A review of refrigerant-based vortex tube separation characteristics: Devices, thermodynamic cycles and system experiments

Vortex tube is a device with energy self-separation and no moving parts. The existing studies mainly focused on the energy separation mechanism of vortex tube with air as the working fluid. The environmental impact of refrigerants needs to be considered when integrating vortex tube into refrigeration systems. Closed systems complicate the separation environment. Refrigerants, as non-ideal gases, may undergo phase change during energy separation in vortex tube, and the generated two-phase flow may lead to a deterioration or loss of energy separation. The separation characteristics of refrigerant as working fluid and its application in refrigeration systems are challenging and have not been systematically summarized. Therefore, this review innovatively analyzes the separation characteristics of refrigerant-based vortex tube (RBVT) from three aspects: devices, thermodynamic cycles and system experiments. The analysis indicated that RBVT can enhance the coefficient of performance (COP) of theoretical cycles when used as a throttling, cooling or separating device. Moreover, the optimal separation characteristics of RBVT in system require a deeper understanding of refrigerant behavior, vortex tube optimization mechanism, cycle construction and matching between components. This review completes the research progress of vortex tube at cryogenic temperature and provides a reference and future research directions for integrating vortex tube into refrigeration systems.