Numerical investigation of the thermo-hydraulic characteristics for annular vortex tube: A comparison with Ranque-Hilsch vortex tube

In this work, a new configuration of the vortex tubes (VTs), called annular VTs, is proposed to improve the temperature separation performance. In the proposed configuration, a compartment has been added on the top of the tube wall that the separated hot outlet is repassed inside it over the hot tube. An axisymmetric swirl model of the Ranque–Hilsch (RH) and annual VTs is numerically simulated, and the thermo-hydraulic characteristics of them are compared for cold mass fractions ranging 0.2–0.8. The results illustrated that a small secondary circulation is created near the cold outlet of the RHVT that is not observed in the annular model. This secondary circulation is a destructive mechanism in VTs that results in more mixing and higher temperature in the cold outlet section. Analyzing the results indicates that using annular VT causes up to 12.51% increment of the hot outlet temperature compared to the RHVT model (which occurs at a mass fraction of 0.23). Also, up to 9.23% reduction of the cold outlet temperature is occurred (which occurs at a mass fraction of 0.37). These explanations prove the improvement of the annular VT compared to that of the conventional VTs.