A stainless steel ball (p = 8055 kg/m², C, = 480 J/kg -°C) of diameter D = 15 cm is removed from the oven at a uni-form temperature of 350°C. The ball is then subjected to the flowof air at 1 atm pressure and 30°C with a velocity of 6 m/s. Thesurface temperature of the ball eventually drops to 250°C. Deter-mine the average convection heat transfer coefficient during thiscooling process and estimate how long this process has taken.

Given: Diameter of ball D = 15 cm Velocity v = 6 m/s Cp = 480 J/Kg Uniform temperature T = 350°C…

Answered: A stainless steel ball (p = 8055 kg/m²,…

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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A hot steel ball of 5 mm in diameter initially at 100 oC is left to cool down in air at 20 oC. Assume a constant convective heat transfer coefficient h = 15 W/m2K through the course of the cooling process. Cp, steel = 0.49 kJ / kg K , k,steel = 45.0 W / m K , rho, steel = 7800 kg/m^3 Cp,air = 1.00 kJ/kg K ; k_air = 0.025 W / m K; rho,air = 1.2 kg/m^3 a) Calculate the rate of convective heat transfer when the steel ball is uniformly at 100 oC. b) Assuming the steel as a lumped system, find the temperature of the steel ball after 0.5 s.
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