Have A Blast (Of Cold Air) With EXAIR Vortex Tubes & Spot Cooling Products

The operation of a Vortex Tube is one of the more peculiar phenomena in fluidics, and a particularly unique method of producing cold air. Since they don’t perform “heat transfer” in the classical sense (see below), there’s no RATE of heat transfer…they’re generating cold air, at rated flow and temperature, instantly.

Compressed air enters the Vortex Tube (blue arrow) where the Generator imparts a spinning motion to the flow, which continues towards the “hot end” (red ribbon). The flow is forced to change directions and continue spinning, flowing in the opposite direction (blue ribbon). It’s at this point that the flow gives up energy in the form of heat, which is exhausted through the Hot Valve (red arrows) while the cold flow makes its way to the opposite end, where it exits at temperatures up to 129F colder than the compressed air supply.

EXAIR Corporation’s Vortex Tubes come in a range of sizes & cooling capacities, and are integrated into a number of Spot Cooling Products which add convenience and flexibility to their operation. Consider:

  • Vortex Tubes themselves are perfect for the most basic of installations. Small and Medium models weigh only a few ounces; you can thread them directly onto an existing 1/8 NPT (Small) or 1/4 NPT (Medium) fitting, if you have one (or can get one) adjacent to where you want to blow the cold air. Hot and Cold Mufflers can be added for sound attenuation, and the Cold Caps have 1/4 NPT (Small) or 3/8 NPT (Medium) female threads if you want to use a short pipe or hose to direct the cold flow.
  • Most spot cooling applications are best handled with the higher air flows and moderate temperature drops associated with a Vortex Tube product set to a high cold fraction. We have three distinct products that have a pre-set, non-adjustable cold fraction, aimed at these situations:
    • Mini Cooler Systems are quiet, compact, and ready to install in minutes via a Swivel Magnetic Base. They’re ideal for cooling small tools, needles in industrial sewing machines, saw blades, or lens grinders, just to name a few of the more popular applications. These come with built-in hot muffler, and are available with a Single or Dual Outlet Cold Air Hose Kit.
    • For applications that call for a higher cooling capacity, we offer the Cold Gun Aircoolant Systems. These have a bar magnet built in to the Cold Gun itself, integral Hot and Cold Mufflers, and, like the Mini Coolers, come with Single or Dual Outlet Cold Air Hose Kits. They’re most popularly specified to replace mist coolant in machine tools, but are also used on routers, grinders, drills, larger saws, and even some non-machining applications like chill rolls and setting hot melt adhesives.
    • For even higher cooling capacities than that, the High Power Cold Gun can be used. Size-wise, it’s identical to the Cold Gun, but it generates twice the Cold Gun’s flow of cold air.
Mini Cooler (left) and Cold Gun (right).

One of the main advantages of using these Vortex Tube products with the pre-set higher cold fractions is the prevention of freeze-up…while the cold air generated is usually just a little below 32F (0C), ambient conditions in the areas where they’re used typically add enough heat to prevent mass freezing of any moisture condensed in the cooling process. A number of applications, however, do indeed call for much colder air flow than this, and for those, we’ve got the Adjustable Spot Cooler:

EXAIR Adjustable Spot Coolers can generate temperatures as low as -30°F (-34°C) instantly, and on demand.

Their versatility makes them a great “utility player” – when very cold air (well below zero) is needed, the Temperature Control Knob is turned counterclockwise. If another application calls for higher flow (like the Mini Coolers or Cold Guns), it can be turned clockwise for instant adjustment of flow and temperature.

Adjustable Spot Cooler Systems are available with Single or Dual Point Cold Air Hose Kits, and come with three Generators: 15 SCFM (installed), 25 SCFM, and 30 SCFM, to select the compressed air consumption, and hence, the overall flow range.

If you’ve got a spot cooling application, EXAIR Corporation has a Vortex Tube solution for you. Give me a call; let’s talk cold air!.

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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How to Best Apply Vortex Tube Cooling

So, you have found yourself with a little bit of a conundrum. You need to cool a part but don’t know where to start and there are so many different options to choose from. In most cases when it comes to cooling with compressed air there are two different paths you can take. First is using a large volume of air at room temperature to blow across the surface area of the product. The other option is to use cold air from a vortex tube to drop the part’s temperature. In most case a large volume of air can be used to cool things down to relatively cooler temperatures; think cooling a cup of coffee using your breath. The issue you run into is when the temperature of the room air gets closer to the temperature you want to achieve in the end. In other words, when the temperature difference between your cooling air and your desired end temperature is small there is less cooling taking place with that same volume of air.

