Optimum residence time for steel productivity and energy saving in a hot rolled reheating furnace

A mathematical model is developed to calculate temperature distribution of a slab in a hot rolled reheating furnace by considering thermal radiation in the furnace and transient conduction in the slab. The furnace is modeled as a radiating medium with spatially varying temperature. Radiative heat flux within the furnace, including the effects of the furnace walls, combustion gases, skid beams, and buttons, is calculated through finite volume method with weighted sum of gray gases model and is applied as the boundary condition in the transient conduction equation of the slab. After validating the predictions of the present models with experimental data, the variations in the heating characteristics of the slab are investigated with residence time in the furnace at two different charging and furnace gas temperatures. The optimum residence time for the slab in the furnace is examined with regard to slab exit temperature, temperature difference between the upper surface and centerline of the slab, and skid mark.