Closed-cycle gas turbines and the Brayton–Joule model State whether the following is correct: “A closed-cycle gas turbine operates on the Joule (Brayton) cycle under air-standard assumptions.”

Introduction / Context:Gas turbines—open or closed—are commonly analyzed with the Brayton (also called Joule) cycle: isentropic compression, constant-pressure heat addition, isentropic expansion, and constant-pressure heat rejection. The question asks if this framework applies to closed-cycle configurations.

Given Data / Assumptions:

• Air-standard or ideal-gas modeling is used for cycle description.
• Closed cycle recirculates a working fluid through external heat exchangers.
• Compression and expansion are treated as isentropic in the ideal model.

Concept / Approach:Both open- and closed-cycle gas turbines follow the same Brayton–Joule sequence in idealized analysis. The difference lies in how heat is supplied and rejected: open cycles burn fuel directly, while closed cycles use external heaters/coolers and may include recuperation. Despite these hardware differences, the thermodynamic cycle remains Brayton.

Step-by-Step Solution:Identify the four ideal processes: isentropic compression, constant-pressure heating, isentropic expansion, constant-pressure cooling.Recognize that closing the loop with heat exchangers does not change the process sequence.Therefore, the statement is correct: a closed-cycle gas turbine operates on the Joule (Brayton) cycle.

Verification / Alternative check:Textbook T–s and p–v diagrams for closed Brayton cycles mirror those of open cycles; only the placement of combustor vs. external heater differs.

Why Other Options Are Wrong:

• “Only helium” or “only without a recuperator” adds unnecessary conditions; the cycle identification is independent of working fluid or recuperation.
• Rankine is the vapor power cycle (phase change), not applicable to gas turbines.

Common Pitfalls:Equating “closed cycle” with a different thermodynamic cycle; closure refers to fluid recirculation, not to a change in the ideal process sequence.

Final Answer:True