Assessment of advanced RANS models to predict the heat transfer for supercritical fluids in vertical tubes

The extreme thermophysical property changes of fluids near the pseudocritical point lead to strong buoyancy and acceleration effects, posing challenges for turbulence modelling. This paper aims to assess the performance and applicability of various turbulence models, with the intention of providing a useful reference for quickly selecting appropriate models and for models' further improvement. Additional Favre-averaged turbulence models were implemented through user-defined scalars in ANSYS Fluent and compared to published experimental and high-fidelity simulation data. This study found that the tested turbulence models have different sensitivities to mo-lecular Prandtl numbers, buoyancy effects, and flow acceleration. For forced convection, all turbulence models can be applied in the case of the flow acceleration number Kv < 1.37 x 10(-8), and the ZXY model has the widest application range. None of the tested turbulence models showed generalizability under mixed convective con-ditions. The Lien-PSA model qualitatively reproduced the wall temperature trends for all tested cases.

Automated summary

This study aims to evaluate the performance and applicability of different turbulence models near the pseudocritical point of fluids, and it found that these models have different sensitivities to molecular Prandtl numbers, buoyancy effects, and flow acceleration. Under forced convection conditions, appropriate turbulence models can be selected by limiting the flow acceleration number. However, none of the tested turbulence models showed generalizability under mixed convective conditions.