## People of Interest: Daniel Bernoulli

Whenever there is a discussion about fluid dynamics, Bernoulli’s equation generally comes up. This equation is unique as it relates flow energy with kinetic energy and potential energy. The formula was mainly linked to non-compressible fluids, but under certain conditions, it can be significant for gas flows as well. My colleague, Tyler Daniel, wrote a blog about the life of Daniel Bernoulli (you can read it HERE). I would like to discuss how he developed the Bernoulli’s equation and how EXAIR uses it to maximize efficiency within your compressed air system.

In 1723, at the age of 23, Daniel moved to Venice, Italy to learn medicine. But, in his heart, he was devoted to mathematics. He started to do some experiments with fluid mechanics where he would measure water flow out of a tank. In his trials, he noticed that when the height of the water in the tank was higher, the water would flow out faster. This relationship between pressure as compared to flow and velocity came to be known as Bernoulli’s principle. “In fluid dynamics, Bernoulli’s principle states that an increase in the speed of fluid occurs simultaneously with a decrease in static pressure or a decrease in the fluids potential energy”1. Thus, the beginning of Bernoulli’s equation.

Bernoulli realized that the sum of kinetic energy, potential energy, and flow energy is a constant during steady flow. He wrote the equation like this:

Equation 1:

Not to get too technical, but you can see the relationship between the velocity squared and the pressure from the equation above. Being that this relationship is a constant along the streamline; when the velocity increases; the pressure has to come down. An example of this is an airplane wing. When the air velocity increases over the top of the wing, the pressure becomes less. Thus, lift is created and the airplane flies.

With equations, there may be limitations. For Bernoulli’s equation, we have to keep in mind that it was initially developed for liquids. And in fluid dynamics, gas like air is also considered to be a fluid. So, if compressed air is within these guidelines, we can relate to the Bernoulli’s principle.

1. Steady Flow: Since the values are measured along a streamline, we have to make sure that the flow is steady. Reynold’s number is a value to decide laminar and turbulent flow. Laminar flows give smooth velocity lines to make measurements.
2. Negligible viscous effects: As fluid moves through tubes and pipes, the walls will have friction or a resistance to flow. The surface finish has to be smooth enough; so that, the viscous effects is very small.
3. No Shafts or blades: Things like fan blades, pumps, and turbines will add energy to the fluid. This will cause turbulent flows and disruptions along the velocity streamline. In order to measure energy points for Bernoulli’s equation, it has to be distant from the machine.
4. Compressible Flows: With non-compressible fluids, the density is constant. With compressed air, the density changes with pressure and temperature. But, as long as the velocity is below Mach 0.3, the density difference is relatively low and can be used.
5. Heat Transfer: The ideal gas law shows that temperature will affect the gas density. Since the temperature is measured in absolute conditions, a significant temperature change in heat or cold will be needed to affect the density.
6. Flow along a streamline: Things like rotational flows or vortices as seen inside Vortex Tubes create an issue in finding an area of measurement within a particle stream of fluid.

Since we know the criteria to apply Bernoulli’s equation with compressed air, let’s look at an EXAIR Super Air Knife. Blowing compressed air to cool, clean, and dry, EXAIR can do it very efficiently as we use the Bernoulli’s principle to entrain the surrounding air. Following the guidelines above, the Super Air Knife has laminar flow, no viscous effects, no blades or shafts, velocities below Mach 0.3, and linear flow streams. Remember from the equation above, as the velocity increases, the pressure has to decrease. Since high-velocity air exits the opening of a Super Air Knife, a low-pressure area will be created at the exit. We engineer the Super Air Knife to maximize this phenomenon to give an amplification ratio of 40:1. So, for every 1 part of compressed air, the Super Air Knife will bring into the air streamline 40 parts of ambient “free” air. This makes the Super Air Knife one of the most efficient blowing devices on the market. What does that mean for you? It will save you much money by using less compressed air in your pneumatic application.

We use this same principle for other products like the Air Amplifiers, Air Nozzles, and Gen4 Static Eliminators. Daniel Bernoulli was able to find a relationship between velocities and pressures, and EXAIR was able to utilize this to create efficient, safe, and effective compressed air products. To find out how you can use this advantage to save compressed air in your processes, you can contact an Application Engineer at EXAIR. We will be happy to help you.

