Entrainment: What is it?

By definition, entrainment is a form of the verb, entrain, which is fluid that is swept along into an existing moving flow.   Whenever there is a discussion about fluid dynamics, the 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 incompressible fluids, but under certain conditions, it can be significant for gas flows as well.  I would like to discuss how EXAIR uses the Bernoulli’s equation for entrainment to maximize efficiency within your compressed air system.

This relationship between pressure as compared to flow and velocity came to be known as the 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. Bernoulli realized that the sum of kinetic energy, flow energy, and potential energy is a constant during steady flow.  He wrote the equation like this:

Equation 1:

P/r + V2/2 + gz = constant

P – Pressure

r – density

V – velocity

g – gravitational constant

z – height difference

 

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.

Since we know the criteria to apply the Bernoulli’s equation with compressed air, let’s look at some EXAIR products.  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.  Remember from the equation above, as the velocity increases, the pressure has to decrease.  When the pressure decreases, the surrounding air will move toward the low pressure.  That low pressure will sweep the ambient air into the air stream; called entrainment.

Compressed air is expensive, but the ambient air is free.  The more ambient air we can entrain, the more efficient the blowing device is.  As an example, 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.  By adding mass to the flow stream, it will reduce the compressed air usage, saving you money, and allow for better cooling and a stronger blowing force.  For a drilled pipe, the amplification ratio is generally only two to three times.

We use this principle for many of our products like the Air Amplifiers, Safety Air Guns, Air Nozzles, Air Knives, and Gen4 Static Eliminators. Daniel Bernoulli was able to find a relationship between velocities and pressures, and EXAIR was able to use 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

Safety Air Guns For Convenience, Ergonomics, and…Safety!

A few weeks ago, I wrote a blog proving beyond a shadow of a doubt why you should be using EXAIR Safety Air Guns in your facility.  Today’s blog, dear reader, is all about how easy it is to be using EXAIR Safety Air Guns in your facility.  Because I’m all about easy. Here we go:

  • Easy hookup: there’s not much to it – all you need is an air hose to run from your compressor, or header, to the Safety Air Gun itself.  These come in different shapes and sizes, depending on what you’re using, and what you’re using it for:
    • Compressed air hose: EXAIR can provide reinforced synthetic rubber supply hose in 3/8″ or 1/2″ ID’s, up to 50ft long.  We offer them with 1/2 or 1/4 MNPT fittings.  The 3/8″ ID hoses with 1/4 MNPT fittings are perfect for most of our Safety Air Guns.
    • Coiled hose: For convenience and portability, we also have a selection of 12ft long Coiled Hoses, with 1/8, 1/4, or 3/8 MNPT swivel connections.
EXAIR offers a variety of supply hoses for your Safety Air Guns, provided from stock.
  • Easy reach: Sometimes the debris you’re blowing off with a handheld device is just out of reach…or maybe even farther:
    • Rigid extensions are available for our Variblast and Soft Grip Safety Air Guns in lengths from 6″ to 72″.  Super Blast Safety Air Guns are about 10-15″ long, but can be fitted with 3ft or 6ft extensions as well.
    • You can also get around corners, behind, over, or under obstacles by using a Soft Grip Safety Air Gun fitted with a Stay Set Hose.  You just bend it to the angle you want to blow at, and it “stays set” (as advertised) until you bend it again.
Model 1310-12 Heavy Duty Safety Air Gun, With 12″ Extension & 1100 Super Air Nozzle
  • Easy safety: No matter what kind of day you’re having, if you make it through without needing first aid, you’ve had a better day than some.  While they DON’T take the place of proper eye protection, Chip Shields fitted to an EXAIR Safety Air Gun can prevent sharp pieces from flying back and cutting you.  They also keep chips, dirt, coolant, oil, grease, etc., from getting all over your clothes.
Chip Shields Offer Safety & Comfort For Operators

If you want to talk about how EXAIR Safety Air Guns – or any of our engineered Intelligent Compressed Air Products – can make life easier for you, give me a call.  Trust me…it’s easy.

Russ Bowman
Application Engineer
EXAIR Corporation
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The Soft Grip Safety Air Gun for OSHA Compliance

Compressed air has many different uses ranging from simple cooling and blow off applications all the way to operating machine cylinders and robotics. One of the most common uses is for simple cleaning; whether its cleaning off a work station or blowing off personnel it can’t be denied that air powered cleaning is very useful. But if the Occupational Safety & Health Administration (OSHA) regulations are not followed it can also be unsafe.

Open-ended blow offs can inadvertently be dead ended (the airflow outlet can be completely blocked), when this happens if the pressure is to high an air embolism can form in an individuals bloodstream. Blowing something off with air can result in airborne particulate traveling at a high velocity that can become embedded into your skin or in your eye.

With all that being said this is where the safety air guns step into the spotlight! It’s pretty easy to make a safety air gun that complies with the dead-end pressure regulation; just give the air another path to take when the outlet is blocked. The most common solution found is a cross drilled nozzle which allows the air to escape when the end is blocked. Generally the problem with this design is that the nozzles can be very loud and inefficient. In most cases these nozzles have paid attention to the dead end problem but ignored the noise level exposure safety issue and completely ignored compressed air efficiency. 

With EXAIR’s Super Air Nozzles you get both the added benefit of being safe, quiet and efficient. Our engineered designed air nozzles are commonly installed onto a Soft Grip Safety Air Gun to make an ergonomic, safe, and quiet Safety Air Gun. These can also have a  Chip Shield added to help prevent particles from flying back and hitting the user. The Soft Grip Safety Air Gun can also be coupled with a pipe extension from 6” to 72”; you can also add one of our Stay Set Hoses 6” in length to 36”.

Soft Grip Safety Air Gun with Stay Set Hose. eg. 1210-6SSH

Here are a few examples of the Soft Grip Safety Air Guns in our product line:

Cody Biehle
Application Engineer
EXAIR Corporation
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EXAIR VariBlast Safety Air Gun

Air guns can be found in nearly any industrial facility that has a compressed air system within it.  From the maintenance department to the production floor, operators potentially use these for anything from, cleaning up work areas,  to blowing product out of a troubled spot in a process. Handheld blowoffs are often overlooked as a means to increase efficiency yet they are often observed as a means to increase safety.

Generic commercial air gun w/ cross cut hole in the nozzle

When evaluating efficiency the length of use for a handheld blowoff is often variable from operator to operator as well as changes even from each use.  Often, operators have several different uses throughout their day that require different levels of force needed to complete the job.  Most safety air guns don’t offer a variable force.  This means operators are full-force for all applications. This means full air consumption whenever that gun is used. EXAIR’s VariBlast Compact Safety Air Gun can help to give operators the adjustability they need.

CE compliant, VariBlast Compact Safety Air Gun saves air and increases safety.

The VariBlast Compact Safet Air Gun is available from stock with over a dozen options of different Super Air Nozzles as the end defector of the Safety Air Gun.  These are any nozzle up to a 1/8″ NPT thread size.  To couple with these engineered nozzles, we offer stock length extensions up to 72″ (1829 mm)  in length. This makes many applications that are hard to reach easily managed by the operators.

Different Length Extensions To Suit Nearly Every Application

To couple with the extensions and make sure the VariBlast Compact Safety Air Guns all meet or exceed OSHA standards for operator safety, we offer a Chip Shield accessory as well.

Chip Shields

If you would like to discuss how to lower the demand placed on your air compressor from blowoffs and want to better experience what true variability as well as what an engineered blowoff is capable of, contact us.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF