Tag: cooling with air

How to Best Apply Vortex Tube Cooling

Published on by codybiehleLeave a comment

So, you have found yourself with a little bit of a conundrum. You need to cool a part but don’t know where to start and there are so many different options to choose from. In most cases when it comes to cooling with compressed air there are two different paths you can take. First is using a large volume of air at room temperature to blow across the surface area of the product. The other option is to use cold air from a vortex tube to drop the part’s temperature. In most case a large volume of air can be used to cool things down to relatively cooler temperatures; think cooling a cup of coffee using your breath. The issue you run into is when the temperature of the room air gets closer to the temperature you want to achieve in the end. In other words, when the temperature difference between your cooling air and your desired end temperature is small there is less cooling taking place with that same volume of air.

Mini Spot Cooler cooling down a bit used in milling plastic

This can be explained by looking at the cooling power formula:

Btu/hr = 1.0746*(CFM)*(Delta T)

In this case the Delta T is the difference between the temperature that you want to cool the product down to and the temperature of the air. This means the smaller the delta T is the higher the CFM flow will need to be to counteract the effect of the temperatures are so close to one another. Here are some examples of cooling a product and you are providing 1000 CFM of air to cool it.

Btu/hr = 1.0746*(1000 CFM)*(150F – 130F)

                Btu/hr = 21,492 Btu/hr

Btu/hr = 1.0746*(1000 CFM)*(150F – 100F)

                Btu/hr = 53,730 Btu/hr

As you can see the closer the Delta T is to 0 the less Btu/hr you get. Getting this kind of CFM flow is easy if you use something like EXAIR’s Super Air Knife or Super Air Amplifier. These systems take a small amount of compressed air and entrain the surrounding ambient air to increase the volume to a large blast. Take a look at model number 120022 which is the 2” Super Air Amplifier, this unit can produce 1,023 CFM while only using 15.5 CFM at 80 psig. But when you get close to cooling the temperature down to that room temperature or below it gets much harder; which only means that the temperature of the air being used to cool needs to be dropped. Dropping the air temperature can only be accomplished by using outside means like air coolers or in this case EXAIR’s Vortex Tubes and Spot Coolers.

EXAIR Air Amplifiers use a small amount of compressed air to create a tremendous amount of air flow.

Vortex Tubes and Spot coolers have some limitations. Generally they are not thought of products that produce large volumes of air (even though we make them up to 150 SCFM). And they are best suited for smaller areas of cooling, spot cooling, if you will. However, EXAIR Vortex Tubes do have one key feature that can help compensate for the lack of volume. LOW TEMPERATURE! The vortex tube can produce temperatures lower than 0F while stile retaining a good portion of air volume from the inlet.

Sub-zero air flow with no moving parts. 3400 Series Vortex Tubes from EXAIR.

For example, let’s look at model number 3240 running at 100 psig with 70% of the air from the inlet exiting the cold side (aka 70% cold fraction). At 100 psig the 3240 will use 40 SCFM at the air inlet and will have a temperature drop of 71F. If the compressed air has a temperature of 70F that means you will be seeing a temperature of -1F. Also, when using the 70% cold fraction you will see 28 SCFM of cold air flow. Now let’s plug those numbers into the cooling power formula.

 Btu/hr = 1.0746*(28 CFM)*(150F + 1F)

                Btu/hr = 4543 Btu/hr

As you can see, using a small amount of compressed air you can still net you a good amount of cooling if the temperature is lower. All in all, the best option for cooling products down to temperatures that are above ambient temperatures is something that can produce a large volume of air. For small areas that require cooling the product down to temperatures to ambient temperature and below, use EXAIR’s Vortex Tube.

If you have questions about our Air Amplifiers and Vortex Tubes, 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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Calculating CFM of Air Needed for Cooling

Published on by Russ BowmanLeave a comment

It’s easy to know that EXAIR’s Vortex Tubes can be used to cool down parts and other items, but did you know that our other engineered compressed air products can be used to cool down these same things? It’s the same process as cooling down hot food by blowing on it. And we can use the physical properties of any material – whether it’s the massive billets of steel in the photo up top, or the bowl of soup to the right, to calculate the amount of air flow required to change a certain mass of the material from one temperature to another.

