The effects of nozzle aspect ratio and nozzle number on the performance of the Ranque–Hilsch vortex tube

An experimental study is carried out to investigate the effects of nozzle aspect ratio and nozzle number on the performance of a vortex tube. Two sets of vortex generator (a single nozzle set with aspect ratio of AR = 0.25, 0.44 and 0.69 and a multiple nozzle set with 2 and 3 nozzle number having the same total flow area) are tested under different inlet pressures. Dry air is used as the working fluid. The experimental results reveal that the nozzle aspect ratio has a great effect on the energy/temperature separation mechanism. The increase in the nozzle aspect ratio leads to the larger mixing zones, which, in turn, decreases the temperature difference between the cold and hot stream, the heating and the cooling performance. The results also showed that the vortex tube with a single nozzle yields better performance than the vortex tube with 2 and 3 nozzles.

► The temperature difference is increasing with increasing inlet pressure.
► The performance of the vortex tube decreases with increasing nozzle aspect ratio.
► The single nozzle yields to better performance than the vortex tube with 2 and 3 nozzles.
► The optimum cold mass fraction varies with the change of nozzle number.