Analysis of energy separation mechanism of vortex tube and collaborative study with cold end aperture based on inlet nozzle diameter

Vortex tube, a mechanical device with simple structure designed for energy separation, is widely used in many fields. The nozzle structure of vortex tube has an important influence on its energy separation performance. At present, most studies only focus on identifying the optimal size parameters and rarely explore the influencing mechanism. This study employs numerical simulation to investigate how the vortex tube’s performance changes with variations in the inlet nozzle diameter and analyzes the internal mechanism of the above variation through flow fields. The findings indicate that reducing the inlet nozzle diameter enhances the velocity gradient and vortex intensity near the hot-end tube, promoting greater energy transfer from inner to outer fluid layers, which improves the vortex tube’s energy separation efficiency. It is also observed that the reverse flow boundary of vortex tube shrinks inward as the inlet nozzle diameter increases. Additionally, the synergistic relationship between the inlet nozzle diameter and the cold-end aperture in affecting the performance of vortex tube is investigated, which indicates as the inlet nozzle diameter increases, there are different optimal cold-end apertures, which make the vortex tube performance optimal.