Effect of Length on Energy Separation of Counter Flow Vortex Tube using Numerical Simulation

Abstract

Ranque-Hilsch vortex tube is a device which enables separation of hot and cold air as compressed air flows tangentially into vortex chamber through inlet nozzles. This separation process of cold and hot air by using principle of vortex tube has got wide range of applications in cooling equipment in CNC machines, refrigerators, cooling suits, heating processes, etc. Its popularity is mainly due to reliability, lack of maintenance and simple inexpensive construction. In general, a vortex tube is constructed to obtain maximum temperature separation. Main design parameters to be considered during vortex tube designing are length and diameter of vortex tube, diameter and location of inlet nozzle, diameter of cold nozzle etc. any of the design parameters which effect flow field within the tube will also affect the performance of vortex tube. Main objective of this present work is to conduct a numerical study on effect of length on temperature difference in vortex tube. A two-dimensional axisymmetric CFD model has been developed. Simulation of turbulent, compressible, highly swirling flow inside vortex tube is performed using RANS approach using ANSYS fluent 16.2 software. The second-order numerical schemes were used to carry out all the computations. In this numerical study, performance of Ranque-Hilsch vortex tubes, with length to diameter ratios of 3,5,6.915,8,9,10 and 15,18 were analyzed. It was found that the best performance was obtained when the ratio of vortex tube length to the diameter was 15.