Experimental study on heat transfer performance of a fluoride salt to salt heat exchanger for Molten Salt Reactors

Abstract: This study experimentally investigated the heat transfer performance of a novel shell-and-tube fluoride Salt to Salt Heat Exchanger (SSHX) featuring baffles with integrated drainage ports, designed to mitigate salt freeze blockage risks during shutdown in Molten Salt Reactors (MSRs). Experiments were conducted in a Scaled Simulation Fluoride Salt-cooled Reactor (SF0) test facility. A new empirical correlation for tube-side heat transfer was proposed as Nu=0.0246Re0.8Pr0.267 (valid for Re=9000~15000 and Pr=8~12), demonstrating excellent agreement with experimental data within a maximum deviation of 5%. Comparative analysis revealed the modified Dittus-Boelter equation is still a suitable choice for predicting fluoride salt convective heat transfer behavior in tubular geometries, outperforming the Gnielinski and Sieder-Tate models, which overpredicted data by 17-25%. For shell-side heat transfer, applying a 31% enhancement factor (ε=1.31) to the Kern correlation aligns predictions with experimental results within an error range of -6.0% to 7.0%. These findings address a critical engineering challenge in SSHXs while preserving thermal efficiency, offering essential experimental data and valuable insights for the design of fluoride SSHXs in MSRs.