In this study, a new geometry is introduced for the cold end side (i.e. where the swirl flow is introduced into the tube), which is called helical swirl flow generator'. Effect of the helical length of the swirl flow generator on the performance of the vortex tube are investigated for varying values of other geometrical parameters as a function of the cold mass fraction, ye. Finally, it's disclosed that the effect of the helical length on the performance changes critically according to the value of L/D. (C) 2010 Elsevier Ltd. All rights reserved.