The Battle of Cooling: Fans Vs. Air Amplifiers

So, you have a cooling application and don’t know what to choose; do you go with the age-old fan or something different. Fans are probably one of the most common items used for cooling in everyday life and chances are you have a few that are always cooling. These fans can be found in cars, at your home, in your computer, and many other places.

But there may be other items that might just blow away the competition (pun intended). This is where EXAIR’s Air Amplifiers step onto the scene. Air Amplifiers use a little bit of compressed air to entrain the surrounding ambient air to turn it into a large volume of air.

Axial Fan being used to cool down an electrical cabinet

When it comes to cooling with air, volume is key. Air cannot hold a lot of thermal energy (heat) so in order to cool something down you need a lot of it. This means that the unit that can produce the largest volume of air is going to produce more cooling. So, what is the difference between a fan and the air amplifiers and which is better?

Fans have been in use since late B.C.E. and are still in use today. Many of the fans used for cooling are centrifugal style fans which are also known as blowers. These systems use an impeller that consists of a central shaft with blades that form a circle around a central opening. Blowers produce a high volume of air at a high velocity and low pressure. Not only do blowers require significant space to install, they also require noticeable maintenance and will eventually need to be replaced. Another, and perhaps more important downside, is that a blower will increase the temperature of the outlet air which further reduces the air’s ability to absorb additional heat and effectively cool.

Super Air Amplifier Family

On the other hand, Air Amplifiers use a source of compressed air to form a thin stream of high velocity laminar flow of air to entrain the surrounding ambient air. By doing so you can create a focused blast of air for cooling. So the downside in this case is that if you do not have a source of compressed air, the Air Amplifier will not function for you. With a small amount of compressed air, Air Amplifiers will multiply the volume of air up to 25 times to produce the large volume of air needed to cool parts, films, castings and more.

Air Amplifiers are extremely inexpensive when compared to blower systems and can out perform a blower in many applications.

If you have questions about our Air Amplifiers, or would like to talk about any of the quiet EXAIR Intelligent Compressed Air® Products, feel free to contact EXAIR or any Application Engineer.

Cody Biehle
Application Engineer
EXAIR Corporation
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Electrical Panel Heat Protection: Limitations of Fan Cooling

In preparation for some labor-intensive outdoor projects, I did some research into heat-related health risks, and their prevention. My first thought on prevention was getting someone else to do it, but my wife made a good case for “pride in ownership”, and I DO have a good many tools suitable for these projects. Also, I am notoriously frugal, so after getting a couple of estimates, I realized the value in a little DIY (do it yourself) and commenced planning.

High on that list of risks was the possibility of heat stroke. It’s recommended that the victim be taken to a cool space (someplace air conditioned, for example). Air flow (like from a fan) can help too, but only if they’re taken someplace where the ambient temperature is less that 95F (35C). If it’s that hot, the air flow can actually make things worse, since heat transfer requires a difference in temperature. If the cooling medium (air, in this case) is the same temperature as the object to be cooled (the human body, in this case), no heat will be transferred – and the heat stroke wins. That’s a bad day in the back yard.

This is, in fact, the exact same limitation with a popular method of electrical panel cooling: fans. We’ve been using mechanical methods of imparting motion to air for cooling purposes for a long, long time: Blowing on a spoonful of soup or a cup of coffee before a warm (but not scalding) sip, waving hand fans at oneself during indoor gatherings, installing electric fans in those same buildings, and the list goes on. Fans are inexpensive to purchase & operate, come in a variety of sizes & configurations, and are oftentimes used to circulate cooling air through occupied rooms, confined spaces, and, of course, electrical & electronic panel enclosures.

These are quite effective for panels with moderate-to-high internal heat loads, as long as the ambient area temperature is less than the temperature you wish to cool the panel’s internal air to. In those situations, the only real concern is the quality of the air in the environment. As you can see in the photo to the right, filters are an absolute “must”, and they’re going to require regular maintenance. This means cleaning or replacing the filters, as well as cleaning the fan grills and blades themselves. It’s still very likely that some of that dust is going to get inside the enclosure, and while we’re on the subject of environmental contamination, so will humidity. I probably don’t need to tell you that dirt and/or water, and electricity, don’t mix.

