Abstract: Existing cryogenic wind tunnels with cooling accomplished by spraying liquid nitrogendirectly into the tunnel circuit must equally discharge cryogenic gaseous nitrogen for keeping thesteadiness of the test flow. The tremendous "cool energy" carried away not only leads to heavydemands on liquid nitrogen and hence refrigerating power but also causes pollution of the localatmosphere.An alternative means of cooling air to cryogenic temperature by relying alone on the compres-sion energy of the air is presented....