Thermo-structural coupling stress analysis and structural strength evaluation of large fillet weld in molten salt storage tanks considering multi-parameter influence

Molten salt storage tank is the core equipment of thermal energy storage systems, and strict stress analysis is the key to ensuring its safe operation. A thermal-structural coupling stress analysis model of storage tanks is established to systematically study the influences of molten salt liquid levels (0.9 m–7.3 m), heat storage temperatures (290–565°C), tank bottom plate-foundation interface friction coefficient (0.2–1.0), and tank materials (304/316L/347H stainless steel, Inconel 625) on the stress distribution of storage tanks. Then, its structural strength is comprehensively evaluated by a multi-strength assessment system. Results show that the weld toe region, a critical location for stress concentration, has a maximum stress value and is mainly dominated by bending stress. The maximum stress is nonlinearly positively and negatively correlated with liquid level and heat storage temperature, respectively. The maximum liquid levels should be strictly controlled in practical engineering. It also linearly positively correlated with the friction coefficient. Controlling the friction coefficient to a lower level ( μ ≤0.5) by selecting a well-graded medium sand/coarse sand and optimizing the compactness of the sand layer can effectively reduce the maximum stress. In addition, the tank material does not significantly influence the stress value and distribution. This study reveals the stress concentration dominant mechanism at the weld toe region, quantifies the maximum stress migration law under multi-parameter coupling, and establishes a multi-criteria strength evaluation system for tank structure, thus forming a multi-dimensional parameter research system covering operating conditions-boundary constraints-structural materials and providing an engineering-operable and cost-controllable strategy for tank stress control, supporting the safe design and structural optimization of molten salt storage tanks.