A copper sphere of internal diameter 2 m and wall thickness 40 mm is insulated with 75 mm of expanded polystyrene. The thermal conductivity of copper is 380 W/mK and that of the polystyrene is 0.04 W/mK. The inside and outside surface heat transfer coefficients are 500 and 12 W/m2K respectively. The inside temperature is 280 C and an ambient temperature is 20 C.
a) derive and evaluate an overall heat transfer coefficient for this situation.
b) using the above heat transfer coefficient, calculate the rate of heat transfer through the spherical wall.
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This solution helps with a problem regarding overall heat transfer coefficient.