The Vortex tube (Ranque-Hilsch type/ RHVT) is a simple device used to obtain both cold and hot gas streams simultaneously from a compressed gas. The obtained cold gas is widely used in many low temperature commercial applications. In this work, the performance of the vortex tube was examined experimentally by studying the effects of inlet pressure variations, conical valve opening percentage, tube diameter and hot gas tube length on the thermal performance of the tube. Four tubes with diameters 14, 21, 25 and 32 mm with four hot exhaust gas lengths; 25, 50, 75 and 100 cm were tested experimentally and the obtained data were analyzed. It was observed that the 75 cm length of the hot side length, gives the maximum coefficient of performance for RHVT, as well as the maximum cold temperature reduction, either with or without insulation. Furthermore, the thermal performance of the RHVT was optimum for the two inner diameters; 14 and 21mm. This indicates that, when the ratio of hot side length to inner diameter (Lh/D) lies between 36 and 50, then the thermal performanmce of the RHVT is optimum and is highly recommended, which agrees with the results published in previous studies and invesitigations. [ABSTRACT FROM AUTHOR]