http://nexflowair.com/vortex_tube.php - Compressed air enters at point (A) .  Inside the Vortex Tube / Hilsch Tube the compressed air is made to spin using a “generator”.   It travels in one direction along the small (hot end) vortex tubes and then back inside itself in the reverse direction creating one stream of air (B) and the second  stream of air  (C) in the opposite direction.  The outside stream of air gets hot and exhausts at point (D).  The centre column of air gets cold and exists at point (E).  Temperatures and capacities can vary by adjusting the hot end plug at (D) and by using different “generators” .