Engine efficiency

  • Thread starter kbyws37
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  • #1
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An engine releases 0.490 kJ of heat for every 0.120 kJ of work it does. What is the efficiency of the engine?

I am having trouble with this problem.
I tried

Wnet/ heat input = efficiency
0.120/0.450 = 0.27
but it says it is the wrong answer. (correct answer is 0.21)
 

Answers and Replies

  • #2
berkeman
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The efficiency is the useful work divided by the total energy. What is the total energy in terms of the useful work and the waste heat generated?
 
  • #3
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thanks!

0.120/(0.450+0.120) = 0.211
 

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