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.GIVENA copper ball with air flowing over itBall diameter (D) = 1.25 cm = 0.0125 mAir temperature (T??) = 26.6?CSpecific heat of ball (c) = 376 J/(kg K)Density of the ball (P) = 8928 kg/m3Thermocouples in the center and the surface registered the same temperatureInitial temperature of the ball (To) = 66?CLapse time = 1.15 min = 69 sThe temperature decrease (To ?? Tf) = 7?CASSUMPTIONSThe heat transfer coefficient remains constant during the coolingperiod.

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Thermocouples Alr +D= 1.25 cm T= 26.6°C Copper Bal