Methods Of Heat Transfer

“Nothing happens until something moves.”
-Albert Einstein

These five words are the foundation on which the science of physics is built upon. This statement not only applies to the things we can see, but to those we can’t…like heat transfer.

OK; technically, we CAN visually observe the EFFECTS of heat transfer…that’s called “reading a thermometer.” But the actual mechanism of heat transfer takes place at a molecular level, and concerns the rate of motion of those molecules: the higher the rate of molecular motion, the higher the heat of the material. Hence, the higher the rate of CHANGE of that molecular motion, the higher the heat transfer rate is.

All you need for heat transfer to occur is a difference in temperature between two materials. Contact, or even proximity, helps…but not always. More on that in a minute. And keeping at least one of the materials in motion can help maintain the temperature differential. We’ll unpack that a little more too.

Let’s start with the three ways that heat is transferred…what they are, and how they work:

Conduction

What it is: The transfer of heat between materials that are in physical contact with each other.

How it works: If you’ve ever touched a hot burner on a stove, you’ve successfully participated in the process of conduction heat transfer.

Convection

What it is: The transfer of heat through a fluid medium, enhanced by the motion of the fluid.

How it works: If you’ve ever boiled water in a pan on a hot stove burner, you’ve successfully participated, again, in the process of conduction heat transfer (as the burner heats the pan) AND convection (as the heated water in the bottom of the pan both transfers heat through its volume, and moves to the surface.)

Radiation

What it is: Remember what I said earlier about how you don’t always need contact or proximity for heat transfer? Well, this is it…the transfer of heat through empty space, via electromagnetic waves.

How it works: If you didn’t actually TOUCH the hot stove burner, but felt your hand getting hot as it hovered, then you’ve successfully participated in the process of radiation heat transfer. OK; it’s a little convection too, since the air between the burner and your hand was also transferring some of that heat. The best example of STRICTLY radiation heat transfer I can think of is the sun’s rays…they literally pass through 93 million miles of empty space, and make it quite warm on a nice sunny day here on Earth.

Regardless of how material, or an object, or a system receives heat, engineered compressed air products can be used to efficiently and effectively remove that heat.  For the record, they employ the principles of both conduction and convection.  If you’d like to discuss a heat transfer application, and the way(s) that an EXAIR product can work in it, give me a call.

Russ Bowman
Application Engineer
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What’s So “Super” About The Super Air Amplifier?

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 free air from the surrounding environment.

“Free air” from the surrounding environment?  You might think it’s too good to be true, and if you think you’re getting something for nothing, you’re right.  If you consider, though, that it’s oftentimes preferable to work smarter, not harder, then the use of engineered compressed air products is too good NOT to be true.  Case in point: the Super Air Amplifier.

The Coanda Effect is the “work smarter, not harder” part of the Super Air Amplifier

Simple and low cost, (hey, “engineered” doesn’t necessarily mean “complex and expensive”) the EXAIR Super Air Amplifier uses a small amount of compressed air to generate a tremendous amount of air flow through entrainment.  How much do they pull in?  Depending on the model, they entrain air at rates of 12:1 (for the 3/4″ Model 120020) to 25:1 (4″ & 8″ Models 120024 & 120028, respectively.)  The larger diameters mean there’s more cross sectional area to entrain air, so there is indeed efficiency to scale, size-wise.  There are a couple of great visuals in this video, if you want to see the entrainment in action (1:50) or the difference that the entrainment makes (1:30):

 

Where can you use a Super Air Amplifier?  The easy answer is, anyplace you want a consistent, reliable air flow.  The pressure supply can be regulated from a “blast to a breeze,” depending on the needs of your application.  The patented shim can be replaced for even higher performance, while maintaining the efficiency that makes it so valuable.  The balanced flow makes for incredibly quiet operation…no more noisy fans, blowers, or open-end compressed air pipes.  The body (3/4″ to 4″ sizes) is cast with a 2-hole flange for ease of installation.

