Is the entropy change of a cyclic device always zero, whether it's reversible or irreversible?

The entropy change of a cyclic device is always zero, whether it's reversible or irreversible. This is because entropy is a state function, meaning its value depends only on the initial and final states of the system, not on the path taken between those states15. In a cyclic process, the system returns to its initial state, so the net entropy change is zero. However, in irreversible cycles, entropy is generated within the system and its surroundings, but the net entropy change of the system itself remains zero5.

To clarify, while the system's entropy change is zero, the total entropy (system plus surroundings) increases in irreversible processes due to entropy generation3. In reversible cycles, the total entropy change is zero because there is no entropy generation3.

Here's a summary:

• Reversible Cycles: The entropy change of the system is zero because there is no entropy generation, and the process is internally reversible3.
• Irreversible Cycles: The entropy change of the system is still zero, but entropy is generated within the system and its surroundings, leading to an increase in total entropy35.