A molded plastic product (p = 1200 kg/m3 · c = 1500 J/kg · K, k = 0.30 W/m · K) 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 mm, which is initially at a uniform temperature of T+ = 80°C. The air jets are at a temperature of T8 = 20°C and provide a uniform convection coefficient of h = 100 W/m2 · K at the cooled surface.
Using a finite-difference solution with a space increment of ?x = 6 mm, determine temperatures at the cooled and insulated surfaces after 1 hour of exposure to the gas jets.