A real (non-Carnot) heat engine, operating between heat reservoirs at temperatures of 650 K and 270 K, performs 4.3 kJ of net work and rejects 8.0 kJ of heat in a single cycle. The thermal efficiency of this heat engine is closest to
A) 0.35
B) 0.31
C) 0.28
D) 0.38
E) 0.42

Question

Quizplus · Accepted Answer

The thermal efficiency of a heat engine is given by the ratio of the net work done to the heat absorbed from the hot reservoir. In this case, the net work done is 4.3 kJ and the heat absorbed from the hot reservoir is 4.3 kJ + 8.0 kJ = 12.3 kJ. Therefore, the thermal efficiency is 4.3 kJ / 12.3 kJ = 0.35.

A Real (Non-Carnot) Heat Engine, Operating Between Heat Reservoirs at Temperatures