Question

A steam power plant operates on Rankine cycle. There is a 20% reduction in net work output (kJ/kg). Find the percentage increase in specific steam consumption (kg/kJ). (Answer in integer).

Hint:

SSC is inversely proportional to net work. A 20% drop in work output directly causes a 25% rise in SSC.

Answer 1

Correct Answer: 25

Specific steam consumption (SSC):
\[ SSC = \frac{1}{W_{\text{net}}} \] Let original net work: \(W_1\). After reduction: \[ W_2 = 0.8 W_1 \] SSC before reduction:
\[ SSC_1 = \frac{1}{W_1} \] SSC after reduction:
\[ SSC_2 = \frac{1}{0.8W_1} = \frac{1}{0.8} \cdot \frac{1}{W_1} = 1.25 SSC_1 \] Percent increase:
\[ %\,\text{increase} = (1.25 - 1) \times 100 = 25% \]