Exorcising Maxwell’s Demon – Not Really

We all have our demons, and James Clerk Maxwell was no different. While he and I weren’t close, I have gotten to know one of his demons over the past 13 years. Okay, so in all seriousness, James Clerk Maxwell is a well-known Scottish Mathematician who throughout his life discovered a way to break the second law of thermodynamics and that became known as Maxwell’s Demon. So what exactly was his demon?

It was in 1867 when Maxwell wrote a letter and described his first encounter with the theory. In this letter, he wrote he spoke of a “finite being” that would control a massless door that separated two chambers of gas. This door would be opened and closed to permit a faster-moving molecule into the fast chamber, which also carried more heat, and then the slower-moving particles from the hot chamber into the slow chamber which was also cooling constantly. Because the velocity of a gas is dependent on the kinetic temperature of the molecule and its surrounding molecules. Since the demon was separating the hot and cold molecules it would permit one chamber to warm up while the other chamber cools down below ambient air conditions. This in turn decreases the total entropy of the system yet doesn’t do any work. Thus, violating the great second law of thermodynamics.

It wasn’t Maxwell that related this “finite being” to a demon, instead it was William Thomson, 1st Baron Kelvin who we associate absolute temperatures with in order to pay our respects of all his work. Lord Kelvin originally, published the thoughts in response to letters that Maxwell had written to other scholars. Kelvin did not mean for this to be a correlation with the malevolent being instead to be related to a daemon from Greek mythology which is a supernatural being who performs work behind the scenes. So why do we connect Maxwell’s demon to anything to do with an Intelligent Compressed Air Product?

In the spirit of Maxwell’s Demon, the separation of air molecules into a cold and hot air stream, without work being done can be directly related to a Vortex Tube. The Vortex Tube does exactly this, as an air stream enters the compressed air inlet, the air enters into the generator chamber where it is spun at very high speeds and sent down what is called the hot tube. As the air is spinning and traveling, it separates into a hot and cold air stream. The cold air is then sent down and out the cold end of the Vortex Tube while the hot air stream is exhausted out the hot end.

How a Vortex Tube Works

The percentage of cold air exit vs hot air exit is deemed the cold fraction and effects the temperature drop and rise for the respective stream of air. This gives us the ability to slightly control the demon, and thus we learn how to make this supernatural being work for us, and thus we never break the second law of thermodynamics, it’s actually this demon.

EXAIR Vortex Tube Performance Chart

In all seriousness, this thought experiment still continues to be a talk of physicists, mathematicians and scholars. They utilize Vortex Tubes in experiments to better understand how Maxwell came up with this thought and just how can they control this supernatural being.

If you would like to discuss how to utilize a Vortex Tube in your application or any of the EXAIR product lines, contact any Application Engineer today.

Brian Farno
Application Engineer

Finding WATTs in your electrical Panel

Picture by Isauvage – Licensed by Pixabay

In 1938 Abbot and Costello first performed their legendary routine of “Who’s on First”. If you haven’t heard this before I only have two things to say to you – 1) I’m sorry and 2) go listen to this. This is one of the funniest routines in comedic history, and you should listen to it at least once a decade. The craziest thing about this is that in 2007 there was a MLB player from the Los Angeles Dodgers that got his first MLB hit and was standing on first base. After 69 years, Abbot and Costello’s famous act came true and Hu was on first. Chin-Lung Hu that is. It was destined to happen one day, but now we have to focus on Watts on second? That’s right— Watts on second.

Photo by 2427999 and licensed by Pixabay

When we size your electrical cabinet, we ask for a current internal temperature of the cabinet. This is critical to us being able to make this calculation. You would think this is an easy request, but surprisingly we get pushback to get this number. The best way to get this number is to simply put a thermometer in the cabinet, let it sit for a few minutes and let us know the temp. The pushback is surprising as this is the most important number to know, as this is the temperature that we are cooling. If I had a nickel for every time I am asked to just guess at a number here, I wouldn’t be rich, but I could buy a soda each month. This temperature is critical for us to know, because it tells us how much cooling is needed to overtake that heat to make your cabinet safe. But, I do understand that there are times when this is not possible. And of course there are new installations where there is not a cabinet there yet… So what do we do next or “second”… You guessed it, Watts on second.

In these instances we need to find the total watts that will be used in this electrical cabinet. How do we find this? In a perfect world there should be a list of every electrical component that is on that cabinet. Each of those components should have paperwork, and or labels on them that state the total watts used. When we have this information it is as easy as adding these watts up (not much, watts up with you?)…. Sorry, that’s the dad in me.

Photo by Momentmal, licensed by pixaby

There are times when we don’t have the data, the label was destroyed etc. So how do we find the watts? Well now we have to digress back to math. Thankfully this is not a math that we have to Google to find a refresher course to remember how to do. We just have to remember the formula. Watt = AMP x VOLT x Efficiency rating (@95%). It really is that easy. As an example, if the current is 4 amps (4A) and the Voltage is 110V, you will multiply 4×110= 440W. This is why watts are sometimes called volt-amps. Next, we take into account a 95% efficiency rate for the electronics – meaning that 95% of the energy is used, and the 5% remaining is the heat that component gives off. This example will give us 440W x 5% = 22 total Watts for this component. We do this for each component and then add them all together for total watts. Volts and amps can be found in most operating manuals, and 99% of the time you can look up common amps and volts on Mr Google.

