The GATE Grind

GATE 2024 ME – Question 21

Thermal Engineering Applications · Power Engineering: vapour and gas power cycles, regeneration and reheat · 1 mark · Multiple choice

Which one of the following statements regarding a Rankine cycle is FALSE?

  1. Superheating the steam in the boiler increases the cycle efficiency.
  2. The pressure at the turbine outlet depends on the condenser temperature.
  3. Cycle efficiency increases as condenser pressure decreases.
  4. Cycle efficiency increases as boiler pressure decreases.

Practise this question in The GATE Grind →

Show answer and explanation

Correct answer: (D) Cycle efficiency increases as boiler pressure decreases.

Explanation

Superheating raises the average temperature at which heat is added, and lowering the condenser pressure lowers the temperature at which heat is rejected, so both raise the efficiency. The turbine outlet pressure is the condenser pressure, which is fixed by the condenser temperature. Raising the boiler pressure raises the average heat addition temperature and so the efficiency, which means that a lower boiler pressure lowers it. Statement D is false.