The Adjustable Spot Cooler – Cold Air to -30°F (-34°C) From Your Compressed Air Supply

The Adjustable Spot Cooler is a low cost, reliable , maintenance free way to provide spot cooling to a myriad of industrial applications. Simply turn the knob, and the temperature can be changed to suit the needs of the process. The Adjustable Spot Cooler delivers precise temperature settings from -30°F (-34°C) to room temperature.

Adjustable Spot Cooler
Adjustable Spot Cooler

The Adjustable Spot Cooler utilizes the Vortex Tube technology that converts compressed air into a cold air stream. To learn more about EXAIR vortex tubes, click here.

  • It can produce temperatures form -30°F to +70°F (-34°C tp +21°C)
  • Parts included for flow rates of 15, 25 and 30 SCFM (425, 708, 850 SLPM.) The unit comes from the factory set at 25 SCFM (708 SLPM)
  • It can produce refrigeration up to 2,000 BTU/hr (504 Kcal/hr.)

A swivel magnetic base allows for easy mounting and portability, you can move it from machine to machine as needed. The flexible cold air outlet tubing holds its position and is easy to aim. Most importantly, there are no moving parts or CFC’s, ensuring maintenance free operation.

asc_onlathecmyk
The Adjustable Spot Cooler maintains critical tolerances on machined plastic parts

How the Adjustable Spot Cooler WorksThe Adjustable Spot Cooler incorporates a vortex tube to convert a supply of compressed air (1) into two low pressure streams, one hot and one cold. With the turn of a knob, the temperature control valve (2) allows some hot air to flow through a muffling sleeve and out the hot air exhaust (3). The opposite end provides a cold air stream (4) that is muffled and discharged through the flexible hose, which directs it to the point of use. The swivel magnetic base (5) provides easy mounting and portability.


The Adjustable Spot Cooler can produce a wide range of air flows and temperatures as determined by the temperature control valve knob setting and the generator installed. The generator controls the total SCFM (SLPM) of compressed air consumption, and is easy to change. From the factory, the 25 SCFM (708 SLPM) generator is installed, producing up to 1,700 BTU/hr (429 Kcal/hr) of cooling. For less cooling, the 15 SCFM (425 SLPM) generator can be installed, providing up to 1,000 BTU/hr (252 Kcal/hr) of cooling. And for more cooling, the 30 SCFM (850 SLPM) generator can be installed, providing up to 2,000 BTU/hr (504 Kcal/hr) of cooling.

Adjustable Spot Cooler Specifications

Two (2) Systems are available as shown below, and include the 15 and 30 SCFM (425 and 850 SLPM) generators, a filter separator, and either a single or dual point hose kit.

Adjustable Spot Cooler Systems3825_3925 adj spot cooler

If you have questions about the Adjustable Spot Cooler 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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The Case for the Cold Gun

Heat is an unavoidable by-product of any cutting or machining operation. Think about it: you’re creating friction on a piece of material with a fast-moving piece of harder material in order to forcibly separate pieces of the original material from its existing shape & size. No matter what, something’s going to get hot: the work piece, the tooling, or (almost always) both. If you don’t do something about it, your parts can become damaged, your tooling can become dull and brittle, and productivity will suffer.

There are ways to alleviate the problem…you can slow the speed of your tooling, but that’s hardly practical, and only marginally effective.  You can use liquid cooling…in fact, you may have to if the particulars of the operation require the lubrication you can only get from a cutting oil or liquid coolant.  But those can be messy, expensive, and the time you spend maintaining the coolant could certainly be spent better elsewhere…like, on machining your products!

The EXAIR Cold Gun Aircoolant System is a novel solution to these problems…heat related and otherwise:

  • The Cold Gun uses compressed air to produce a stream of clean, cold air at 50°F (28°C) below supply air temperature.
  • They use Vortex Tube technology…no moving parts to wear out.
Instant cold air flow with no moving parts!
  • Cold flow and temperature are preset to optimize cooling capability, and are non-adjustable to prevent freeze-up during use.
  • Eliminates the expense of both the purchase & disposal of cutting fluids.
  • Removes the potential for health problems associated with breathing mist & vapors, and the safety issue of slipping on a wet floor.

Cold Gun Aircoolant System selection is easy & straightforward…we offer a standard, and a High Power version to meet your specific needs.

Four systems to choose from, to meet most any need.

