Vortex Tube Cold Fractions Explained

Simply put, a Vortex Tube’s Cold Fraction is the percentage of its supply air that gets directed to the cold end. The rest of the supply air goes out the hot end. Here’s how it works:

The Control Valve is operated by a flat head screwdriver.

No matter what the Cold Fraction is set to, the air coming out the cold end will be lower in temperature, and the air exiting the hot end will be higher in temperature, than the compressed air supply.  The Cold Fraction is set by the position of the Control Valve.    Opening the Control Valve (turning counterclockwise, see blue arrow on photo to right) lowers the Cold Fraction, resulting in lower flow – and a large temperature drop – in the cold air discharge.  Closing the Control Valve (turning clockwise, see red arrow) increases the cold air flow, but results in a smaller temperature drop.  This adjustability is key to the Vortex Tube’s versatility.  Some applications call for higher flows; others call for very low temperatures…more on that in a minute, though.

The Cold Fraction can be set as low as 20% – meaning a small amount (20% to be exact) of the supply air is directed to the cold end, with a large temperature drop.  Conversely, you can set it as high as 80% – meaning most of the supply air goes to the cold end, but the temperature drop isn’t as high.  Our 3400 Series Vortex Tubes are for 20-50% Cold Fractions, and the 3200 Series are for 50-80% Cold Fractions.  Both extremes, and all points in between, are used, depending on the nature of the applications.  Here are some examples:

EXAIR 3400 Series Vortex Tubes, for air as low as -50°F.

A candy maker needed to cool chocolate that had been poured into small molds to make bite-sized, fun-shaped, confections.  Keeping the air flow low was critical…they wanted a nice, smooth surface, not rippled by a blast of air.  A pair of Model 3408 Small Vortex Tubes set to a 40% Cold Fraction produce a 3.2 SCFM cold flow (feels a lot like when you blow on a spoonful of hot soup to cool it down) that’s 110°F colder than the compressed air supply…or about -30°F.  It doesn’t disturb the surface, but cools & sets it in a hurry.  They could turn the Cold Fraction down all the way to 20%, for a cold flow of only 1.6 SCFM (just a whisper, really,) but with a 123°F temperature drop.

Welding and brazing are examples of applications where higher flows are advantageous.  The lower temperature drop doesn’t make all that much difference…turns out, when you’re blowing air onto metal that’s been recently melted, it doesn’t seem to matter much if the air is 20°F or -20°F, as long as there’s a LOT of it.  Our Medium Vortex Tubes are especially popular for this.  An ultrasonic weld that seals the end of a toothpaste tube, for example, is done with a Model 3215 set to an 80% Cold Fraction (12 SCFM of cold flow with a 54°F drop,) while brazing copper pipe fittings needs the higher flow of a Model 3230: the same 80% cold fraction makes 24 SCFM cold flow, with the same 54°F temperature drop.

Regardless of which model you choose, the temperature drop of the cold air flow is determined by only two factors: Cold Fraction setting, and compressed air supply pressure.  If you were wondering where I got all the figures above, they’re all from the Specification & Performance charts published in our catalog:

3200 Series are for max cooling (50-80% Cold Fractions;) 3400’s are for max cold temperature (20-50% Cold Fractions.)
Chocolate cooling in brown; welding/brazing in blue.

EXAIR Vortex Tubes & Spot Cooling Products are a quick & easy way to supply a reliable, controllable flow of cold air, on demand.  If you’d like to find out more, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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Generators for the EXAIR Vortex Tubes

Vortex generator

The EXAIR Vortex Tubes use compressed air to generate cold air down to -50 deg. F (-46 deg. C) without any moving parts, freon, or electricity.  By design, it will produce hot air at one end and cold air at the other.  EXAIR offers different cooling capacities ranging from 135 BTU/hr (34 Kcal/hr) to 10,200 BTU/hr (2,570 Kcal/hr).  This cooling phenomenon begins by spinning the air at a high rate of speed inside the Vortex Tube.  The “separation” of temperatures starts at the generator.  In this blog, I will discuss the features of the generator and how our design allows for an efficient way to cool and heat the air flows.

