Vortex Tube Generators are the internal component that controls the volume of air entering the Vortex Tube and ultimately the volume of cool/cold air produced.
Vortex Family
EXAIR manufactures three sizes of Vortex Tubes, small, medium & large. Each size can produce a range of cooling power that can be changed by installing a different generator that will change the volume output capability of that Vortex Tube. The generators for small size vortex tubes can operate at 2, 4 or 8 SCFM (maximum cooling power of 550 BTU/HR), generators for the medium size at 10, 15, 25, 30, or 40 SCFM (maximum cooling power of 2,800 BTU/HR) and the generators for the large size operate at 50, 75, 100 or 150 SCFM (maximum cooling power of 10,200 BTU/HR). The Vortex Tube is sold with one generator installed.
The generators are marked with a number and a letter. The number indicates the capacity (SCFM of air consumption) and the letter indicates the type of operation (“R” for maximum refrigeration or “C” for maximum cold temperature). The maximum refrigeration (“R”) works best when the majority of the inlet air is exhausted out the cold end of the Vortex Tube. They work most efficiently with smaller temperature drops and larger volume of flow than the other generators. The maximum cold generators (“C”) can produce temperatures below 0°F, and work best when the minority of the inlet air is exhausted out the cold end of the Vortex Tube. The volume of cold air produced is less but you will experience greater temperature drops.
If a different cooling capacity is desired, other generators are available by either purchasing them individually or by purchasing one of the (3) highly versatile Vortex Tube Cooling Kits designated as the 3908 (small), 3930 (medium) or 3998 (large). The Kits include the Vortex Tube, Filter Separator, Vinyl Tubing, Tubing Adapter, Tube Clamps, Cold End Muffler (Optional Hot End Muffler Available) and Both “R” & “C” Generators.
EXAIR Medium Vortex Kit Includes: Vortex Tube, Filter Separator, Vinyl Tubing, Tubing Adapter, Tube Clamps, Cold End Muffler (Optional Hot End Muffler Available, Sold Separately) and Both “R” & “C” Generators (10, 15, 25, 30, or 40 SCFM).
If you would like to discuss Vortex Tubes, their Generators, or any of EXAIR’s safe, quiet & efficient compressed air products, I would enjoy hearing from you…give me a call.
EXAIR has wrote many different articles about how Vortex Tubes work and the applications in which they are used. The idea of making cold air without any freon or moving parts is a phenomenon. This phenomenon can generate cold air to a temperature as low as -50 oF (-46 oC). In this article, I will explain the adjustment of the Vortex Tube to get different temperatures and cooling effects in reference to the Cold Fraction.
To give a basic background on the EXAIR Vortex Tubes, we manufacture three different sizes; small, medium, and large. These sizes can produce a range of cooling capacities from 135 BTU/hr to 10,200 BTU/hr. The unique design utilizes a generator inside each Vortex Tube. The generator controls the amount of compressed air that can enter into the Vortex Tube. As an example, a medium-sized Vortex Tube, model 3240, will only allow 40 SCFM (1,133 SLPM) of compressed air to travel into the Vortex Tube at 100 PSIG (6.9 bar). While a small-sized Vortex Tube, model 3208, will only allow 8 SCFM (227 SLPM) of compressed air at 100 PSIG (6.9 bar). EXAIR manufactures the most comprehensive range from 2 SCFM (57 SLPM) to 150 SCFM (4,248 SLPM).
Vortex Tube Exploded View
After the compressed air goes through the generator, the pressure will drop to slightly above atmospheric pressure. (This is the “engine” of how the Vortex Tube works). The air will travel toward one end of the tube where there is an air control valve, or Hot Air Exhaust Valve. This valve can be adjusted to increase or decrease the amount of air that leaves the hot end. The remaining portion of the air is redirected toward the opposite end of the Vortex Tube, called the cold end. By conservation of mass, the hot and cold air flows will have to equal the inlet flow as shown in Equation 1:
Equation 1: Q = Qc + Qh
Q – Vortex Inlet Flow (SCFM/SLPM)
Qc – Cold Air Flow (SCFM/SLPM)
Qh – Hot Air Flow (SCFM/SLPM)
Cold Fraction is the percentage of air that flows out the cold end of a Vortex Tube. As an example, if the control valve of the Vortex Tube is adjusted to allow only 20% of the air flow to escape from the hot end, then 80% of the air flow has to be redirected toward the cold end. EXAIR uses this ratio as the Cold Fraction; reference Equation 2:
Equation 2: CF = Qc/Q * 100
CF = Cold Fraction (%)
Qc – Cold Air Flow (SCFM/SLPM)
Q – Vortex Flow (SCFM/SLPM)
Vortex Tube Charts
EXAIR created a chart to show the temperature drop and rise, relative to the incoming compressed air temperature. Across the top of the chart, we have the Cold Fraction and along the side, we have the inlet air pressure. As you can see, the temperature changes as the Cold Fraction and inlet air pressure changes. As the percentage of the Cold Fraction becomes smaller, the cold air flow becomes colder, but also the air flow becomes less. You may notice that this chart is independent of the Vortex Tube size. So, no matter the generator size of the Vortex Tube that is used, the temperature drop and rise will follow the chart above.
