Double-layered heat exchanger tubes can effectively reduce the probability of heat exchanger tube rupture accidents from design; however, the thermal contact resistance between tubes may decrease the heat transfer efficiency of the heat exchanger tubes. This is not conducive to the smooth heat export of the first circuit system of lead-bismuth reactor; therefore, there is an urgent need to optimize the design of heat exchanger tubes.

This study aims to optimize the structure of the double-layered tubular main heat exchanger, so as to improve its heat transfer efficiency.

Firstly, the double layer heat exchange tube type main heat exchanger of lead bismuth reactor was taken as the research object, the interstices of double-layered heat exchanger tubes was filled with gallium-based graphene nanofluid as the thermal interface material. Then, the influence of heat exchanger tube length, wall thickness, outer diameter, and spacing on the heat transfer performance were analyzed and results were compared with that of a double-layered tubular main heat exchanger without the thermal interface material. Finally, taking the JF factor and cost efficiency ratio (CER) as optimization objectives and using the aforementioned four parameters as optimization variables, the heat transfer performance of the main heat exchanger was optimized and evaluated on the basis of a genetic algorithm, hence to obtain a new double-layered heat exchanger design for a lead-bismuth reactor.

The results of comparative calculations indicate that the total heat transfer coefficient, first-loop pressure drop, JF factor, and CER factor of optimized main heat exchanger increase by 5.79%, 2.32%, 5%, and 24.62%, respectively.

Filling the gap of double-layered heat exchanger tubes with a gallium-based graphene nanofluid can effectively improve the heat transfer performance of the double-layered tube exchanger while reducing the accident probability of steam generator tube rupture.