Numerical investigation on convective heat transfer performance of liquid lithium in both a round tube and a 19-rod bundle channel

Space lithium-cooled fast reactors (LFRs) have great development potential in the future. Currently, relevant research on the analysis of convective heat transfer performance for liquid lithium (Li) remains lacking. A series of Computational Fluid Dynamics (CFD) simulations were carried out for the purpose of studying the heat transfer performance of liquid Li. The SST k-ω model and the Cheng-Tak turbulence Prandtl number (Pr t ) model were selected in this work. A systematic analysis was undertaken of the variation patterns exhibited by the Nusselt number ( Nu ) for liquid Li in both a round tube and a 19-rod bundle channel, evaluating the applicability of existing Nu correlations. The results indicate that at the same Pe , with increasing tube diameter, the convective heat transfer coefficient ( h ) shows a decreasing trend, while the Nu exhibits an increasing trend. In the 19-rod bundle channel, a maximum h is achieved when the pitch-to-diameter ratio ( P/D ) is 1.10. At P/D is 1.20, liquid Li in the channel near the wall begins to flow into the central channel, and the transverse mixing effect starts to intensify. This work broadens the scope of liquid metal research and provides valuable references for the development of LFRs. • At P/D is 1.20, transverse mixing effect of liquid lithium starts to intensify. • For a round tube, the Nu correlation proposed by Subbtion et al. is recommended. • The convective heat transfer coefficient reaches the maximum value for P/D is 1.10.