Vortex Tube Example
How do you use this chart? As an example, a model 3240 Vortex Tube is selected. It will use 40 SCFM of compressed air at 100 PSIG. We can determine the temperature and amount of air that will flow from the cold end and the hot end. The inlet pressure is selected at 100 PSIG, and the Hot Exhaust Valve is adjusted to allow for a 60% Cold Fraction. Let’s use an inlet compressed air temperature to be 68 oF. With Equation 2, we can rearrange the values to find Qc:
Qc = CF * Q
Qc = 0.60 * 40 SCFM = 24 SCFM of cold air flow
The temperature drop from the chart above is 86 oF. If we have 68 oF at the inlet, then the temperature is (68 oF – 86 oF) = -18 oF. So, from the cold end, we have 24 SCFM of air at a temperature of -18 oF. For the hot end, we can calculate the flow and temperature as well. From Equation 1,
Q = Qc + Qh or
Qh = Q – Qc
Qh = 40 SCFM – 24 SCFM = 16 SCFM
The temperature rise from the chart above is 119 oF. So, with the inlet temperature at 68 oF, we get (119 oF + 68 oF) = 187 oF. At the hot end, we have 16 SCFM of air at a temperature of 187 oF.
With the Cold Fraction and inlet air pressure, you can get specific temperatures for your application. For cooling and heating capacities, these values can be used to calculate the correct Vortex Tube size. If you need help in determining the proper Vortex Tube to best support your application, you can contact an Application Engineer at EXAIR. We will be glad to help.
EXAIRVortex 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.
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.
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.
People who watch way too much TV (like me) will certainly remember the “Real Men of Genius” commercials. Here’s one of my personal favorites:
Local radio stations all over the country made parodies of these, as did sketch comics. While trying to come up with something for my weekly blog, I saw that today was the anniversary of the passing of 19th century physicist James Clerk Maxwell. So, if you’ll try to keep the background music from the video above playing in your head while you read this, let’s see if I can pay proper tribute:
James Clerk Maxwell…even though Albert Einstein is famous for the Special Theory of Relativity, he credited YOU for laying the groundwork. You not only theorized the relationship between electricity, magnetism, and light, but you also proved it mathematically…so Albert didn’t have to. He said your work was “the most profound and the most fruitful that physics has experienced since the time of Newton.”
Singer: Albert Einstein pretty much called you an “Einstein” the way we call geniuses “Einsteins.”
Professor Maxwell…you devoted your life to learning. About EVERYTHING. As if solving Einstein’s problem with the Theory of Relativity (40 years before he knew he had a problem with it) wasn’t enough, you decided to find out what the rings of Saturn were made of. Over 100 years before we could send the Voyager spacecraft to find out for sure. And you were right.
Then you discovered how to take color photographs by experimenting with light filters.
Singer: Not only did you tell us what Saturn’s rings were made of, we have color photographs of them thanks to you….
James Clerk Maxwell…your theory that a “friendly little demon” could somehow separate gases into hot and cold flows, while unproven in your lifetime, did actually come to fruition by the development of the Vortex Tube. Which does just that.
So here’s to you, James Clerk Maxwell…may we continue to recognize your brilliance, and be inspired by your drive to push forward in scientific developments.
Singer (building to final crescendo): James Clerk Maxwell, a Real Hero Of Sci-i-i-i-i-ence!
If you’d like to hear the musical parts of this actually get sung, or if you’d like to find out more about Vortex Tube products and their uses (it might be best to stick with that second part actually,) give me a call.
Russ Bowman
Application Engineer
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