The heat transfer Coefficient for air flowing over a sphere is to be determined by observing the temperature -time history of a sphere fabricated from pure copper. The sphere, which is 25 mm in diameter is at 95C before it is inserted into an airstream having a temepature of 27 C. A thermocouple on the outer surfaceof the sphere inddicates a temprature of 55 C after a time interval of 120 seconds. Assume and then justify that the sphere between as a space-wise isothermal object and calculates the heat transfer cofficient
provide numerical values for the following quantities:
a) Biot number
b) Time constant
c) Heat transfer Cofficient