Question

A solar energy bases heat engine which receives $80$ kJ of heat at ${100}^{o}C$ and rejects $70$ kJ of heat to the ambient of ${30}^{o}C$ is to be designed. The thermal efficiency of the heat engine is

• A. $18.8$%
• B. Indetermine
• C. $70$%
• D. $12.5$%

Answer 1

The correct option is D $12.5$%


Given data: $Q_1=80kJ$
$T_1={100}^{o}C=373K$
$Q_2=70kJ$
$T_2={30}^{o}C=(30+273)K=303K$
Thermal efficiency,
$\eta =\frac{W}{Q_1}=\frac{Q_1-Q_2}{Q_1}=\frac{80-70}{80}$
$0.125=12.5$%