Choosing Max Refrigeration Or Max Cold Temp Vortex Tubes

Vortex Tubes have been studied for over 90 years. These “phenoms of physics” and the theory behind them have been discussed on this blog before. But, when it comes to the practical use of a Vortex Tube it is good to discuss how to correctly select the model that may be needed in your application. The reason being, there are different flow rates and an option for maximum refrigeration or maximum cold temperature.

The tendency is to say, well I need to cool this down as far as possible so I need the coldest air possible, give me the maximum cold temperature. More times than not, the maximum cold temperature model is not the best solution for your application because maximum cooling power and maximum cold temperature are not the same thing.  A maximum cold temperature Vortex Tube is best for spot cooling processes that require greater than 80F temperature drop covering a small area – spot cooling at its finest. Theis very cold air is delivered in a low volume. A maximum cooling power Vortex Tube is the best mix of cold temperature and volume of flow. This cold air (50F-80F temperature drop) is delivered at higher volumes which has the ability to remove more heat from certain processes. If you do not know which is bets for your application, follow these next steps. 

The first step, is to call, chat, or email an Application Engineer so that we can best outfit your application and describe the implementation of the Vortex Tube or spot cooling product for you. You may also want to try and take some initial readings of temperatures. In a perfect world you would be able to supply all of the following information to us, but recognizing how imperfect it all is…some of this information could go a long way toward a solution. The temperatures that would help to determine how much cooling is going to be needed are listed below:

Part temperature:
Part dimensions:
Part material:
Ambient environment temperature:
Compressed air temperature:
Compressed air line size:
Amount of time desired to cool the part:
Lastly desired temperature:

With these bits of information, we can use standard cooling equations to determine what temperature of cold air stream and volume of air is needed in order to produce the cooling and your desired outcome. To give an idea of some of the math we have used, check out this handy educational video of how Newton’s law of cooling was used to calculate the amount of time it takes to cool down a room temp beverage in an ice cold refrigerator. 

If you would like to discuss a cooling application, heating application, or any point of use compressed air application, contact an Application Engineer today.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

1 – ThinkWellVids – Newton’s Law of Cooling – Feb. 27, 2014 – retrieved from https://www.youtube.com/watch?v=y8X7AoK0-PA

Ultraviolet Curing and Vortex Tube Cooling

Recently EXAIR worked on a project to cool down parts that were using Ultraviolet (UV) light to cure a surface coating. Ultraviolet curing is a photochemical process that uses UV light to cure/dry certain inks, coatings, and adhesives. Due to the fact that UV light produces a good amount of heat the product would heat up during the curing process and create issues for them down the line which slowed down production in order let them cool. The simple solution to this was the use of the vortex tube to blow on the product to cool it down during the process. By doing so they were able cool the product down to a suitable temperature for the process to speed up.

EXAIR’s Small, Medium, and Large Vortex Tubes


EXAIR’s Vortex Tubes are great for cooling down surfaces to temperatures below ambient thanks to the cold air stream that is produced from the vortex tube. Vortex tubes use a source of compressed air to create both a hot and cold stream of air simultaneously which allows the unit to be used for cooling but also heating applications. The amount of air flow coming out of either end of the Vortex Tube can be controlled; by doing so one can adjust the temperature of the air streams coming out.

There are numerous methods to distribute the cold air flow from a lone, or a series of, Vortex Tubes.

Although the main application for the Vortex Tube is to be used for cooling, it is occasionally used to heat as well. Heating applications are uncommon, but they are still possible. Since a vortex tube creates a cold and hot stream of air; by controlling what the fraction of air is flowing out of the cold end you can create a temperature rise (a rise from the starting air temp) of up to 195F! Now that is hot.

If you have any questions about compressed air systems or want more information on any of EXAIR’s products, give us a call, we have a team of Application Engineers ready to answer your questions and recommend a solution for your applications.

Cody Biehle
Application Engineer
EXAIR Corporation
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Convective Heat Transfer: How Do We Use It?

