The strength and stability of tires may be enhanced by heating both sides of the rubber (k = 0.14 W/m ∙ K. a = 6.35 x 10-8 m2/s) in a steam chamber for which T∝ = 200°C. In the heating process, a 20-mm-thick rubber wall (assumed to be un-treaded) is taken from an initial temperature of 25°C to a mid plane temperature of 150°C.

(a) If steam flow over the tire surfaces maintains a convection coefficient of h = 200 W/m2 ∙ K, how long wi1l it take to achieve the desired mid plane temperature?

(b) To accelerate the heating process, it is recommended that the steam flow be made sufficiently vigorous to maintain the tire surfaces at 200°C throughout the process. Compute and plot the mid plane and surface temperatures for this case, as we1l as for the conditions of part (a).