We also offer Single & Dual Point Hose Kits, to further meet the needs of your application.  Right now, you don’t have to decide up front…order a Cold Gun Aircoolant System with a Single Point Hose Kit before December 31, 2018, and we’ll throw in the Dual Point Hose Kit for free.

If you’d like to find out more about how Cold Gun Aircoolant Systems can improve your machining or cutting operations, give me a call.

Russ Bowman
Application Engineer
EXAIR Corporation
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The Theory of the Vortex Tube

There are many theories regarding the dynamics of a vortex tube and how it works. Many a graduate student has studied them as part of their research requirements.

VT_air2

The Vortex Tube was invented by accident in 1928, by George Ranque, a French physics student. He was performing experiments on on a vortex-type pump that he had developed and noticed that warm air exhausted from one end and cold air from the other! Ranque quickly stopped work on the pump, and started a company to take advantage of the commercial possibilities for this odd little device that produced both hot and cold air, using only compressed air, with no moving parts. The company was not successful, and the vortex tube was forgotten until 1945 when Rudolph Hilsch, a German physicist, published a widely read paper on the device.

A vortex tube uses compressed air as a power source, has no moving parts, and produces hot air from one end and cold air from the other. The volume and temperature of the two air streams is adjustable with a valve built into the hot air exhaust.  Temperatures as low as -50°F (-46°C) and as high as 260°F (127°C) are possible.

Here is one widely accepted explanation of the physics and the phenomenon of the vortex tube.VT

Compressed air is supplied to vortex tube and passes through nozzles that are tangent to to an internal counterbore (1). As the air passes through it is set into a spiraling vortex motion (2) at up to 1,000,000 rpm. The spinning stream of air flows down the hot tube in the form of a spinning shell, like a tornado (in red). The control valve (4) at the end allows some of the warmed air to escape (6) and what does not escape reverses direction and heads back down the tube as a second vortex (in blue) inside of the low pressure area of the larger warm air vortex. The inner vortex loses heat and exits the through the other end of as cold air (5).

It is thought that that both the hot and cold air streams rotate in the same direction at the same angular velocity, even though they are travelling in opposite directions. A particle of air in the inner stream completes one rotation in the same amount of time that an air particle in the outer stream. The principle of conservation of angular momentum would say that the rotational speed of the inner inner vortex should increase because the angular momentum of a rotating particle (L) is equal to the radius of rotation (r) times its mass (m) times its velocity (v).  L = r•m•v.  When an air particle moves from the outer stream to the inner stream, both its radius (r) and velocity (v) decrease, resulting in a lower angular momentum. To maintain an energy balance for the system, the energy that is lost from the inner stream is taken in by the outer stream as heat. Therefore, the outer vortex becomes warm and the inner vortex is cooled.

At EXAIR, we have harnessed the cooling power of the vortex tube, and it can be found and utilized in such products as Spot Coolers, Cabinet Coolers, and the Vortex Tube themselves.

Harnessing the cooling power of the vortex tube 

If you have questions about Vortex Tubes, or would like to talk about any of the EXAIR Intelligent Compressed Air® Products, 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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Going Outside The Box With Vortex Tubes

Among EXAIR’s comprehensive line of Intelligent Compressed Air Products, the Vortex Tube stands out as a unique, and fascinating, solution for a variety of applications requiring a flow of cold air:

  • Cabinet Cooler Systems: clean, cold air to protect electrical and electronic components housed in an enclosure.  Installs in minutes; no moving parts; reliable & maintenance free.
  • Cold Gun Aircoolant Systems:  Direct, focused flow of cold air to replace messy coolant in machining, cutting, drilling, grinding, etc., applications.  Integral magnet base for quick & easy installation; single or dual outlet hose kits; standard or High Power to meet any need.  Optimized flow for maximum cooling and freeze prevention.
  • Adjustable Spot Cooler: Similar to the Cold Guns in many ways, but with variable performance for specific applications.  Cold air to -30°F (-34°C) on demand.
  • Mini Cooler: Similar to the Cold Guns and Adjustable Spot Coolers – magnetic base mounting and single or dual outlet hose kits, but more compact.  Lower flows for smaller jobs.

