Super Air Amplifiers vs. Electric Fans

EXAIR’s product offerings contain many products that can be used for cooling. The focus of this blog will be Super Air Amplifiers. These often times get placed in a head to head competition with an electric fan. The best part, they easily come out on top.

Our own Tyler Daniel produced a great video showcasing how efficient it is to cool a part using the Super Air Amplifier rather than a fan.

When looking at the benefits other than performance and rate of cooling due to air entrainment, many customers prefer the Super Air Amplifier due to the fact there are no moving parts. This comes into play when cooling within in a hard to reach area or within a harsh process is needed.  Placing an electric motor with a blade held on by fasteners may not be desirable from a maintenance standpoint. The Super Air Amplifiers do not require electricity, meaning there is not a motor or bearings that would need to be replaced or inspected.

Another benefit is the small footprint of the Super Air Amplifier. This can also be seen within the video above where the Air Amplifier is shown is able to produce 341 SCFM (9,650 SLPM) in amplified airflow.  This gives the ability to place a small unit inside of a chamber that needs large volumes of air flowed through it.  For instance, a rotomolded part that has a large chamber and it needs surfaces to be cooled in order for the part to hold its shape from the mold rather than warp.  This can also be coupled with the fact that a Super Air Amplifier can be ducted on either the suction or discharge side in order to retrieve cool air or move the warm air out of the area.

Speaking of warm, the Super Air Amplifiers are also manufactured to withstand up to 275°F (135°C) from stock.  Stainless Steel and High-temperature models go well beyond that temp, as seen above. Custom-designed (flanges and different materials are common) versions are also available in short lead-times.

If you would like to discuss the benefits to a Super Air Amplifier further, feel free to contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

Cooling With Compressed Air: Air Knife vs. Vortex Tube Products

One of the popular applications for the EXAIR Super Air Knife is cooling. When mounted so that the air flow sweeps across the surface of a product, the laminar nature of the air flow works to maximize the contact time with the surface, which also maximizes the heat transfer…which means better product cooling than, say the turbulent air flow from a fan or blower.

Still, it’s common for us to get questions about how to provide even faster cooling.  Well, the two main variables in heat transfer are the time the air is in contact with the product, and the difference in temperature between the product surface and the air.

We’ve already touched on “time in contact”…sweeping the laminar flow across the surface at as low of an angle as you can, against the direction of travel, is ideal.  Combine that with the extraordinarily high air flow due to the entrainment level of the Super Air Knife, and you get an awful lot of air in contact with the surface, for a (relatively) long time.

Super Air Knives cool steel casting from 1,725°F (940°C) to 200°F (93°C) in under 20 minutes.

The difference in temperature, though, is a little trickier to deal with.  Because the developed flow from the Super Air Knife is mostly entrained ambient temperature air from the surrounding environment, you’re at the mercy of that ambient temperature.  One of the most common question – of the common questions about faster cooling – is, can you feed a Super Air Knife with cold air from a Vortex Tube?  The answer is no, for two big reasons:

  • The Vortex Tube’s cold flow can’t be back pressured, which would happen if you fed it through the plenum of a Super Air Knife and tried to make it come out the 0.002″ gap.
  • Even if it did work, the entrained air which, remember, makes up most of the flow, is still room temperature…meaning the total developed flow is a lot closer to room temperature than however cold the air you fed the Super Air Knife would be.

If the surface area to be blown on, to effect the desired cooling, is suitably sized, a Vortex Tube can be installed at a low angle to sweep its flow across.  The cold air flow from a Vortex Tube can also be distributed to more than one point, to cover more surface area.  That’s exactly what we do with our Dual Point Hose Kits for our Adjustable Spot Coolers, Mini Coolers, and Cold Gun Aircoolant Systems:

Dual Point Hose Kits can distribute air to both sides of a part, or onto a wider surface, than a single point discharge.

In fact, both the Single and Dual Point Hose Kits have a variety of tips they can be fitted with for tighter, or broader, flow patterns:

In some cases, multiple Vortex Tube products can be used, and, in other situations, the cold air can be directed through a manifold of some sort:

There are numerous methods to distribute the cold air flow from a lone, or a series of, Vortex Tubes.