Once we have the total Watts of the cabinet cooler components, we simply multiply that by the 3.41 conversion rate to give us the BTU/HR needed for the internal heat load.

With this information we can finalize the calculations for the Cabinet Cooler by calculating the outside heat transfer. This is pretty easy, as we simply find the temp difference between the max external temp and the max desired internal temp. We take that temp difference and match it to this top secret table (right). We then multiply the BTU/HR by the square footage of the cabinet to find the external heat load.

SPOILER ALERT: To find the total heat load for your enclosure you add the internal and external heat loads together, and botta being, botta boom, Bob’s your uncle.

There are times when the sizing gets complicated with large heat loads. Please do not hesitate to reach out and talk to myself, or one of the other application engineers for this, or any other product.

Thank you for stopping by,

Brian Wages

Application Engineer

Visit us on the Web
Follow me on Twitter

Cover photo by JayMantri , Spoiler photo by emkanicepic, both sponsored by Pixabay

Single Acting Reciprocating Air Compressor

With all the options when it comes to air compressors, I wanted to take a deeper diver into Single acting Reciprocating compressors and see why they are so popular across all industry.

First, What is a Single acting Reciprocating air compressor, and how does it work? A single-acting compressor is a type of air compressor that uses only one end of the piston for the suction and compression. So the first stroke of the piston sucks the air inside the compressor while the air compression occurs in the second stroke.

To explore the internals a bit closer, a mechanical linkage, or connecting rod, is attached to a piston and a crankshaft.  For every rotation of a motor, the piston will move up and down.  Air is being drawn into the cylinder and then compressed.  The volume of the cylinders, the number of cylinders, and the rotations per minute will determine the amount of compressed air that can be produced.  The advantages with reciprocating compressors are that they can produce high pressure, compress different types of gases, and have a cheap and rugged design.  The disadvantages would be high vibration and noise levels as well as being oversize as compared to capacity.  (See the photo below)

Piston goes down: air draws in. Piston goes up: air is pushed out.

Let’s expand on the advantages and disadvantages a bit to see if that explains the heavy use of this style air compressor!


  • Cost! Single acting Reciprocating air compressors just cost less than other styles of air compressors!
  • They are typically easy to maintain.
  • They work great for medium duty applications
  • They require less traveling of the compressed air.


  • The piston only works in one direction at a time
  • The piston spring takes up space limiting the cylinders working stroke.
  • They are less efficient than centrifugal type compressors

No matter the type of air compressor that you use, they are very expensive to use.  Air compressors are considered to be the fourth utility within a manufacturing plant.  To help use it efficiently and safely, EXAIR offers a range of products to clean, cool, blow, clean, conserve, and convey.  This would include our Super Air Knives, Super Air Nozzles, Safety Air Guns, Cabinet Coolers, and much more.  If you want to save energy, increase safety, and cut overhead costs, you can contact an Application Engineer at EXAIR.  We will be happy to help. 

Jordan Shouse
Application Engineer

Send me an Email
Find us on the Web 
Like us on Facebook
Twitter: @EXAIR_JS

Compressor internals image courtesy of h080Creative Commons License.

EXAIR Super Air Knife Helps Bakery Protect Sheet Pan Coating

A bakery had a process where they cleaned baking sheets after they made cakes, breads, and donuts.  The system consisted of scraping the pans with brushes prior to running them through a washing system.   The excess crust material had to be removed as it could cause problems with the washing machine.  The baking sheets had a non-stick coating to help in the baking process.  The issue that they were having was that the brushes would start to remove the non-stick coating over time, causing the pans to rust.  If you needed more iron in your diet, this would not be the proper way.  The baking sheet was 18” (457mm) wide by 36” (914mm) long.  They contacted EXAIR to see if we had a better way to clean these sheets without damaging the coating. 

EXAIR has been supplying powerful non-contact ways to clean, dry, and cool products.  For this application, I recommend the model 110218SS Super Air Knife Kit.    The kit includes an 18” (457 mm) 303SS Super Air Knife, a filter, a regulator, and a shim set.  The stainless-steel construction would protect against the harsh detergents that are used in the process.  If additional protection is required, EXAIR also provides 316SS material.  The unique feature of the Super Air Knife is that it entrains ambient air at a rate of 40:1 to deliver a hard-hitting force with a small amount of compressed air.  In addition, the filter would capture any contamination from the compressed air line to keep the surface clean.  The regulator and shim set would be used to control the amount of force required to remove the debris. 

The Super Air Knife was placed just before the washing system to remove the baked contamination.  The brush system was removed.  As a bonus, they realized that they did not need to replace the brushes quarterly, which added replacement costs and maintenance time.  Sometimes these savings are overlooked.  The setup was really easy, as they only had to run compressed air to the Super Air Knife and mount anywhere from 3” (76mm) to 12” (305mm) from the sheet instead of having to periodically adjust the brushes due to the bristles shortening.

After the installation, they were amazed at the power of the Super Air Knife.  And with the non-contact cleaning, the non-stick surface was able to last much longer without having to replace the pans.  Currently, the baking sheets are lasting twice as long as they were before they started using our product.  If you have an application, where you would like to protect the surface, EXAIR has a variety of products that can create a non-contact way to clean, dry, and cool.  An Application Engineer can assist you. This customer above could now have their cake and eat it, too.

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb