Engineering, 18.02.2020 18:57 ElizabethF

The heat transfer coefficient for hydrogen 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 20 mm in diameter, is at 75°C before it is inserted into the gas stream having a temperature of 27°C. A thermocouple on the outer surface of the sphere indicates 55°C 97 s after the sphere is inserted into the hydrogen. A) Assume and then justify that the sphere behaves as a spacewise isothermal object and calculate the heat transfer coefficient. B) What is the value of the specific heat of the copper at the average temperature of the process, in J/kg·K?C) What is the value of the lumped thermal capacitance of the sphere, in J/K?D) Solve for the thermal time constant, in sec. E) What is the value of the heat transfer coefficient, in W/m2· K?F) What is the value of the Biot number?

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