When can you use a Super Air Amplifier?  Another easy answer: anytime you want.  If you need a continuous air flow, there are no moving parts to wear or electrical components to burn out.  Supply them clean, dry air, and they’ll run darn near indefinitely, maintenance free.

Alternately, if you need intermittent air flow, starting & stopping operation is as simple as opening & closing a valve in the compressed air supply line.  They produce rated flow immediately, and cut it off just as fast.

Some of the more popular applications are ventilation/exhaust, cooling, drying, cleaning, and dust collection.  There are five distinct models to choose from, and they’re all in stock.  We’re also happy to discuss special requirements that might lead to a custom product too.  Our Application Engineers work with Design & Production all the time to meet specific needs of particular situations.

If you’d like to find out more about letting the Super Air Amplifier, or any of EXAIR’s Intelligent Compressed Air Products work smarter for you, give me a call.

Russ Bowman
Application Engineer
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Crescent Hammers, Phillips Head Punches, and Other Cautionary Tales

I don’t want to sound “preachy,” but I’m a stickler for using the right tool for the job. Case in point: just the other day, I noticed (OK; my wife told me about) a loose drawer handle. I went to my toolbox in the garage to get a flat-head screwdriver, even though the drawer in question had a selection of butter knives, any one of which could have been used to tighten that screw.

I can trace this, without doubt or hesitation, to my service in the US Navy, under the direction of Senior Chief Cooper.  Proper tool selection & use was VERY important to him.  He stressed the issues of safety, quality, and performance, but if that didn’t work, he’d make his point with an offer to demonstrate the use of a specific tool (a ball peen hammer) on a sensitive part of your anatomy (it’s exactly the part you’re thinking of.)  At that point, it would have been unwise (and unsafe) to question whether that was a proper use of the tool or not.

Only one of these is a hammer………………..….only one of these is a punch………………..…..only one of these is a chisel.
Choose wisely.

Likewise, there are safety, quality, and performance issues associated with compressed air blow offs.  At EXAIR, we’re ALL sticklers about this, and we get calls all the time to discuss ways to get more out of compressed air systems by using the right products.  Here’s a “textbook” example:

A hose manufacturer contacted me to find out more about our Air Wipes, and how they might be a better fit for their various cleaning & drying applications (spoiler alert: they are.)  The blow offs they were using were made of modular hose, designed (and very successfully used) for coolant spraying in machine tools.

Only one of these is a compressed air blow off. Again…choose wisely.

The selection process was two-fold: they purchased one Model 2401 1″ Super Air Wipe to verify performance, and they sent in some of their modular hose assemblies for Efficiency Lab testing.  The first part was just as important as the second because, no matter how much air they were going to save (another spoiler alert: it was significant,) it wouldn’t matter if it didn’t get the job done.  At the station shown above, the Super Air Wipe resulted in superior performance, and a compressed air cost savings of over $400.00 annually.  For that one station.  Based on that, they outfitted TWENTY FIVE stations with engineered product sized for their different hoses, using our Model 2400 (1/2″), 2401 (1″), 2402 (2″) and 2403 (3″) Super Air Wipes.

If you’d like to find out how using the right product for the job can help your operation, give me a call.

Russ Bowman
Application Engineer
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Digital Flowmeter Improves Production Scheduling And Upgrade Budgeting

“You can’t manage what you can’t measure” might be the most popular axiom in any process improvement endeavor. And it’s true. We hear it almost every time we discuss a Digital Flowmeter application, and a conversation I just had with a customer was no exception.

Their business is growing, and they’re pushing the limits of their compressed air system. The use compressed air to run their CNC mills in their machine shop, for blow off/cleaning as they assemble products, as well as a variety of pneumatic tools throughout the shop. The CNC machines’ air load was pretty consistent…the rest of the shop; not so much. So they wanted to find out when their compressed air demand peaked, and what it peaked at, in order to make a more informed decision about upgrading their compressor.

