BTU/hr. vs. Cold Air Temperature

 

Way back in 1983 the founder of EXAIR began producing Vortex Tubes.  Using only compressed air, these small devices produce extremely cold air through the Ranque-Hilsch effect.  As the compressed air enters the Vortex Tube, it begins to spin, reaching over 1,000,000 rpm.  When the spinning airflow reaches the end of the tube, an adjustable percentage is forced to change directions and decrease in diameter.  This decrease in diameter requires a decrease in energy, which the airflow does in the form of heat.  What is left is a hot airstream from one end of the tube and a cold airstream from the other.

An EXAIR Vortex Tube

A key component in the creation of the Vortex Tube effect is the apparatus which starts the spinning of the air inside the tube.  At EXAIR we refer to this piece as the generator, and we can significantly impact the performance of the Vortex Tube based on the dimensional characteristics of this component.

By changing one dimension of the generator we can increase or decrease the total volume of air which flows through the Vortex Tube; and by changing another dimension we can “force” a certain percentage of air to exit the hot end of the Vortex Tube.  These small dimensional changes will result in either a high volume of very cold air, or a low volume of INSANELY cold air.  So, how is this possible?

EXAIR Vortex Tube Performance Chart

To thoroughly answer this, we have to look at something called cold fraction.  A cold fraction is the percentage of air which enters the Vortex Tube and exhausts through the cold end.  An 80% cold fraction will direct 80% of the air which enters the Vortex Tube to exhaust through the cold end.  For example, using a 10 SCFM Vortex Tube with an 80% cold fraction will produce 8 SCFM of flow through the cold end of the tube and 2 SCFM of flow through the hot end of the tube.

Adjusting the cold fraction of a Vortex Tube is as simple as turning the brass valve on the hot end of the tube.  The more the valve is opened, the lower the cold fraction.  As the valve is opened it allows more air to “escape” the Vortex Tube through the hot end, resulting in a lower flow (and also lower temperature air) from the cold end of the tube.  These cold fractions determine the temperature drop of the incoming compressed air, and therefore the outlet temperature of the cold air from the Vortex Tube.  But, this adjustment limited, based on the geometry of the generator mentioned above.

An EXAIR Cooling Kit, complete with Vortex Tube, cold air muffler, generator kit, and automatic drain filter separator.

At EXAIR we produce multiple styles of Vortex Tube generators which produce different cold fraction bandwidths.  Our “C” style generators are better suited to produce a cold fraction between 0-60%, and our “R” style generators are better suited to produce a cold fraction between 40-100%.  These cold fractions are independent of airflow volume, allowing for different outlet temperature ranges with the same inlet compressed air volume.  (You will notice some overlap of cold fraction in the 40-60% range.  Generally, our practice is to use “R” style generators down to 50% cold fraction.)

So, which one is better?

The answer depends on the target temperature needed in the application.  If the absolute coldest temperature is necessary, such as when trying to reach more of a cryogenic type of temperature on a small component or for a test, a “C” style generator may be the best choice.  But, if maximum cooling power is needed, the “R” style generator will prove to have an advantage.  It may seem counter-intuitive at first, but extremely low temperature air from a “C” style generator at less volume will produce less cooling effect than the moderately low temperature air at higher volume from an “R” style generator.

To illustrate this effect, let’s take a look at calculating BTU/hr. of a Vortex Tube.  This is done in the following steps:

  1. Determine inlet airflow to the Vortex Tube.
  2. Determine cold flow value at specified cold fraction.
  3. Use the cold fraction chart to determine temperature drop of incoming compressed air.
  4. Subtract temperature drop from the temperature of the incoming air.
  5. Determine the ΔT between the temperature of the air you are producing and the required temperature in the application.
  6. Place these values into the refrigeration formula shown below.

 

1.0746 x Cold Flow in SCFM (step 2 value) x ΔT in °F (step 5 value) = BTU/hr.

 

Now, using the process above, let’s compare a “C” style Vortex Tube and an “R” style Vortex Tube in terms of BTU/hr.  For this exercise we will compare a model 3425 “C” style Vortex Tube with a model 3225 “R” style Vortex Tube, using a supply pressure of 100 PSIG and a compressed air temperature of 70°F.

