Q$2.$ The inner layer wall of a drying oven is made of an insulative material $(k=0\mathrm{.}01\frac{W}{m}.K)$

and is sandwiched between thin metal sheets. The air inside the oven has the temperature of

$T_{,i}=400C$ and the corresponding convection coefficient is $h_i=25\frac{W}{m^2.K}.$ The inner wall

surface absorbs a radiant flux of $q_{\text{r}\text{a}\text{d}}^{\text{'}\text{'}}=100\frac{W}{m^2}$ from hotter objects within the oven. The

room air is at $T_{,0}=25C,$ and the overall coefficient for convection and radiation from the

outer surface is $h_o=10\frac{W}{m^2*K}$

a$)$ Draw the thermal circuit for the wall and label all temperatures, heat rates and thermal

resistances.

$(4$ points: $2$ points assumptions $+2$ points for the thermal circuit$)$

b$)$ What insulations thickness $L$ is required to maintain the outer wall surface at

temperature $T_0=30c?$

$(6$ points: $2$ points energy balance $+4$ points for calculation$)$