NOTATION L, d, vortex tube length and diameter; dd, diaphragm diameter; Ld, distance between the tangential inlet channels and the location of the pressure, transducer; Fin, area of the tangential inlet channels; AP, pressure drop in the vortex tube; AP'h.f., AP/.I., AP' E, amplitudes of the low-and high-frequency pressure fluctuations and the total pressure fluctuation level; f/.f., fh.f., low-and high-frequency pressure fluctuation frequencies; p, relative mass flow rate of the cooled air; and ATx, ATg, air cooling and heating effects in the vortex tube.