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

So, they purchased a Model 9095-DAT Digital Flowmeter for 2″ SCH40 Pipe, with USB Data Logger. They installed it immediately, with the USB Data Logger set to record once a second…this told them their consumption at any given time over the course of the day. Every day at closing time, the shop manager pulls the USB Data Logger from the Digital Flowmeter and transfers the data to his computer. After just a few days, he knew exactly how much air they were using…and exactly when they were using it. He’s now using this data (in the short term) to plan certain operations around peak scheduling, and (in the long term) to know what they’re looking at for their next air compressor.

Do you know as much about your compressed air usage as you should? If you’d like to talk about how to measure…and manage…your air consumption, give me a call.

Russ Bowman
Application Engineer
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Two Birds With One Stone (and A Shim)

Blowing off bottles is such a popular application for the EXAIR Super Air Knife, it’s been featured on the cover of our Catalog…several times…and is the “banner” pictures on the Super Air Knives page on our website:

This always makes me thirsty for orange soda.

I had the pleasure of helping a caller from a bottling plant recently with just such an application.  Thing is, they run a couple of different size bottles, and it’s not a very big facility…they didn’t want to, or have room to, install different lengths of Air Knives, and also didn’t want to waste air flow when they were running the shorter bottles.

9″ Air Knives were required for the taller bottles, but their shorter bottles were a little under 6″ tall.  They had considered buying both 6″ and 9″ Air Knives, but called me to see if there was a less expensive, and possibly, easier way.  (There is!)

EXAIR makes, and stocks, every product in our 208 page catalog right here in this building in Cincinnati, Ohio.  We also make custom parts when the need arises…and custom Air Knife shims were the solution to this customer’s application.

By installing two Model 110009 9″ Aluminum Super Air Knives, one on either side of the conveyor (just like the photo above,) they’re able to blow off the taller bottles.  When they run the shorter bottles, they change out the shims for ones that limit the flow to a 6″ curtain.

So…for a little under $50.00 (2017 cost for those custom shims,) they’re going to save almost $550.00 per year in compressed air costs – AND make sure that their compressed air system is optimized & available for other loads throughout the plant.

EXAIR offers the Super Air Knife in lengths from 3″ to 108″, with a 0.002″ shim installed.  They’re ideal for most industrial and commercial blow off applications, right out of the package.  If your application calls for something a little “outside the box,” you may only be a shim away from success.  If you have such an application, give me a call.

Russ Bowman
Application Engineer
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EXAIR Cabinet Cooler Systems Vs. Refrigerant-Based Panel Cooling Options

If you’ve got an electrical enclosure that needs heat protection, you’ve got a good number of options at your disposal. Frankly, if any one of them were the “be-all and end-all” solution, the rest of us would be looking for something else to do. Fact is, there are certain situations where one particular method makes more sense than the others, and other situations where one method just won’t work but several others will.

In industrial and commercial settings, these situations will often present conditions where there is indeed an ideal solution. Today, we’ll explore the ones where the choice comes down to a compressed air-operated EXAIR Cabinet Cooler System or refrigerant-based panel cooling.  Let’s consider:

Environment – Now, we’re all going to make sure we protect our gear from the elements, as much as is humanly possible. Your company’s computer server is likely a lot closer to the climate controlled office spaces than the welding or grinding stations. But what happens when sensitive electronics need to be in close proximity to the machinery they’re controlling? And that machinery isn’t in climate controlled office spaces?

EXAIR NEMA 4 Cabinet Cooler System on an enclosure in a hot steel mill.

Even if an A/C type panel cooler would fit on this box, it would be problematic:

  • See all that dust on the ducts? And the belt? And the rails? And the…well, everywhere? Yeah; would be in the filters, condenser coils, the compressor motor bearings and eventually, inside the panel.
  • They make condensate. The big thing about air conditioners is that they lower the humidity…and that water has to go somewhere. Even if a small drain line is easy enough to run, what happens when it gets clogged (that dust is going to find its way here too, by the way)?
  • They’re sensitive to vibration. Every fastener, every brazed joint, every electrical connection, risks cyclical failure if they’re shaken about.

