Tag: cooling tubes

What is a Vortex Tube, and How Do You Use It?

Published on by Jordan T ShouseLeave a comment

Vortex Tubes are highly adjustable tools in which you can use cold air or hot air for a wide variety of applications. We can obtain such freezing or hot air with nothing more than compressed air and the Vortex Tube. We can adjust the temps very easily with the turn of a screw. Before we dive into how to adjust and get the right temps for your application, let me share a diagram of how the Vortex Tube works:

The unique physical phenomenon of the Vortex Tube principle generates cold air instantly, and for as long – or short – a time as needed.

Now that we have seen how it works, we need to define how to make it work for your specific application! First we need to set the cold fraction… Setting the “cold fraction” is all about how cold or hot you need the air to be. When we talk about this cold fraction, we are talking about the amount of cold air that comes out of the cold side of the Vortex Tube, which also affects the temperature of that cold air. In other words, a 60% cold fraction equals 60% of the input compressed air exiting the Vortex Tubes cold side.

For example, if you are supplying 100 psi to our medium-sized Vortex Tube, you will be generating between 10 and 40 SCFM (depending on the size of the generator). Let’s assume for this example that you are using our 3230 Vortex Tube, generating 30 SCFM. At an 80% cold fraction, 24 SCFM (80% of 30) will be flowing out of the cold end of the Vortex Tube. And it will be flowing at a temperature that is 54 °F colder than the temperature of the compressed air provided. Yes, that is correct, assuming that your inlet air temp is 72 °F, you will be flowing 24 SCFM of 18 °F air from the cold end of the Vortex Tube. But what about the other 6 SCFM? Well, it will flow out of the hot end at a whopping 263 °F. We must take into account both ends of the Vortex Tube. You can see the performance table below.

EXAIR Vortex Tube Performance Chart

Let’s look at one more example of this same Vortex Tube 3230. Let’s assume that we need to heat something up. Assuming that your compressed air is 72 °F, and we want to heat something up to 115 °F, we need to add 43 °F to the temp of the compressed air. We can see in the chart that by supplying 80 psig of compressed air, and a 30% Cold Fraction on the Vortex Tube, that we can add 43° to the temp of the air. We know that the cold end will give us 9 SCFM (30% of the overall 30 SCFM) and it will flow at -110 °F, or -38 °F. But we will reach our 115 °F desired temp on the hot end, but that will only be at 21 SCFM. If we still need that higher SCFM, we may need to change the generator (explained below) or increase to a larger Vortex Tube all together.

As you can see from the above performance table, there are many ways to get to your desired temperature, be it hot or cold.

Next comes the question of how we adjust the cold fraction. 1st, let me note that, unless specified, these always ship set at or close to the 80% cold fraction, but, if you want them set to a precise cold fraction, we can permanently set these for you prior to shipping. As you see in the picture to the left, the slotted valve can be turned to adjust the cold fraction. For precision purposes, it is always recommended to use a thermometer to set it where you need it (insert the thermometer into the cold flow of air). As a guide, you should seat the valve softly, and back off an 1/8th, a 1/4, or a 1/2 turn (for the small, medium, and large sizes respectively) to drop approximately 20% on the cold fraction scale.

We offer 3 sizes of Vortex Tubes; small, medium and large. Each size offers 3-5 different interchangeable sized generators, with a total offering of 12 stock Vortex Tubes. The size of the generator will determine the BTU/hr, as well as the SCFM generated. See the following table for more details:

There are a few other key details to know about the Vortex Tubes. They do not like back pressure. As you can imagine, the magic that makes them work is spinning the generator inside. If that is slowed down due to back pressure, it will hinder the results of the entire Vortex Tube. Many people have air coolers or heaters in their compressed air system. Keep in mind that the temps generated by the Vortex Tubes are ± the temperature of the compressed air, so it is important to know the temp of your compressed air.

Vortex Tubes can be very loud. We almost always sell these with Cold and Hot Mufflers. In order to keep most of them under the OSHA standards for sound, you will want mufflers. Lastly, as with all of EXAIR’s products, it is recommended to use a pressure regulator with a gauge at the point of use. With the Vortex Tubes, it is imperative if you are looking for an accurate temperature.

If you have any questions about the Vortex Tubes, or any of our intelligent air products, please do not hesitate to reach out.

Jordan Shouse
Application Engineer
Email: Jordanshouse@exair.com
Twitter: @EXAIR_JS

Vortex Tubes: What is Cold Fraction?

Published on by John BallLeave a comment

EXAIR has written 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 of physics that has been referred to by many names including Ranque Tube, Ranque-Hilsch Tube and Maxwell’s Demon.  The modern name is Vortex Tube.  It can generate cold air to a temperature as low as -50 oF (-46 oC) simply by spinning compressed air at high RPM.  In this article, I will explain the adjustment of the Vortex Tube to get different temperatures and cooling effects with reference to the Cold Fraction.

