Cooling process in a closed-cycle gas turbine plant: In the external cooler of a closed Brayton (Joule) cycle, the working gas is cooled at which thermodynamic condition?

Introduction / Context:
Closed-cycle gas turbines circulate a working gas (e.g., helium, nitrogen) through compressors, heaters, turbines, and coolers. Understanding which processes are at constant pressure versus constant volume clarifies how the Brayton cycle is realized in hardware.

Given Data / Assumptions:

• Steady flow through a heat exchanger (cooler).
• Negligible pressure drop in ideal analysis.
• Standard Brayton sequence: compression → heating → expansion → cooling.

Concept / Approach:

In the ideal Brayton (Joule) cycle, both heat addition and heat rejection occur at constant pressure in flow heat exchangers. The cooler removes heat at essentially constant pressure as the gas flows through tubes/plates, reducing temperature from turbine exhaust value back toward compressor inlet temperature.

Step-by-Step Solution:

Verification / Alternative check:

T-s and p-V diagrams of Brayton cycle show horizontal heat-rejection line at constant pressure; textbooks label both the heater and cooler as constant-pressure devices.

Why Other Options Are Wrong:

Constant volume would require a rigid, closed vessel without flow; constant temperature would be ideal only with variable pressure and is not how the Brayton cooler is defined; “none” contradicts standard cycle representation.

Common Pitfalls:

Confusing closed-cycle (recirculated gas) with constant-volume processes; assuming coolers behave like tanks rather than flow heat exchangers.

Final Answer:

Constant pressure