Question 2.47: A source S1 can supply heat energy at the rate of 200 kJ/s a...

Principles of Mechanical Engineering

A source $S_1$ can supply heat energy at the rate of 200 kJ/s at 320° C and source $S_2$ can supply 2000 kJ/s at 75° C. Which source would you choose to supply energy to an ideal reversible heat engine if the temperature of surroundings is 35° C ?

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Source $S_1$ : $Q_1=200 \ kJ / s$

$\begin{aligned}&T_1=320+273=593 \ K \\ &T_2=35+273=308 \ K \\ \\&\eta_1=1-\frac{T_2}{T_1}=1-\frac{308}{593}=0.4806 \text { or } 48.06 \%\end{aligned}$

Source $S_2$ : $Q_1=200 \ kJ / s$

$\begin{aligned}&T_1=75+273=348 \ K \\&T_2=35+273=308 \ K \\ \\&\eta_2=1-\frac{T_2}{T_1}=1-\frac{308}{348}=0.1149 \text { or } 11.49 \%\end{aligned}$

Work delivered : $W_1$ = 200 × 0.4806 = 96.12 kJ/s
$\quad \quad W_2$ = 2000 × 0.1149 = 229.8 kJ/s

Choose $S_2$ .

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