Inspection and Operation of a Vapor-Cycle Cooling System
What is used as the refrigerant in a vapor-cycle air conditioning system?
A Freon-type liquid refrigerant known as Refrigerant 12, or the more environmentally friendly R-134a.
What safety equipment should be worn when charging a vapor-cycle cooling system?
A safety face shield
What are two types of air conditioning systems that may be installed on an aircraft?
Air-cycle systems and vapor-cycle systems
How should the components in the low side of a properly operating vapor-cycle cooling system feel?
Cool
How is a vapor-cycle cooling system checked for leaks?
Hold the probe of an electronic leak detector below any suspect fitting or component. If there is a leak, the detector will make a tone.
What is the state of the refrigerant as it leaves the compressor?
It is a high-pressure gas.
What is the state of the refrigerant as it leaves the condenser?
It is a high-pressure liquid.
What is the state of the refrigerant as it leaves the thermostatic expansion valve?
It is a low-pressure liquid.
What is the state of the refrigerant as it leaves the evaporator?
It is a low-pressure vapor.
How is refrigerant put into the system?
It is put into the system through service valves on the low side of the system using a manifold gage set.
What is the function of the thermostatic expansion valve?
It meters just enough liquid refrigerant into the evaporator that all of it will be evaporated by the time it leaves the evaporator coils.
How is the compressor lubricated?
Refrigerati0n oil is mixed with the refrigerant and it circulates through the compressor and the entire system.
How is the heat removed from an aircraft cabin with a vapor-cycle air conditioning system?
The cabin heat is absorbed by the refrigerant in the evaporator, then carried outside the aircraft where it is given up to the outside air in the condenser.
What produces the cool air in a vapor-cycle air conditioning system?
Warm cabin air is blown across the evaporator, where its heat is transferred into the refrigerant. The air that leaves the evaporator is cool.