Vortex Tubes have been studied for decades, close to a century. These phenoms of physics and the theory behind them have been discussed on this blog before. Many customers gravitate toward Vortex Tubes when needing parts and processes cooled. The fact of the matter is there is still more to be discussed on how to correctly select the which product may be needed in your application. The reason being, area, temperatures, and air flow volumes play a large role in choosing the best product for cooling. The tendency is to say, well I need to cool this down as far as possible so I need the coldest air possible which leads to the assumption that a Vortex Tube will be the right solution. That isn’t always the best option and we are going to discuss how to best determine which will be needed for your application. The first step, is to call, chat, or email an Application Engineer so that we can learn about your application and assist with the implementation of the Vortex Tube or other cooling product for you. You may also want to try and take some initial readings of temperatures. The temperatures that would help to determine how much cooling is going to be needed are listed below:
  • Part temperature
  • Part dimensions
  • Part material
  • Ambient environment temperature
  • Compressed air temperature
  • Compressed air line size
  • Amount of time desired to cool the part: Lastly desired temperature

With these bits of information, we use cooling equations to help determine what temperature and volume of air will best suit your needs to generate the cooling required. One of the equations we will sometimes use is the Forced or Assisted Convective Heat Transfer. Why do we use convective heat transfer rather than Natural Heat Transfer? Well, the air from EXAIR’s Intelligent Compressed Air Products® is always moving so it is a forced or assisted movement to the surface of the part. Thus, the need for Convective Heat Transfer.
Calculation of convection is shown below: q = hc A dT Where: q = Heat transferred per unit of time. (Watts, BTU/hr) A = Heat transfer area of the surface (m2 , ft2) hc= Convective heat transfer coefficient of the process (W/(m2°C), BTU/(ft2 h °F) dT = Temperature difference between the surface and the bulk fluid (compressed air in this case) (°C, °F)

The convective heat transfer coefficient for air flow is able to be approximated down to hc = 10.45 – v + 10 v1/2

Where: hc = Heat transfer coefficient (kCal/m2 h °C) v = relative speed between the surface of the object and the air (m/s)

This example is limited to velocities and there are different heat transfer methods, so this will give a ballpark calculation that will tell us if we have a shot at a providing a solution.  The chart below is also useful to see the Convective Heat Transfer, it can be a little tricky to read as the units for each axis are just enough to make you think of TRON light cycles. Rather than stare at this and try to find the hidden picture, contact an Application Engineer, we’ve got this figured out. convective_heat_transfer_chart

1 – Convective Heat Transfer Chart
Again, you don’t have to figure any of this out on your own. The first step to approach a cooling application is to reach out to an Application Engineer, we deal with these types of applications and equations regularly and can help you determine what the best approach is going to be.
Brian Farno Application Engineer BrianFarno@EXAIR.com @EXAIR_BF
1 – Engineering ToolBox, (2003). Convective Heat Transfer. [online] Available at: https://www.engineeringtoolbox.com/convective-heat-transfer-d_430.html [02/10/2021]

EXAIR Cold Gun Prevents Melting of Chocolate During Filling

With Valentine’s Day coming up in the U.S. many of us will be buying chocolates for our significant other. My wife (somehow) doesn’t particularly care for chocolate, so I buy some for her anyway knowing that it will sit around until I eat it. I think most of us would agree that chocolate is even more delicious when melted and drizzled all over the top of just about anything. But, melted chocolate isn’t always a good thing.

I recently worked with a company that manufactures chocolate products. They came out with a new line of small candies and were encountering an issue during packaging. In their process, the chocolates are formed, cooled, and packaged for resale. During the packaging process they were experiencing a problem that caused the chocolates to melt. The bags are heat-sealed along the sides and bottom. This heat was transferring from the bag to the chocolates and causing them to melt. Rather than having a finished package of individual candies, they were melting together to form one large lump. Not exactly what they are hoping to deliver to their consumers.

 

Video of the bag filling process

Fortunately, EXAIR offers a range of different products that are suitable for cooling. For this application, they utilized a Model 5330 High Power Dual Outlet Cold Gun. With the fan-type nozzle installed, they were able to cool both sides of the package immediately after sealing and just before filling the bags with chocolates.

EXAIR’s Cold Gun was a Product of the Year finalist in 2007. Using only a source of compressed air, the Cold Gun and High-Power Cold Gun produces a stream of clean, cold air 50° (28°C) below your compressed air supply temperature. The Cold Gun is very quiet at only 70dBA and has no moving parts to wear out. Just supply it with clean, dry compressed air and its maintenance free! It’s available as both a standard and High-Power option, providing 2x the cooling power. Each style is available with either a single or dual cold outlet flow.

The Cold Gun is pre-set to an 80% Cold Fraction. In other words, 80% of the compressed air supplied to it will exhaust from the cold end of the tube, 20% from the hot end. This prevents the Cold Gun from freezing up during use and optimizes the gun’s cooling capacity. The Cold Gun is an ideal alternative to messy and expensive coolant mist systems. It eliminates the cost of purchase and disposal of cutting fluids as well as worker related health problems from breathing airborne coolant or slipping on wet floors. Replacing a coolant-based system also eliminates the need for secondary cleaning operations after milling or drilling.

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

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