Simulation analysis of heat transfer and flow characteristics of a U-tube heat exchanger in a molten salt reactor

Abstract

BackgroundThe primary heat exchanger (PHX) used in the 10 MWt Molten Salt Reactor Experiment (MSRE) at Oak Ridge National Laboratory (ORNL), is a U-tube heat exchanger, where the shell side (hot side) contains the fuel salt from the primary loop and the tube side (cold side) carries the coolant salt from the secondary loop.PurposeThis study aims to deepen the understanding and mastery of the operational characteristics of molten salt heat exchangers, and to accumulate experience in their design and operation within molten salt reactors.MethodsFirstly, based on the design parameters, the MSRE-PHX was modeled, and theoretical calculations for shell and tube hear exchanger were conducted using the Kern method and the Bell-Delaware method. Then, software simulations were performed using HTRI Xchanger Suite, and computational fluid dynamics (CFD) simulations were also carried out with Ansys Fluent. Finally, critical performance metrics, such as the heat transfer coefficient, the pressure drop, and the heat transfer power, were obtained and compared to the MSRE operation data.ResultsThe comparison results indicate that the discrepancies from theoretical calculations, HTRI software, and CFD simulations, are all within acceptable margins to the experimental data. Notably, the greatest variance is found with the Kern method, which showed a deviation in heat transfer quantity of about 15%, while the smallest discrepancy is observed in the overall heat transfer coefficient calculated using HTRI software, differing by merely 0.16% from the experimental data.ConclusionsAll of the methods are suitable and applicable for designing and studying a molten salt shell and tube heat exchanger. Moreover, the CFD simulation can provide fine localized details of the heat transfer and flow of the molten salt fluid. This offers substantial theoretical support and practical guidance for the future design and improvement of molten salt heat exchangers.

Keywords

• molten salt heat exchanger
• kern method
• bell-delaware method
• htri xchanger suite
• cfd simulation