The Cooling Pack, or Air Condition Pack, is an air cycle refrigeration system that uses the air passing through and into the airplane as the refrigerant. This is accomplished by a combined turbine and compressor machine, called Air Cycle Machine (A.C.M.), valves for temperature and flow control, and heat exchangers using outside air to dispense waste heat. The air condition pack provides essentially dry, sterile, and dust free conditioned air to the airplane cabin at the proper temperature, flow rate and pressure to satisfy pressurization and temperature control requirements.
Basic Operation : Pressurized and hot air coming from the airplane Bleed System enters the Primary Heat Exchanger where it’s temperature is reduced, then enters the compressor section of the Air Cycle Machine where it’s temperature and pressure is raised again, then the air enters the Secondary Heat Exchanger reducing again it’s temperature, and finally it enters the Turbine section of the Air Cycle Machine expanding and releasing it’s energy to rotate the Turbine and the Compressor wheels being on the same shaft, with the temperature dropping down to 0 degree Celsius or below. At this temperature the moisture is condensed and is removed by a Water Separator.
The early Jet airplanes Air Conditioning System configuration was close to the basic system in addition of a Flow Control Valve and an Ice control system.
Last generation Airplane Air Conditioning System Cooling Pack consists ofa Flow Control Valve, Primary and Secondary Heat Exchangers, Air Cycle Machine, Primary and Secondary Temperature Control Valve, Re heater, Condenser, Ozone Converter, a Water Separation System, Check Valves, and many sensors.