Numerical investigation of a double-circuit Ranque–Hilsch vortex tube

• A numerical simulation of double circuit Ranque–Hilsch vortex tube is proposed for the first time.
• Different turbulence models have been tested, highlighting the complexity of the velocity field.
• LES model results to be the best choice, but it requires high computational capabilities.
• SAS-SST model can be seen as a good compromise between computational efficiency and accuracy.

The present paper reports a numerical investigation of a double-circuit Ranque–Hilsch vortex tube. Different turbulence models, namely k–ε, k–ε RNG, SAS-SST, RSM-LRR and LES, have been tested, in order to understand which is the most suitable for the considered problem. The analysis is conducted on a full three-dimensional model and the results show that LES turbulence model provides the best accuracy of temperature separation prediction, standard k–ε and k–ε RNG have the worst accuracy, whereas RSM-LRR and SAS-SST turbulence models take an intermediate position. On the contrary, LES model is the most expensive in terms of computational time and resources. The results obtained with LES highlight very high radial velocity values, which result in the enhancement of the turbulent heat and mass transfer, which implies a more accurate prediction of the temperature separation effect. The present study concludes that LES model provides the best accuracy for the simulation of a double-circuit Ranque–Hilsch vortex tube, but at the same time RSM-LRR and SAS-SST models are a good compromise between computational efficiency and accuracy.