic feet, or $0.25/1000SCF.  To calculate an annual savings, let’s use a blow-off operation of 8 hours/day for 250 days a year.   Replacing the drilled pipe with the model 110024 Super Air Knife, it will save you (174 SCFM – 55.2 SCFM) = 121.8 SCFM of compressed air.  To put this into a monetary value, the annual savings will be 121.8 SCFM *$0.25/1000SCF * 60 Min/hr * 8hr/day * 250 day/yr = $3,654 per year.

With the Total Annual Cost and the Project Cost known, we can insert these values into Equation 1 to calculate the ROI:

ROI = (Total annual savings – Total Project Cost) / Project Cost * 100

ROI = ($3,654 – $516.00) / $516.00 * 100

ROI = 608%

With a percentage value that high, we are looking at a payback period of only 52 days.  You may look at the initial cost and be discouraged; but in a little over a month, the model 110024 will have paid for itself.  And after using it for one year, it will save your company $3,654.00.  Some things that may be overlooked are safety issues.  With some inexpensive blow-off devices, the noise levels are over the OSHA limits.  The drilled pipe had a noise level of 91 dBA while the Super Air Knife only had a noise level of 65 dBA.

In my experience, a loud blowing noise from your equipment is generally coming from an inefficient and safety-concerned product.  With these “cheap” ways to blow compressed air, it will cost your company a lot of money to use as shown in the example above.  If you would like to team up with EXAIR to set up ways to increase savings, improve productivity, and promote safety, an Application Engineer can help you to get started.

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

EXAIR, Manufacturing Locally Equals Quick Customizations

Dryer with corn cob material

A manufacturing company contacted EXAIR about their metal tube processing. They made industrial precision tubes from start to finish. This would include turning, cutting, coating, washing and drying metal tubes to specific diameters and lengths.

For one specific problem area, they manufactured a tube with the dimensions of 1” (25.4mm) in diameter and 6” (152mm) in length. They would run a batch of 750 tubes through a wash cycle and then through a vibrating dryer with a drying material made from corn cobs. At the bottom of the vibrating dryer, the tubes would fall to an open mesh shaker table to transfer the tubes to Quality Control. The idea was to remove the excess cob material from the surface of the tubes before inspection and to recycle the drying material. But the problem was static.

When non-conductive materials slide, hit, peel, and vibrate; electrons from the surface can move from one atom to another; thus, creating static. The type of material and the amount of movement governs the positive and negative charges, and the amount of static forces.

The corn cob material is a non-conductive material, but what about the metal tubes? Since the metal tubes were coated for corrosion and abrasion protection, the surface is now a non-conductive area which will contain static. Since opposite charges attract each other, the cob material would cling to the outside surface of the metal tubes (reference photo below). Being a precision tube manufacturer, they did not want to send “dirty” tubes to their customers or allow the drying material to contaminate their measuring equipment. And, with the required quality control, the measurements had to be exact.

Tubes with cob material

The shaker table was 8 feet (2.4 meters) long and 2 feet (0.6 meter) wide with rigid walls. The top of the shaker table was covered with a canvas to allow for a vacuum system to collect the excess material and dust. About half way down, there was a 2” (51mm) drop to help jolt additional cob material off of the tubes as they landed. But the static forces were too strong to release the material. Thus, the static had to be removed from the surface, so they contacted EXAIR to see if we could find a solution.

They sent photos of their setup which always helps us to diagnose and find solutions. The target place that they suggested would be near the 2” (51mm) drop as the tubes would be suspended for just a moment. My recommendation was to use a Gen4 Super Ion Air Knife to blow ionized air around the tubes as they fell. By blowing air, we can use the non-contact force to remove the static and the cob material at the same time. But we had two issues to overcome. The width was fixed at 2 feet (0.6 meter), and the operation controls were 10 feet (3 meters) away from the mid-section of the shaker table.

Gen4 Super Ion Air Knives

EXAIR stocks many Gen4 Super Ion Air Knives ranging from 3” (76mm) to 108” (2.74meters) in incremental lengths for quick shipments. But our standard 24″ product was not able to fit inside that area nor was the five foot electrical cable long enough to reach the control panel. (As a note, it was important for the operator to be able to manually turn on and off the unit from the control panel.)

