A 12 mm diameter aluminum sphere is heated to a uniform temperature of 400C and then suddenly subjected to room air at 20C with a convection heat transfer coefficient of 10 W m2C Calculate the time for the center temperature of the sphere to reach 200C ...

A 12-mm-diameter aluminum sphere is heated to a uniform temperature of 400C and then suddenly subjected to

Question:

A 12-mm-diameter aluminum sphere is heated to a uniform temperature of 400ºC and then suddenly subjected to room air at 20ºC with a convection heat-transfer coefficient of 10 W/m2·ºC. Calculate the time for the center temperature of the sphere to reach 200ºC.