Answer :
The ideal efficiency of the engine 12%
Efficiency (n) = 1 - (Tc / Th)
n = 1 - (15 / 975) = 0.985
n = 1 - (4 / 13) = 0.692
n = 1 - ( 282 / 320) = 0.12
Even the most efficient heat engines have poor ideal efficiency, typically, it is much below 50%. Consequently, a significant amount of energy is wasted when it is lost to the environment by heat engines. Even though modern cogeneration, combined cycle, and energy recycling schemes are starting to harness this heat for other uses, a significant portion of the fuels produced worldwide are used to power heat engines, wasting up to half of the useable energy produced worldwide. There are three reasons for this inefficiency. The Carnot efficiency is a general term used to describe the temperature-related upper limit on any heat engine's efficiency. Second, due to the inherent irreversibility, some engine types are limited in terms of efficiency.
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