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

## Video Demonstration of Compounding Sound Levels

In industrial settings, having a single air nozzle or other blowoff product is often not the scenario that is seen.  Many applications require multiple points of blowoff, even if not in the same direction or for the same position within the machine.  In the scenario where multiple nozzles are used, sound levels can get tricky to calculate and is often thought of as a mystery.  If you follow our blog then you may have seen this excellent blog that shows all the math behind calculating the total decibels when multiple sources of noise will be present. The video below gives a demonstration of utilizing two of the EXAIR model 1100 – 1/4″ FNPT Super Air Nozzle.

In the video you see a model 1100 being operated and producing a sound level of 74 dBA from 3′ away from the nozzle point.  When the second nozzle is turned on (also producing 74 dBA individually), the pressure is adjusted back up to the same input pressure and the sound level meter registers 78 dBA from 3′ away.  Following the math laid out in the “excellent blog” link above, the sound level calculated comes out to be the same 78 dBA that is shown in the video using EXAIR’s Digital Sound Level Meter.

If you would like help determining the sound levels within your facility, check out the EXAIR Digital Sound Level Meter as well as reach out to an Application Engineer.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

## Engineered Compressed Air Nozzles and Utility Rebates

When EXAIR started to manufacture compressed air products, we created a culture in making high quality products that are safe, effective, and efficient.  Being leaders in this industry, we created a program, the Efficiency Lab, to compare blow-off devices with EXAIR products in noise levels, flow requirements, and force measurements.  With calibrated test equipment, we compare the data in a qualified report to share with our customers.  This information can be helpful to determine the total amount of air savings and safety improvements that EXAIR products can offer.

In conjunction with the Efficiency Lab, we created a Cost Savings Calculator.  It is a quick way to view payback periods and annual savings when using EXAIR products.  As an example, I used a 1” Flat Super Air Nozzle, model 1126, and compared it to a 1/8” open pipe.  (The reason behind the comparison is that the model 1126 can screw onto the end of the 1/8” NPT pipe.)  With an operation of 24 hours/day for 250 days a year, the amount of air used by an 1/8” open pipe is near 70 SCFM (1,981 SLPM) at 80 PSIG (5.5 Bar).  The model 1126 has an air consumption of 10.5 SCFM (297 SLPM) at 80 PSIG (5.5 Bar).  By putting the information in the Cost Savings Calculator, it determined that the ROI was in 2.1 days.  The annual savings was \$5,355 USD per year.  Imagine if you replaced ten blow-off spots in your facility, the amount of money that could be saved.  Here is the worksheet below:

The people that started to notice the savings were the utility companies that make electricity.  Depending on your location, electrical suppliers initiated a rebate program to use engineered nozzles in your facility.  Similar to other energy saving rebates, like LED light bulbs and high efficiency furnaces, the electrical providers notice a big savings when using EXAIR products.  If you qualify, the total cost to purchase and implement the EXAIR Super Air Nozzles are reduced.(Even if a rebate program has not been implemented in your area, the idea of saving energy and compressed air makes it very profitable and environmentally sound in changing over to EXAIR products).

To see if your utility offers rebates on compressed air optimizations, go to the DSIRE database. This database is easy to search and informative.

For Example, here in Ohio Duke Energy has a Prescriptive Incentive Program for its customers. The Prescriptive Incentive Program makes it easy for Duke Energy customers to receive an incentive for their natural gas and electric energy efficiency projects. Prescriptive Incentives are energy efficient measures paid per-unit, reimbursing the customer up to the total cost (including materials and labor) after the measures have been installed. See the image below for their incentives for using Engineered Nozzles;

https://www.duke-energy.com/business/products/smartsaver/industrial-equipment

To discuss your application and how an EXAIR Intelligent Compressed Air Product can help your process and save you money, feel free to contact EXAIR and myself or one of our Application Engineers can help you determine the best solution.

Jordan Shouse
Application Engineer

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## The Bernoulli Principle

What do baseball, airplanes, and your favorite singer have in common? If you guessed that it has something to do with the title of this blog, dear reader, you are correct.  We’ll unpack all that, but first, let’s talk about this Bernoulli guy:

Jacob Bernoulli was a prominent mathematician in the late 17th century.  We can blame calculus on him to some degree; he worked closely with Gottfried Wilhelm Leibniz who (despite vicious accusations of plagiarism from Isaac Newton) appears to have developed the same mathematical methods independently from the more famous Newton.  He also developed the mathematical constant e (base of the natural logarithm) and a law of large numbers which was foundational to the field of statistics, especially probability theory.  But he’s not the Bernoulli we’re talking about.

