Walls of a cubical oven are of thickness l, and they are made of material of thermal conductivity k. The temperature inside the oven is 100°C and the inside heat transfer coefficient is „3k/l'. If the wall temperature on the outside is held at 25°C, what is the inside wall temperature in degree centigrade ?
Correct answer: C. 81.25
- A. 35.5
- B. 43.75
- C. 81.25
- D. 48.25
Explanation
At steady state, conduction through the wall equals convection from the oven air: (T_w − 25)k/l = (100 − T_w)(3k/l). Solving gives T_w = 81.25°C, so the large inside coefficient makes the inside wall temperature close to the oven temperature.
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