EXAIR uses an electromagnetically shielded cable to carry high voltage from our Gen4 Power Supply to our shockless, non-radioactive Gen4 Ionizing Bar. Our  stocked length for our armored cable is 5 feet (1.5 meter). After discussing the amount of movement with the table and the desired distance to the control panel, EXAIR could not use an item off the shelf. But not to worry… Since we are the manufacturer, we have the ability to make a special design for this customer.

Super Ion Air Knife Part Numbering System

I recommended a model 112220-10 special length Gen4 Super Ion Air Knife Kit. (Reference model numbering system above). Specials are non-returnable and non-cancelable, but for this customer, it was exactly what they needed. The Gen4 Super Ion Air Knives are engineered to efficiently blow ionized air to the target and remove static charge and debris.

For this special model, it was made to a specific width where the Super Air Knife was manufactured to a length of 20” (508mm), and the high voltage cable was lengthened to 10 feet (3 meters). The kit includes the Gen4 Power Supply to power the Ionizing Bar, a filter to clean the compressed air, a regulator to control the force, and a shim set to change force rates. This complete kit had everything required to begin operations to remove static and cob material from their precision tubes. The customer was able to mount the special length Gen4 Super Ion Air Knife within the shaker table and mount the power supply near the control panel.

Static can be an issue even with coated metal parts. For the customer above, EXAIR was able to make a special length Gen4 Super Ion Air Knife to work in their system. If you believe that static is causing issues, EXAIR has a great range of Gen4 Static Eliminators to remove that nuisance. You can discuss further with an Application Engineer as EXAIR for help; even if you need a custom product.

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

Controlling Compressed Air can be Easy, and Save Thousands of Dollars

The history of automated controls can be traced back to inventors in ancient Greece & Egypt, who sought ways to keep more accurate track of time than afforded by sundials and hourglasses.  Their efforts, dating as far back as 300BC, produced devices actuated by water flow, which is actually quite reliable and repeatable: a set amount of water will flow via gravity through a fixed conduit in the exact same amount of time, every time.  These were in fairly common use until the invention of the mechanical clock in the 14th century.

The Industrial Revolution grew the need for automated processes exponentially…the need to control objects or tooling in motion, fluid flow, temperature, and pressure, just to name a few.  As time passed, the sky was literally the limit: modern aircraft & spacecraft rely on a staggering amount of automated processes from production to operation.

All throughout history, though, the benefits of automation remain the same: making processes more efficient.  That’s where the EXAIR EFC Electronic Flow Control comes in, for automating processes involving compressed air use, by turning air flow off when it’s not needed.  In fact, not only do they provide simple on/off control to blow only when a part is “seen” by the photoelectric sensor, there are eight distinct modes to incorporate delay on or off, flicker on or off, signal on/off delay, interval, or “One-Shot,” where the sensor detects the part, delays opening the valve per the timer setting, and blows for one second.

EFC Electronic Flow Control Systems are already assembled & wired for quick & easy installation.

The EXAIR EFC Electronic Flow Control is a true “plug and play” solution for automating a compressed air application.  Mount the sensor, plumb the valve, plug it in, and you’re ready to go.  There’s no complicated PLC wiring or programming, although the aforementioned mode selections do offer a great deal of flexibility other than “on when the sensor sees it; off when it doesn’t” operation, if desired.  Here are some prime examples of that flexibility, and the monetary benefits due to the compressed air consumption savings:

(Left) On/Off Delay setting used in tank refurbishment application to operate a “halo” of Super Air Knives for blow off as tanks exit oven where old paint is burnt off – $3,393 annual air savings. (Center) Interval setting actuates a Super Ion Air Knife for flat panel display dust blow off/static elimination – $2,045 annual air savings. (Right) Interval setting actuates a “halo” of Super Ion Air Knives to clean & remove static charge from plastic automotive bumper covers prior to painting – $5012 annual savings.

If you’d like to find out more about the EFC Electronic Flow Control can save you time, air, and money, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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