Abstract:

A coupled thermal stress integration model of the molten salt-packed-bed thermal storage tank is developed. The dynamic thermal and stress performances under various charging and discharging cycles are calculated using this model. High-temperature creep and plastic yield failure areas are also explored. For the single cycle, the results demonstrate that ①there exist four variation tendencies of the tank wall temperature: sharply rise and stabilization stages in the charging process, gently decline and sharply decrease stages in the discharging process. Meanwhile, the creep phenomena would occur at the tank's outermost portion. ②The 1-5 shell section walls are in an elastic condition with lower stress levels, resulting in stress concentration at the bottom. Besides, the peak stress presents the first rise and then fall tendencies in the charging and discharging processes, respectively. ①The highest temperature of the tank wall displays a cyclic fluctuation condition between 631 and 836 K over the multiple cycles. Under the impact of decreased stress and creep, damage to the tank wall in the elastic condition would likely accrue, increasing the danger of tank failure. ②Particularly, because the peak stress of the inner wall also varies in the period between 275 and 423 MPa, the low-cycle fatigue fracture failure is induced by the high stress (greater than yield strength) that could occur during the charging and discharging cycles. This research might give a useful reference approach for determining the fatigue life of a packed bed tank under dynamic load.

Key words: concentrating solar power, molten salt, packed-bed thermal storage tank, creep, stress