Which component of the APU assists in the process of cooling?

The compressor assembly plays a crucial role in the cooling process of the Auxiliary Power Unit (APU). It is responsible for compressing the air that enters the APU, which is a necessary step in generating the power and airflow required for the engine to operate efficiently. The compressed air can then be directed through an air conditioning unit, enhancing the cooling capabilities when the aircraft is on the ground or during certain operational modes. This ability to manage temperatures is vital for both comfort in the cabin and functionality of the aircraft systems.

In contrast, the other components do not directly contribute to the cooling process in the same way. The power turbine is involved in converting thermal energy into mechanical energy but does not manage air cooling directly. The accessory drive assembly serves to power various components, like the fuel pump or generator, but also does not play a direct role in cooling. Fuel lines, while crucial for delivering the necessary fuel to the APU, do not have a function related to cooling air or maintaining temperatures. Thus, the compressor assembly is the key component linked to air cooling in the APU system.