What is the purpose of the water separator of the air cycle machine?

• A. To remove the excess moisture which is caused by rapid lowering of the air temperature
• B. To remove dust
• C. To remove oil
• D. To cool the air

Answer: (A)

Moisture removal in the air cycle system is being tested. When bleed air is cooled rapidly in the air cycle machine, water vapor condenses into liquid water. The water separator captures this condensate so that dry air continues on to the conditioning stages and into the cabin, preventing water-related problems like icing or water damage in the system. That’s why removing excess moisture is the primary purpose.

Dust is handled by filters upstream in the system, not by the water separator. Oil removal is a different process that deals with oil vapors and droplets, not the condensate from moisture. And cooling the air is accomplished by the heat exchangers and the turbine expansion in the air cycle machine, not by the water separator.