Mini Spot Cooler cooling down a bit used in milling plastic

This can be explained by looking at the cooling power formula:

Btu/hr = 1.0746*(CFM)*(Delta T)

In this case the Delta T is the difference between the temperature that you want to cool the product down to and the temperature of the air. This means the smaller the delta T is the higher the CFM flow will need to be to counteract the effect of the temperatures are so close to one another. Here are some examples of cooling a product and you are providing 1000 CFM of air to cool it.

Btu/hr = 1.0746*(1000 CFM)*(150F – 130F)

                Btu/hr = 21,492 Btu/hr

Btu/hr = 1.0746*(1000 CFM)*(150F – 100F)

                Btu/hr = 53,730 Btu/hr

As you can see the closer the Delta T is to 0 the less Btu/hr you get. Getting this kind of CFM flow is easy if you use something like EXAIR’s Super Air Knife or Super Air Amplifier. These systems take a small amount of compressed air and entrain the surrounding ambient air to increase the volume to a large blast. Take a look at model number 120022 which is the 2” Super Air Amplifier, this unit can produce 1,023 CFM while only using 15.5 CFM at 80 psig. But when you get close to cooling the temperature down to that room temperature or below it gets much harder; which only means that the temperature of the air being used to cool needs to be dropped. Dropping the air temperature can only be accomplished by using outside means like air coolers or in this case EXAIR’s Vortex Tubes and Spot Coolers.

EXAIR Air Amplifiers use a small amount of compressed air to create a tremendous amount of air flow.

Vortex Tubes and Spot coolers have some limitations. Generally they are not thought of products that produce large volumes of air (even though we make them up to 150 SCFM). And they are best suited for smaller areas of cooling, spot cooling, if you will. However, EXAIR Vortex Tubes do have one key feature that can help compensate for the lack of volume. LOW TEMPERATURE! The vortex tube can produce temperatures lower than 0F while stile retaining a good portion of air volume from the inlet.

Sub-zero air flow with no moving parts. 3400 Series Vortex Tubes from EXAIR.

For example, let’s look at model number 3240 running at 100 psig with 70% of the air from the inlet exiting the cold side (aka 70% cold fraction). At 100 psig the 3240 will use 40 SCFM at the air inlet and will have a temperature drop of 71F. If the compressed air has a temperature of 70F that means you will be seeing a temperature of -1F. Also, when using the 70% cold fraction you will see 28 SCFM of cold air flow. Now let’s plug those numbers into the cooling power formula.

 Btu/hr = 1.0746*(28 CFM)*(150F + 1F)

                Btu/hr = 4543 Btu/hr

As you can see, using a small amount of compressed air you can still net you a good amount of cooling if the temperature is lower. All in all, the best option for cooling products down to temperatures that are above ambient temperatures is something that can produce a large volume of air. For small areas that require cooling the product down to temperatures to ambient temperature and below, use EXAIR’s Vortex Tube.

If you have questions about our Air Amplifiers and Vortex Tubes, or would like to talk about any of the quiet EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR or any Application Engineer.

Cody Biehle
Application Engineer
EXAIR Corporation
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Vortex Tubes Cool a UV Scanner

Copper smelting furnace

Safety is important when it comes to gas furnaces; and with large ovens, equipment is used to protect workers and equipment.  A copper company was using natural gas for smelting, and they had a UV scanner to monitor the flames.  If the burners go out, the scanner will turn off the gas valves to stop a potential explosion.   As with many instruments, it is important to keep the electronics cool for proper measurements.  In this case, they were having issues with accuracy from the high heat.  They contacted EXAIR for a solution. 

Air path flow for UV scanner

With their UV scanner, it was designed for a “cooling” device already.  This was basically compressed air that would blow around the instrument.  Because of the location, the compressed air was heating up to 125oF (52oC).  This heat would not cool the scanner properly, and it was causing unreliable readings and premature shutdowns.  They gave me the design specifications, and the scanner required 3.2 SCFM (90 SLPM) of air at atmospheric pressure with a maximum of 77oF (25oC).  I mentioned that we had the perfect solution to keep the UV scanner cool and operational; the EXAIR Vortex Tube.   This product can take elevated temperatures of compressed air and reduce it to lower temperatures.   It is a low cost, reliable, maintenance-free solution that uses compressed air to produce cold air as low as -50oF (-46oC).  With a range of cooling capacities from 135 BTU/hr to 10,200 BTU/hr, I was sure that we could meet the requirements for proper cooling. 

To determine the correct size, I had to look at the temperature drop and the flow requirement.  The temperature had to decrease from the 125oF (52oC) incoming compressed air to at least 77oF (25oC).  This would equate to a 48oF (27oC) temperature drop.  The other requirement was the amount of air flow, 3.2 SCFM (90 SLPM).  With the chart below, I see that we are able to get a 52oF (29oC) temperature drop at a 70% Cold Fraction and 40 PSIG (2.8 bar) inlet pressure.  EXAIR Vortex Tubes are very adjustable to get different outlet temperatures by changing the inlet pressure and the Cold Fraction.  The Cold Fraction (CF) is the amount of air that will be coming out the cold end.  With a 70% CF, that means that the adjusting screw on the hot end of the Vortex Tube is turned to allow 70% of the incoming compressed air to go out the cold end.  So, with that information, we can size to the correct model. 

