Analysis of various separation characteristics of Ranque-Hilsch vortex tube and its applications - A review

The Ranque-Hilsch vortex tube (RHVT) is a compact thermo-fluidic device primarily used to split a highly pressurized gaseous fluid into two different temperature streams. Vortex tubes are mainly known for their energy separation characteristic. But the interesting fact is that the vortex tube can also separate constituents of the fluid mixture into various phases. In some instances, the highly swirling fluid inside the RHVT gets split into distinct species at the outlets. This paper reviews previous vortex tube studies on energy, phases, and species separation to analyze the mechanism and their influencing parameters. The paper also includes a brief CFD study conducted on five working gases to show the nature of thermal separation. The effect of nozzle number and nozzle geometry, L/D ratio and divergent angle of the main tube, and conical valve geometry are discussed for each separation behavior. Operating parameters such as inlet pressure, temperature, and thermo-physical properties of working fluids are discussed for the efficient and optimized operation of RHVT. Reviewing the previous literature supported exploring more novel ideas in optimizing separation techniques, such as the appropriate selection of tube material, cooling of the hot tube, and insulation near the cold end. The analysis presented a broad application of RHVT utilizing its energy and mass separation behavior in several mechanical processes. The study also led to an understanding of the utility of RHVT in trans-critical refrigeration systems, water droplet separation, and liquid oxygen collection systems.(c) 2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.