Calculations for model 3425 “C” style Vortex Tube

  1. Determine inlet airflow to the Vortex Tube.
    1. 25 SCFM
  2. Determine cold flow value at specified cold fraction.
    1. With a range of 0-60%, we will utilize a value of 40% for this comparison. This will yield a cold flow volume of 10 SCFM.
  3. Use the cold fraction chart to determine temperature drop of incoming compressed air.
  4. Subtract temperature drop from the temperature of the incoming air.
    1. At a supply pressure of 100 PSIG and 40% cold fraction, the temperature drop will be 110°F. With a compressed air temperature of 70°F we will have an outlet temperature of -40°F.
  5. Determine the ΔT between the temperature of the air you are producing and the required temperature in the application.
    1. An application using a “C” style generator will normally have a low target temperature, such as 0°F. This will yield a ΔT of 40°F.
  6. Place these values into the refrigeration formula shown below.

 

1.0746 x Cold Flow in SCFM (10 SCFM) x ΔT in °F (40°F) = 430 BTU/hr.

 

Calculations for model 3225 “R” style Vortex Tube

  1. Determine inlet airflow to the Vortex Tube.
    1. 25 SCFM
  2. Determine cold flow value at specified cold fraction.
    1. With a range of 50-100%, we will utilize a value of 70% for this comparison. This will yield a cold flow volume of 17.5 SCFM.
  3. Use the cold fraction chart to determine temperature drop of incoming compressed air.
  4. Subtract temperature drop from the temperature of the incoming air.
    1. At a supply pressure of 100 PSIG and 70% cold fraction, the temperature drop will be 71°F. With a compressed air temperature of 70°F we will have an outlet temperature of -1°F.
  5. Determine the ΔT between the temperature of the air you are producing and the required temperature in the application.
    1. For most applications using an “R” style generator we aim for a target temperature of 95°F. This will yield a ΔT of 96°F.
  6. Place these values into the refrigeration formula shown below.

 

1.0746 x Cold Flow in SCFM (17.5 SCFM) x ΔT in °F (96°F) = 1,805 BTU/hr.

 

In this comparison we have proven that although the “C” style Vortex Tube will produce a lower temperature airflow, it will not produce a greater cooling effect in an application.  Maximum cooling is achieved with the “R” style generator.  For this reason, 9 out of 10 applications utilize the “R” style 3200 series EXAIR Vortex Tube.  These units produce an extremely cold output air with high volume to effectively remove heat.  The “C” style units are also effective at removing heat, but are normally suited for applications aiming to achieve the lowest temperature airflow possible.

But, no matter the style of generator installed into the Vortex Tube, the cold air output is useful for industrial applications.  Whether the need is for spot cooling electronic components, grinding wheels, milling and drilling equipment, or laser cutting heads, we have a Vortex Tube solution.  If you have an application and would like to discuss an EXAIR Vortex Tube solution, contact our Application Engineers.  We’ll be happy to help.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

How Do I Estimate The Cost Of My Compressed Air?

Saving Money and Compressed Air

One of the best features of EXAIR products is the engineering behind the designs.  For example, our nozzles are designed to generate a maximum force possible per CFM of compressed air.  This means that the compressed air consumed by the device is at its maximum possible efficiency, which in turn reduces the compressed air demand in an application, reducing the cost of the solution.

But, how do you determine the cost of a compressed air driven product?

Step 1 – Quantify flow

The first step to determine compressed air cost is to quantify the flow rate of the product.  Most pneumatic equipment will have a spec sheet which you can reference to determine air consumption, but open pipe blowoffs and drilled holes won’t provide this type of information.  In those cases, or in any case where the compressed air flow is unknown or questionable, a compressed air flow meter can be used.  (We have Digital Flowmeters for use on compressed air piping, with or without data logging capability, and with serial or wireless communication.)

Step 2 – Calculate flow over time

Once the flow rate is known, it’s time to determine flow rates per day/week/month/year.  To do so, we will perform a bit of short and easy math.  What we will do, is use the known flow rate of the device, and multiply this by the total time in operation to determine daily, weekly, monthly, and annual usage rates.  For example:

A 1/8” open pipe blowoff will consume 70 SCFM.  In an 8 hour shift there are 480 minutes, resulting in a total consumption of 33,600 SCFM per 8 hour shift.

Step 3 – Determine cost

With a quantified flow rate, we can now determine the cost.  Many facilities will know the cost of their compressed air per CFM, but for those which don’t, a cost of ($0.25/1000 standard cubic feet) can be used.  This value is then multiplied by the total compressed air consumption from above, to give a quantified dollar amount to the compressed air driven device.

Using the flow rate from above:

If (1) shift is run per day, 5 days per week and 52 weeks per year, this open pipe blowoff will have an annual cost of $2,184.00.

Step 4 – Compare

At this point we know the real cost of the device.  The benefit to quantifying these flow rates, is when making a comparison to an alternative such as an engineered solution.  For example, if we were to replace the open pipe blowoff reference above with an EXAIR 1010SS 1/8” NPT nozzle, the compressed air demand would drop to 13 SCFM, yielding the following flow rates and costs:

If (1) shift is run per day, 5 days per week and 52 weeks per year, this open pipe blowoff will have an annual cost of $405.60.