In comparing the above information to the catalog data at 100 PSIG (6.9 bar), we have to consider the difference in absolute pressures.  With an atmospheric pressure of 14.5 PSIG (1 bar), the equation looks like this:

Qv = (Qc / CF) * (Pc + 14.5 PSIA) / (Ps + 14.5 PSIA)

Qv – Catalog Vortex Tube flow (SCFM)

Qc – Cold Air Flow (SCFM)

CF – Cold Fraction

Pc – Catalog Pressure – 100 PSIG

Ps – Supply Pressure – PSIG (Chart above)

From this equation, we can solve for the required Vortex Tube: 

                Qv = (3.2 SCFM / 0.7) * (100 + 14.5 PSIA) / (40 + 14.5 PSIA) = 9.6 SCFM. 

In looking at the catalog data, I recommended our model HT3210 Vortex Tube which uses 10 SCFM of compressed air at 100 PSIG.  The HT prefix is for our High Temperature models for use in temperatures in the range of 125oF to 200oF (52oC to 93oC).  So, after installing, the Vortex Tube was able to supply 73oF (23oC) air at a flow of 3.3 SCFM (94 SLPM); keeping the UV scanner reading correctly and accurately. 

Sometimes compressed air by itself is not enough to “cool” your instruments.  The EXAIR Vortex Tubes can reduce the temperature of your compressed air to very cold temperatures.  If you believe that your measuring equipment is being affected by elevated temperatures like the company above, you can contact an Application Engineer at EXAIR to find the correct solution for you. 

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

Which to Choose: Cabinet Coolers Vs. Coolant Driven A/C Units

From ancient times humans have sought ways to cool themselves down, from the invention of the manual fan in ancient times to the modern A/C systems that are used to cool down entire buildings. Anymore these days there is a cooling system for just about anything; gaming PC’s have there own cooling system, personal fans that mist water for cooling down people, climate-controlled boxes for artifacts in museums, etc. But what about your electrical cabinets in your facility? Electrical cabinets that overheat can cause expensive shut downs and lead to unsafe operations where the doors are left open with fans blowing in. When it comes to electrical cabinets there are two well-known ways that are used to cool down electrical cabinets which are fans and A/C units. But there is a third option you can go with which is EXAIR’s Cabinet Coolers.

EXAIR’s High Temp Cabinet Coolers

Cabinet Coolers are compressed air powered cooling units that utilize a source of compressed air and vortex tubes to cool down enclosed areas. But why would you choose a Cabinet Cooler over an A/C coolant driven system? Each system has pros and cons that can be weighed against each other.

A/C Coolant Driven Systems:
Can produce higher cooling loads effectively

Expensive up front
Constant maintenance

Cabinet Coolers:

Inexpensive upfront cost, lower lifetime cost
No moving Parts / No actual maintenance

Smaller range for effective cooling

Even in extremely aggressive environments, EXAIR Cabinet Cooler Systems provide reliable heat protection for your sensitive electronics and controls.

A/C Units operate in most cases using a chemical known as Dichlorodifluoromethane more commonly referred to as Freon (Freon is a registered trademark of Chemours Co.). By compressing and decompressing the liquid you can cause significant temperature drops in the surrounding air that can be blown into an area. This process requires a lot of moving parts that will eventually wear out and need to be replaced at a cost. Cabinet Coolers don’t have that issue, since they use vortex tubes there are no moving parts to wear out. As long as you provide clean dry air to a Cabinet Cooler the system will run indefinitely. Another thing to keep in mind is that although Dichlorodifluoromethane is a safer version of the older CFC’s , the chemical is not completely safe. Freon can be harmful to the environment as it can breakdown ozone, and due to its its density it will displace oxygen and can cause rapid suffocation.

Cabinet Coolers use compressed air, air which we breath and is all around us. So, no hazards with its energy source.

How the EXAIR Cabinet Cooler System Works

Lastly, although A/C units are cheaper to run they are much more expensive upfront cost and upkeep cost. This means in the long run it is actually cheaper to use a Cabinet Cooler because it does not have any upkeep cost for maintenance and repairs, along with being much cheaper to begin with.

EXAIR’s Cabinet Coolers are currently on promotion – receive a free AC Sensor with the purchase of any Cabinet Cooler.

Take advantage of our promo today!

If you have any questions or want more information on EXAIR’s Cabinet Coolers or like products. Give us a call, we have a team of application engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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