Heat Transfer - GATE practice papers - Mechanical for Q. 370

Q.  A copper plat has dimensions 1m × 2m × 0.08m. The one of the largest surfaces is kept at 100 °C and other one is at 0 °C. Thermal conductivity of the copper plate k is 400 W/mK. What is the rate at which energy flows through the plate and the thermal resistance of the plate? (Marks: 02)
- Published on 19 Oct 15

a. 800 kW, 1 × 10– 3 K/W
b. 800 kW, 1 × 10– 4 K/W
c. 80000 W, 1 × 10– 3 K/W
d. 80000 W, 1 × 10– 4 K/W

ANSWER: 800 kW, 1 × 10– 4 K/W
 
According to the Fourier's law of heat conduction,
Rate of heat flow is given by,

qk = ( k A ΔT ) / l

= (400 × 1 × 2 × (80 – 0)) / 0.08
=800 kW

And thermal resistance is given by,

Rt = l / kA

= 0.08 / (400 × 1 × 2)
=1 × 10– 4 K/W

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