Comparing these two solutions on an annual basis yields a difference of $1,778.40.  This means an air savings which correlates to $1,778.40 per year – just by replacing ONE open pipe blowoff with an engineered solution.  Replacing multiple open pipe blowoffs will yield repeat savings.

The 1010SS EXAIR Micro Air Nozzle

Determining the cost of a compressed air driven device can clarify the impact of a truly engineered solution.  If you have an interest in determining the cost of the compressed air devices in your facility, contact an EXAIR Application Engineer.  We’ll be happy to help.

 

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

EXAIR Cabinet Coolers, Solve Your Overheating Issues Today!

EXAIR NEMA 4X Cabinet Coolers

Industrial facilities incorporate a variety of processes and procedures to meet customer demands.  The ability to convert incoming resources into the desired output hinges upon proper up-time inside of the facility.  Whether producing raw materials, performing value-adding services, or manufacturing consumer goods, downtime and failed systems inside of an industrial facility mean lost throughput, lost profit, and increased cost.

As temperatures begin to rise across the US, heat related equipment failures become more prevalent.  Industrial facilities need a way to alleviate the problems caused by these increased temperatures and to mitigate the risk of failing electrical devices due to heat.

EXAIR Cabinet Coolers provide this solution using nothing but compressed air.

EXAIR Cabinet Coolers convert a source of compressed air into a very cold stream of air, capable of cooling a sealed enclosure.  They are mounted directly to the enclosure, feeding in air as low as 18°F (-8°C) to bring the internal temperature of the cabinet down to acceptable levels.  While the cold air generated by the Cabinet Cooler is fed into the enclosure, hot air is simultaneously removed, maintaining relative humidity inside the enclosure at 45%.

Rated for use in NEMA 12 (IP54), NEMA 4, and NEMA 4X (IP66) environments, EXAIR Cabinet Coolers are available in aluminum, 303 stainless steel, and 316 stainless steel.  No matter the material of construction, EXAIR Cabinet Coolers can provide 275 – 5,600 BTU/hr. of cooling capacity in industrial applications with ambient temperatures up to 125°F (52°C).  For hotter environments up to 200°F (93°C), High Temperature Cabinet Coolers are available.

In extremely dirty environments, Non-Hazardous Purge systems provide a continuous stream of air (1 CFM) into the enclosure, maintaining a positive pressure and preventing any dust intrusion.

Each system type and material are available to ship from stock*, allowing fast delivery to your facility and quickly solving an overheating condition of your devices.

Never do this! This setup forces dust and contaminants into the control panel, compromising the electrical components inside.

Fans and traditional air conditioners can effectively remove heat, but they provide no separation between the sensitive components inside of an enclosure and the dirty industrial environment outside.  Simply installing a fan or AC unit can allow dust, oil, and other ambient contaminants into the enclosure, leading the failure of the expensive equipment inside.  And, these solutions degrade over a finite lifespan (the Cabinet Cooler does not), they require routine maintenance (the Cabinet Cooler does not), and they need more time to install (Cabinet Cooler installation is fast and simple).  Curious how easy it is to install an EXAIR Cabinet Cooler?  Check out this video and see just how easy it really is.

For those applications without enough spacing to mount a Cabinet Cooler on top of the enclosure, Side Mount Kits are available.  These kits are also available from stock and are just as easy to install:

All EXAIR Cabinet Coolers are available with thermostat controls to regulate internal cabinet temperatures and compressed air consumption.  EXAIR thermostats feature a bimetallic contact strip to open and close the electrical circuit in response to air temperatures.  These thermostats quickly respond to changes in air temperature and are specifically suited for their intended use.  Preset for 95°F (35°C), a suitable temperature for most electronic devices, these thermostats are fully adjustable for specific application needs.

In the event a more sophisticated thermostat control is needed, Electronic Temperature Control units can be implemented.  These standalone units utilize a thermocouple to determine internal cabinet temperatures which display onto a digital readout.  Push-button controls on the digital readout board allow for easy modification of the internal cabinet temperature set-point.  When the desired internal temperature is reached, the Cabinet Cooler will turn off automatically.

Is it really that easy?  Can a Cabinet Cooler provide real cooling for sensitive devices and last for years without any maintenance?  Well, here’s an example:

(Click for larger view) The image on top shows year one of the Cabinet Cooler’s life, and the image on the bottom shows year six.

