A Numerical Study on the Effect of Length to Diameter Ratio and Stagnation Point on the Performance of Counter Flow Ranque-hilsch Vortex Tubees

In this numerical study, performance of Ranque-Hilsch vortex tubes, with a length to diameter ratios (L/D) of 8, 9.3, 10.5, 20.2, 30.7, and 35 with six straight nozzles, on the basis of experimental results were investigated. Also, this study has been done to understanding the effects of stagnation point location on the performance of RHVT. CFD analysis is employed to achieve the highest temperature separation and optimum length to diameter (L/D) ratio of the Ranque-Hilsch vortex tubes. The temperature separation phenomenon in the vortex tube has been obtained by a 3D compressible turbulent CFD model. It was found that the best performance was obtained when the ratio of vortex tubeʹs length to the diameter was 9.3 and also at this model the stagnation point was found the farthest from the inlet. The results showed that the closer distance to the hot end will provide large amounts of temperature difference. The location of stagnation point calculated by the two methods and were compared for various lengths of vortex tubes. Moreover, it is found that increasing the cold mass fraction decreases the cold temperature difference and efficiency. Finally the computed results such as velocity and temperature variations calculated and discussed in more details. Presented results in this paper shown good agreement with experimental results