Solving the heat transfer boundary condition of billet in reheating furnace by combining “black box” test with mathematic model

Abstract

Comprehensive radiant heat transfer coefficient, convective heat transfer coefficient and furnace temperature are the key parameters constituting the boundary conditions of the billet heat transfer model. This paper presents a novel method to obtain these parameters by combining "black box" test with mathematical model. Average relative errors of the calculated surface temperature and centre temperature of the case reheating furnace compared with the measured values are 2.34% and 3.51%, which verifies the method's feasibility. Influence law of furnace temperature characteristic parameters on billet temperature is analyzed. When the intercept, slope and amplitude change, the regions where the billet temperature field changes significantly is in or near the HEⅠsection, which are the key section to adjust the billet temperature field through single characteristic parameter. The longer the period is, the smoother the change of billet temperature in the same spatial region is, which is conducive to the uniform heating of billet. However, if only increasing the period, there may be a situation that the billet discharging temperature exceeds the target. Change of single characteristic parameter has its limitations. In order to achieve the accurate control of billet temperature, the collaborative change of each characteristic parameter is required.