Vortex tube is the device that can separate small particles from the compressed gas, as well as compressed gas into hot and cold flow. In this study, design parameters are orifice diameter and nozzle number. Orifice diameter is the critical design factor for a vortex generator because a orifice diameter divides cold and hot flow. The number of nozzle controls the intensity and uniformity of swirl flow. As a result, the vortex generator with orifice diameter 0.7D and 8 inlet nozzles shows the best energy separation effect.