## Vortex Tube Cold Fraction and how it Affects Flow and Temperature Control

Vortex Tubes are the perfect solution when dealing with a variety of spot cooling applications. They use compressed air to produce a cold air stream and a hot air stream, with temperatures ranging from as low as -50°F  up to +260°F (based on ambient supply temperature) and providing as much as 10,200 Btu/hr. of cooling capacity. By simply adjusting the valve in the hot end of the Vortex Tube, you are able to control the “cold fraction” which is the percentage of air consumed by the vortex tube that is exhausted as cold air versus the amount of air exhausted as hot air. Our small, medium and large Vortex Tubes provide the same temperature drop and rise, it’s the volume of air that changes with the various sizes.

When looking at the below performance chart, you will see that “Pressure Supply” and “Cold Fraction %” setting all play a part in changing the performance of the Vortex Tubes. Take for example, an operating pressure of 100 PSIG and cold fraction setting of 20%, you will see a 123°F drop on the cold side versus a 26°F temperature rise on the hot side. By the using the same Vortex Tube and keeping the operating pressure at 100 PSIG but changing the cold fraction to 80%, you will now see a 54°F temperature drop on the cold side and a 191° rise at the hot end.

We’ve looked at how the cold fraction changes the temperature, but how does it change the flow for the various Models?

Say you are using a Model # 3240 Medium Vortex Tube which consumes 40 SCFM @ 100 PSIG. Again with the cold fraction set at 80% (80% of the consumed compressed air out of the cold end), you would flow 32 SCFM at the cold air exhaust.

40 SCFM x 0.8 (80% CF) = 32 SCFM

Using the same Model # 3240 Medium Vortex Tube but now with a 20% cold fraction (20% of consumed compressed air out of the cold end), you would flow 8 SCFM at the cold exhaust.

40 SCFM x 0.20 (20% CF) = 8 SCFM

As you can see, to achieve the colder air temperatures, the volume of cold air being exhausted is reduced as well. This is important to consider when making a Model selection. Some other considerations include the operating pressure which also has a significant effect on performance. The compressed air supply temperature is important because the above temperatures are temperature differentials, so in the example of the 80% cold fraction there is a 115F temperature drop from your inlet compressed air temperature.

If you need additional assistance, you can always contact myself or another application engineer and we would be happy to make the best selection to fit your specific need.

Jordan Shouse
Application Engineer

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## EXAIR’s Adjustable Spot Cooler: A Versatile Tool for Your Cooling Needs!

If you’re looking at replacing messy coolant mist systems, look no further than the Adjustable Spot Cooler. EXAIR’s Adjustable Spot Cooler incorporates Vortex Tube technology to produce temperatures ranging from -30°F – +70°F. A Vortex Tube works by imparting a rapid spinning motion to the supplied compressed air. This airflow makes its way to the end of the tube where it is forced to abruptly change directions. It is during this change of direction that energy is given off in the form of heat. The hot air then exits the tube from the hot end, while cold air exits the other end of the tube. As the valve is opened to allow more air to exhaust from the hot end, the temperature at the cold end will decrease. At a sound level of just 73 dBA when operated at 100 psig and stock generator installed, this compact cooler will keep your operation cool, clean and dry without causing unnecessarily high noise levels.

When looking at a Vortex Tube based solution, the variety of options can sometimes be daunting. This is where the versatility of the Adjustable Spot Cooler shines. Through a simple turn of the control knob, you can easily adjust the temperature and cold fraction of the unit. Additionally, the kits come with (2) extra generators (15-H and 30-H) that can be swapped out for the stock generator for more/less cooling power and air consumption. The 15-H generator will deliver up to 1,000 Btu/hr of cooling capacity and the 30-H will provide up to 2,000 Btu/hr of cooling capacity. We have (2) different kits available, the Model 3825 Single Point and the Model 3925 Dual Point Kit. The 3825 is recommended for use in applications where you’re cooling a small surface such as solder joints, hot melts, or drilled plastics. The 3925 system is better served when heat is generated over a larger surface area such as saw blade cooling. The kits use flexible Loc-Line hose to allow you to precisely position the cold airflow onto your target. The Adjustable Spot Cooler provides easy mounting with a swivel magnetic base, allowing you to mount the cooler directly at the most critical point that heat is being generated.

If you’re tired of cleaning up your coolant or have an application that requires dry machining, get one of the Adjustable Spot Cooler systems on order today. They’re in stock ready to ship!

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

## Vortex Tube Cold Fractions

Vortex Tubes are the perfect solution when dealing with a variety of spot cooling applications. They use compressed air to produce a cold air stream and a hot air stream, with temperatures ranging from as low as -50°F  up to +260°F (based on ambient supply temperature) and providing as much as 10,200 Btu/hr. of cooling capacity. By simply adjusting the valve in the hot end of the Vortex Tube, you are able to control the “cold fraction” which is the percentage of air consumed by the vortex tube that is exhausted as cold air versus the amount of air exhausted as hot air. Our small, medium and large Vortex Tubes provide the same temperature drop and rise, it’s the volume of air that changes with the various sizes.

When looking at the below performance chart, you will see that “Pressure Supply” and “Cold Fraction %” setting all play a part in changing the performance of the Vortex Tubes. Take for example, an operating pressure of 100 PSIG and cold fraction setting of 20%, you will see a 123°F drop on the cold side versus a 26°F temperature rise on the hot side. By the using the same Vortex Tube and keeping the operating pressure at 100 PSIG but changing the cold fraction to 80%, you will now see a 54°F temperature drop on the cold side and a 191° rise at the hot end.

We’ve looked at how the cold fraction changes the temperature, but how does it change the flow for the various Models?

Say you are using a Model # 3240 Medium Vortex Tube which consumes 40 SCFM @ 100 PSIG. Again with the cold fraction set at 80% (80% of the consumed compressed air out of the cold end), you would flow 32 SCFM at the cold air exhaust.

40 SCFM x 0.8 (80% CF) = 32 SCFM

Using the same Model # 3240 Medium Vortex Tube but now with a 20% cold fraction (20% of consumed compressed air out of the cold end), you would flow 8 SCFM at the cold exhaust.

40 SCFM x 0.20 (20% CF) = 8 SCFM

As you can see, to achieve the colder air temperatures, the volume of cold air being exhausted is reduced as well. This is important to consider when making a Model selection. Some other considerations would be the operating pressure which you can see also has a significant effect on performance. Also the compressed air supply temperature because the above temperatures are temperature differentials, so in the example of the 80% cold fraction there is a 115F temperature drop from your inlet compressed air temperature.

If you need additional assistance, you can always contact myself or another application engineer and we would be happy to make the best selection to fit your specific need.

Justin Nicholl
Application Engineer
justinnicholl@exair.com
@EXAIR_JN