Question

An engine extracts 452.8kJ of heat from the burning of fuel each cycle, but rejects 266.7 kJ of heat (exhaust, friction,etc) during each cycle. What is the thermal efficiency of the engine?

Answer 1

Answer: The thermal efficiency of the engine is 41.09 %.

Explanation:

Efficiency is the ratio of the useful work performed to the total energy expended or heat taken in.

Formula for thermal efficiency of engine is

$\eta=1- \frac{Q_2}{Q_1}\times 100$

$\eta$ = efficiency

${Q_2}$ = heat rejected = 266.7 kJ

${Q_1}$ = heat extracted = 452.8 kJ

Putting in the values we get:

$\eta=1- \frac{266.7 kJ}{452.8 kJ }\times 100$

$\eta=0.41\times 100$

$\eta =41.09\%$

The thermal efficiency of the engine is 41.09 %.