How is 600-degree air from the engines cooled for cabin comfort?

The process of cooling 600-degree air from the engines for cabin comfort primarily involves the utilization of bleed air. Bleed air, which is extracted from the engine compressors, is usually at a much lower temperature than the exhaust gases exiting the turbine. This cooler bleed air can be mixed with the hotter air from the engines or ducted separately to ensure that the cabin environment remains comfortable for passengers and crew.

Utilizing bleed air for cooling is efficient as it comes from a part of the engine that is already functioning to generate thrust. The air is pressurized and can effectively lower the temperature when mixed or transformed into a breathable environment within the cabin, maintaining a safe and pleasant atmosphere during flight.

The other options do not adequately describe the primary cooling mechanism: passing through the combustion chamber would not cool the air but rather heat it; heat exchangers could potentially play a role but are not the main method used in this scenario; and while adding cold air from outside is a possibility, the immediate and primary source of airflow for cabin comfort typically relies on the engine's bleed air system.