Vortex tubes used as expansion device in vapor compression systems

The vortex tube is an intriguing device which can separate an incoming high pressure fluid stream into two low pressure fluid streams with different temperatures. The internal flow separation is achieved without any moving parts, which makes the device robust and inexpensive to design and manufacture. Commercially available vortex tubes are almost exclusively used for spot cooling in industrial applications and use compressed air as the working fluid. Fluids such as carbon dioxide which display substantial throttling losses justify research on expansion devices that can recover expansion work. Most of the work on vortex tubes used for refrigeration has been on numerical studies, and many of them predict very optimistic energy efficiency improvements. However, the operating conditions for vortex tube in these cycles are usually not possible to produce significant thermal separation as expected. In this paper, vortex tube thermal separation performance for air and a more conventional low-pressure refrigerant is provided. Suitable vortex tube operating conditions have been identified and actual work recovery effects have been demonstrated experimentally. Based on this knowledge, novel vortex tube cycles are proposed which are able to utilize the demonstrated improvement potentials of vortex tube when applied to vapor compression systems.