Issues and prospects of energy separation in vortex tubes: Review

A vortex tube is a device that separates entering compressed fluid into hot and cold fluid streams simultaneously. This energy separation phenomenon inside the tube is a mystery and the mechanism that causes heat transfer needs attention. Since the invention of the vortex tube, the scientific community has taken efforts to search for energy separation mechanisms. Performance augmentation and the physics of energy separation was the objective of many experimental studies. The performance of the vortex tube varies with changes in geometric and operational parameters. Most of the theoretical studies addressed the issue of energy separation. Prospects and issues of energy separation in a vortex tube in view of the literature is the core of this paper. The main objective is to discuss efforts made in order to justify the physics and to identify new areas for research.