For any material, there’s a certain amount of energy required to cause a certain temperature change of a certain mass of the material. This property is called Specific Heat (Cp), and it’s commonly expressed in Joules per gram per degree Celsius (J/g°C), or Btu’s per pound (mass) per degree Fahrenheit. (Btu/lbm°F). The Specific Heat of the material allows us to calculate the amount of heat that has to be removed to cool it from its starting to its desired temperature, using a standard heat transfer equation:

q = mCp ΔT, where:

  • q is the amount of energy it’ll take to cause the temperature change.
  • m is the mass of the material that you want to change the temperature of.
  • Cp is the Specific Heat we talked about above.
  • ΔT is the starting temperature, minus the desired temperature.

Once we know the amount of heat to be removed, we can then apply units of time, and calculate the rate of cooling you’ll need to achieve in order to get the material to the temperature you want, in the time that you want. Let’s work through an example, using a piece of steel weighing 50lbs that needs to be cooled from 300 °F to 200°F:

q = m * Cp * ΔT, where:

  • m = 50lbm
  • Cp = 0.117 Btu/lbm°F
  • ΔT = 300°F – 200°F = 100°F
  • q = 50lbm * 0.117 Btu/lbm°F * 100°F = 585 Btu of energy (heat) to be transferred

Now, let’s say we have two minutes to cool this piece of steel:

585 Btu/2 minutes X 60 minutes/hr = 17,550 Btu/hr

That’s the rate of cooling required for this application. Now, we can use another equation that’s commonly used in the HVAC industry to determine the amount of room temperature (70°F) air flow that’ll remove that amount of heat. It’s called the cooling power formula:

Q̇ = 1.0746 * ΔT * ṁ, where:

  • Q̇ is the rate of heat transfer
  • 1.0746 is a constant
  • ΔT is the difference between the desired temperature and the air temperature
  • ṁ is the flowrate of air in cubic feet per minute

Since “Q̇” is the unknown value, we have to get to use a little algebra and rearrange the equation:

ṁ = Q̇/(1.0746 * ΔT), where:

  • Q̇ = 17,550 Btu/hr
  • 1.0746 = 1.0746 (remember, it’s a constant)
  • ΔT = 100°F – 70°F = 30°F
  • 17,550 Btu/hr/(1.0746 * 30°F) = 544.4 cubic feet per minute

Now, this assumes that equilibrium will be reached (i.e. all of the heat than CAN be transferred to the air flowing past the steel WILL be transferred), but that’s not going to happen. Depending on the geometry of the material to be cooled, there are ways to maximize the contact time between the material and the cooling medium. For example, constructing a tunnel over a section of a conveyor so the airflow can blow in the opposite direction that the material is traveling. Even then, though, it’s unlikely you’ll reach equilibrium, so we’ll apply a service factor, and say our airflow is going to be 30% efficient in cooling the steel (which is really quite high) so we’ll need:

544.4 CFM/0.3 = 1,815 CFM

EXAIR Air Amplifiers are an excellent option for providing this kind of cooling flow. They’re compact, quiet, and efficient. Using the following table, we see that a 3″ Adjustable Air Amplifier supplied at 80psig has a total developed flow rate (Air Volume at Outlet) of 774 SCFM:

So, three of them will generate a total cooling flow of 2,322 SCFM, and that’s not counting the air entrained in the immediate discharge (Air Volume at 6″). That’s even more than we THINK we need…but that can be adjusted and/or regulated.

Another thing I like about the Adjustable Air Amplifiers for an application like this is that they’re, well, adjustable (it’s right there in the name). Turning the exhaust plug in or out will decrease or increase the air flow – this is how you can make gross adjustments to the air flow. A Pressure Regulator in the supply line then allows for precise ‘tweaks’ so you can dial in the performance to the level you need, without using any more compressed air than you have to.

With sixteen distinct models to choose from, EXAIR Air Amplifiers are a quick and easy way to provide a tremendous amount of cooling air flow from a compact, lightweight product.