EXAIR Cabinet Cooler Systems are impervious to all of these conditions:

  • The only air they use comes straight from your compressed air supply. We even provide Automatic Drain Filter Separators to make sure this is clean & dry.
  • There are no moving parts. Vibration is not a problem.
  • We offer different levels environmental considerations to meet most any challenge:
    *NEMA 12 (dust tight, oil tight) are ideal for general industrial environments.
    *NEMA 4 (splash resistant) keep liquids out too, and are indoor/outdoor rated.
    *NEMA 4X (corrosion resistant) also keep liquids out, and are stainless steel construction. They’re also available in 316SS construction for the most exacting, harshest, and critical environments such as food service, pharmaceutical, or highly corrosive atmospheres.
    *High Temperature Cabinet Cooler Systems are specified for installation in areas where ambient temperatures exceed 120°F (52°C.)

Location – Sometimes, there’s just not room to mount an air conditioner. The compressor, and, especially, the condenser coils have to take up a finite amount of space, by design.

When there’s no room to use a bulky air conditioner, a compact EXAIR Cabinet Cooler System is ideal.

EXAIR Cabinet Cooler Systems have a small footprint…a NEMA 12 550 Btu/hr system, for example, installs through a ½ NPS knockout, is under 6” tall, and just over 1” in diameter.

Reliability – We talk to callers all the time about the frustration of:

  • Having to replace a burned out Variable Frequency Drive because their panel cooler failed.
  • Constantly resetting controls that have tripped due to an overheat condition because they missed, or don’t have time for, their panel cooler’s maintenance.
  • Down time and lost production while waiting for replacement parts…or a whole new panel cooler.

Even in less aggressive environments, filters and coils can slowly accumulate dirty buildup, which reduces the unit’s cooling power.  Then, a heat wave hits early in the season, and your machine trips out (if you’re lucky) or burns out (if you’re not) -either way, that part or process you were in the middle of is scrap, and you’re back to step one.

EXAIR Cabinet Cooler Systems are not affected by this – in fact, a system with thermostat control may just sit there dormant through the winter, and “spring” (pun intended) into action when that first heat wave rolls through.  And it’ll be just as powerful as that last hot day, the previous autumn.

Availability – Let’s say you installed some new equipment recently, and its first exposure to the heat of summer created one of the frustrating situations above.  An air conditioner-type panel cooler will require:

  • “Invasive surgery” on your enclosure. Most of these require a sizeable rectangular hole for installation.
  • These systems can pull 5 amps or more, which might mean a dedicated circuit breaker & wiring.
  • Many are built-to-order, so you might have to wait, depending on their assembly schedule.  And they might be busy, because if the heat just started causing you problems, you’re probably not the only one.
  • Once it’s received, installed, and wired up, you may still have to wait for the compressor’s oil (special oil for use with refrigerant) to settle before you start it up the first time.

EXAIR Cabinet Cooler Systems are stock products.  We ship same day, across the country, with orders received by 3pm EST.  They install in minutes, and most of the preparation can be done today, so you’re ready to install when it comes in tomorrow – which isn’t a big deal…most Cabinet Cooler Systems weigh only 5lbs or less, so expedited shipping isn’t near as painful to your wallet as a big box full of electric motor, copper coil, and refrigerant.

Environment (friendly, that is) – No matter how well they’re built, a refrigerant system is going to leak sooner or later.  And every whiff through an aging seal, or sudden loss through a failed tube, will contribute to the ozone depletion that today’s strict controls and high attention to CFC’s are trying to prevent.

Our Cabinet Cooler Systems are solely compressed air operated…the only thing they exhaust is the air from inside the enclosure.

Durability – Refrigerant leaks. Electric motors wear out.  Coils corrode.  Filters clog.  A GOOD warranty on an air conditioning type panel cooler is two years.  And it won’t cover environmental effects.

