Melting process of non-uniform molten salt slurry in direct absorption solar storage

Concentrating Solar Power on Demand (CSPonD) system is a cost-effective approach for thermal energy utilization. The phase change of the molten salt particles complicates the calculation of incident radiation absorption by molten salt. In the present study, a radiation absorption model with a variable attenuation coefficient is established to describe the temporal and spatial non-uniformities in radiation absorption caused by phase changes. The model couples the phase change process of molten salt with the radiation absorption process, accounting for changes in the morphology and volume fraction of solid particles during melting. The findings reveal that the attenuation capacity of the phase-change molten salt slurry decreases with increasing temperature, exhibiting a sharp drop at 501.5 K, which is near the complete melting point of 503 K. The behavior leads to un-melted solid particles in the molten salt surface, hindering energy absorption and melting progress. The melting rate of molten salt increases with the feeding ratio and initial average particle size. In present work, the melting rate at the feeding ratio of 0.5 increased by 93.2 % compared to a ratio of 0.1. Additionally, the melting rate for 85 μm particles rose by 9.0 % relative to that for 10 μm particles.