Present paper is aimed towards reporting CFD study carried out on counter-flow vortex tube using different gases at various values of cold mass fraction and using different turbulence models. In CFD analysis of counter flow vortex tube, various working gases have been seldom used and their energy separation effect studied relative to cold mass fraction. Also, computational efforts to compare results of one equation Spalart Allmaras model used for analysis of counter-flow vortex tube with other two equation turbulence models, that is, Standard k-epsilon and Standard k-omega model as well as RSM (Reynolds Stress Model) have been seldom reported. All turbulence models are observed to predict similar flow physics inside vortex tube, however, with different magnitude. Spalart Allmaras model over predicts while RSM under predicts temperature separation magnitude. Nitrogen as working fluid of vortex tube produces highest temperature separation, while it is least for CO2 among the working fluids studied. Cold mass fraction is an important parameter which directly affects the temperature separation. Cooling power separation should also be considered as an important performance parameter of vortex tube, instead of cold end temperature alone. Results of present CFD study are in better agreement with experimental results than previous CFD results. (C) 2015 Elsevier Ltd. All rights reserved.