Numerical study on heat transfer and flow performance of fluoride molten salt in Zigzag printed circuit heat exchanger based on orthogonal experimental design method

BackgroundThe Printed Circuit Heat Exchanger (PCHE) is a type of heat exchanger characterized by high heat transfer efficiency, compact structure, and long service life. It can be widely applied in advanced nuclear reactors and other emerging energy systems.PurposeThis study aims to enhance the heat transfer and flow performance of high-Prandtl-number fluoride molten salt with Zigzag PCHEs.MethodsThe Computational Fluid Dynamics (CFD) program Fluent was employed to design and optimize the structure of Zigzag PCHE in high temperature molten salt heat exchanger. Orthogonal experimental design and range analysis were employed to investigate the effects of structural parameters including channel diameter, characteristic angle, and pitch length on the Nusselt number, Fanning friction factor, and overall performance factor; hence find out the arrangement of Zigzag channel with the highest overall performance factor. Additionally, a further analysis was performed to explore the impacts of inlet temperature and inlet velocity on performance, and based on the simulation data, the applicability of existing correlations was evaluated. New empirical correlations for the Nusselt number and Fanning friction factor were proposed for the optimized Zigzag structure.ResultsThe computation results indicate that the highest overall performance factor is obtained when the channel diameter is 4 mm, characteristic angle is 15°, and pitch length is 10 mm. Thereafter, the channel diameter has the most significant impact on overall performance, followed by characteristic angle, while the influence of pitch length is relatively minor. The analysis findings reveal that the inlet velocity is the dominant influencing factor whilst the inlet temperature has a weak effect. Optimized Zigzag structure is within the ranges of 240Re2 102 and 14.86Pr22.07, showing maximum deviations of 10% and 6%, respectively.ConclusionsThis study provides theoretical insights for the design of Zigzag-channel PCHEs in molten salt reactors (MSRs), contributing to the engineering development of compact heat exchangers in advanced energy systems.