Through numerical simulations conducted with FLUENT software, vortex tubes with circular and rectangular nozzles, both of the convergent and straight types, having the same inlet area, were studied. This research investigated the refrigeration effects of these four types of vortex tubes at pressures of 0.3, 0.4, and 0.5 MPa and analyzed the temperature field, pressure field, and velocity field at 0.5 MPa to understand the internal flow patterns, mechanisms, and cooling performance. It was found that under a pressure of 0.5 MPa, the rectangular straight-type nozzle demonstrated the best energy separation performance; meanwhile, the rectangular convergent-type nozzle showed stable cooling effects at all operating pressures and had superior flow stability. The results indicate that the convergent nozzles, due to their more uniform pressure distribution and significant radial pressure gradient, positively contribute to enhancing the cooling efficiency and operational stability of vortex tubes.