In this paper, a Ranque–Hilsch vortex tube (RHVT) has been optimized utilizing convergent (*φ*), straight, and divergent (*θ*) axial angles for hot-tube. Effects of divergent (*θ*) and convergent (*φ*) angles on the flow behavior have been investigated by computational fluid dynamic (CFD) techniques. By using a renormalization group (RNG) k–*ε* turbulence model based on finite volume method, all the computations have been carried out. The isentropic efficiency (η_{is}) and coefficient of performance (COP) of machine was studied under five different divergent angles (*θ*), namely 1 deg, 2 deg, 3 deg, 4 deg, and 6 deg, two different convergent (*φ*) angles (*φ*) namely 1 deg and 2 deg adjusted to the hot-tube. Furthermore, some geometrical and operational parameters including cold outlet diameter, hot-tube length, and different inlet pressures and mass flow rates have been analyzed in detail (spanwisely) in order to optimize the cooling efficiency of vortex tube (straight). The results show that utilizing the divergent hot-tubes increases the isentropic efficiency (η_{is}) and COP of device for most values of inlet pressures, and helps to become more efficient than the other shape of vortex tubes (straight and convergent). Finally, some results of the CFD models have been validated by the available experimental and numerical data, which show reasonable agreement, and others are compared qualitatively.