Then there are the Vortex Tubes themselves…at the heart of all of these products, but perfectly capable all on their own.  In fact, in certain situations, “plain old” Vortex Tubes have been used to do the exact same jobs as all of the above products.  They can even be customized, in and of themselves, to meet specific installation, operation, and/or performance needs:

  • High Temperatures: It should come as no surprise that cold air is often needed because a heat-sensitive item is located in a high heat environment.
    • Vortex Tubes come standard with plastic Generators and Buna o-rings, which are good for ambient temperatures up to 125°F (52°C).
    • High Temperature Vortex Tubes are fitted with brass Generators and Viton o-rings for environments where the temperature can reach 200°F (93°C).
High Temperature Vortex Tubes are suitable for use in environments up to 200F (93C).
  • Preset temperature & flow: Many times, the ability to adjust the performance of a Vortex Tube is a big benefit, but occasionally it’s a liability.
    • I know none of your co-workers are like this (nor are mine) but I’ve heard of people who think they “know better” and are prone to tampering with something that is (or WAS) working just fine, thank you very much.
    • Perhaps you actually DO know better, through experimentation and experience, the optimal performance setting for your application.  Let’s say, for example, you install Vortex Tubes on a line of your products, and a technician has to “dial it in” to a specific Cold Fraction.
    • Any Vortex Tube can be fitted with a drilled orifice (or “Hot Plug”) to replace  the Hot Valve, which presets performance to a specific, non-adjustable value.  If you know the Cold Fraction you need, it’s as easy as that.  If not, it’s as easy as getting a stock Vortex Tube, setting the Cold Fraction where you want it, securing the Hot Valve in position (piece of tape works just fine,) and sending it in.
Preset Vortex Tubes feature a fixed plug, replacing the Hot Valve shown in this picture.

If you’ve got any other specific requirements – special materials, fittings, custom flow/temperature parameters, etc., give me a call; let’s talk.

Russ Bowman
Application Engineer
EXAIR Corporation
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Vortex Tube Cooling Capacities and Generators

vortex_generator
Vortex  Medium Generator

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
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.

How A Vortex Tube Works

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.

Vortex kit
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.

Steve Harrison
Application Engineer
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Vortex Tubes: What is a Cold Fraction & How to use it to Your Benefit

Vortex Tubes

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.

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

Controlling Temperature and Flow in a Vortex Tube

VT_air2

A few weeks ago, we looked at the Vortex Tube and provided a general overview of the device (see that blog here.)  In a nutshell – a Vortex Tube uses an ordinary supply of compressed air as a power source, creating two streams of air, one hot and one cold – resulting in a low cost, reliable, maintenance free source of cold air for spot cooling solutions.

One of the features of the Vortex Tube is that the temperature of the cold air and the cold air flow rate is changeable. The cold air flow and temperature are easily controlled by adjusting the slotted valve in the hot air outlet.

Vortex Tube Hot Valve Adjustment
Hot Valve Adjustment for a Vortex Tube

Opening the valve (turning it counterclockwise) reduces the cold air flow rate and the lowers the cold air temperature.  Closing the valve (turning it clockwise) increases the cold air flow and raises the cold air temperature.

VT Adjustment Table

As with anything, there is a trade off – to get higher a cold air flow rate, a moderate cold air temperature is achieved, and to get a very cold air temperature, a moderate air flow rate is achieved.

An important term to know and understand is Cold Fraction, which is the percentage of the compressed air used by the Vortex Tube that is discharged through the Cold End.  In most applications, a Cold Fraction of 80% produces a combination of cold flow rate and and cold air temperature that results in the maximum refrigeration or cooling output form a Vortex Tube.

For most industrial applications – such as process cooling, part cooling, and chamber cooling, maximum refrigeration is best and the 32XX series of Vortex Tubes are preferred.  For those applications where ‘cryogenic’ cooling is needed, such as cooling lab samples, or circuit testing, the 34XX series of Vortex Tube is best.

To set a Vortex Tube to a specific temperature, simply insert a thermometer into the cold air exhaust and adjust the hot valve.  Maximum refrigeration, at 80% Cold Fraction, is achieved when the cold air temperature drop is 50°F (28°C) from the incoming compressed air temperature. See the video posted here for measuring and lowering and the cold air temperature.

For those cases when you may be unsure of the required cold air flow rate and cold air temperature to provide the needed cooling in an application, we would recommend an EXAIR Cooling Kit.  The Cooling Kit contains a Vortex Tube, Cold Air Muffler, Air Line Filter, and a set of Generators that will allow for experimentation of the full range of air flows and temperatures possible.

gh_VTcoolingkit_750x696p
EXAIR Vortex Tube Cooling Kit

To discuss your application and how a Vortex Tube or any EXAIR Intelligent Compressed Air Product can improve your process, feel free to contact EXAIR, myself, or one of our other Application Engineers. We can help you determine the best solution!

Brian Bergmann
Application Engineer

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