Johann Bernoulli was Jacob’s younger brother.  He shared his brother’s passion for the advancement of calculus, and was among the first to demonstrate practical applications in various fields.  So for engineers especially, he can share the blame for calculus with his brother.  But he’s not the Bernoulli we’re talking about either.

Johann’s son, Daniel, clearly got his father’s math smarts as well as his enthusiasm for practical applications, especially in the field of fluid mechanics.  His kinetic theory of gases is widely known as the textbook (literally) explanation of Boyle’s law.  And the principle that bears his name (yes, THIS is the Bernoulli we’re talking about) is central to our understanding of curveballs, airplane wings, and vocal range.

Bernoulli’s Principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure (e.g., the fluid’s potential energy.)

• In baseball, pitchers love it, and batters hate it.  When the ball is thrown, friction (mainly from the particular stitched pattern of a baseball) causes a thin layer of air to surround the ball, and the spin that a skilled pitcher puts on it creates higher air pressure on one side and lower air pressure on the other.  According to Bernoulli, that increases the air speed on the lower pressure side, and the baseball moves in that direction.  Since a well-thrown curveball’s axis of rotation is parallel to the ground, that means the ball drops as it approaches the plate, leaving the batter swinging above it, or awkwardly trying to “dig it out” of the plate.
• The particular shape of an airplane wing (flat on the bottom, curved on the top) means that when the wing (along with the rest of the plane) is in motion, the air travelling over the curved top has to move faster than the air moving under the flat bottom.  This means the air pressure is lower on top, allowing the wing (again, along with the rest of the plane) to rise.
• The anatomy inside your neck that facilitates speech is often called a voice box or vocal chords.  It’s actually a set of folds of tissue that vibrate and make sound when air (being expelled by the lungs when your diaphragm contracts) passes through.  When you sing different notes, you’re actually manipulating the area of air passage.  If you narrow that area, the air speed increases, making the pressure drop, skewing the shape of those folds so that they vibrate at a higher frequency, creating the high notes.  Opening up that area lowers the air speed, and the resultant increase in pressure lowers the vocal folds’ vibration frequency, making the low notes.
• Bonus (because I work for EXAIR) Bernoulli’s Principle application: many EXAIR Intelligent Compressed Air Products are engineered to take advantage of this phenomenon to optimize efficiency:

If you’d like to discuss Bernoulli, baseball, singing, or a potential compressed air application, give me a call.  If you want to talk airplane stuff, perhaps one of the other Application Engineers can help…I don’t really like to fly, but that’s a subject for another blog.

Russ Bowman
Application Engineer
EXAIR Corporation
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## People of Interest: Daniel Bernoulli (2/8/1700-3/17/1782)

Daniel Bernoulli was born in the Netherlands in February of 1700. Mathematics was in his bloodline as the son of renowned Swiss mathematician, Johann Bernoulli. He and Johann’s brother, Jakob, both took jobs as professors at a university in Basel, Switzerland. Fittingly, Johann taught Daniel mathematics at a very young age. Daniel Bernoulli spent some time studying a variety of topics including philosophy, logic, and medicine. Daniel obtained his Bachelor’s Degree at the age of just 15, earning his Master’s Degree just one year later.

Daniel was well-known and was highly regarded among scholars throughout Europe. After spending some time teaching Botany, he switched to physiology topics in 1743. This continued for several years when in 1750 he was appointed to the chair of physics where he taught at Basel for 26 years. During this time, he also received a total of 10 grand prizes from the Paris Academy of Sciences for work he completed in astronomy, a variety of nautical topics, and magnetism.

Daniel is most commonly known for his work in developing what is now called Bernoulli’s Principle, which discusses 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 air entrainment properties of some of EXAIR’s Intelligent Compressed Air Products can be explained through Bernoulli’s Principle. As high-velocity air exits the nozzle of a Super Air Knife, for example, a low-pressure area is created that speeds up and draws in ambient air at an astonishing rate of 40:1. The same also occurs with the Super Air AmplifiersAdjustable Air Amplifiers, and Air Nozzles. To find out how you can utilize this advantage to save compressed air in your processes, give us a call. An Application Engineer will be happy to help assist you in determining the most suitable products for your application.

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

## Intelligent Compressed Air: Avoid Pressure Drop

A critical component to optimal performance of any compressed air operated product is ensuring sufficient compressed air flow. Simply put, inadequate air flow won’t allow you to get the job done.

