A heat engine is supplied with 800 kJ/s of heat at 600 K, and heat rejection takes place at 300 K. Which of the following results report a reversible cycle?

Question

Question

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JKSSB JE ME 2015 Official Paper

Answer 1

Concept:

As per Clausius Inequality

If \(\oint \frac{{\partial Q}}{T} = 0\) the cycle is reversible.

If \(\oint \frac{{\partial Q}}{T} < 0\) the cycle is irreversible.

If \(\oint \frac{{\partial Q}}{T} > 0\) the cycle is impossible.

Calculation:

Given:

Q₁ = 800 kJ/sec, T₁ = 600 K, T₂ = 300 K.

As per Clausius Inequality

For reversible cycle:

\(\oint \frac{{\partial Q}}{T} = 0\)

\(\frac{Q_1}{T_1}+\frac{Q_2}{T_2}=0\)

\(\frac{800}{600}+\frac{Q_2}{300}=0\)

∴ Q₂ = -400 kJ/sec rejected (∵ negative implies rejected).