Entrainment: How it Works and Why EXAIR Products are Engineered to Use it.

Published on by John BallLeave a comment
EXAIR Super Air Nozzle entrainment

Because of the large amount of energy required to run an air compressor, the pneumatic system is considered the fourth utility in a manufacturing plant.  And saving this commodity and using it as efficiently as you can, should be a priority.  EXAIR has many products that can save energy by using less compressed air.  And the story behind this is entrainment explained by Bernoulli’s equation. 

Bernoulli’s principle explains how a high velocity fluid can generate a low pressure.  (You can read more about Bernoulli’s principle HERE.)  Let’s start by looking at Equation 1.

Equation 1:

P + d * V2/2 = C 

P – pressure

d – density of the fluid

V – velocity

C – a constant

As you can see from Equation 1, when the velocity goes up, the pressure must go down.  When we have a lower pressure, then the surrounding fluid will fill that void.  Since air is a fluid, we can use high velocity to entrain the surrounding ambient air.  The free air will add to the compressed air to give the airstream mass for a hard-hitting force.  This ratio of ambient air to compressed air is called entrainment.  The higher the entrainment, the more efficient the product.  Bernoulli’s Principle can be applied in two ways; as a Coanda and as a Venturi.  EXAIR uses both methods in our products for creating low-pressure effects. 

Compressed air flows through the inlet (1) to the Full Flow (left) or Standard (right) 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 first way is from a Coanda profile.  Coanda, named after Henri Coanda, noticed that a fluid would “hug” a curved surface.  (You can read more about Henri Coanda HERE.)  The high velocity air going around the curved surface will generate a low pressure above it.  You can imagine an airplane wing generating that low pressure to fly.  We use this with our FullFlow and Standard Air Knives, our Air Wipes, and our Air Amplifiers.  With a Coanda profile, we can get an amplification ratio up to 30:1, which means that for every 1 part of compressed air, 30 parts of ambient air is entrained.  We are able to create an efficient blow-off device by using the Coada profile. 

To generate even lower pressure, this can be done by a Venturi.  This phenomenon is named after Giovanni Venturi, who discovered that by increasing the velocity through an orifice, the surrounding fluid will move with it, generating a lower pressure.  (You can read more about Giovanni Venturi HERE.)  Remember the higher the velocity, the lower the pressure from Equation 1 above.  We use the Venturi effect on our Super Air Knives, E-Vacs, Line Vacs, and Super Air Nozzles.  As compared to our FullFlow and Standard Air Knives, the Super Air Knives can generate an amplification ratio of 40:1.  As an engineered product, we were able to increase efficiency even further. 

EXAIR has been manufacturing Intelligent Compressed Air® products since 1983.  We can provide solutions that are efficient, effective, and safe for blow-off systems.  In comparison, the other blow-off devices are like incandescent light bulbs, while EXAIR products are like LED light bulbs.  Entrainment of free ambient air can save you a lot of money when using your compressed air system.  If you would like to discuss solutions to use less compressed air and improve your bottom dollar, an Application Engineer at EXAIR is available to help.   

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

Video Blog: Starter Guide Series – Air Wipes

Published on by Jordan T ShouseLeave a comment

EXAIR manufactures two types of Air Wipes; the Standard Air Wipe™ and the Super Air Wipe™.  They are designed to blow an airstream in a concentric pattern around the outside of pipes, cables, extruded shapes, hoses and much more. The video below is a starter guide to the Air wipe product line.

If you would like to discuss  any of EXAIR’s safe, quiet & efficient compressed air products, I would enjoy hearing from you…give me a call or shoot me an email!

Jordan Shouse
Application Engineer

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Twitter: @EXAIR_JS

E-Vac Porous vs Non-Porous

Published on by jasonkirbyLeave a comment

The E-Vac by EXAIR is an efficient compressed air-powered vacuum pump designed for rapid and reliable pick and place operations, offering instantaneous response times for improved productivity and versatility in various industrial applications. The E-Vac vacuum generators are designed with advanced technology to optimize performance and reduce air consumption. This contributes to lower operational costs by minimizing energy use, ultimately enhancing productivity in processes requiring vacuum handling.

When determining which E-Vac type, you have to consider the material you will be lifting is porous or non-porous. An example of a porous material would be wood, which will allow some air to move through the material. An example of a non-porous material would be glass, which will not allow air to move through the material.

Porous low vacuum generators max. vacuum= 21″Hg (71 kPa).

Non-porous high vacuum generators max. vacuum= 27″ Hg (91 kPa)

Low vacuum units up to 21″ Hg (71 kPa) with vacuum flows up to 18.5 SCFM are typically used for porus materials such as cardboard and delicate materials. The relatively lower level vacuum prevents warping, marring, dimpling or disfiguring of the surface due to excessive vacuum. This style generates more vacuum flow to overcome porosity and leakage through the target material.

High vacuum units up to 27″ Hg (91 kPa) with vacuum flows up to 15.8 SCFM are typically used for non-orous materials such as glass, steel sheet, and plastic. There are 7 In-Line models that vary by flow to accommodate larger and more vacuum cups in an application.

For additional information on the E-Vac by EXAIR, or any of our EXAIR compressed air products, please feel free to contact our Application Engineers. We are always happy to assist you with your product or application questions.

Jason Kirby
Application Engineer
Email: jasonkirby@exair.com
Twitter: @EXAIR_jk

Compressed Air and Pressure Drop: Explained

Published on by Tyler DanielLeave a comment

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 the walls of the pipe, tube, hose, etc. The diameter of the pipe, length, number of direction changes, and finished 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. If the line is undersized, this pressure drop will be great enough to impact the performance of the product. 

When designing and maintaining your compressed air system, pressure measurements should be taken at 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
  • Inter-stage on multistage compressors
  • After-cooler
  • 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 will include the separator and after-cooler.

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 or undersized air lines, hose, or tube. 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. 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 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 a modular style hose, some pressure is able to build 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 right up to the point of discharge and minimize the pressure drop. This, in addition to the air entrainment, 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, CCASS

Application Engineer

E-mail: TylerDaniel@EXAIR.com

X: @EXAIR_TD