Vortex Family

EXAIR stocks three different sizes of the Vortex Tubes; small, medium, and large.  Each Vortex Tube will use a generator to define the cooling capacity and compressed air usage.  When compressed air enters the Vortex Tube, it will have to pass through the generator first.  The generators are engineered with vane openings to initiate the spinning of the air and to control the amount of air that can pass through it.  As an example, for a medium-sized Vortex Tube, a model 10-R generator will only allow 10 SCFM (283 SLPM) of air at 100 PSIG (6.9 Bar).  While in that same size body, a model 40-R generator will allow 40 SCFM (1,133 SLPM) of air at 100 PSIG (6.9 Bar) to be used.  Precision in the design of the generators is what sets EXAIR apart with efficiency and effectiveness in cooling.

EXAIR Vortex Tube Performance Chart

EXAIR created a chart to show the temperature drop for the cold end and temperature rise for the hot end, relative to the incoming compressed air temperature.  Across the top of the chart, we have Cold Fraction and along the side, we have the inlet air pressure.  The Cold Fraction is the percentage of the inlet air that will blow out the cold end of the Vortex Tube.  This is adjustable with a Hot Exhaust Air Valve at the hot end.

As you can see from the chart, the temperature difference changes as the Cold Fraction and inlet air pressure changes.  You may notice that it is independent of the size of the generator.  So, no matter which size Vortex Tube or generator is used, the temperature drop and rise will follow the chart above.  But just remember, cooling capacity is different than cooling temperature.  At the same settings, a larger generator will give you more mass of air to cool faster.

Now, let’s look inside the Vortex Tube (reference photo above).  As the compressed air passes through the generator, the change in pressure will create a powerful vortex.  This spinning vortex 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 hot air that leaves the Vortex Tube.  The remaining part of the air is redirected toward the opposite end as the cold flow, or Cold Fraction.

Now, what separates EXAIR Vortex Tubes from our competitors are the three different styles of generators and two different materials for each size.  These generators are engineered to optimize the compressed air usage across the entire Cold Fraction chart above.  With temperatures above 125 oF (52 oC), EXAIR offers a brass generator for the Vortex Tubes.  The same precision design is applied but for higher ambient temperatures.  With the wide range of Vortex Tubes and generators, we can tackle many types of cooling applications.

If you would like to discuss your cooling requirement with an Application Engineer at EXAIR, we will be happy to help.  This unique phenomenon to generate cold air with no moving, freon, or electricity could be a great product to use in your application.

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

Applying a Vortex Tube and Adjusting Temperature

Throughout my tenure with EXAIR there are may days where I have tested different operating pressure, volumetric flow rates, back pressures, lengths of discharge tubing, generator compression, and even some new inquiries with cold air distribution all on a vortex tube.  These all spawn from great conversations with existing customers or potential customers on different ways to apply and applications for vortex tubes.

Many of the conversations start in the same spot… How exactly does this vortex tube work, and how do I get the most out of it?  Well, the answer is never the same as every application has some variation.  I like to start with a good idea of the area, temperatures, and features of exactly what we are trying to cool down.  The next step is learning how fast this needs to be done.  That all helps determine whether we are going to be looking at a small, medium, or large vortex tube and which cooling capacity to choose.   After determining these factors the explanation on how to adjust the vortex tube to meet the needs of the application begins.

This video below is a great example of how a vortex tube is adjusted and what the effects of the cold fraction have and just how easy it is to adjust.  This adjustment combined with varying the air pressure gives great versatility within a single vortex tube.

The table below showcases the test points that we have cataloged for performance values.  As the video illustrates, by adjusting the cold fraction lower, meaning less volumetric flow of air is coming out of the cold side and more is exhausting out the hot side, the colder the temperature gets.

EXAIR Vortex Tube Performance Chart

This chart helps to determine the best case scenario of performance for the vortex tube.  Then the discussion leads to delivery of the cold or hot air onto the target.  That is where the material covered in these two blogs, Blog 1, Blog 2 comes into play and we get to start using some math.  (Yes I realize the blogs are from 2016, the good news is the math hasn’t changed and Thermodynamics hasn’t either.)  This then leads to a final decision on which model of vortex tube will best suit the application or maybe if a different products such as a Super Air Amplifier (See Tyler Daniel’s Air Amplifier Cooling Video here.)is all that is needed.

