A vortex tube is a device that separates an incoming compressed gas into two streams, one having a lower temperature and the other having a higher temperature than the incoming gas. An experimental study on the vortex tubes having a different curvature was reported here with air as the working medium. With the increase in inlet pressure, the temperature separation and cooling capacity increased. Isentropic efficiency and cooling capacity as two performance parameters for a vortex tube were reported here. The U-shaped tube had better performance in terms of temperature separation and cooling capacity for the higher cold mass fraction at all inlet pressures. When compared to results reported by others, the use of the rectangular inlet instead of the circular inlet lead to better performance of the vortex tube. The plot of isentropic efficiency with respect to the cold mass fraction was flatter at low inlet pressure. Irrespective of the inlet pressure, the maximum isentropic efficiency for all types of tubes lies between 0.20 and 0.33. The flow visualization using dye was done on three different types of Perspex® tubes at low pressure. The curved and U-shaped tube had the larger number density of helices near the inlet, which resulted in higher temperature separation and subsequently cooling capacity in a vortex tube. © 2019 by Begell House, Inc.