Molten salt pebble-bed reactor is a new type of reactor with a complicated heat transfer process in the reactor cavity, the verification of the reliability and accuracy for the Computational Fluid Dynamics (CFD) software applied to the heat transfer process analysis in the reactor cavity of molten salt reactor (MSR) is crucial. Therefore, a simulated experimental facility for 2 MWt solid fuel Thorium Molten Salt Reactor (simulated reactor) is set up, and the experimental data from different experiment conditions are verified by FLUENT software of CFD.

The study aims to understand the heat transfer process in the reactor cavity of MSR in detail, and to validate the reliability and accuracy of CFD method for the heat analysis for the reactor silo of MSR.

First, a one-fourth scale three-dimensional calculation model for the reactor cavity of simulated MSR was established, meshed the calculation model and performed the mesh independence analysis. Subsequently, based on the experimental data, a UDF (User-Defined Function) was programmed to define the temperature boundary condition at the interface between the upper and lower reactor cavity models. Finally, the heat transfer process in the upper and lower reactor cavity of simulated reactor was analyzed using the CFD method and verified against the experiment data under 5 experimental conditions.

The calculation results indicate that the temperature distribution of the air in the upper and lower reactor cavity is fairly uniform, with many eddy zones present in the upper reactor cavity. As the wall temperature of the pressure vessel increases, the increase rate of heat transfer power due to both radiation and convection gradually accelerates, with radiation heat transfer power increasing more rapidly. The calculated values obtained by CFD are almost consistent with the experimental values, the largest deviations for upper and lower reactor cavity are 9.6% and 4.3%, respectively. Consequently, the CFD verification results for all temperature measuring points are fairly ideal and meet the deviation tolerances for engineering calculations.

This study verifies the accuracy of CFD analysis method when applied to the heat analysis for the reactor cavity of molten salt reactor, providing an important reference for subsequent thermal hydraulic analysis of the reactor cavity of a 100 MW molten salt reactor.