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.
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