An industrial furnace employs a hollow brick lining. The inside and outside surfaces of hollow brick lining are maintained at 900 K and 430 K by placing the radiation shields in between the hollow space. The heat loss to the furnace surroundings at 300 K is both by radiation and natural convection. By sketching the arrangement, calculate the number of radiation shields needed. The emissivity of the wall and the shields may be taken as 0.85.The convective heat transfer coefficient is governed by the expression, h = 1.5 (DT)0.33W/m2K.