Where this all boils down to is, if you have any questions on how to apply a vortex tube or other spot cooling product, please contact us.  When we get to discuss applications that get extremely detailed it makes us appreciate all the testing and experience we have gained over the years.  Also, it helps to build on those experiences because no two applications are exactly the same.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

EXAIR Cabinet Cooler Eases Maintenance Schedule, Replaces A/C System for Beverage Manufacturer

CC_Actionshot

During a recent visit with our distributor in Lima, Peru I had the pleasure of visiting a beverage manufacturing facility to discuss EXAIR’s Cabinet Coolers. They have several panels throughout the facility with A/C units installed. A lack of adherence to scheduled maintenance was causing the filters to clog and restrict the cooling power of the A/C unit. Due to staffing issues, their maintenance department was very thin and regular maintenance items were getting missed.

When the filters would clog, the panels would overheat and stop production. Their solution was to open the panel up and blow fans on them, forcing even more dust into the enclosure. In their search for an alternative solution, they came across EXAIR’s Cabinet Cooler Systems and reached out to our distributor. The A/C unit that was installed on the panel had a capacity of 800W (2,728 Btu/hr). EXAIR offers a 2,800 Btu/hr system from stock that matched up perfectly for them.

They installed a Model 4340-24VDC Nema 12 Cabinet Cooler System with 24VDC thermostat control and removed the A/C system. With no moving parts and no refrigerants, there’s absolutely no maintenance required. Just set it and forget it! The Cabinet Cooler has kept the electronics inside at 95°F, preventing any potential for heat related shut downs. Since all Cabinet Coolers must be installed onto a sealed enclosure, there is no need for filters on the enclosure to prevent dirty ambient air from entering. They’re now working to replace each of the A/C units in the facility with an EXAIR Cabinet Cooler.

EXAIR manufactures Cabinet Coolers for any industrial environment. Cabinet Coolers maintain Nema 4, Nema 4X, and Nema 12 integrity on the enclosure and are also UL Listed and CE Compliant. For applications that may be in a classified area, the Hazardous Location Cabinet Cooler has been approved by UL for use in Class 1 Div 1 – Groups A, B, C, and D; Class II Div 1 – Groups E, F, and G; and in Class III areas. Cooling capacities as high as 5,600 Btu/hr can be achieved with one of our Dual Cabinet Cooler Systems.

Stop wasting precious time maintaining you’re A/C systems, or dealing with heat related shutdowns and get a Cabinet Cooler on order today. Fill out the sizing guide online, and one of our Application Engineers will be in touch to provide you with the most suitable model for your application. Act fast, the current Cabinet Cooler promotion expires at the end of August!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@EXAIR.com
Twitter: @EXAIR_TD

Applications for Vortex Tube Spot Cooling

The EXAIR Mini Cooler family is one of the many vortex tube based Spot Cooler products that EXAIR offers.  This is the smallest of the group coming in at 550 BTU/hr of cooling capacity.  The Mini Cooler Systems  are available in two options.

minicoolerWFAM_500
EXAIR’s Mini Cooler is available with a single point hose kit or a dual point hose kit.
  • The Single Point Outlet option will give you ten inches of flexible cold outlet to easily position the cold air stream near the target point.
  • The Dual Point Outlet option gives ten inches of 1/4″ flexible outlet that then splits to two separate four inch lengths of 1/4″ flexible cold outlet hoses.
  • Both include point or flat fan tips for the cold air outlets
  • Both include a manual drain filter separator
  • both include the swivel magnetic base with 100 lb. pull magnet.
minicooler_appli400
The Single Point Mini Cooler with a Flat Fan Tip installed on a milling application where liquid coolant cannot be used due to material constraints.

The single point hose kit is ideal for small diameter milling or drilling applications where the cold air can cover the contact area of the cutter.  It can also be used on soldering, industrial sewing, ultrasonic welding, or even small punching applications to list just a few.

