> Entropy and the Second Law > Entropy
Hilsch-Ranque vortex tube
compressed air supply
thermocouple probe with digital
Connect the hose to the compressed
and open the valve all the way. The tube separates the faster and
slower moving molecules in the incoming airstream and sends them to
exits. Use the thermometer to show that colder air comes out the
short end of the tube and warmer air comes out the long end. Tc
< 0° C is easily obtained.
The air enters the tube
and follows a vortical path with faster moving molecules at the outer
and slower ones at inner radii. The hot air exhaust is at the
of the tube and the cold air exhaust is at the center.
The airflow at the hot air
Opening up the valve reduces the fraction of air ejected from the cold
air exhaust and lowers its temperature. Closing it down results
less but hotter hot air.
R. Hilsch, The Use of the
in A Centrifugal Field as Cooling Process, The Review of Scientific
vol. 18(2), 108-1113, (1947).
C. L. Stong, The "Hilsch" Vortex Tube,
Amateur Scientist, Scientific American, 514-519.
J. J. Van Deemter, On the Theory of
Cooling Effect, Applied Science Research 3, 174-196.