4. A copper spherical ball (15 cm in diameter) with a density of 8933 kg/m³, specific heat capacity of 385 J/kg-K and thermal conductivity of 401 W/m-K is removed from an oven at a uniform temperature of 140 °C. The ball is then left to cool down in steady air at 20 °C. Calculate the heat transfer coefficient for this process and the time for the surface of the ball to drop to 40 °C. Use the following equation to solve this problem (characteristic dimension of the sphere is the diameter). 0.589 · Ra Nu = 2+ 0.469 T6 Pr Note: you should check for the Lumped system analysis criteria for the final solution!

4. A copper spherical ball (15 cm in diameter) with a density of 8933 kg/m³, specific heat capacity of 385 J/kg-K and thermal conductivity of 401 W/m-K is removed from an oven at a uniform temperature of 140 °C. The ball is then left to cool down in steady air at 20 °C. Calculate the heat transfer coefficient for this process and the time for the surface of the ball to drop to 40 °C. Use the following equation to solve this problem (characteristic dimension of the sphere is the diameter). 0.589 · Ra Nu = 2+ 0.469 T6 Pr Note: you should check for the Lumped system analysis criteria for the final solution!

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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