Experimental investigation of the flow characteristics driving the Ranque–Hilsch phenomenon

The Ranque–Hilsch vortex tube (RHVT) is a device that separates a pressurized inlet stream into two decompressed streams of different temperature, flowing to the so-called hot and cold outlets. In this study, the flow structures within the vortex tube were examined qualitatively. The examination considered both compressible and incompressible fluids, using pressurized air and water as working fluids. A parametric study was conducted, in which the fluid inlet pressure and the vortex tube length were varied. Three tubes, with the same diameter but differing lengths (100, 180, and 240 mm) were utilized. The flow inside the tube was investigated using a flow visualization technique, which was employed in a variety of configurations and setups contingent on the specific fluid conditions under examination. The visualization process required the use of aerosol injection in the case of air, and kalliroscope particles in the case of water investigation. The research enabled the visualization of the flow structure within the vortex tube, thereby significantly advancing the comprehension of the underlying physical processes. The findings of the experimental research demonstrated the existence of phenomena of considerable scientific value. The internal vortex and its spatial and temporal structure observed in the RHVT were consistent with literature data. This was achieved despite the so-far established consensus that this type of research is challenging and not entirely reliable. In the course of water-based investigation, the cavitation phenomenon was observed in the vicinity of the internal vortex. This discovery is likely to be the first of its kind and may contribute significantly to the advancement of research on the Ranque–Hilsch phenomenon.