Numerical investigation of natural convection characteristics of a heat pipe-cooled passive residual heat removal system for molten salt reactors

The limited availability of studies on the natural convection heat transfer characteristics of fluoride salt has hindered progress in the design of passive residual heat removal systems (PRHRS) for molten salt reactors. This paper presents results from a numerical investigation of natural convection heat transfer characteristics of fluoride salt and heat pipes in the drain tank of a PRHRS. Simulation results are compared with experimental data, demonstrating the accuracy of the calculation methodology. Temperature distribution of fluoride salt and heat transfer characteristics are obtained and analyzed. The radial temperature of liquid fluoride salt in the drain tank shows a uniform distribution, while temperatures increase with increase in axial height from the bottom to the top of the drain tank. In addition, natural convection intensity increases with increase in height of the heat pipes in the tank. Spacing between heat pipes has no obvious effect on the natural convection heat transfer coefficient. This study will contribute to the design of passive heat removal systems for advanced nuclear reactors.