There are other methods of cooling (panel a/c, thermoelectric coolers, water cooled heat exchangers, heat pipes, etc.) that limit environmental contamination, but they’re still going to need periodic (oftentimes frequent) attention: filters will clog, refrigerant coils will get fouled and corrode, moving parts will wear, motors & switches will burn out, etc. Even with the advances made in refrigerant technology, the leaks that panel a/c and heat pipes are prone to are still bad for the environment.

If this sounds like your environment, and you’re looking for safe, dependable, durable heat protection, look no further than EXAIR Cabinet Cooler Systems. Using the Vortex Tube phenomenon, they generate cold air from your compressed air supply, with no moving parts to wear or electric devices to burn out. Systems are on the shelf & ready to ship in cooling capacities to 5,600 Btu/hr. We also “tailor-make” systems for higher heat loads, from stock products, that can usually ship right away as well. Once installed on a sealed enclosure, the only thing the internals of that enclosure are ever exposed to again is clean, moisture free, cold air. All of our Cabinet Cooler Systems come with an Automatic Drain Filter Separator – the only preventive maintenance that’s ever required for the systems is the periodic replacement of the filter’s particulate element.

Inside, outdoors, high temperature, dirt/dust/humidity, corrosive and classified environments are no problem for EXAIR Cabinet Cooler Systems

We can quickly and accurately specify a Cabinet Cooler System to meet your needs with just a few key pieces of information – you can fill out a Sizing Guide (or complete one online) and send it in to us, or you can call an Application Engineer with the data. It only takes a minute to do the calculations, and we do them over the phone all the time. Installation is straightforward and usually only takes a matter of minutes. We have a number of short “how to” videos on our website that cover all aspects of installation, and if you ever have specific questions or concerns, an Application Engineer is a phone call away. We look forward to hearing from you!

Russ Bowman, CCASS

Application Engineer
EXAIR Corporation
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Super Air Knife Cools Laminated Packaging Material

I recently worked with one of our distributors on a Super Air Knife application for a manufacturer of flexible packaging material. They create the plastic material that is commonly wrapped around the outside of a wide variety of different containers. The material exits the laminating machine at about 129°F (54°C) and must be cooled to close to room temperature before it is able to be rolled without the material sticking together.

IMG_20180509_103254_HDR
Model 110012, positioned to maximize counter-flow

They performed a test with a Model 110012, recording the temperature after the knife and determined that it would be suitable for them. Prior to using the Super Air Knife, they had been using a series of fans to cool down the material. This worked to some degree, but they had been experiencing quality issues as a result of inadequate levels of cooling and were forced to slow down the laminating machine in order to compensate. By implementing the Super Air Knife, they were able to cool the material down to ambient temperatures without having to slow production. As an added measure, they ordered a second knife to install on the underside to further decrease the temperature of the material.

sak_cooling
Graph showing the effectiveness of a Super Air Knife vs. fans or no cooling method.

The laminar airflow of the Super Air Knife is critical to the success of any cooling application. A fan “slaps” the air which provides random spikes of air at moderate velocities. The uniform, high velocity, laminar sheet of air from the Super Air Knife, in addition to the low compressed air consumption, makes it a much more effective cooling method than fans. The design of the Super Air Knife allows it to entrain ambient air at a rate of 40:1, maximizing the force and flow from the knife while keeping compressed air usage to a minimum.

super-air-knife-flow
The design of the Super Air Knife allows it to entrain air from the top and bottom, creating a 40:1 air amplification ratio.

Super Air Knives are available in a range of different materials and sizes. From stock EXAIR carries knives from 3”-108” in Aluminum, 303 Stainless Steel, 316 Stainless Steel, and 3”-54” in PVDF (Polyvinylidene Fluoride) for superior resistance to highly corrosive materials. In addition to being an excellent tool for cooling, the Super Air Knife can solve a wide range of drying and blowoff applications. If you have an application that would be better served with one of EXAIR’s Super Air Knives, reach out to us today and get yours on order! We ship same day from stock with orders received by 3:00 pm EST, stop wasting time with ineffective cooling or blowoff methods!

