The Heat Transfer Model of Oriented Silicon Steel Coil in Annular Furnace during the Heating Stage of High-Temperature Annealing

A 2D numerical model is built to simulate the heat transfer across the oriented silicon steel coil in annular furnace during the heating stage of high-temperature annealing. A new method is proposed to calculate the view factors in the radiation submodel. The numerical result is verified through the comparison with the results of in situ experiments. For a coil with 1710 mm outside and 510 mm inside diameters, the heat absorbed by the outer surface of the coil is the highest, but the heat flux density along the axial direction of the coil is larger than the radial direction. The heat flux density of the outer surface shows an 86% rise depending on the increase in radial thermal conductivity after 75% H(2)and 25% N(2)is applied as the protective atmosphere at a heating time of 37 h. The temperature difference inside the coil ranges from 143 to 476 degrees C till the furnace reaches its designate temperature at 58 h, but the heating rate is nearly the same across the coil above 700 degrees C. The difference of property inside the coil is probably related to the difference of heating rate during the first soaking.