Answer Happy

A rectangular iron ingot 15 cm x 15 cm x 30 cm is supported at the centre of a reheating furnace. The furnace has walls of silica-brick at 1400 K, and the initial temperature of the ingot is 290 K. How long will it take to heat the ingot to 600 K? It may be assumed that the furnace is large compared with the ingot-size, and that the ingot remains at uniform temperature throughout its volume; convection effects are negligible. The total emissivity of the oxidised iron surface is 0.78 and both emissivity and absorptivity are independent of the surface temperature. Density of iron 7.2 Mg/m³; specific heat of iron = 0.50 kJ/kg-K.