Masoud Rahimi - M.Sc. Student, Department of Mechanical Engineering, Urmia University of Technology, Urmia
Nader Pourmahmoud - Associate Professor, Department of Mechanical Engineering, Urmia University, Urmia
Seyyed Ehsan Rafiee - M.Sc. Student, Department of Mechanical Engineering, Urmia University of Technology, Urmia
Amir Hassanzadeh - Ph.D. Student, Department of Mechanical Engineering, Urmia University, Urmia

Vortex tube refrigerator is a mechanical device with no moving parts that is capable of generating cold and hotgas flows from compressed gas. A source of pressurized gas enters the vortex tube tangentially through one ormore inlet nozzle intakes with high speed. The gas stream inside the vortex tube develops a strong swirlingflow and separates into a cold and hot stream. Experimental studies show that using divergent hot tubeimproves the cooling performance of vortex tube. The purpose of this paper is to investigate the effect of usinga divergent hot tube on vortex tube refrigeration capacity. The computational fluid dynamics (CFD)model used here is a three-dimensional steady compressible model that utilizes the k-ɛ turbulence model. In this numerical research, different divergence angles of the hot tube (β=0°, 1°, 2°, 3°, 4°, and 6°) have been simulated in order to analyze the performance of the vortex tube. The results showed that as the anglediverges from the cylindrical model (β=0°), the cold temperature separation improves at cold mass fractionsgreater than about 0.4, but increasing the angle to more than 4° impairs the cold temperature separationcompared with the cylindrical model because of the development of a secondary circulation in the vortextube. Validation of a previous experimental study that used a cylindrical vortex tube has also been carried outin this research.

Vortex tube; Divergent hot tube; Numerical simulation; Energy separation