Numerical study on temperature and thermal stress behaviors in silicon carbide heating elements within high-temperature annealing furnaces

In response to global sustainability goals, the transition from fossil fuel-based to electric silicon carbide (SiC) heating elements in continuous annealing furnaces is critical for reducing emissions, enhancing safety, and improving operational environments in the steel industry. This study investigates the cross-sectional temperature profiles and the resultant thermal stress of hollow cylindrical SiC heating elements under varied design conditions. To independently analyze the complex effects of multiple factors, both theoretical and numerical analyses were conducted using simplified boundary conditions in two dimensions, which closely simulate the actual temperature profiles observed in heaters within a continuous annealing line. The results indicate that the radial temperature gradient and resulting thermal stress in these elements are directly proportional to the surface heating load, with the maximum axial tensile stress occurring at the outer surface of the heater. Scenarios involving closely spaced multiple heaters or the introduction of cold steel strips lead to increased axial thermal stress due to additional circumferential temperature gradients. Conversely, the application of shield tubes, despite increasing the heater's temperature, reduces thermal stress by homogenizing radiation within the tube. Consequently, optimizing heater configuration and operational conditions is essential in furnace design to effectively manage heaters’ temperature and thermal stress, thereby ensuring both efficiency and service longevity of the heating elements.