Fluidics, Boundary Layers, And Engineered Compressed Air Products

Fluidics is an interesting discipline of physics.  Air, in particular, can be made to behave quite peculiarly by flowing it across a solid surface.  Consider the EXAIR Standard and Full Flow Air Knives:

Compressed air flows through the inlet (1) to the Full Flow (left) or Standard (right) Air Knife, into the internal plenum. It then discharges through a thin gap (2), adhering to the Coanda profile (3) which directs it down the face of the Air Knife. The precision engineered & finished surfaces serve to optimize the entrainment of air (4) from the surrounding environment.

If you’ve ever used a leaf blower, or rolled down the car window while traveling at highway speed, you’re familiar with the power of a high velocity air flow.  Now consider that the Coanda effect can cause such a drastic redirection of this kind of air flow, and that’s a prime example of just how interesting the science of fluidics can be.

EXAIR Air Amplifiers, Air Wipes, and Super Air Nozzles also employ the Coanda effect to entrain air, and the Super Air Knife employs similar precision engineered surfaces to optimize entrainment, resulting in a 40:1 amplification ratio:

EXAIR Intelligent Compressed Air Products such as (left to right) the Air Wipe, Super Air Knife, Super Air Nozzle, and Air Amplifier are engineered to entrain enormous amounts of air from the surrounding environment.

As fascinating as all that is, the entrainment of air that these products employ contributes to another principle of fluidics: the creation of a boundary layer.  In addition to the Coanda effect causing the fluid to follow the path of the surface it’s flowing past, the flow is also affected in direct proportion to its velocity, and inversely by its viscosity, in the formation of a boundary layer.

High velocity, low viscosity fluids (like air) are prone to develop a more laminar boundary layer, as depicted on the left.

This laminar, lower velocity boundary layer travels with the primary air stream as it discharges from the EXAIR products shown above.  In addition to amplifying the total developed flow, it also serves to attenuate the sound level of the higher velocity primary air stream.  This makes EXAIR Intelligent Compressed Air Products not only as efficient as possible in regard to their use of compressed air, but as quiet as possible as well.

If you’d like to find out more about how the science behind our products can improve your air consumption, give me a call.

The Case Is Mounting For Stay Set Hoses

So, you’ve selected a quiet, efficient, and safe EXAIR Super Air Nozzle for your blow off application – good call! – and now you’re thinking about how to install it.  Sometimes, it’s as simple as replacing whatever you’re using right now:

EXAIR Intelligent Compressed Air Products have common NPT (or BSP) connections, making for easy replacement of most any existing threaded device.

Or maybe you’re using an open end blow off…in which case, you’re just an adapter away:

EXAIR Super Air Nozzles are quick and easy to install on existing copper tube, via a simple compression fitting.

Perhaps, though, it’s a new installation, or the existing supply lines aren’t suitable for one reason or another.  In those cases, we’ve still got you covered…consider the EXAIR Stay Set Hose:

Precise aiming and location is a breeze with EXAIR Stay Set Hoses.

Available in a variety of lengths from 6″ to 36″, they’re positionable, and re-positionable with a simple bending action.  They won’t kink or easily fatigue like copper tubing.  The supply end is 1/4  MNPT, and you have your choice of 1/4 MNPT or 1/8 FNPT on the other end, depending on which Super Air Nozzle, Air Jet you need to use it with.

We also offer Blow Off Systems, which are a combination of a specific Air Nozzle (or Air Jet,) fitted to a Stay Set Hose:

Model 1126-9262, for example, is a Model 1126 1″ Flat Super Air Nozzle with a 9262 Stay Set Hose.

For added convenience and ease of installation, these products can also come with a Magnetic Base:

Mag Bases come with one or two outlets. Stay Set Hoses come in lengths from 6″ to 36″.

Stay Set Hoses are also available with a variety of our Soft Grip Safety Air Guns, and they make the GEN4 Stay Set Ion Air Jet one of our most popular Static Eliminator products.  They’ve even been successfully applied with small Air Amplifiers and Air Knives…with certain limitations (spoiler alert: trying this with a 108″ Super Air Knife is going to be a definite “no.”)

Model 110003 3″ Aluminum Super Air Knife with 6″ Stay Set Hose & Magnetic Base.

From the beginning in 1983, EXAIR’s focus has been on being easy to do business with, and that goes from our friendly customer service to our expert technical support to our 99.9% on-time shipments (22 years and running) to designing our engineered products and value-added accessories with efficiency, safety, and ease of installation in mind.  If you want to find out more, give me a call.

