Investigation on Laminar Flow and Heat Transfer of Helium-Xenon Gas Mixtures with Variable Properties

The space Brayton nuclear reactor system usually adopts the helium-xenon gas mixture (He-Xe) as the working fluid. The flow of He-Xe in the micro channel regenerator of the system is generally laminar. Since the properties of He-Xe are significantly different from those of common pure gases, the impact of this difference on the laminar flow and heat transfer needs to be evaluated. In present study, the numerical simulations of laminar convective heat transfer for helium, nitrogen and He-Xe are conducted by Ansys Fluent. Compared with simulation results, the applicability of existing laminar friction factor (f) and Nusselt number correlations is evaluated. By establishing the functions of property ratios with the temperature ratio and the mixing ratio, a new laminar f correlation for property-variable He-Xe is proposed. Results show that the calculation error of existing f correlations for He-Xe is obviously large, exceeding 13%. With the new f correlation, the predictions of laminar f for He-Xe are in good agreement with the simulation results in the fully developed region, and the calculation error is reduced to 3%.