Stirling Cycle — Process Composition The ideal Stirling cycle consists of which set of four processes (with perfect regeneration)?

Introduction / Context:
The Stirling cycle is an external combustion cycle known for using a regenerator to recycle heat internally. It is often contrasted with Ericsson and Brayton cycles and is important for understanding high-efficiency external heat engines.

Given Data / Assumptions:

• Ideal gas working fluid.
• Perfect regeneration with no losses.
• Quasi-static, reversible processes.

Concept / Approach:
The ideal Stirling cycle comprises two isothermal processes (heat addition at high temperature and heat rejection at low temperature) and two constant-volume (isochoric) regenerative processes, during which heat is transferred to and from the regenerator without net heat exchange with external reservoirs.

Step-by-Step Solution:
Identify isothermal expansion at T_high with external heat input.Isochoric regeneration: working fluid gives heat to the regenerator while volume is held constant.Isothermal compression at T_low with external heat rejection.Isochoric regeneration: working fluid receives heat back from the regenerator at constant volume.

Verification / Alternative check:
With perfect regeneration, the Stirling cycle can theoretically achieve Carnot efficiency between the same temperature limits because external heat is exchanged isothermally at the extremes while internal heat shuttling occurs at constant volume.

Why Other Options Are Wrong:
Options with isentropic segments belong to Otto/Brayton-like cycles; constant-pressure versions describe Ericsson-type behavior, not Stirling.

Common Pitfalls:
Confusing Stirling (isochoric regeneration) with Ericsson (isobaric regeneration) and with Brayton (no isothermal legs).

Final Answer:
two constant volume and two isothermal processes