A critical review of temperature separation in a vortex tube

The vortex tube is a simple device used in industry for generation of cold and hot air streams from a single compressed air supply. This simple device is very efficient in separation of air streams of different temperatures and has been the focus of investigation since the tube’s discovery. Different explanations for the phenomenon of the energy separation have been proposed, however there has not been a consensus in the hypothesis. The purpose of this paper is to present a critical review of current explanations on the working concept of a vortex tube. Hypotheses of pressure, viscosity, turbulence, temperature, secondary circulation and acoustic streaming are discussed in the paper, and presumably, future research will benefit from this discussion.