The turbine in a steam power takes steam from a boiler at 427°C and exhausts into a low-temperature reservoir at 77°C. What is the maximum possible efficiency?
Correct answer: D. 50%
- A. 10%
- B. 20%
- C. 30%
- D. 50%
- E. 70%
Explanation
The maximum theoretical efficiency of the system is the one corresponding to the efficiency of a Carnot cycle operating between the same temperatures of the system:η=1−Tc /ThWhere Tc and Th are the cold and hot temperatures, respectively.In our problem, Tc =350K and Th =700KTherefore, the maximum theoretical efficiency isη=1−350/700 = 0.50 × 100 = 50%
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About Energy Losses and Efficiency
Efficiency compares useful output energy or power with the total input, usually expressed as a percentage. The topic covers energy losses through friction, heating, resistance and sound, along with power ratings and Sankey diagrams. Efficiency is not the same as conservation of energy, because lost energy is transferred rather than destroyed.
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