Dynamic temperature characteristics and creep evolution of packed-bed molten salt thermal energy storage systems

A three-dimensional transient numerical model of a packed-bed molten salt thermal energy storage (TES) system was developed in this study. Numerical simulations revealed the dynamic temperature evolution patterns of the tank structure and its creep damage mechanisms under multi-cycle charging/discharging conditions. The results demonstrate that in a single-tank TES system subjected to repeated thermal cycles, a significant temperature differential exists between the upper and lower sections of the tank wall. The wall temperature evolution exhibits three distinct phases: an initial heating phase, a transitional cooling phase, and a thermal equilibrium stabilization phase. A predictive correlation for the maximum wall temperature was established. Numerical calculations indicate that after 438 operational cycles, the upper wall temperature reaches the creep threshold temperature (650 °C) of 304 stainless steel. With continued cycling, this region forms a persistent high-temperature creep zone, rendering the upper section a high-risk area for creep damage.