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GATE 2026 ME – Question 44

Thermal Engineering Applications · Power Engineering: vapour and gas power cycles, regeneration and reheat · 2 marks · Multiple choice

For an ideal regenerative Rankine cycle, as shown in the figure below, which one of the following options is the correct representation of temperature-entropy (T-s) diagram?

A boiler, a turbine drawn with a heat-exchange coil around it, a condenser and a pump. The pump output (state 2) is heated while it flows past the turbine on its way to the boiler (state 3), and the steam leaves the boiler at state 4 and the turbine at state 5. Four T-s diagrams labelled A to D are given as options.
  1. The T-s diagram labelled (A) in the figure
  2. The T-s diagram labelled (B) in the figure
  3. The T-s diagram labelled (C) in the figure
  4. The T-s diagram labelled (D) in the figure

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Correct answer: (C) The T-s diagram labelled (C) in the figure

Explanation

In an ideal regenerative cycle the feed water is heated by the steam as it expands in the turbine, with heat exchange that is reversible. So the heating line 2 to 3 on the T-s diagram runs parallel to the expansion line 4 to 5. The diagram in which these two lines are parallel is (C).