A Tale of Two Super Ion Air Knives

A manufacturer of plastic bottles had a problem with static charge. Right after the bottles are extruded and cooled, they have an apparatus that “unscrambles” them and places them, single file, onto a conveyor. It does so with some fabric belts and plastic rollers. If you know anything of static electricity, dear reader, you probably recognize that there aren’t too many better ways to generate a static charge than to rub plastic against plastic, or (even worse) plastic & fabric together.  Here’s a prime example of the kind of static charge you can get, just from unrolling plastic film.

The separation of the non-conductive surfaces (like when this plastic film is unrolled) is capable of generating an incredible amount of static charge.

Now, the bottle makers didn’t have a static meter, but they didn’t need one to know they had issues:  the bottles that the “unscrambler” was putting on the belt were still very much “scrambled.”  They installed a Model 112209 9″ GEN4 Super Ion Air Knife Kit, to blow ionized air up from under the bottles as they entered the belt conveyor, and they did see what they’d call an improvement, but not quite what they’d call a solution.

Unfortunately, dissipating the static from just about half of the surface area of the bottle was still leaving them with half a problem.  However, by adding a Model 112009 9″ GEN4 Super Ion Air Knife (the 112209 Kit’s Power Supply has two outlets, and its Filter Separator & Pressure Regulator are capable of handling the flow to two 9″ Air Knives,) they were able to blow ionized air down from the other side, and up from where the first one was installed.  A soft “breeze” was all it took…a stronger air flow would have worked against the “unscrambler” anyway…because even at very low supply pressures, the Super Ion Air Knives produce an extremely fast static dissipation rate.

Even with a 5psig supply…which makes for just a “whisper” of air flow, the EXAIR GEN4 Super Ion Air Knife eliminates a 5kV charge in under half a second.

If you’ve got problems with static charge, we’ve not only got improvements; we’ve got solutions. Give me a call to find out how we can help.

Liquid Handling With Compressed Air: An Overview

There are some very good reasons to consider an EXAIR compressed air operated Industrial Housekeeping Product for liquid applications:

*Durability. No moving parts means nothing to wear or get damaged.
*Safety. No electricity means no dragging an energized cord through a wet area.
*Convenience. All you need is a supply of compressed air.
*Reliability. If you supply it with clean, dry air, it’ll run darn near indefinitely, maintenance free.

Depending on the needs of the application, we have different models to choose from:

Reversible Drum Vacs

If you’ve got a closed top steel drum that’s in good condition, look no further than the Reversible Drum Vac System.  It comes with everything you need to turn that drum into a powerful, 2-way liquid pumping system.  This is great if you just need to park the drum in one spot and suction out a sump or tank on a regular basis, using its 10 foot Vacuum Hose & Suction Wand.  They’re in stock for your existing 30, 55, and 110 gallon drums.  A 5 Gallon Mini Reversible Drum Vac System is also available; it includes the drum as well.

Reversible Drum Vac Systems come in sizes from 5 to 110 gallons.

If you’d like a little mobility, and a way to clean up floor spills, then the Deluxe Reversible Drum Vac System might be what you’re looking for.  It adds a Drum Dolly and our Spill Recovery Kit…it consists of a floor-length wand and a dual squeegee tool.  It also comes with a set of plastic tools (crevice tool, small skimmer, and two 20″ extensions) and a Tool Holder with clips for the tools, and magnets to attach to the drum.  We keep them in stock for your existing 30 and 55 gallon drums.  It also comes in the 5 Gallon Deluxe Mini Reversible Drum Vac System (drum included.)

 

Deluxe Systems add a Spill Recovery Kit, and a Dolly for your drum.

For a complete system, the Premium Reversible Drum Vac Systems have everything you need for most any liquid drum transfer job: they add a drum, lid & latch ring, as well as a compressed air supply hose & shutoff valve, and an upgrade to Heavy Duty Aluminum Tools.  They’re available with 30, 55, or 110 gallon drums; in stock.

Premium Reversible Drum Vac Systems come with everything you need, right out of the box.

Any of the 30, 55, or 110 Gallon systems are also available with our High Lift Reversible Drum Vac.  These provide for increased performance with more viscous liquids, and/or when the liquid needs to pumped from a depth of up to 15 feet.  They are outfitted identically to the standard Reversible Drum Vac Systems, except they come with a 20 foot Vacuum Hose.

The High Lift Reversible Drum Vac System converts a drum and dolly into a mobile pumping system.

As versatile as the Reversible Drum Vacs are, we also incorporate them into another 2-way pumping system, designed to help you get maximum life and performance from machine tool coolant and cutting oils:  The award-winning Chip Trapper Systems.

The vacuum hose (1) is attached to the barbed connection of the Chip Trapper (2). The directional flow control valve on the top of the drum (3) and knob on the pump (4) are set to the “fill” position. The air supply valve is opened to permit compressed air at 80-100 psig (5.5-6.9 BAR) to flow through the pump which pulls the liquid through the hose, then into the reusable filter bag (5). When all liquid is in the drum, the air supply is turned off. The filtered liquid can then be pumped out by setting the directional flow control valve on top of the drum and the knob on the pump to the “empty” position. Once the air supply valve is opened, the air pushes the liquid back through the hose while all solids remain in the reusable filter bag.