As compressed air moves through the distribution system, it encounters friction inside of the walls of the pipe, tube, hose, etc. The diameter of the pipe, length, number of direction changes, and finish surface of the inner wall all play a part in this. A drop in air pressure will occur as a result of this friction. In addition to pressure drops experienced due to the distribution system, they can also occur at the point of use.

When designing and maintaining your compressed air system, pressure measurements should be taken across varying points to identify (and fix) any issues before they create a greater problem down the road. According to the Compressed Air Challenge, these are the places you should take regular pressure measurements to determine your system operating pressure:

• Inlet to compressor (to monitor inlet air filter) vs. atmospheric pressure
• Differential across air/lubricant separator
• Interstage on multistage compressors
• Aftercooler
• At treatment equipment (dryers, filters, etc.)
• Various points across the distribution system
• Check pressure differentials against manufacturers’ specifications, if high pressure drops are noticed this indicates a need for service

*More recent compressors will measure pressure at the package discharge, which would include the separator and aftercooler.

Once you’ve taken these measurements, simply add the pressure drops measured and subtract that value from the operating range of your compressor. That figure is your true operating pressure at the point of use.

If your distribution system is properly sized and the pressure drops measured across your various equipment are within specifications, any pressure drop noticed at the point of use is indicative of an inadequate volume of air. This could be due to restrictive fittings, undersized air lines, hose, or tube, or an undersized air compressor. Check that the point of use product is properly plumbed to compressed air per the manufacturer’s specifications.

EXAIR Products are designed to minimize this pressure drop by restricting the flow of compressed air at the point of use. The more energy (pressure) that we’re able to bring to the point of use, the more efficient and effective that energy will be. The photo below shows two common examples of inefficient compressed air usage. With an open-ended blow off, a pressure drop occurs upstream inside of the supply line. If you were to measure the pressure directly at the point of use, while in operation, you’d find that the pressure is significantly lower than it is at the compressor or further up the line. In the other photo with modular style hose, some pressure is able to be built up but if it gets too high the hose will blow apart. These types of modular style hose are not designed to be used with compressed gases.

EXAIR’s Super Air Nozzles, on the other hand, keep the compressed air pressure right up to the point of discharge and minimize the pressure drop. This, in addition to the air entrained, allows for a high force while maximizing efficiency. If you’d like to talk about how an EXAIR Intelligent Compressed Air Product could help to minimize pressure drop in your processes give us a call.

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

Pressure gauge photo courtesy of Cliff Johnson via Flickr Creative Commons License

## Super Air Nozzles and Stay Set Hoses to Replace Open Tubes

I recently worked with an company that performs energy audits and they were working with a food company to review and propose ways to reduce the energy consumption throughout the plant. One area where we were able to help was on an onion peeling machine, shown below:

The area of machine in question used a screw conveyor and friction source to help loosen the peels and fifteen (15) 1/4″ O.D. open ended tubes, which were noisy and unsafe, to blow the peels completely off and away form the onion. The auditor was able to install an air flow meter on the system and found that the machine was consuming 220 SCFM of compressed air for this operation.

We proposed to replace the tubes with a 6″ Stay Set Hose and the model 1103 Mini Super Air Nozzle.  Each model 1103 Mini Super Air Nozzle will consume just 10 SCFM of 80 PSIG compressed air. Attached to the 6″ Stay Set Hose, the nozzle can be placed exactly where needed and aimed appropriately. A strong blast of air rated at 0.56 lbs (9 ozs.), and ultra quiet at 71 dBA, the Mini Super Air Nozzle delivers the results needed.

The Stay Set Hose has “memory” and will not creep or bend, simply install the 1/4 NPT fitting into the compressed air supply side, an thread the 1/8 NPT Mini Super Air Nozzle into the other end and position as needed!

Fifteen (15) of the Mini Super Air Nozzles will pass 150 SCFM of compressed air compared to the current usage of 220 SCFM, resulting in a 70 SCFM drop, or a 31.8 % reduction.  At a typical cost of \$0.25 per 1000 Cubic Feet of Compressed Air, the nozzles would save \$1.05 per hour of operation. Rate of Return yields a full pay-off in just 43 days of operation (24 hours per day operation)!

If you are looking for ways to save on compressed air usage in your facility that is safe to operate and quiet to use, we will have a solution for you.

If you have questions about any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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