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GATE 2021 ME (ME1) – Question 21

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

In which of the following pairs of cycles, both cycles have at least one isothermal process?

  1. Diesel and Otto
  2. Carnot and Stirling
  3. Brayton and Rankine
  4. Bell–Coleman and vapour-compression refrigeration

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Correct answer: (B) Carnot and Stirling

Explanation

Carnot includes isothermal heat addition and rejection. Stirling also includes two isothermal processes, connected by constant-volume regenerative processes.

Thus **Carnot and Stirling (B)** qualify. Otto, Diesel, Brayton and Bell–Coleman do not have isothermal legs in their standard ideal forms.