You complete a preliminary design of a heat engine, following the Rankine cycle with saturated steam leaving the boiler. Which of the following modifications to the cycle would you expect to increase the efficiency of the cycle?
A. Subcool the liquid in the condenser.
B. Subcool the liquid before it reaches the condenser.
C. Superheat the liquid before it reaches the pump.
D. Install a higher efficiency throttling valve between the condenser and boiler.
E. None of these options
A. Incorrect. This will require more energy added in the boiler.
B. Incorrect. The working fluid cannot be subcooled before it is completely condensed (in the condenser).
C. Incorrect. “Superheating the liquid” isn’t plausible; adding heat to a saturated liquid will boil it, not “superheat” it.
D. Incorrect. Heat engines do not use throttling valves; refrigerators do. In a heat engine the work out is obtained from the expansion and possibly partial condensation of the working fluid in a turbine.
E. Correct. None of these options will improve the efficiency of a Rankine cycle.
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