CFD simulations of the helium-xenon mixture flow and heat transfer

Helium-xenon gas mixtures are generally proposed for the working fluid of gas-cooled space nuclear reactors with Brayton cycle to achieve a compact design. The Prandtl number (Pr) of helium-xenon mixtures at certain mixing ratios can be significantly lower than that of pure gases, inducing problems in describing the turbulent heat transfer. In this paper, investigations are performed to study the feasibilities of different CFD methods which were used to simulate the flow and heat transfer of helium-xenon mixtures. The thermophysical properties that are used in the simulation are firstly re-examined. Then, various turbulent models are employed to test their applicability by comparing the simulations with experimental data. It shows that all calculations have a general consistent tendency with, but lower than, experimental data. The SST κ-ω model has a better prediction ability. Considering the fact that the turbulent Prandtl number (Pr_t) varies perpendicular to the wall surface for the low Pr fluids, the Kays-Crawford Prt model is introduced into the SST κ-ω model, and the simulation results prove to be improved significantly in various cases. (author)