Computer Simulation of the Slab Reheating Furnace

Abstract

The development of a mathematical model for predicting steady-state heat transfer within the push-type slab reheating furnace is described and preliminary model predictions presented. Radiative exchange within the furnace chambers is calculated using the zone method, while the thermal response of the slabs moving through the furnace is obtained using a finite difference approximation for transient two-dimensional conduction, neglecting axial effects. The model accounts for the presence of the skidrail structure and the furnace sidewalls, but in its current form requires knowledge of the temperature distribution within the furnace gas. In addition to longitudinal temperature and heat-flux profiles, contour plots of slab temperature in the transverse plane of the furnace are presented. At any longitudinal distance into the furnace, heat flux to the slab surface is shown to vary significantly across the slab, even for the case of uniform transverse gas temperature. In agreement with other studies, the primary cause of skidmark formation is found to be radiative shielding of the slab surface by the skidrail structure. The model indicates that skidmark severity can be expected to increase with furnace throughput, but this situation could be alleviated by reducing the size of the skidrail structure. The effectiveness of reflective coatings applied to the skidrail surfaces, in reducing skidmark effects, is found to depend upon the temperature of the surfaces relative to the local slab surface temperature.