So9lve the below problem:
Q: The heat transfer coefficients for the flow of 26.6°C air over a 1.25 cm diameter sphere are measured by observing the temperature-time history of a copper ball of the same dimension. The temperature of the copper ball (c = 376 J/(kg K), ρ = 8928 kg/m3) was measured by two thermocouples, one located in the center, and the other near the surface. Both of the thermocouples registered, within the accuracy of the recording instruments, the same temperature at a given instant. In one test run, the initial temperature of the ball was 66°C and in 1.15 min, the temperature decreased by 7°C. Calculate the heat transfer coefficient for this case.
GIVEN
A copper ball with air flowing over it
Ball diameter (D) = 1.25 cm = 0.0125 m
Air temperature (T∞) = 26.6°C
Specific heat of ball (c) = 376 J/(kg K)
Density of the ball (P) = 8928 kg/m3
Thermocouples in the center and the surface registered the same temperature
Initial temperature of the ball (To) = 66°C
Lapse time = 1.15 min = 69 s
The temperature decrease (To - Tf) = 7°C
ASSUMPTIONS
The heat transfer coefficient remains constant during the coolingperiod.
