Numerical investigation of buoyant effect on flow and heat transfer of Lithium–Lead Eutectic in DFLL–TBM

Thermal–hydraulic behaviors of Lithium–Lead Eutectic (PbLi) in Chinese ITER Dual Functional Lithium–LeadTest Blanket Module (DFLL–TBM) were investigated numerically by using CFD code ANSYS CFX. The influences of buoyant effect on flow and heat transfer of PbLi were analyzed and the validity of Boussinesq approximation for liquid PbLi with non-uniform heat generation was discussed. Comparisons between two scenarios with and without buoyancy were made and the results shown that the flow field was significantly modified compared with the case of non-buoyancy effect. The local reverse flow phenomena and recirculation flows in the front duct near the first wall (FW) were found. Furthermore, a fractional outflow was also observed at inlet under the condition of inlet mass flow rate 2.165 kg/s. The results indicated that the buoyancy-induced mixed convection occurred in front duct can enhance the heat transfer process and made the temperature field of PbLi more uniform that can improve the operational safety of DFLL–TBM. The present work is expected to be helpful for the designs of DFLL–TBM.

► High-speed local reverse flows on the surface of FW are observed.
► Temperature field becomes more uniform, especially FW.
► Outflow phenomenon at inlet is found and length of counter-flow region reaches 1.65m.
► Decrease of velocity gradient may cause tritium accumulation.
► Boussinesq approximation is not appropriate for large temperature differences.