EXAIR’s Mini Cooler System w/ Dual Point Hose Kit keeping UHMW cool while being machined

The dual point hose kit is ideal for two separate small diameter cutters, one larger diameter cutter, rotary style knives where there material is being slit, or larger diameter multi-point ultrasonic welders/punches.

When using the Mini Cooler the adjustable cold outlet stays in place and can easily bend around fixtures, spindles, welding horns, or dye aligning pins.  The swivel magnetic base gives additional adjustment at the base of the cooler to aid in the versatility of this product.   To further the adjustability of the cooler the operating pressure can easily be adjusted to lower or raise the cooling capacity of the Mini Cooler to meet the demands of the precise application.

If you believe you have an application that would benefit from the use of a Mini Cooler, or you are unsure which product would be ideal for your application please contact an Application Engineer.  we are all here, willing to help however possible to get your application improved in both safety and efficiency.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

 

EXAIR Cabinet Coolers vs. Air to Air Heat Exchangers

At EXAIR we’ve been providing enclosure cooling solutions for decades, and in many cases those cooling solutions have remained in place for decades as well.  In the time we’ve been in the market with industrial enclosure cooling solutions we’ve encountered a number of alternative means for enclosure cooling.  One of those methods is an air-to-air heat exchanger.

heat exchanger 1
Heat exchanger

An air-to-air heat exchanger uses the temperature differential between the ambient air surrounding an enclosure and the hot air inside an enclosure to create a cooling effect.  A closed loop system exchanges the heat inside the enclosure with the outside air in an effort to maintain a set internal temperature.  The heat exchange of most air-to-air unit relies on a heat pipe, a heat-transfer device which converts an internal refrigerant liquid into vapor by placing one end of the pipe in contact with the hot environment.  The heated vapor travels to the other end of the pipe which is in contact with a cooler environment.  The vapor condenses back into a liquid (releasing latent heat) and returning to the hot end of the pipe and the cycle repeats.

But, this type of a solution does give some cause for concern, especially when considering their use in an industrial environment.  Here are the key points to keep in mind when comparing an air-to-air cooler to an EXAIR Cabinet Cooler.

Cabinet Cooler Family
EXAIR Cabinet Coolers

Required temperature differential based on ambient air temp

An air-to-air heat exchange relies on the ΔT between the ambient air temperature and the internal enclosure air temperature to produce cooling.  If this ΔT is low, or the ambient temperature rises, cooling is diminished.  This means that as the temperatures in your facility begin to rise, air-to-air heat exchangers become less and less effective.  Larger air-to-air heat exchangers can be used, but these may be even larger than the enclosure itself.

EXAIR Cabinet Coolers rely on the ΔT between the cold air temperature from the Cabinet Cooler (normally ~20°F) and the desired internal enclosure temperature (normally 95°F).  The cold air temperature from the Cabinet Cooler is unaffected by increases in ambient temperatures.  The large ΔT and high volume cold air flow produced by a Cabinet Cooler results in more cooling capacity.  And, we can increase cooling capacity from a Cabinet Cooler without increasing its physical footprint, which is already much, much smaller than an air-to-air type of unit.

 

Cooling in high temperature environments

Due to their nature of operation, an air-to-air heat exchanger must have an ambient temperature which is lower than the desired internal temperature of the enclosure.  If the ambient air has a higher temperature, air-to-air units provide zero cooling.

Cabinet Coolers, on the other hand, can be used in hot, high temperature environments up to 200°F (93°C).

EXAIR's High Temp Cabinet Cooler Systems
High temperature Cabinet Coolers

 

Cooling in dirty environments

Dirt in the ambient environment will impact cooling performance with an air-to-air heat exchanger.  In order for the air-to-air unit to effectively remove heat, the heat pipe must have access to ambient air.  With any exposure to the ambient environment comes the possibility for the ambient end of the heat pipe to become covered in ambient contaminants such as dust.  This dust will create an insulation barrier between the heat pipe and the ambient air, decreasing the ability for the heat pipe to condense the vapors within.  Because of this, most air-to-air devices use filters to separate the heat pipe from the ambient environment.  But, when these filters become clogged, access to ambient temperatures are reduced, and cooling capacity of the air-to-air unit reduces as well.