All EXAIR Compressed Air Products have a Five Year Built To Last Warranty.  But if you supply your Cabinet Cooler System with clean, dry air, it’s going to run darn near indefinitely, maintenance free.

Don’t trust your critical electronics to anything less than the assurance provided by an EXAIR Cabinet Cooler System. If you’d like to find out which one(s) are right for your needs, give me a call.

Russ Bowman
Application Engineer
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EXAIR Vortex Tubes: As Much Cold Air As You Need, As Cold As You Need It

If you’re looking for a reliable, consistent flow of cold air, there’s really no better way to produce it than with a Vortex Tube. There are no moving parts…the air flow and temperature from a particular model, set to a specific cold fraction, is only influenced by the compressed air supply pressure & temperature.

Pressure is easy to control…all you need is a suitable regulator.  Temperature CAN be a variable, depending on your type of compressor, if you have a dryer system (and what type it is,) and sometimes, ambient conditions…if, for example, a long pipe is run through a very hot environment like a foundry or a blast furnace operation.  In cases where supply pressure and/or temperature can be limitations, a higher capacity Vortex Tube, set to a lower Cold Fraction, may be specified.  Which brings me to the user inquiry that inspired today’s blog…

This particular customer uses our Model 3215 Vortex Tubes (15 SCFM, 1,000 Btu/hr) to provide cooling to analyzer systems that monitor certain quality parameters in their manufacturing processes.  The ability to precisely control the temperature in these systems makes for repeatable and accurate measurement of these parameters.   Their compressed air supply in this area is regulated to 80psig, they have a refrigerant-type dryer and climate-controlled facility, so their supply temperature is a consistent 70°F.  You couldn’t ask for better conditions for a successful Vortex Tube application, and they’ve worked great, for years.

Now, due to a plant expansion, they’re installing some of these analyzer systems in a location where the compressed air supply is limited to 60psig.  The required cooling capacity is going to be the same, so the Project Manager reached out to us to see if they could get the same amount of cooling with this new pressure limitation.  Here’s how they’re doing it:

We publish the rated performance of Vortex Tube products for a supply pressure of 100psig.  The Model 3215 Vortex Tube consumes 15 SCFM @100psig and, when set to an 80% Cold Fraction (meaning 80%…or 12 SCFM…of the 15 SCFM supply is directed to the cold end,) the cold air will be 54F colder than the compressed air supply temperature.  Here’s the performance table, so you can follow along:

EXAIR Vortex Tube Performance Table

Now, their supply is at 80psig.  Since air consumption is directly proportional to absolute supply pressure (gauge pressure PLUS atmospheric, which is 14.7psi at sea level,) we can calculate their units’ consumption as follows:

(80psig + 14.7psia) ÷ (100psig + 14.7psia) = 0.83 X 15 SCFM (@100psig) = 12.4 SCFM (@80psig)

So, with a 50°F temperature drop (from a supply @70°F,) they were getting 12.4 SCFM of cold air at 20°F.

As you can see from the table above, they’ll only get a 46°F drop at 60psig…and the flow won’t be as high, either.  So…we’ll need to get more air through the Vortex Tube, right?  Let’s use a little math to solve for what we need.

We still need 20°F cold air from 70°F compressed air, so, at 60psig, we’re looking at a Cold Fraction of ~70%.  And we still need 12.4 SCFM, so:

12.4 SCFM ÷ 0.7 = 17.7 SCFM @60psig (required supply)

Our Model 3230 Vortex Tube uses 30 SCFM @10opsig…at 60psig it’ll consume:

(60psig + 14.7psia) ÷ (100psig + 14.7psia) = 0.65 X 30 SCFM (@100psig) = 19.5 SCFM (@60psig)

That’s about 10% more flow than they needed, theoretically, which was close enough to start.  From there, they “dialed in” performance by regulating the supply pressure and Cold Fraction (see video, below):

If you’d like to find out more, or work through a cooling application, give me a call.

Russ Bowman
Application Engineer
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