How does the expansion turbine affect the air in an air-cycle cooling system?

In an air-cycle cooling system, the expansion turbine plays a crucial role by allowing the pressurized air to expand. When air passes through the expansion turbine, it undergoes a drop in both temperature and pressure. This is a fundamental principle of thermodynamics, specifically the Joule-Thomson effect, where expanding a gas results in cooling due to a decrease in pressure.

As the air expands, it loses energy, which translates to a drop in temperature, leading to the cooling effect necessary for maintaining a comfortable cabin environment. The simultaneous decrease in pressure is an inherent characteristic of the expansion process as the gas transitions from a high-pressure state to a lower pressure state.

The reduction in temperature is essential for effective cooling, as it allows the air to absorb heat from the cabin, contributing to the overall cooling cycle of the air-cycle system. Thus, the correct choice highlights the dual role of the expansion turbine in managing both temperature and pressure within the system, which is vital for optimal cabin climate control.