Applications like the two on the right above (setting molten chocolate in molds, and keeping those white plastic parts during ultrasonic welding, respectively,) commonly start out as Air Knife inquiries, but the need for refrigerated air leads to creative Vortex Tube solutions.

If you’d like to discuss whether your application is best served by a Super Air Knife or a Vortex Tube Spot Cooling Product, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Super Air Amplifiers and Amplification Ratio

Super Air Amplifier Family

In the pneumatic industry, there are two types of Air Amplifiers.  One type will amplify the inlet air pressure to a higher compression.  The other type uses the inlet air pressure to amplify the air volume.  EXAIR manufactures the volume type called the Super Air Amplifiers™.

This change in air volume is called the amplification ratio.  So, what does this mean?  The definition of a ratio is the relation between two amounts showing the number of times one value is contained within the other.  For the Super Air Amplifier, it is the value that shows the amount of ambient air that is contained within the compressed air.  The higher the ratio, the more efficient the blowing device is.  With the EXAIR Super Air Amplifiers, we can reach amplification ratios up to 25 to 1.  This means that 25 parts of ambient “free” air is introduced for every 1 part of compressed air.

Air Amplifiers Are Great For blowing!

Why an EXAIR Super Air Amplifier?  Like a fan, they are designed to move air.  But fans use motors and blades to push the air toward the target.  The fan blades “slap” the air which creates turbulent air flows and loud noises. The Super Air Amplifiers do not use any blades or motors to move the air.  They just use a Coanda profile and a patented shim to create a low pressure to draw in the ambient air.  In physics, it is much easier to pull than it is to push.  The process of pulling air through the Super Air Amplifiers make them a more efficient, uniform, and quiet way to blow air.

Most people think that compressed air is free, but it is most certainly not.  Because of the amount of electricity required, compressed air is considered to be the fourth utility in manufacturing plants.  To save on utility costs, it is important to use compressed air as efficiently as possible.  In reference, the higher the amplification ratio, the more efficient the compressed air product.  Manufacturing plants that use open fittings, copper tubes, and drilled pipes for blowing are not properly using their compressed air system.  These types of products generally only have between a 2:1 to 5:1 amplification ratio.  The Super Air Amplifiers can reach a 25:1 ratio.

EXAIR manufactures and stocks five different sizes ranging from ¾” (19mm) up to 8” (203mm) in diameter.  Some of the benefits that the Super Air Amplifiers have is the inlet and outlet can be ducted for remote positioning.  They are very compact and can fit into tight places.  They do not have any moving parts to wear or need electricity to run.  They only need clean compressed air to operate; so, they are maintenance-free.

Another unique feature of the EXAIR Super Air Amplifier is the patented shim which optimizes the low-pressure to draw in more ambient air.   With extracting welding smoke, increasing cooling capacities, and moving material from point A to point B; the more air that can be moved, the better the performance.  And with the patented shim inside the EXAIR Super Air Amplifiers, it provides that.  As an added bonus, they are OSHA safe and meet the standards for noise level and dead-end pressure.

Super Air Amplifier Patented Shims

To explain things in every day terms; the amplification ratio can be represented by gas mileage.  Like your car, you want to get the most distance from a gallon of gasoline.  Similarly, with your compressed air system, you want to get the most for your pneumatic equipment.  An EXAIR Super Air Amplifier has a 25:1 amplification ratio.; so, in other words, you can get 25 mpg.  If you use drilled pipes, open fittings, copper tubes, etc. for blowing, then you are only getting 2 to 5 mpg.  If you want to get the most “distance” from your compressed air system, you should check the “gas mileage” of your blow-off components.  If you need assistance, an Application Engineer at EXAIR can help you to “tune up” your compressed air system.

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

People of Interest: Daniel Bernoulli

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:

Bernoulli’s Equation

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.

Super Air Knife has 40:1 Amplification Ratio

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

  1. Wikipedia https://en.wikipedia.org/wiki/Bernoulli%27s_principle