Powered by the Reversible Drum Vac, the Chip Trapper System draws the incoming liquid into the drum through a Filter Bag, which retains (or “traps”) any particulate as the drum fills with liquid.  Then, the freshly filtered liquid can be immediately pumped back out, while the particulate remains in the bag.  Once the bag is full, simply remove the drum lid, unhook the bag, empty it out, and return it to service.  The Chip Trapper System comes with two Filter Bags, in fact, so you can clean one while you use the other.  They are available, from stock, in 30, 55, and 110 gallon sizes.  They are all three available in High Lift configuration as well, with a 20 foot Vacuum Hose.

If you’d like to find out more about safe, reliable and effective liquid handling with EXAIR’s compressed air operated Industrial Housekeeping Productsgive me a call.

Russ Bowman
Application Engineer
Find us on the Web 
Follow me on Twitter 
Like us on Facebook

How To Make Compressed Air Get Cold…A Couple Of Different Ways

The Vortex Tube makes cold air for the same reason that a can of compressed air gets cold when I clean my computer keyboard, right?

That’s a common question, and since they both start with compress air and end up with cold(er) air, it’s not an unreasonable assumption.  But the answer is no; they’re not the same.   Both are curious physical phenomena, though:

Cans of compressed air get cold while they’re discharging because of a thermodynamic principle known as the adiabatic effect.  When you pressurize a gas by compressing it into a container, you’re putting all those molecules into a smaller volume of space…and you’re adding potential energy by the compression.  Then, when you release that gas back to atmospheric pressure, that energy has to go somewhere…so it’s given off in the form of heat – from the air inside the can, as the pressure inside the can decreases.  Now, the air that’s not under as much pressure as it was when you pushed the button on top of the can is going to start coming out of the can pretty soon.  I mean, there’s only so much air in there, right?  So, since it’s given off that energy immediately upon the drop in pressure, when it comes out of the can, it’s at a lower temperature than it was before you started spraying it out.

Vortex Tubes, on the other hand, generate a flow of cold air by a completely different phenomenon of physics called, maybe not so curiously, the Vortex Tube principle:

You can get a lot more cold air – and a much lower temperature – from a Vortex Tube than you can from a can of compressed air.

If you need a reliable and dependable flow of cold air, look no further than EXAIR’s comprehensive line of Vortex Tubes and Spot Cooling Equipment.  We’ve got 24 models of Vortex Tubes to choose from, as well as “out of the box” solutions for cooling applications like the Adjustable Spot Cooler, Mini CoolerCold Gun Aircoolant Systems. and, to protect your sensitive electrical and electronic enclosures from heat, Cabinet Cooler Systems.  If you’d like to find out more, give me a call.

Russ Bowman

Application Engineer
Find us on the Web 
Follow me on Twitter 
Like us on Facebook

 

Sound Power Level and Sound Pressure

Energy…all day (and night) long, we humans are surrounded by – and bombarded by – all kinds of energy. Sometimes, the effects are pleasant; even beneficial: the warmth of the sun’s rays (solar energy) on a nice spring day is the sure-fire cure for Seasonal Affective Disorder, and is also the catalyst your body needs to produce vitamin D. Good things, both. And great reasons to get outside a little more often.

Sometimes, the effects aren’t so pleasant, and they can even be harmful. Lengthy, unprotected exposure to that same wonderful sun’s rays will give you a nasty sunburn. Which can lead to skin cancer. Not good things, either. And great reasons to regularly apply sunblock, and/or limit exposure if you can.

Sound is another constant source of energy that we’re exposed to, and one we can’t simply escape by going inside. Especially if “inside” is a factory, machine shop, or a concert arena. This brings me to the first point of today’s blog: sound power.

Strictly speaking, power is energy per unit time, and can be applied to energy generation (like how much HP an engine generates as it runs) or energy consumption (like how much HP a motor uses as it turns its shaft) For discussions of sound, though, sound power level is applied to the generation end. This is what we mean when we talk about how much sound is made by a punch press, a machine tool, or a rock band’s sound system.

Sound pressure, in contrast, is a measure of the sound power’s intensity at the target’s (e.g., your ear’s) distance from the source. The farther away you get from the sound’s generation, the lower the sound pressure will be. But the sound power didn’t change.

