3.14 The wall of a drying oven is constructed by sandwich.ing an insulation material of thermal conductivity k=0.05 W/m K between thin metal sheets. The oven air is at Tmi

= 300°C, and the corresponding convection coefficient is h, = 30 W/m? · K. The inner wall surface absorbs a radiant flux of qd = 100 W/m? from hotter objects within the oven. The room air is at T= 25°C,and the overall coefficient for convection and radiation from the outer surface is h, = 10 W/m2· K. (a) Draw the thermal circuit for the wall and label an temperatures, heat rates, and thermal resistances.(b) hat insulation thickness L is required to maintain the outer wall surface at a safe-to-touch temperature of T,= 40°C?