Max Refrigeration vs. Max Cold Temp Vortex Tubes

Here at EXAIR, our vortex tubes are offered in two separate series. The reason for this is to optimize the performance of the cold air temperature drop when operating with opposite ends of the cold fraction chart. The maximum refrigeration vortex tubes, 32xx series, perform optimally when they are set to a greater than 50% cold fraction.  The maximum cold temp vortex tubes, 34xx series, perform optimally when they are set to a less than or equal to 50% cold fraction. The cold fraction is discussed more in-depth within this link from Russ Bowman, Vortex Tube Cold Fractions Explained. This blog is going to explain a little further why one series of vortex tubes would be chosen for an application over another.

Cold Fraction
EXAIR Vortex Tube Performance Chart

Maximum refrigeration (32xx) vortex tubes are the most commonly discussed of the two types when discussing the optimal selection of the vortex tube for an application. The 32xx series vortex tubes achieve a maximum refrigeration output when operated at 100 psig inlet pressure with around  80% cold fraction. This would give a temperature drop from incoming compressed air temperature of 54°F (30°C). The volumetric flow rate of cold air will be 80% of the input flow which means only 20% is being exhausted as warm exhaust air. By keeping the flow rate higher the air is able to cool a higher heat load and is the reason the vortex tube is given a BTU/hr cooling capacity.

Vortex Tube Hot Valve Adjustment

Maximum cold temperature (34xx) tubes are less common as their applications are a little more niche and require a very pinpoint application. Rather than changing the temperature inside of a cooling tunnel or cooling an ultrasonic welding horn, the max cold temp vortex tube is going to have a minimum cold flow rate, less than 50% of input volumetric flow.  This minimal flow will be at temperature drops up to 129°F (71.1°C) from the incoming compressed air temperature.  This air is very cold and at a low flow. A 20% cold fraction exhausts 80% of the input volume as hot air. This type of volume would be ideal for sensor cooling, pinpoint cooling of a slow-moving operation, or thermal testing of small parts.

In the end, EXAIR vortex tubes perform their task of providing cold or hot air without using any refrigerants or moving parts. To learn more about how they work, check out this blog from Russ Bowman. If you want to see how to change the cold fraction, check out the video below. If you would like to discuss anything compressed air related, contact an application engineer, we are always here to help.

Brian Farno
Application Engineer
BrianFarno@EXAIR.com
@EXAIR_BF

 

Minor Adjustments, Advice From An Expert Source

It’s not every day that we hear a customer say that our products aren’t consuming ENOUGH air, but that’s exactly what happened to me yesterday. I received a call from one of our long-standing customers who was experiencing reduced air consumption with our Model # 3202 Vortex Tube. The Vortex Tube uses compressed air to create a stream of cold air and a stream of hot air, providing a temperature range from -50°F to +260°F and cooling capacity up to 10,200 Btu/hr. Also, these units have no moving parts and are virtually maintenance free, making them the ideal choice for a variety of industrial spot cooling applications.

Vortex Tubes

This particular customer has been purchasing this model for several years, so they are pretty familiar with the performance and operation of the unit. They advised they were used to seeing air consumption at approximately 60 liters/minute or 2 SCFM (exactly what the Model # 3202 is designed to consume at 100 psig inlet pressure) but were starting to experience about a 50% drop to 30 liter/minute or 1 SCFM. We discussed the common troubleshooting:

  • Low supply pressure? (measuring at the inlet of the Vortex Tube during operation)
  • Compressed air inlet temperature? (warmer than ambient air – reducing performance)
  • Reduced cold flow? (possible clog from contaminants in the compressed air supply)
  • Unit seeing any back pressure? (up to 2 PSIG is acceptable, 5 PSIG will reduce approximately 5°F)
  • Over-tightened Cold Cap or Cold Muffler? (is it too tight?)

The customer advised they were using a push-to-lock fitting, where they drilled out the center and then would install it in the Cold Cap of the Vortex Tube. Their operator would hold the body of the Vortex Tube, by the air inlet, then take a wrench and thread the fitting into the ¼” NPT female opening on the Cold Cap. Without realizing, the operator was also turning the Cold Cap which was causing it to become over-tightened.  This in turn would reduce the consumption of the unit because it would shrink the internal air chamber.

Vortex Tube Exploded View

 

I made the suggestion to my customer to slightly loosen the Cold Cap and see if that didn’t fix the consumption issue. They called me back about an hour later and were very pleased to advise that now the unit was “working great!”.

We want to help you maximize our products, while optimizing your compressed air system. If you have a similar performance issue or would like to discuss your application, please contact us.

Justin Nicholl
Application Engineer
justinnicholl@EXAIR.com
@EXAIR_JN