A slab of copper with dimensions of 1.90 m by 1.50 m and 2.10 cm thick is heated

Question

A slab of copper with dimensions of 1.90 m by 1.50 m and 2.10 cm thick is heated on one side to 550 deg. C. If the other side of the material is at a temperature of 26 deg. C, what is the rate of heat transfer through the slab?

A cylinderical brass rod with a radius of 1.90 cm and length of 1.30 m is placed in a fire with temperature of 530 deg. C. If the other end of the rod is at a temperature of 25 deg. C, what is the rate of heat transfer through the rod (ignore any heat loss from the sides of the rod). (posted before but got wrong answer, thank you)

Explanation / Answer

(a) rate of heat transfer Q/t = k*A*deltaT/d

where k is the thermal conductivity of the material k=385 W/mK

A = 1.9*1.5 = 2.85 m^2

=> Q/t = 385*2.85*524/ 1.9 = 302.61*10^3 J/s

(b) thermal conductivty of the brass k = 109 W/mK = 109 (J/s)/mK

A = pi*r^2 = pi*(0.019)^2 = 1.13*10^-3 m^2

=> Q/t = k*A*deltaT/d = 109*1.13*10^-3*505/1.3 = 28.41 J/s

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