Numerical and experimental study of solidification dangers in a molten salt receiver for cloudy conditions

Abstract

Molten salts have high solidification temperatures, so they easily solidify in the receiver tube when the incident energy fluxes are very low due to clouds drifting and floating across the sky. Additional energy and time are then wasted to thaw the frozen solid with the salt freeze/thaw cycles eventually damaging the receiver. Therefore, operators need to adopt appropriate operating strategies to ensure that the salt remains molten during extended cloudy periods. The present study presents a thermo-hydraulic dynamic model of a molten salt receiver to investigate the heat transfer processes. The model is based on the Badaling 1 MWth receiver experiment with three experimental groups of tests modeled to validate the thermal hydraulic model in both the direct-filling mode and the S-type flow mode. The model results agree well with the experimental measurements with maximum relative errors of 0.4% for the outlet temperature and 0.9% for the surface temperatures. Then, a sensitivity analysis is conducted to better illustrate the flow distribution and surface temperatures, including the effects of the flow resistance, inlet temperature, cloudy duration, and valve abnormalities. Finally, the results indicate that the S-type flow mode should be used to prevent solidification for cloudy conditions.