Chapter 5, Problem 5.117P

A molded plastic product $\left(\rho =1200{\text{kg/m}}^{\text{3}},c=1500\text{J/kg}\cdot \text{K,}k=0.30\text{W/m}\cdot \text{K}\right)$ is cooled by exposing one surface to an array of air jets, while the opposite surface is well insulated. The product may be approximated as a slab of thickness $L=60\text{mm,}$ which is initially at a uniform temperature of $T_i=80°\text{C}\text{.}$ The air jets are at a temperature of $T_{\infty }=20°\text{C}$ and provide a uniform convection coefficient of $h=100{\text{W/m}}^{\text{2}}\cdot \text{K}$ at the cooled surface.

Using a finite-difference solution with a space increment of $\Delta x=6\text{mm,}$ determine temperatures at the cooled and insulated surfaces after 1 h of exposure to the gas jets.