Buy one, get one free is a phrase many of us are familiar with. Most of the time it is a good thing; we all like free stuff. What would you say to buy one, get 30 free? Or even 40 free? That’s not far off how our Air Knives perform. They entrain large volumes of ambient air, so for every 1 SCFM of compressed air you are paying for, you are getting 30–40 SCFM of additional free ambient entrained air.

So how are our Air Knives able to do this? We explain this phenomenon in more detail in this blog here, but in summary, a Super Air Knife takes advantage of the Venturi Effect. Named after Giovanni Venturi, who found out that when you increase the speed of a fluid through an orifice, the surrounding fluid will move along with it. This creates a region of low pressure, and the faster the speed, the lower the pressure. With low pressure, the air around rushes in to fill that gap and join the airstream. The quantity of ambient air that gets ‘pulled’ into the airstream is entrained air, or free air.

The engineered surface of the Super Air Knife is designed to minimize as much loss in air speed as possible, which maximizes the amount of free air that is being entrained. The ratio between free air and compressed air used is called the amplification ratio. Super Air Knives have an amplification ratio of 40:1, with our Standard Air Knives having an amplification ratio of 30:1. For comparison, a pipe with holes drilled will have an amplification ratio of between 2:1 and 5:1. As you can see, with a Super Air Knife you are getting a much better deal on your compressed air usage.

This additional free air adds more mass, which allows the Super Air Knife to do more work. You will get a harder hitting force than a comparable product while using less compressed air. This makes Super Air Knives especially good for cooling and drying applications, where moving large volumes of air is ideal.

It’s not just our Air Knives that take advantage of the Venturi effect to produce large amplification ratios. Many of our products are designed with efficiency in mind, including our Air Amplifiers, Air Wipes, and Air Nozzles and Jets, to name a few. If you would like to discuss how an EXAIR engineered compressed air product can amplify your process, then give us a call!

Al Wooffitt
Application Engineer

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