To give a basic background on the EXAIR Vortex Tubes, we manufacture them in three different body sizes: small, medium, and large.  These sizes can produce a range of cooling capacities, from 135 BTU/hr to 10,200 BTU/hr (34 Kcal/hr to 2,570 Kcal/hr).  The unique design utilizes a generator inside each Vortex Tube.  To read more about the type of generators, you can find this here: Maximum Effort!!! The Two Types of Vortex Tube Generators. The generator controls the amount of compressed air that can enter the Vortex Tube as well as initiating the spinning of the air inside.  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 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).

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 side of the Vortex Tube will blow hot air.  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 air 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)

The percentage of inlet air flow that exits the cold end of a vortex tube is known as the Cold Fraction.  As an example, if the Hot Air Exhaust 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 is 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 Inlet Flow (SCFM/SLPM)

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 the amount of cold air flow becomes less.  You may notice that this chart is independent of the Vortex Tube size.  So, no matter the size of the Vortex Tube that is used, the temperature drop and rise will follow the chart below.

EXAIR Vortex Tube Performance Chart

How do you use this chart?  As an example, we can select a model 3240 Vortex Tube.  It will use 40 SCFM (1133 SLPM) of compressed air at 100 PSIG (6.9 Bar).  We can determine the temperature and amount of air that will flow from the cold end and the hot end.  For our scenario, we will set the inlet pressure to 100 PSIG, and adjust the Hot Exhaust Valve to allow for a 60% Cold Fraction.  Let’s say the inlet compressed air temperature is 68oF.  With Equation 2, we can rearrange the values to find the Cold Air Flow, Qc:

Qc = CF * Q

Qc = 0.60 * 40 SCFM = 24 SCFM of cold air flow

The temperature drop shown in the chart above is 86oF.  If the inlet temperature is 68oF, the temperature of the cold air is (68oF – 86oF) = -18oF.  So, at the cold end, we will have 24 SCFM of air at a temperature of -18oF.  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 shown in the chart above is 119oF.  So, with the inlet temperature at 68oF, we get (119oF + 68oF) = 187oF.  So, we have 16 SCFM of air at a temperature of 187oF coming out of the hot end.

With the Cold Fraction and inlet air pressure, you can get specific temperatures for your application.  For cooling and heating capacities, flow and temperature can be used to calculate the correct Vortex Tube size for your application.  If you need help determining the proper Vortex Tube to best support your application, you can contact an Application Engineer at EXAIR.  We will be glad to help.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

EXAIR Mini Cooler Is Ideal For Small Spot Cooling Applications

Published on by Russ BowmanLeave a comment

It was 23 °F (minus 5 °C) when I walked out the door this morning, and it was a shock to my system. The primary reason for that shock was the heat (generated from my house’s furnace) that maintains a comfortable temperature inside my home. Relief from that cold came when the internal combustion of gasoline that powers my car’s engine provided heat to the coils that the cabin fan passes air through on its way to the vents that maintain a comfortable temperature inside my car. Heat is a good thing this time of the year.

Heat, however, isn’t always a good thing. Just a few short months ago, I walked out of the building here at quitting time and the 100 °F (37.8 °C) temperature similarly shocked my system. The reason for that was I had just walked out of a comfortably air-conditioned building…and relief came when my car’s trusty air conditioning system started blowing refrigerated air from the same vents that heated air comes out of during these winter months.

Heat from processes like machining, welding, soldering, brazing, electrical losses, rotating or reciprocating equipment, etc., causes problems as well, and it’s not simply a matter of comfort. Removing heat from these processes is critical to sustained operation. Sometimes, a great amount of heat has to be removed. Power plants that generate electricity, for example, have massive pumps that send thousands of gallons of water per minute through huge heat exchangers that condense steam from turbines so that it can be boiled again to keep those turbines spinning.

On the other end of that spectrum are equipment like industrial sewing needles, lens grinders, skitters or small cutting tools, and soldering guns, just to name a few. These can all be successfully addressed with a focused stream of cold air…just like you get from an EXAIR Mini Cooler.

EXAIR Model 3308 Mini Cooler System w/ Dual Point Hose Kit is used to remove heat from this UHMW Polyethylene part, and the cutting tool. This not only keeps the plastic from melting, but also extends the tool life.

The Mini Cooler uses the Vortex Tube phenomenon to generate cold air from compressed air, with no moving parts, on demand. Since it’s a physical phenomenon, as opposed to a direct transfer of heat, the Mini Cooler is generating cold air at rated flow & temperature as soon as you open the supply of compressed air to it. You can turn it on & off as often, or as seldom, as needed. There are no moving parts to wear or electrical components to burn out. With a compressed air consumption of only 8 SCFM @100psig, even fairly small compressors (as low as 3HP for some) can operate a Mini Cooler continuously.

If an application requires a higher rate of cooling, other Vortex Tube operated products are available from stock:

If you’re not sure which Cooling Product fits your needs, EXAIR Application Engineers are standing by to help specify the right one for you…give me a call.

Russ Bowman, CCASS

Application Engineer
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VIDEO Blog: Vortex Tubes and Cooling Kits

Published on by Jordan T ShouseLeave a comment

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.

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.

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 or shoot me an email!

Jordan Shouse
Application Engineer

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