Numerical Investigation on the Principle of Energy Separation in the Vortex Tube

A vortex tube is a simple device that separates incoming gas into cold and hot gases. Several theories have been proposed to explain the principle of energy separation in the vortex tube. Existing theories have advantages and defects. Recently, various studies employed numerical simulations to study the flow in the vortex tube. As a result, flow structures were well clarified. However, in most cases, the temperature separation was partially discussed based on the temperature distribution in the radial direction. This study aimed to explain the principle of energy separation in the vortex tube. To do so, the relative contributions of the radial pressure gradient, axial pressure gradient, and viscous dissipation to the temperature separation were investigated using numerical simulations and energy equation analysis. The results indicated that the axial pressure gradient in the near-axis region was the major contributor to an increase in hot exit temperature. In addition, the reason for the increase in hot exit temperature with an increase in cold mass fraction was explained. The reason for the decrease in cold exit temperature with an increase in cold mass fraction was also explained.