Tag: balloon

Hot Air In The Aerospace Industry

Published on by Russ BowmanLeave a comment

Mankind’s adventures in aviation began with hot air, and it’s still kind of a big deal (for one particular EXAIR customer, that is) today.

How it started: In the 1780s, two French brothers, Joseph and Étienne Montgolfier, worked in their family’s paper mill. They noticed, along with everyone else, that pieces of paper were sometimes carried airborne in billows of smoke from the fires that heated the boilers. But unlike everyone else, they became curious as to why this happened…and how they might exploit this strange phenomenon to send something more substantial than some paper scraps through the air.

After a good deal of experimentation and trips “back to the drawing board” (they thought it was the smoke, not the heat, that caused the rise for a while), they began making public demonstrations of their first successful hot-air balloons in the summer of 1783. By autumn, having flown a sheep, a duck, and a rooster in a tethered balloon (to an altitude of about 1,500 feet on a flight that lasted about 8 minutes), they constructed a balloon large enough for two humans which flew successfully for almost half an hour, to a height of 3,000 feet. Early enthusiasts who came out to witness some of these flights included King Louis XVI, Queen Marie Antoinette, and American statesman (and quite the inventor himself) Benjamin Franklin.

The Montgolfier brothers decorated their balloons with the fleur-de-lis, zodiac symbols, and portraits of the King. I think it says a lot about ballooning that nowadays we have Sylvester the Cat, Tweety Bird, and even Spider-Pig.

How it’s going: I’m not going to lie; your level of fascination with the rest of this blog will depend on how fascinating you find the phenomenon of the Vortex Tube…which was, in fact, discovered by another French inventor, Georges Ranque:

The unique physical phenomenon of the Vortex Tube principle generates cold – and hot – air instantly, and for as long – or short – a time as needed.

Most Vortex Tube applications involve the use of the cold air flow, but a number of customers do indeed use the hot air flow. A material supplier to the aircraft & aerospace industry makes a flexible, porous strand of material that, after fabrication, passes through a wash tank prior to cutting to size. They wanted to speed up the drying time, but it was impractical to use electrically powered hot air blowers or heat guns. By using an EXAIR Model 3275 Large Vortex Tube set to a 70% Cold Fraction, they’re able to blow a little over 22 SCFM of 220°F air onto the strand, which effectively dries it to their specification, quickly & safely.

The EXAIR Vortex Tube. Cold air from one end; hot air from the other. Fully adjustable. You can use either…it’s fine with us; whatever you need.

Other EXAIR products that have been notably popular in the aerospace industry are engineered Air Nozzles, Static Eliminators, Air Amplifiers, and some even use Vortex Tubes & Spot Cooling Products for their COLD air flow. If you’d like to find out more about getting the most out of your compressed air system like the folks in the aerospace industry do, give me a call.

Russ Bowman, CCASS

Application Engineer
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Standard Temperature and Pressure: What is STP?

Published on by John BallLeave a comment

When it comes to volumetric flow rates, you probably noticed the prefix of an “S” for SCFM and SLPM, or an “N” for NM3/hr.  The “S” prefix is for Standard conditions, and the “N” prefix is for Normal conditions.  For practical reasons, they are the same thing.  What does this mean? 

Let’s look at the Ideal Gas Law in Equation 1:

Equation 1:

PV = nRT 

P – Pressure

V – Volume

n – No. of moles

R – Ideal Gas constant

T – temperature

Since air is compressible, it will react in different ways.  If we keep the volume the same and lower the temperature, the gas pressure will go down.  If we keep the temperature the same and decrease the volume, the gas pressure will go up.  If we go to a higher elevation, the number of moles is reduced, which will lower the gas pressure.  With the different degrees of changes, it is difficult to compare.  So, organizations decided to place a standard on these conditions to help compare results.  The definition is referred to as STP, or Standard Temperature and Pressure. 

In most cases, the Standard Temperature and Pressure is set at 20oC and 1 atm (1.013 bar).  If we transition all pneumatic units to this condition, we can then compare the results for each product.  We can determine which units actually use less compressed air or have higher forces.  Or if we decide to use a different STP, we can do that as well as long as we use the same temperature and pressure. 

I like to think of it like an air-filled balloon floating on top of the water.  This would be the “Standard” or “Normal” condition.  As you take the balloon into deeper water, more pressure is applied to the balloon, and the volume will decrease.  This is because air is compressible.  The balloon still has the same amount of air by weight (as the volume decreases, the density increases).  If you return to the surface, the balloon will expand back to the original size.  When doing comparisons, we need to be in the same condition, or for the balloon example, it will look like the balloon will need less air at lower depths than at the surface.   

The reason for this explanation is that some competitors like to use lower pressures to rate their products.  As an example, Competitor A rates their nozzles at 5 bar (72.5 psig).  EXAIR uses 5.5 bar (80 psig) for most of our products.  By comparison, we cannot say if one unit uses more or less compressed air unless we set them at the same conditions.  The best place to compare is at a Standard Temperature and Pressure, or STP.   I go into more detail in my blog about air flows with “CFM, ICFM, ACFM, SCFM: Volumetric Flow Rates Explained”.  EXAIR offers Super Air Knives, Super Air Nozzles, and Super Air Amplifiers to efficiently blow compressed air.  So, when a company states a compressed air flow, verify the pressure and temperature at which they recorded that information.  It will help you to be more in tune with what you are getting (allow for an apples to apples comparison). If you need any help in doing comparisons, an Application Engineer at EXAIR will be happy to assist you. 

John Ball
Application Engineer

Email: johnball@exair.com
Twitter: @EXAIR_jb

Photo:  balloon helium air flying bright by stux.  Pixabay license