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 12.7 mm in diameter, is at 66 °C before it is inserted into an air-stream having a temperature of 27 °C. A thermocouple on the outer surface of the sphere indicates 55 °C69 seconds after the sphere is inserted in the air stream. Assume and then justify that the sphere behaves as a space-wise isothermal object and calculate the heat transfer coefficient.