If you have any questions about using compressed air for cooling, give me a call.

Russ Bowman, CCASS

Application Engineer
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EXAIR Cabinet Cooler Systems – How Do they Work?

Published on by Jordan T ShouseLeave a comment

Cabinet Cooler systems eliminate heat related problems by providing a temperature controlled environment inside of electrical enclosures. Typically set to maintain 95F (but also adjustable) a Cabinet Cooler system can withstand harsh, remote environments with little maintenance. They cool heat loads up to 5600 Btu/Hr and are UL listed to maintain your cabinet’s NEMA integrity. 

Compressed air enters the vortex tube powered Cabinet Cooler and is converted into two streams, one hot and one cold. Hot air from the vortex tube is muffled and exhausted through the vortex tube exhaust. The cold air is discharged into the cabinet through the included cold air distribution kit. The displaced hot air in the cabinet rises and exhausts to atmosphere through the cabinet cooler body. The control cabinet is both cooled and purged with cool, clean air. Outside air is never able to enter the control panel.

sl17_Nema4
How it works! 

EXAIR’s compressed air operated, Cabinet Cooler Systems are a low cost, reliable way to cool and purge electronic control panels. There are no moving parts to wear out and no filters to replace, eliminating the need for constant monitoring.

NEMA Type 12 (IP54) and NEMA 4 and 4X (IP66) models are available that are very compact and mount in just minutes through an ordinary electrical knockout.

Cabinet Cooler Family
EXAIR Cabinet Cooler Sizes 

Available in a wide range of cooling capacities, ranging from 275 Btu/hr. for our smallest system, up to 5,600 Btu/hr. for our largest Dual System.

Thermostat control systems are the most efficient way to operate a Cabinet Cooler as they limit compressed air use by operating only when the temperature inside the enclosure approaches critical levels. Continuous Operating Systems are recommend when constant cooling and constant positive pressure inside the panel is required.

Thermostat controlled Cabinet Cooler Systems are the best option when experiencing fluctuating heat loads caused by environment or seasonal changes. Thermostatically Controlled Systems include a Cabinet Cooler, adjustable thermostat, solenoid valve, cold air distribution kit consisting of tubing and self adhesive clips to duct the cold air inside the panel and a filter separator to remove any water or contaminants from the supply.

Thermostat and ETC

If you would like to discuss our cabinet cooler systems or any of EXAIR’s engineered solutions, I would enjoy hearing from you…give me a call.

Jordan Shouse
Application Engineer
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Cold Guns for Spot Cooling or Replacing Mist Systems

Published on by Jordan T ShouseLeave a comment

By using only a source of compressed air, the Cold Gun and High Power Cold Gun produces a stream of clean, cold air 50°F (28°C) below your compressed air supply temperature. The Cold Gun is very quiet at only 70 dBA and has no moving parts to wear out. Just supply it with clean compressed air and it’s maintenance free.

How does it work, and what are the benefits?

  • The Cold Gun uses compressed air to produce a stream of clean, cold air at 50°F (28°C) below supply air temperature. Generally this will be 20°F-30°F outlet temperature.
  • They use Vortex Tube technology…no moving parts to wear out.

How A Vortex Tube WorksInstant cold air flow with no moving parts!

  • Cold flow and temperature are preset to optimize cooling capability, and are non-adjustable to prevent freeze-up during use.
  • Eliminates the expense of both the purchase & disposal of cutting fluids when replacing expensive mist systems.
  • Removes the potential for health problems associated with breathing mist & vapors, and the safety issue of slipping on a wet floor.

Cold Gun Aircoolant System selection is easy & straightforward…we offer a standard, and a High Power version to meet your specific needs.

CG
Four systems to choose from, to meet most any need.

We also offer Single & Dual Point Hose Kits, to further meet the needs of your application.

One of the best applications I have seen with our cold gun came from a customer in Peru. They are a gold mining operation and they were having trouble with the liquid they were using to cool a saw. Read all about it here!

IMG_20180613_094120_HDR

If you have an application that you believe would be better served by the use of an EXAIR Cold Gun, give us a call.

Jordan Shouse
Application Engineer
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