Tag: heat removal

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

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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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Twitter: @EXAIR_BB

 

Siphon Fed Atomizing Nozzle Improves Roll Forming Process

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Last week I worked with a gutter manufacturer who was looking for a way to spray a light coating of vanishing oil on the rollers of a forming machine. Roll forming is commonly used when needing to maintain a constant and consistent shape or feature across the length of the part. In this particular case, a sheet of aluminum, used as a cover for the gutter, is fed into the machine where it passes over a series of dyes that bends “ribs” and punches small holes into the part to keep leaves or debris from settling on top, while allowing the rainwater to pass through the holes and into the gutter.

They were needing to apply the oil to the rollers because they were starting to see some irregularities in hole size as well as some deformities to the shape of the ribs due to heat being generated during the forming process. The customer was interested in using some type of atomizing spray nozzle in the hopes that providing an atomized mist of liquid may provide for a faster evaporation of the oil so there wasn’t much residue left on the part before packaging.

After further discussing the details, they advised that they were going to have the oil in a container about 12″ below the machine but didn’t have a way to pressurize or pump the liquid to the nozzle. Once again, EXAIR has the perfect solution with our 1/4 NPT Siphon Fed Atomizing Nozzles. These nozzles are the ideal solution where pressurized liquid isn’t available as they use the compressed air to the draw the liquid into the nozzle, up to 36″ of suction height, and mix it internally to produce a mist of atomized liquid spray. For this particular application, the Model # SR1010SS was a good solution as it provides a low flow rate of only 0.8 GPH and a tight spray pattern to focus right at the rollers to avoid any waste or overspray.

sr1010ss
Model # SR1010SS Siphon Fed Round Pattern Atomizing Spray Nozzle – 303ss construction, fully adjustable flow rate

EXAIR offers an extensive range of Atomizing Nozzles that can be used for light coating applications, like above, or for wider coverage areas or higher flow rates. For help selecting the best option to fit your needs, contact one of our application engineers for assistance.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN

Cooling Punch Points with a Super Air Knife

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A stamping facility had a high speed perforating operation. The idea was to punch holes into a matrix at a fast feed rate.  In their operation, they started to see issues with the punched holes, and they also noticed that the punch points were prematurely failing.  With a tight punch-to-matrix clearance, heat was building up from the friction.  This effect was galling the material and affecting the hole appearance and dimensions.  They also noticed heat damage to the punch points.  They either had to slow their process down, or find a way to cool the punch points.  They contacted EXAIR to see if we could help.

To remove heat, you need to have a fluid moving across the material to carry the heat away. For this customer, the fluid would be air.  Just like a hot cup of coffee, you can cool it by blowing across the top of it.  In this instance, EXAIR can blow a lot of air with using very little amount of compressed air.  Because of the gap opening of the tool die was narrow, I suggested the Super Air Knife.  It has a compact design and can blow nicely between the upper and lower die.  With slight modifications, they were able to mount the Super Air Knives right into the base set.  Because the tool die was a “bowl” type design, I suggested that they should use two pieces of the model 110206 Super Air Knife.  They could mount one to each side to make sure to hit all the punch points.  (Reference the picture below).

Punch Press with a Super Air Knife
Punch Press with a Super Air Knife installed

EXAIR Super Air Knives are the most efficient compressed air knives in the market. It is designed to have a 40:1 amplification ratio.  That means for every one part of compressed air, it will entrain 40 parts of the free ambient air.  As with the coffee reference above, the more air that you can blow, the better the cooling effect.  With the Super Air Knife, we can reach a velocity of 11,800 feet per minute at 80 PSI.  After the customer installed the Super Air Knives, they were able to increase production by 10%.  Also, they found that the punch points were lasting twice as long.  They were so impressed with the effectiveness of the Super Air Knives, they mounted them to all their punch press machines.

Super Air Knife
Super Air Knife

If you find that heat is affecting your process, EXAIR could have a product to help you. We have a variety of efficient air movers to cool your parts.  As for this customer above, we were able to increase production and extend the life of their tools.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb

Wearing Out Your Sole

Published on by John BallLeave a comment
3925 Adjustable Spot Cooler
3925 Adjustable Spot Cooler

A shoe manufacturer had a special abrasion test that was required by his customer to test special rubber compounds. The set up was to run a small chain across the bottom of the rubber sole.  The chain was looped to continuously rub against the sole of the shoe.  As they began their wear testing, they noticed that the chain was getting hot from the friction.  The heat would get high enough to change the composition of the rubber and cause a premature failure.  To properly test for wear, they needed to cool the chain.

As they discussed their application with me, they required the chain to be at a specific temperature. I suggested the model 3925 Adjustable Spot Cooler System.  This system comes with a dual point hose kit, a magnetic base, a filter separator, and two additional generators.  The generators of the Adjustable Spot Cooler are a piece which controls the total volume of air through the cooler. They can be switched in and out to produce more or less cooling capacity of the Adjustable Spot Cooler. The main concern was to keep the chain temperature constant.  With a temperature control knob and the additional generators, they could dial in the cooling capacity to keep the chain at the desired temperature.  If the chain was too cold, the sole would not wear properly, and if the chain was too hot, it would change the composition of the rubber material.

They mounted the Adjustable Spot Cooler to the abrasion machine with the dual points blowing on each side of the chain. They quickly noticed that they could keep the chain cooler than the specified temperature.  As a trial, they replaced the generator to the 30 SCFM (850 SLPM) flow rate.  This increased the cooling capacity of the Spot Cooler.  With the higher cooling capacity, they could increase the speed of the abrasion machine to shorten the failure cycle.  This was a great benefit to have as they were testing different rubber compounds to determine the best product; a pronounced advantage in research and development.

If you find out that heat is causing problems in your application, you can contact an Application Engineer at EXAIR for help in finding the correct cooling product. In this instance, friction was the culprit and the Adjustable Spot Cooler was the solution.

John Ball
Application Engineer
Email: johnball@exair.com
Twitter: @EXAIR_jb