10 Questions
What is the purpose of the receiver-dryer in the vapour cycle machine?
To filter and dry the refrigerant
Why is it important to remove all moisture from the system?
To prevent the formation of hydrochloric acid
What is the purpose of the sight glass in the receiver-dryer?
To indicate the amount of charge in the system
Where is the pickup tube located in the receiver-dryer?
At the top of the receiver-dryer
What is the purpose of the filter in the receiver-dryer?
To prevent particles from entering the expansion valve
What would happen if the charge in the system is low?
Bubbles would be seen in the sight glass
What is the purpose of the desiccant in the receiver-dryer?
To dry the refrigerant
What would happen if a single drop of water enters the system?
The water would react with the refrigerant to form hydrochloric acid
Where is the receiver-dryer located in the system?
Between the condenser and the expansion valve
What is the purpose of the condenser in the vapour cycle machine?
To condense the refrigerant
Study Notes
Vapour Cycle Air Conditioning System
- The receiver-dryer serves as a reservoir for the liquid refrigerant and filters out moisture from the system.
- It is located in the high side between the condenser and the expansion valve.
Compressor and Refrigeration Cycle
- The system is divided into two sides: the low side (accepts heat) and the high side (disposes of heat).
- The compressor increases the pressure and temperature of the refrigerant vapour.
- The refrigeration cycle starts at the receiver-dryer and flows through the expansion valve, evaporator, and compressor.
Evaporator and Cooling Process
- The evaporator is the unit that produces the cold air, where heat is absorbed by the refrigerant.
- Warm air is blown through the thin metal fins that fit over the evaporator coils, and the heat is absorbed by the refrigerant.
- When heat is absorbed, the refrigerant changes from a liquid to a gas without increasing its temperature.
Refrigerant and System Requirements
- R134a is the exclusively used refrigerant in aircraft applications due to its low environmental impact.
- The refrigerant must be highly volatile (high vapour pressure and low boiling temperature).
- Only the refrigerant specified in the aircraft manufacturer's maintenance manual should be used for servicing the system.
Importance of Moisture Removal
- Moisture must be removed from the system, as a single drop can freeze in the expansion valve and stop the entire air conditioning process.
- Water reacts with the refrigerant to form hydrochloric acid, which is highly corrosive to the metal in the system.
This quiz covers the components and functioning of an aircraft air conditioning system, including the receiver-dryer, thermal expansion valve, and evaporator. Learn about the properties of refrigerants and their applications in aircraft.
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