SAM Code Validation for High Prandtl Number Flow in Molten Salt Natural Circulation Facility

The high Prandtl number of molten salt provides unique flow characteristics that must be well studied in natural circulation loops to ensure the efficiency of passive safety systems in advanced reactor designs. Closure models used in reduced-order modeling, such as the System Analysis Module (SAM) code, were developed with traditional heat transfer fluids and must be validated for use in molten salt. A natural circulation loop was modeled in SAM based on an experimental facility at Texas A&M University. Four experimental data sets were obtained for each working fluid, water and salt, at increasing heater power. A one-dimensional fluid flow model was used with input parameters for the net heat input to the system and minimum temperature in the loop. Steady-state results were found for each test case using the default friction factor in SAM and the friction factor found from experimental results. The temperature difference and velocity in the loop were used for validation efforts. It was found that the experimental friction factor was less than the friction factor calculated in SAM. As a result, the experimental friction factor improved the accuracy of the model in predicting the velocity in the loop. The results for the temperature difference in water were found to be statistically the same as the results in the experimental data. In the salt cases, the temperature difference was better predicted as the Prandtl number decreased. It was found that at high velocities and high Prandtl numbers, the development of the flow field was significant and deviated from the simulation results.