Just like the power made by an engine and used by a motor are both defined in the same units – usually horsepower or watts – sound power level (e.g. generation) and sound pressure (e.g. “use” by your ears) use the same unit of measure: the decibel.  The big difference, though, is that while power levels of machinery in motion are linear in scale, sound power level and pressure scales are logarithmic.  And that’s where the math can get kind of challenging.  But if you’re up for it, let’s look at how you calculate sound power level:

Sound Power Level Equation

Where:

Wis reference power (in Watts,) normally considered to be 10-12 W, which is the lowest sound perceptible to the human ear under ideal conditions, and

W is the published sound power of the device (in Watts.)

That’s going to give you the sound power level, in decibels, being generated by the sound source.  To calculate the sound pressure level:

Sound Power Level to Sound Pressure Equation

Where:

Lis the sound power level…see above, and

A is the surface area at a given distance.  If the sound is emitted equally in all directions, we can use the formula for hemispheric area, 2πrwhere r=distance from source to calculate the area.

These formulas ignore any effects from the acoustic qualities of the space in which the sound is occurring.  Many factors will affect this, such as how much sound energy the walls and ceiling will absorb or reflect.  This is determined by the material(s) of construction, the height of the ceiling, etc.

These formulas may help you get a “big picture” idea of the sound levels you might expect in applications where the input data is available.  Aside from that, they certainly put into perspective the importance of hearing protection when an analysis reveals higher levels.  OSHA puts the following limits on personnel exposure to certain noise levels:

Working in areas that exceed these levels will require hearing protection.

EXAIR’s line of Intelligent Compressed Air Products are engineered, designed, and manufactured with efficiency, safety, and noise reduction in mind.  If you’d like to talk about how we can help protect you and your folks’ hearing, call us.

 

Six Steps To Optimizing Your Compressed Air System – Step 1: Measure

“To measure is to know – if you cannot measure it, you cannot improve it.”
-Lord Kelvin, mathematical physicist, engineer,and pioneer in the field of thermodynamics.

This is true of most anything. If you want to lose weight, you’re going to need a good scale. If you want to improve your time in the 100 yard dash, you’re going to need a good stopwatch. And if you want to decrease compressed air consumption, you’ll need a good flowmeter. In fact, this is the first of six steps that we can use to help you optimize your compressed air system.

Six Steps To Optimizing Your Compressed Air System

There are various methods of measuring fluid flow, but the most popular for compressed air is thermal mass air flow.  This has the distinct advantage of accurate and instantaneous measurement of MASS flow rate…which is important, because measuring VOLUMETRIC flow rate would need to be corrected for pressure in order to determine the true compressed air consumption.  My colleague John Ball explains this in detail in a most excellent blog on Actual (volume) Vs. Standard (mass) Flows.

So, now we know how to measure the mass flow rate.  Now, what do we do with it?  Well, as in the weight loss and sprint time improvements mentioned earlier, you have to know what kind of shape you’re in right now to know how far you are from where you want to be.  Stepping on a scale, timing your run, or measuring your plant’s air flow right now is your “before” data, which represents Step One.  The next Five Steps are how you get to where you want to be (for compressed air optimization, that is – there may be a different amount of steps towards your fitness/athletic goals.)  So, compressed air-wise, EXAIR offers the following solutions for Step One:

Digital Flowmeter with wireless capability.  This is our latest offering, and it doesn’t get any simpler than this.  Imagine having a flowmeter installed in your compressed air system, and having its readings continually supplied to your computer.  You can record, analyze, manipulate, and share the data with ease.

Monitor your compressed air flow wirelessly over a ZigBee mesh network.

Digital Flowmeter with USB Data Logger.  We’ve been offering these, with great success, for almost seven years now.  The Data Logger plugs into the Digital Flowmeter and, depending on how you set it up, records the flow rate from once a second (for about nine hours of data) up to once every 12 hours (for over two years worth.)  Pull it from your Digital Flowmeter whenever you want to download the data to your computer, where you can view & save it in the software we supply, or export it directly into Microsoft Excel.

From the Digital Flowmeter, to your computer, to your screen, the USB Data Logger shows how much air you’re using…and when you’re using it!

Summing Remote Display.  This connects directly to the Digital Flowmeter and can be installed up to 50 feet away.  At the push of a button, you can change the reading from actual current air consumption to usage for the last 24 hours, or total cumulative usage.  It’s powered directly from the Digital Flowmeter, so you don’t even need an electrical outlet nearby.

Monitor compressed air consumption from a convenient location, as well as last 24 hours usage and cumulative usage.

Digital Flowmeter.  As a stand-alone product, it’ll show you actual current air consumption, and the display can also be manipulated to show daily or cumulative usage. It has milliamp & pulse outputs, as well as a Serial Communication option, if you can work with any of those to get your data where you want it.

With any of the above options, or stand-alone, EXAIR’s Digital Flowmeter is your best option for Step One to optimize your compressed air system.

Stay tuned for more information on the other five steps.  If you just can’t wait, though, you can always give me a call.  I can talk about compressed air efficiency all day long, and sometimes, I do!