An automotive radiator manufacturer experienced a problem with an overheated motor drive, causing one of their production lines to come to a stop.  The root cause of the failure was a leaking refrigerant-based air conditioner, which failed and allowed water into the enclosure housing the motor controls.  When the water entered the enclosure, it shorted the motor drive and caused the production line stoppage. The new drive cost over $20,000 and a month of down time to purchase, receive, and install.

Following this failure, the customer searched for a more suitable cooling solution and installed an EXAIR model 4330 NEMA 12 2,000 BTU/hr. Cabinet Cooler System.  With an included thermostat control, this system provided proper cooling for the application without any need for required maintenance or potential to leak water into the enclosure.

Fast forward six years and this same customer reached out to EXAIR for another application.  During the conversation they mentioned the Cabinet Cooler they purchased many years before was still in operation, still providing proper cooling for the enclosure, and that no maintenance had been performed (Cabinet Coolers do not require routine maintenance).  Even in the dirty industrial environment of this manufacturing facility, the EXAIR Cabinet Cooler continued to function flawlessly.

When exploring industrial solutions, required routine maintenance is a common concern.  The cost of replacement components and time required to perform necessary maintenance weigh heavily on decision makers.  Fortunately, EXAIR Cabinet Coolers do not require any maintenance, and with clean, dry compressed air their lifespan can be 20 years or more.  There are no moving parts to wear out or routine maintenance services to be performed.

If you’re in need of a suitable cooling solution for an industrial enclosure, consider an EXAIR Cabinet Cooler.  They’re smaller than traditional AC units, faster to install, and require little-to-no-maintenance.  Feel free to contact an EXAIR Application Engineer with any questions, or fill out our online Cabinet Cooler Sizing Guide to have an Application Engineer contact you.

 

Lee Evans
Application Engineer

LeeEvans@EXAIR.com
@EXAIR_LE

*Orders received by 3pm Eastern time will ship same-day.

 

Moving Small Particles with a Heavy Duty Line Vac

The material in this hose is conveyed vertically over 7m using an EXAIR Heavy Duty Line Vac

The image above shows a test at a customer’s facility to move a small particulate to a height of 7m (23’) with an EXAIR Line Vac.  This particulate is used in the production of hand warmers and the end user needed a method to convey the material out of 55 gallon drums.

This same customer purchased a 2” Heavy Duty Line Vac from EXAIR in 2014 which is still in use and functioning well.  So, when it came time to find a pneumatic conveyance solution for this material, they knew where to go.

This is the material which needed to be pneumatically conveyed.

And, we knew just the questions to ask to determine the best Line Vac solution.  In order to do so, we had to determine the following:

  • Bulk density of the material
  • Size of the material
  • Conveyance height
  • Conveyance distance
  • Required conveyance rate
  • Available compressed air supply

Bulk density was rather low at 320kg/m³ (~20 pounds/ft³), with a particle size between 3-5mm (~1/8”-3/16”).  The conveyance height in this application was 5-7m (16.5-23ft.), with a distance of 1-2m (3.3-6.6ft) and a desired conveyance rate of over 4kg (8.8 pounds) per minute.

Testing with a 2″ Heavy Duty Line Vac

The customer ran a test with the 2” Line Vac they have on site and the results were excellent.  Their only question was whether they could achieve the needed conveyance with a smaller unit, thereby reducing compressed air consumption and operating cost of the application.

In this case the answer was clear that a smaller Line Vac could be used due to the low bulk density of the material.  By reducing the size of the Line Vac to 1”, or perhaps 1.5” we could reduce the compressed air consumption and still meet the required performance need.

EXAIR Line Vacs have, once again, brought a viable solution to this industrial facility.  If you have a similar application or would like to discuss pneumatic conveyance needs, contact an EXAIR Application Engineer.  We’ll be happy to help.

Lee Evans
Application Engineer

LeeEvans@EXAIR.com
@EXAIR_LE

Adding Atomized Water To A Starch Blending Application

Starch blending takes place at the top of this tower

The image above shows a material transfer process for starch.  At the top of the tower the starch rests inside of tumbling tanks (shown below) which blend larger pieces into small, finely blended particles.  In order to achieve the proper blend, an hydration level of 5% water must be maintained within the tank.  For the water introduced to the tank, the smaller the droplet size of the water particles, the better the blend.  The current setup in this application is to spray water directly into the tanks, by hand, using a pump sprayer.

These are the tanks at the top of the tower shown in the photo above

The investigation into droplet sizes led this customer to EXAIR Atomizing Nozzles, searching for a method to introduce small droplet water particles into the blending tanks.  The ultimate question was “How small of a particle size can we achieve with an EXAIR Atomizing Nozzle?”

