Energy separation procedure of vortex tube can be improved by using convergent nozzle. In the experimental investigation, the parameters are focused on the convergence ratio of nozzle, inlet pressure and number of nozzle intakes. The effect of the convergence ratio of nozzle is investigated in the range of 1-2.85. The most objective of this investigation is the demonstration of the successful use of computational fluid dynamics (CFD) in order to develop a design tool that can be utilized with confidence over a range of operating conditions and geometries, thereby providing a powerful tool that can be employed to optimize vortex tube design as well as assess its utility in the field of new applications and industries. A computational fluid dynamics model was developed to predict the performances of the vortex tube system. The numerical investigation was carried out by full three-dimensional (3D) steady state CFD simulation using FLUENT 6.3.26. This model utilizes the k-epsilon turbulence model to solve the flow equations. Experiments were also conducted to validate results obtained for the simulation. First purpose of numerical study in this case was validation with experimental data to confirm these results and the second was the optimization of experimental model to achieve the highest performance. (C) 2013 Elsevier Ltd. All rights reserved.