Understanding Air Entrainment

EXAIR uses the word entrainment a lot, all of our blowoff products use the principle to amplify the air stream and increase efficiency. But, what is entrainment and what causes the phenomenon? Entrainment can be defined as a fluid that is swept along into an existing moving fluid. This brings Bernoulli’s equation into the picture. When looking at specific situations and conditions Bernoulli’s equation can show some interesting significance with gases.

Bernoulli’s Equation

Bernoulli’s equation takes into account four main variables which are Pressure (P), Density (r), Velocity (v), and a height difference (z); along with a single constant for gravity. 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. Now we have to look at how fluids like to behave. Fluids within a system like to be at a constant pressure when at the same height and reach a state of equilibrium. This means that fluids will always flow towards a low pressure area, which means that if you create a constant low pressure area you can amplify the air stream. This is the same principle as to why airplanes can fly.

EXAIR Super Air Nozzle entrainment

Since compressed air can be an expensive utility, it is good to minimize it and maximize the surrounding entrained air. Therefore we have designed our products to use this entrainment principle to amplify the air blast while using less compressed air and more entrained ambient air. Products like our Super Air Knife can see an amplification ratio (ambient air to compressed air) of up to 40:1; this means for every 1 SCFM of compressed air used we are entraining 40 SCFM of ambient air.

EXAIR’s Super Air Knife

We use this principle for our Air Amplifiers, Air Knifes, Air Nozzles and Jets, Safety Air Guns, and our Gen4 Static Eliminators. Our goal is to save you money and give you better results in the process.  

If you have questions about any of our engineered Intelligent Compressed Air® Products, feel free to contact EXAIR or any Application Engineer.

Cody Biehle
Application Engineer
EXAIR Corporation
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EXAIR Vortex Tubes are for a Variety of Spot Cooling Applications

Vortex tube
Cooling or Heating with the Vortex Tube

EXAIR Vortex Tubes are a low cost, reliable and maintenance free solution to a wide variety of industrial spot cooling problems.  They only requirement is a supply of compressed air as the power source.  Vortex Tubes have no moving parts and can produce temperatures that range from -50°F to +260°F (-46°C to +127°C).

Vortex Tubes produce two air streams one cold and one hot, the percentage of cold air flow from the inlet flow is referred to as the cold fraction.  The cold fraction is adjustable by the hot valve on the hot discharge side of the vortex tube.  Adjusting the hot valve results in both air temperature and air volume changes. The colder the air becomes, the volume of that cold air declines. So for very cold temperatures, a smaller volume of air is produced compared to a warmer air temperature.

For the vast majority of industrial cooling applications a larger volume of cool air will provide more efficient cooling than a lesser amount of very cold air.  Generally speaking the highest Btu/Hr values are in the 70-80% cold fraction range.

The exception to this would be in labs or special cases where the coldest temperatures are desired.  Adjusting a Vortex Tube is easy, simply insert a thermometer/thermocouple in the cold air exhaust and set the temperature by adjusting the valve on the hot end of the Vortex Tube.  You will know when you reach max refrigeration (80% cold fraction) as the cold air temperature will be 50°F (28°C) lower than the compressed air supply temperature.

EXAIR Vortex Tubes are constructed from stainless steel.  This ensures excellent wear resistance, corrosion resistance and assures years of reliable operation.  They are offered in 3 different size ranges (small, medium & large).  There are generators located inside the tube (user serviceable) that will change the volumetric flow.  The generators are available in a plastic construction or brass construction for high temperature applications.  The ranges 2 SCFM – 8 SCFM are designated as small Vortex Tubes, 10 SCFM – 40 SCFM are medium and 50 SCFM – 150 SCFM are large.  This feature allows you to customize or change your Vortex Tube for greater flexibility in a wide range of applications.

Vortex generator

Large Vortex Tubes are specified when a high flow of cold air is needed. There are 16 models to choose from in total.  Capable of providing 3,400 BTU/HR up to 10,200 BTU/HR of cooling power.  These have been used to cool high heat loads that are centrally located or to help cool samples of gases for testing.

Medium Vortex Tubes are the most popular – there are twenty to choose from, depending on the cold air flow rate and temperature you’re looking for. These can produce temperatures as cold as -40°F (-40°C) when set to a 20% Cold Fraction (which is the percentage of total supply air that’s directed to the cold end) and cold air flows as high as 32 SCFM when set to an 80% Cold Fraction, which will produce a cold air temperature of about 20°F (-7°C). Some common uses are cooling ultrasonic welds and brazed joints.

The Medium Vortex Tubes are so popular, in fact, that they’re incorporated into our Adjustable Spot Cooler and Cold Gun Systems. They come ready-to-go with mufflers, cold air hose kits, and magnetic bases, so they couldn’t be easier to use.

Adjustable Spot Cooler

Cold Gun Lineup

Small Vortex Tubes are great when low flows (less cooling power) will succeed, or if compressed air supply is limited.  There are 12 models in total to choose from. These are specified for much smaller applications, like cooling the needle of a sewing machine, small drill bits, etc. You can also get one with a cold air hose & magnetic base…that’s the Mini Cooler System.

Mini Cooler

If you would like to discuss Vortex Tubes, Spot Cooling, efficiency of your compressed air usage, quieter compressed air products and/or any EXAIR product,  I would enjoy hearing from you…give us a call.

EXAIR team
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