Abstract Scope |
The molten salt hot tank is a critical component of thermal energy storage system in concentrating solar power plants, which is made of 347H stainless steel (SS). Initial generation of hot tank floor was constructed by welding assembly of 347H SS thin rectangular plates. However, weld-induced residual stress can adversely impact the reliability of hot tank floors. This study aims to develop a finite element model of the tank floor to quantify residual stress across the entire structure. By quantifying these factors post-fabrication and pre-deployment, the model serves as a crucial precursor, providing essential inputs for subsequently predicting the tank’s operational lifespan. In this work, a sequentially coupled thermo-elastic-plastic method was adopted for welding models. Initially, a solid element model with a two-pass welding procedure for two plates in tank floor was established to investigate residual stress using material database obtained from thermomechanical testing and literature. The solid element model was validated by neutron diffraction residual strain mapping. Subsequently, a shell element model with a simplified equivalent one-pass welding procedure was developed to closely match the outputs from the solid element model. Thereafter, this shell element approach was utilized for calculation of residual stress in the entire tank floor. Computational fluid dynamics simulation of stress evolution in tank floor during service conditions, i.e., storage of hot salt, was conducted by the collaboration team to compare the impact of pre-deployment stress conditions. The outcomes offer critical insights and guidance for mitigating failures of existing tanks and optimizing design of future tanks. |