A furnace is made of a refractory brick wall of thickness 0.5 metre and thermal conductivity 0.7 W/m.°K For the same temperature drop and heat loss, this refractory wall can be replaced by a layer of diatomaceous earth of thermal conductivity 0.14 W/m.K and thickness ______________ metre?
Correct answer: B. 0.1
- A. 0.01
- B. 0.1
- C. 0.25
- D. 0.5
Explanation
For equal heat loss and temperature drop, wall resistance must be equal: L1/k1 = L2/k2. Thus L2 = 0.5(0.14/0.7) = 0.10 m, so the lower-conductivity diatomaceous earth layer can be thinner.
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