Tyler Daniel
Application Engineer
E-mail: TylerDaniel@exair.com
Twitter: @EXAIR_TD

Not a Fan of Fans Because Rising Air Temp Will Kill Your Electronics

Using a fan is a popular method for machine builders to provide cooling for an electrical enclosure.  The electrical panel stays cool for machine acceptance at the factory, and possibly for even the first 6-8 months of operation and then one day, there is a problem, and the machine shuts down due to an over heated component within the panel. This leads to opening up the panel, possibly placing an external fan, and operation of the machine in an unsafe condition, to meet the daily production needs.  What has led to this situation?  Summertime!

To better understand the situation, let’s review the heat formula.  The total heat content of air consists of the sensible and latent heat factors. Latent heat is the heat that is required to change the state of a material, say from liquid to solid.  Water to ice is an easy way to understand this type of heat.  When heat is removed from water at 32°F it turns to ice at 32°F.  There is no temperature change, but heat has been removed. Sensible heat is dry heat, it is a result in change of temperature, but not change in state or moisture.  For fan cooling, the air and moisture only change temperature and not state, we can focus on the sensible heat portion.

In English units:  Q = Cp x ρ x q x ΔT x 60 min/hr

And for air:

Q –  is the sensible heat flow in BTU/hr

Cp – is the specific heat in BTU/lb °F – 0.2388 BTU/lb °F

ρ – is the air density at standard conditions – 0.075 lb/ft3

q – is measured air flow in ft3/min – CFM

ΔT – is the temperature difference in °F – Final Air Temperature – Starting Air Temperature

Plugging in the constant values, gives us:

Q = 1.0746 x CFM x ΔT

It is common to chart the above formula for various ΔT values, plotting Q vs. CFM values on a dual logarithmic scale, as shown below-

BTU-CFMGraph4

As an example, for an internal heat load of 1300 BTU/hr, to ensure that the temperature rise (from ambient) in the cabinet does not exceed 20°F, 60.5 CFM of air flow is required (the red line above).  A fan with this CFM rating is specified and installed in the panel.

This works  when the ambient temperature is a comfortable 75°F, in a climate controlled factory, or the cooler months of the year.  The problem occurs when the ambient temperature increases to 95°, 100°, or even 105°F,  not uncommon in the summer, and in plants that create large amount of heat, like metal production, and near boiler systems and furnaces.  Under these conditions, the fan will still maintain the 20°F difference, but the internal temperature of the cabinet will rise to 115°-125°F, temperatures where electrical components start to fail or shut down.  The solution to this issue?  Lower the Starting Air Temperature.

The EXAIR Cabinet Cooler Systems use our Vortex Tube technology to take compressed air and provide a cold flow of air that enters the enclosure at 5o°F less than the compressed air temperature.  With a compressed air temperature of 70°F, common for industrial compressed air systems, the Cabinet Cooler will deliver cold air at 20°F.  Again using the chart above, flowing just 20 SCFM of this air will absorb the 1300 BTU/hr of heat (the green line), and result in an internal air temperature 80°F no matter the ambient air temperature.  The electronics in this enclosure will run trouble free, for a long time. This ambient air temperature problem is also true of air-to-air heat exchangers, as the ambient air temperature rises the ability to remove heat diminishes.

Another consideration, the fan system is bringing in air from the surroundings, which is hot and dirty, passing it through a filter (which gets clogged, reduces air flow, and needs to be replaced.) The Cabinet Cooler System, includes an automatic drain filter separator, which filters the compressed air to be free of dirt, dust and moisture. The air entering the enclosure is cool, dry and fee of dust and debris.

ETC CC
NEMA 4 Cabinet Cooler System with Optional Electronic Temperature Control

To discuss your application and how the EXAIR Cabinet Cooler System can be a benefit at your facility, feel free to contact EXAIR and myself or one of our other Application Engineers can help you determine the best solution.

Brian Bergmann
Application Engineer

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