The answer to that question can be found here on our website and in our catalog as well.  Our smallest confirmed droplet size is currently 22µm when using our 1/4″ NPT Siphon Fed Atomizing Nozzles, which was more than enough for this application.

Model SR1010SS EXAIR Atomizing Nozzle

By installing SR1010SS atomizing nozzles into this application this customer is able to achieve the required hydration level with small droplet size water particles.  These particles ensure proper blending of the starch and proper quality for the final product.  And, the atomizing nozzles prevent an operator from having to manually add the necessary water to achieve the required hydration in the blending tanks.

If you have a solution in need of an atomized liquid solution, contact an EXAIR Application Engineer.  We’re here to help.

 

Lee Evans
Application Engineer

LeeEvans@EXAIR.com
@EXAIR_LE

Line Vac Brings Additional Solution To Alumina Spill Recovery

Mobile spill recovery unit

In my last blog post I wrote about vacuuming alumina dust in an aluminum manufacturing plant in South America.  In that application we were returning spilled alumina to the original hopper so that processing could continue.

This same customer has an additional application to vacuum spilled material, but the new need is to assist mobile spill recovery vehicles (shown above) in vacuuming spills of varying volume. These mobile vehicles are effective for most of the spillage demands they can access, but there are times where additional vacuum is needed, such as when the spill location is beyond the hose length of the system.  In those scenarios additional vacuum hose can be added, but line losses render the performance too low to produce real results.  With this in mind, the end user looked for a point-of-use vacuum boosting solution, and thought about again using an EXAIR Line Vac.

Considering the potential use of a Line Vac, we approached this in the same way as any other pneumatic conveying application, gathering the required information to allow a proper model number selection.  As with the previous application we confirmed the following:

  •      Bulk density of the material
  •      Size of the material
  •      Conveyance height
  •      Conveyance distance
  •      Required conveyance rate
  •      Available compressed air supply

The spills in this facility are comprised of alumina dust with a bulk density of 1.1g/cm³ (68.7 pounds/ft³).  From the floor to the maximum height of the vehicle is a distance of 3.25m (~11ft), and conveying distances were in a range of 3-10 meters (10-30 feet).  The customer had no required conveyance rate, only a requirement to boost vacuuming capacity when needed.

With this information confirmed we were able to make a model number recommendation, the 2″ Heavy Duty Line Vac model 150200.  Adding the 150200 Heavy Duty Line Vac to this mobile spill recovery unit brings additional vacuum flow and conveyance of the alumina through a high velocity airstream, making mobile spill recovery efforts more effective.

If you’re in need of a pneumatic conveying solution, contact an EXAIR Application Engineer (1-800-903-9247).  We’ll be happy to help.

Lee Evans
Application Engineer
LeeEvans@EXAIR.com
@EXAIR_LE

83% Cyle Time Improvement with EXAIR Super Air Amplifiers

EXAIR Super Air Amplifier – an easy way to quickly move large air volumes

 

At a shipyard in Finland, our distributor found an application using blowers which needed a more viable solution.  The application was to dry the interior of large tanks after coating, and the original solution was to use a blower mounted to a 12” opening on top of the tank.  The airflow from the blower was forced into the tank in an effort to dry the coating but often ended up without any drying effect at all.

This problem was due to vapors (non-combustible vapors) produced by the coating process which are more dense than the ambient air, causing them to collect on the bottom of the tank.  The airflow produced by the blower was not sufficient to force these vapors from the tank, causing a long drying cycle for the coating process or no drying at all.

But, these same tanks feature a 3” diameter plug in the bottom of the tank to allow for draining if needed.  And, this opening is almost perfectly sized for a 2” EXAIR Super Air Amplifier model 120022.  (Model 120022 has an outer diameter of 2.95” at the side which provides incoming ambient air.)  By removing the plug in the bottom of the tank and installing a 2” Super Air Amplifier, this tank can be fully dried in a fraction of the time required for an electric blower setup.  The end user estimated an 83% reduction in drying times (from one hour per tank to ~10 minutes), and gained confidence that the tanks would be 100% dry and free of vapor when using the EXAIR solution.

One additional benefit of this Super Air Amplifier solution was increased reliability.  The electrical supply to this shipyard is unstable, resulting in blackouts and surges which shut down electric blowers.  But because the Air Amplifiers do not rely on electricity and sufficient storage capacity was available for compressed air, these units are unaffected by electrical supply problems.

If you have a similar application or would like to discuss a problem currently present in your production facilities, contact an EXAIR Application Engineer.  We’re here to help.

Lee Evans
Application Engineer

LeeEvans@EXAIR.com
@EXAIR_LE

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