Experimental study on flow and heat transfer characteristics of lead-bismuth eutectic in circular tube under solidification condition

Lead-bismuth eutectic possess a high melting point and have the potential to solidify in critical components of the reactor during fast reactor operation, thereby creating additional thermal resistance and affecting normal reactor operation. In order to study the effect of this phenomenon, an experimental study was carried out on the flow and heat transfer characteristics of LBE when solidification phenomena occur during flow. With solidification, the experimental results demonstrated that the overall Nu decreased by approximately 19.5 %–62.5 % in comparison with the Nu under normal operating conditions (Pe: 986–2767). Furthermore, the solidification phenomenon leads to a 132.84 %–1277.05 % of increase in Eu. The distribution and morphology of solidified LBE in the steady state demonstrate that different cooling conditions alter the thickness of solidified LBE and the solidification initiation position, and affect the surface roughness of solidified LBE. The findings demonstrate that the presence of solidified LBE layer hindered the heat transfer between LBE and the wall, and leading to an additional pressure drop. Furthermore, the flow of lead-bismuth eutectic is also affected by the differing surface morphology of solidified LBE layer.