Experimental study of the energy separation in a vortex tube

•The influences of inlet pressure and cold mass fraction were explored.•The static temperature of the return flow is higher than that of the annular part.•When the cold fraction increases to a certain value, the stagnation point appears.•With the decrease of the inlet pressure, the stagnation point moves to the cold end.•With the increase of the cold fraction, the stagnation point moves to the cold end.

A vortex tube is a simple-structure device which can separate a compressed stream into a hot and a cold stream. The accurate flow pattern inside the vortex tube remains elusive and no satisfactory explanation of its energy separation mechanism has been put forward yet. In this work, the influences of inlet pressure and cold mass fraction on the performance of the vortex tube were explored.The experimental results show that the static temperature in the center of vortex tube is higher than that of the peripheral part. Besides, the stagnation point inside the vortex tube moves to the cold end with the decrease of the inlet pressure or the increase of the cold mass fraction. This paper also tries to present an explanation for the maximum cooling effect and the maximum heating effect when the cold mass fraction is about 0.3 and 0.8, respectively.