At the end of its manufacturing process, a silicon wafer of diameter D = 150 mm, thickness d = 1 mm, and emissivity e = 0.65 is at an initial temperature of Ti = 325°C and is an owed to cool in quiescent, ambient air and large surroundings for which T8 = Tsur = 25°C.
(a) What is the initial rate of cooling?
(b) How long does it take for the wafer to reach a temperature of 50°C? Comment on how the relative effects of convection and radiation vary with time during the cooling process.