Numerical benchmark of a Ranque–Hilsch vortex tube working with subcritical carbon dioxide

Abstract

A numerical benchmark of a Ranque–Hilsch vortex tube using subcritical carbon dioxide as the working fluid is performed. Predictions using different thermodynamic and two-equation turbulence models in high or low-Reynolds number formulations are compared to experimental data available in the literature. The results show that the k−ω SST model outperforms both the Standard k−ϵ model and the SAS-SST model in terms of cold and hot outlet total temperature predictions. Considering real-gas equations of state improves the accuracy even at subcritical conditions. In this regard, the multi-parameter Span–Wagner equation of state yields the best hot outlet total temperature prediction, especially at high operating pressure. Hence, the k−ω SST model in conjunction with the Span–Wagner equation of state are selected to examine internal flow features and discuss the validity of most common assumptions made by one-dimensional thermodynamic models. Finally, the exergy efficiency of the present vortex tube at various cold mass fractions is quantified.