Thermal inertia and stress of steam separator during variable load process based on fluid-structure-heat coupling

The enhancement of the load cycling rate of coal-fired power plants is of considerable importance to the power grid with renewable energy, but the thermal inertia and stress during the variable load process pose a challenge to the safe operation of these plants. The present study investigates the effect of load cycling rate (vc), thermal conductivity (λ), density (ρ), and load interval on the thermal inertia and the stress of the steam separator during variable load processes based on fluid-structure-heat coupling. Results show that increasing vc, increasing λ, and decreasing ρ can reduce the equilibrium time. The load interval exerted little effect on the equilibrium time. The thermal stress increased with an increase in vc, ρ, and load interval, decreased with an increase in λ. The mechanical stress is determined by the internal steam pressure, synchronized with the load interval, and independent of vc, λ, and ρ. The peak total stress of the load-down process is greater than that of the load-up process. The coupling mechanism of thermal stress and mechanical stress under different influencing factors was also analyzed. The findings of this research provide support for the design and selection of steam separators for flexible coal-fired power plants.