Cabinet Coolers have no problem operating in dirty environments.  In fact, it is one of their strengths.  Without any moving parts to wear out or any need to contact ambient air for cooling purposes, a dirty environment poses no problems.  In fact, check out this blog post (and this one) about EXAIR Cabinet Coolers operating maintenance free for years in dirty environments.

exair-cabinet-cooler-03-2002-2008
NEMA 12 Cabinet Cooler in a Dirty Environment

Size and time required to install

Air-to-air heat exchangers vary in size, but even the smallest units can have large dimensions.  Many applications have limited space on the enclosure, and a large, bulky solution can be prohibitive.  Couple this with the time and modification required to the enclosure to install a large air-to-air unit, and the “solution” may end up bringing additional problems.

Another key aspect of the Cabinet Cooler is its size.  Small, compact, and easy to mount on the top or side of an enclosure, Cabinet Coolers install in minutes to remove overheating problems.

 

Heat within an electrical cabinet can be a major issue for manufacturing companies. The costs associated with down time and repairs on sensitive electronics that fail due to heat or environmental contaminants, are an unnecessary burden. If you have any questions about how an EXAIR Cabinet Cooler can solve problems in your facility, contact an EXAIR Application Engineer.

Jordan Shouse
Application Engineer
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Twitter: @EXAIR_JS

Choosing the Right Vortex Tube – Max Refrigeration vs. Max Cold Temperature

The Vortex Tube is a low cost, reliable, maintenance free way to provide cooling to a wide variety of industrial spot cooling problems.

VT_air2

There are two (2) popular uses for the Vortex Tubes.  One is to spot cool a warm item as fast as possible.  The other is to chill an item to as low a temperature as possible. Because these are very different requirements, different Vortex Tube configurations exist to handle each.

For those applications of spot cooling, we recommend the 3200 series of Vortex Tubes. They are designed to be most efficient at providing maximum refrigeration, which is a function of high cold air flow rate and moderate temperature differential of the cold air to the warm item.

And for those applications of chilling an item to a very low temperature at low flow rate , we recommend the 3400 series of Vortex Tubes.  They are designed to be most efficient at providing maximum cold air temperatures, but with a lower cold air flow rate.

An important parameter for the Vortex Tubes is the Cold Fraction.  By adjusting the hot valve on a vortex tube, the amount of air that is discharged through the cold end changes. When expressed as a percentage of the total compressed air that is supplied to the vortex tube, we get the Cold Fraction.  For example, if the hot valve is adjusted so that for every 10 parts of compressed air supplied, we get 7 parts of cold air, then we have a 70% Cold Fraction. When you know the Cold fraction setting and the compressed air supply pressure, you can use the Vortex Tube Performance tables and get the cold air discharge temperature.

Using the table below left, at 100 PSIG compressed air pressure and a 70% Cold Fraction, we can expect the cold air discharge temperature drop to be 71°F.  With 70 ° compressed air temperature, the cold air will be at -1°F.

Vortex Tube Charts
Vortex Tube Performance Tables

The 3200 series of Vortex Tubes are for use in the 50-80% Cold Fraction range, and the model 3400 series is designed for use in the 20-50% Cold Fraction ranges, to maximize the performance of each.

In summary, the selection of the Vortex Tube that best meets the application needs is based on the desired cold air flow rate, and the temperature of air desired. Once these are known, using the tables can provide the information needed to select the best option.

For those applications where we are unsure what will work best, we offer the EXAIR Cooling Kits, that include a Vortex Tube (small, medium, or large) and an array of Generators, to allow the configuration of the full range of Vortex Tubes within each size family.

  • Model 3908 – Small Vortex Tube Cooling Kit – build models 3202, 3204, 3208, and 3402, 3404, 3408
  • Model 3930 – Medium Vortex Tube Cooling Kit – build models 3210, 3215, 3225, 3230, 3240, and 3410, 3415, 3425, 3430, 3440
  • Model 3998 – Large Vortex Tube Cooling Kit – build models 3250, 3275, 3298, 3299, and models 3450, 3475, 3498, 3499

3930

If you have questions about Vortex Tubes or any of the 16 different EXAIR Intelligent Compressed Air® Product lines, feel free to contact EXAIR and myself or any of our Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer
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