Liquid lithium metal is characterized by low density, high heat capacity and high thermal conductivity, which makes it suitable for cooling the reactor core in the space environment. Liquid metal has low Prandtl number (Pr), which is different from the flow and heat transfer characteristics of conventional fluid such as air and water. Therefore, the flow and heat transfer characteristics of liquid lithium need to be studied in depth to make up for the shortcomings of the existing heat transfer correlations.

This study aims to analyze the flow and heat transfer characteristics of liquid lithium in the rod bundle channel using numerical simulation for the space lithium-cooled fast reactor.

The single component rod bundle channel of the SP-100 reactor core was used as the research object in this study. Firstly, the accuracy of the SST k-ω turbulent model coupled with the Cheng turbulent Pr model used for calculating the flow and heat transfer characteristics of liquid lithium was validated. Secondly, the effect of the Peclet number (Pe) on the flow and heat transfer characteristics of liquid lithium at the same heat flux was investigated. Then, the heat flux was changed to analyze the effect of heat flux on the flow and heat transfer characteristics of liquid lithium. Finally, the variation trend of pressure drop with Pe were analyzed.

Numerical simulation results show that, with the gradual increase of the Pe, the heat transfer performance of liquid lithium is gradually enhanced whilst the pressure drop in the flow process is increased. The conduction effect of liquid lithium at Pe of 120 in this assembly is comparable to the convection effect with a Nusselt number (Nu) of about 1. The size of the heat flux has a small effect on the flow heat transfer performance of liquid lithium. The pressure drop is positively correlated with Pe. The pressure drop is less than 1 kPa when Pe is in the range of 15 to 60, and when Pe reaches 1 500, the pressure drop is up to 124 kPa.

This study can provide a reference for the core design and safety analysis of space lithium-cooled fast reactor.