Numerical investigation of energy separation in a vortex tube under different axial angles of injection nozzles

In this article, effect of axial angle of injection nozzles on the flow field structure in a Low-Pressure Vortex tube has been investigated by computational fluiddynamics (CFD) techniques. Numerical results of compressible and turbulent flows are derived by using of the standard k-ε turbulence model, where throughoutthe vortex tube was taken as a computational domain. The dimensions of studied vortex tubes are kept thesame for all models and the performance of machine isstudied under 6 different axial angles (β) of nozzles, including 0, 2, 4, 6, 8 and 10. Achieving to a minimumcold exit temperature and reduction of pressure at the end of nozzles is the main goal of this numerical research. The results show that utilizing this kind of nozzle changes the flow characteristic and energy separation of device such as hot and cold exit temperature differences. As a critical parameter, inletpressure is analyzed and for most of inlet pressures, using axial angle, device efficiency improved.Considering total pressure of cold flow, a new parameter, ξ is defined and it presents the gradient of cold flow’s total pressure along center line of vortextube in the corresponding maximum and minimum pressure points. We believe that changing the amount of ξ can affect the cold exit temperature directly. Finally,some results of the CFD models are validated by the available experimental data which show reasonableagreement, and other ones are compared qualitatively.