Particle thermal stress characteristics in energy storage fluidized beds: Implications for mechanical performance

Thermal stress accumulation in particle-based energy storage systems significantly influences structural integrity and overall system efficiency. This study presents a detailed simulation of CaO particles under forced convection, localized contact heating, and fluidized bed energy storage conditions. The results reveal that thermal stress evolution is highly sensitive to heat transfer modes and particle contact configurations. Freestanding particles exhibit surface-concentrated stress patterns, with maximum stress reaching 1.3 MPa under a 10 K temperature gradient, while contact constraints induce early high-stress regions up to 1.8 times higher, which diminish as thermal uniformity improves. In multi-contact scenarios, stress dissipation accelerates by approximately 40 % due to enhanced heat conduction. Within the bed, regions adjacent to the wall and distributor plate show high thermal stress and attrition levels, with a stress–attrition spatial correlation exceeding 75 %, attributed to constrained thermal expansion and steep gas–solid gradients. Parametric studies demonstrate that increased particle hardness (from 190 to 390 MPa) raises attrition mass loss by 39.6 %, yet reduces cumulative breakage by 12.5 %, while higher thermal conductivity (from 0.5 to 2.5 W m−1 K−1) significantly reduces average internal stress by 10.5 % and breakage count by 24.0 %. These findings provide critical insights into designing durable particle materials for thermochemical energy storage applications.