Chapter 5, Problem 5.8P

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 $66°\text{C}$ before it is inserted into an airstream having a temperature of $27°\text{C}\text{.}$ A thermocouple on the outer surface of the sphere indicates $55°\text{C}$ 69 s after the sphere is inserted into the airstream. Assume and then justify that the sphere behaves a spacewise isothermal object and calculate the heat transfer coefficient.