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 airstream having a temperature of 27°C. A thermocouple on the outer surface of the sphere indicates 55°C 69 s after the sphere is inserted in the airstream. Assume, and then justify, that the sphere behaves as a spacewise isothermal object and calculate the heat transfer coefficient. 3 p = 8933 kg/m’, cp = 389 J/kg-K, k = 398 -T(0) = 66°C T(69s) =55°C Too =27°C -D=12.7mm

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 airstream having a temperature of 27°C. A thermocouple on the outer surface of the sphere indicates 55°C 69 s after the sphere is inserted in the airstream. Assume, and then justify, that the sphere behaves as a spacewise isothermal object and calculate the heat transfer coefficient. 3 p = 8933 kg/m’, cp = 389 J/kg-K, k = 398 -T(0) = 66°C T(69s) =55°C Too =27°C -D=12.7mm

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Question

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 airstream having a
temperature of 27°C. A thermocouple on the outer surface of the
sphere indicates 55°C 69 s after the sphere is inserted in the
airstream. Assume, and then justify, that the sphere behaves as a
spacewise isothermal object and calculate the heat transfer
coefficient.
3
p= 8933 kg/m, cp = 389 J/kg-K, k= 398
-T(0)= 66°C
T(69s) =55°C
To =27°C
-D=12.7mm

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