Vortex Tubes & Back Pressure

EXAIR Vortex Tubes are designed and manufactured to be the ideal solution for spot cooling applications.  They are ideal for end of arm tooling, in process checks, post welding, even to try and set a molten material before additional processing.   The Vortex Tubes work amazing with direct exposure to the point that needs to be cooled.   What if I had a 12″ wide weld that I was trying to cool in order to keep the heat from warping the material, could I simply connect a Super Air Knife that is 12″ long to the cold air output of a Vortex Tube?   The answer is you physically can, but the performance will not be optimal.

Cooling with the Vortex Tube
The EXAIR  Vortex Tube


EXAIR Super Air Knife
EXAIR Super Air Knife

The reason behind this is the Vortex Tubes performance continues to diminish as back pressure increases.  Once you reach 3 psig of back pressure you will begin to see decreased cooling in the cold air flow, once you reach 5 psig of back pressure the temperature out of the cold end of a vortex Tube can be as much as 5 degrees Farenheit warmer than without any back pressure at all. While a  Vortex Tube is capable of feeding cold air into a Super Air Knife it will be under significant back pressure and eliminate much of its cooling capacity. The Super Air Knife also becomes a heat sink which absorbs a great deal of the Vortex Tube’s cold air.

How an EXAIR Vortex Tube Works
How an EXAIR Vortex Tube Works.

To think about why the Vortex Tube reacts that way, think of the Vortex Tube as a pipe tee.   If you put compressed air into one leg and put no restrictions on the other two, a.k.a. the hot and cold end, the air flows freely out both open legs,  now if you start to restrict flow by adding piping and other restrictions, a.k.a. a Super Air Knife, onto one leg and leave the other leg open, then you will simply get decreased flow out of the restricted side and more flow out of the open leg. The good news is, if you have an application where a slight back pressure on the cold outlet is not avoidable then you can compensate for this and we can help you as long as we know all the variables.

That still doesn’t really help me with cooling my 12″ wide weld. What I would recommend in the scenario of cooling a longer length would be to try and control the volume of the area you need to cool.  In other words, if you could put a tube around the weld area where you can blow just the cold air down this cooling tunnel then you would have a controlled volume of air that will be much easier to maintain a cool temperature and keep the airflow against the surface of the part.

If you would like to discuss a cooling application, please contact us.

Brian Farno
Application Engineer Manager


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