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Steam keeps the inner surface of a 50 cm long rubber tube at 120°C; the tube has inner radius 1.0 cm and outer radius 1.2 cm. The room is at 30°C. Taking the thermal conductivity of rubber as 0.15 J/m-s-°C, find the rate of radial heat conduction through the tube wall.

1. 183 J/s
2. 207 J/s
3. 233 J/s
4. 280 J/s

Correct answer: 233 J/s

Solution

Using the cylindrical-shell conduction formula with ln(1.2) ≈ 0.182 gives about 233 J/s.

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