Question

why do fuel-burning devices have efficiency less than 100%​

Answer 1

Heya❣

❁Heat engines turn heat into work. The thermal efficiency expresses the fraction of heat that becomes useful work. The thermal efficiency is represented by the symbol η, and can be calculated using the equation:

η=W/QH

❁Heat engines often operate at around 30% to 50% efficiency, due to practical limitations. It is impossible for heat engines to achieve 100% thermal efficiency (η=1) according to the Second law of thermodynamics. This is impossible because some waste heat is always produced  in a heat engine. Although complete efficiency in a heat engine is impossible, there are many ways to increase a system's overall efficiency.

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Answer 2

Efficiency is typically less than 100% because there are inefficiencies such as friction and heat loss that convert the energy into alternative forms. ... For engines where a fuel is burned there are two types of thermal efficiency: indicated thermal efficiency and brake thermal efficiency.





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