Chapter 3, Problem 3.19P

The wall of a drying oven is constructed by sandwichingan insulation material of thermal conductivity $k=0.05\text{W/m}\cdot \text{K}$ between thin metal sheets. The oven air is at $T_{\infty ,i}=300°\text{C,}$ and the corresponding convection coefficientis $h_i=30{\text{W/m}}^2\cdot \text{K}\text{.}$ The inner wall surface absorbsa radiant flux of $q_{\text{rad}}^{"}=100{\text{W/m}}^2$ from hotter objectswithin the oven. The room air is at $T_{\infty ,o}=25°\text{C,}$ and theoverall coefficient for convection and radiation fromthe outer surface is $h_o=10{\text{W/m}}^2\cdot \text{K}\text{.}$

1. Draw the thermal circuit for the wall and label alltemperatures, heat rates, and thermal resistances.
2. What insulation thickness L is required to maintainthe outer wall surface at a safe-to-touch temperatureof $T_o=40°\text{C?}$