Heating and Cooling Systems Flashcards
What 3 things do turbine aircraft air conditioning systems use bleed air for?
Heating
Cooling
Pressurization
Explain the 2 components of an Air Cycle Machine
Compressor Turbine: used to compress air from the primary heat exchanger, increasing the pressure and temperature.
Expansion Turbine: Used to spin the compressor turbine, extracting heat energy from the air coming from the secondary heat exchanger, then air expands the air and cools even further.
What are the 3 sources of bleed air for a turbine aircraft?
Bleed air tapped from the compressor section of a turbine engine w/engine running
APU wAPU running (ground and flight if required)
Ground air source (huffer cart or jet bridge conditioned air)
Explain the 2 ways an anit-ice valve is controlled?
Vernatherm: automated non-electric temperature sensing control operated by a pneumatic control valve
Thermistor: electrically senses w/a wheatstone bride circuit and electrically controls anti-ice valves
Name the 10 major PACK components
Pack valve
Flow control valve
ACM
Primary heat exchanger
Secondary heat exchanger
Temperature control valve
Water separator
Anti-ice valve
Ground fan
Ram-air Inlet Doors
What is the purpose of the compressor in the vapor cycle system and how can it be powered?
A pump that compresses and circulates the freon, separates the high side from the low side.
Engine drive, electric motor, or hydraulic motor
What happens if moisture gets into a vapor cycle system?
Moisture reacts w/refrigerant and creates acids that corrode the system internally
Moisture freezes and blocks flow of refrigerant (usually in the expansion valve)
What are the high pressure side components and the low pressure side components in a vapor cycle system?
Low pressure side: expansion valve outlet, evaporator, compressor inlet
High pressure side: compressor outlet, condenser, receiver-dryer expansion valve inlet
What is the purpose and location of the condenser?
Radiator like heat exchanger that uses ambient airflow over coils carry high pressure, high temperature vapor refrigerant and cools it changing the state from a vapor to a liquid. Located between the compressor outlet and the receiver-dryer inlet
Which component controls the amount of refrigerant going into the evaporator?
The expansion valve, by sensing the temperature of the cabin and adjusts refrigerant flow rate
Name the things the A&P mechanic is required to have to service a vapor cycle system
EPA certificate
Proper PPE
AMM
Proper equipment/servicing chart
What are the differences between R12 and R134a refrigerant?
R12 is older and no longer produced, it is bad for the environment (destroys ozone layer) boils at -21 degrees F
R134 is newer and most common, boils at -15 degrees F
Name 4 ways to check for a leak in a vapor cycle system?
Soapy solution applied to fittings and lines, look for bubbles to indicate that the refrigerant is leaking
Leak detection dyes mixed in w/refrigerant if leaking can see with either a UV light or stains
Visual inspection and observation of system
Electronic leak detectors that give visual or aural indication when probe is near a leak
When adding refrigerant to a vapor cycle system what two places can you service from?
High side port (normally)
Low side port can be damaging to the compressor if refrigerant doesn’t evaporate before the compressor (follow AMM)
Explain the maintenance procedure when changing a part in the vapor cycle cooling system
All refrigerant is pumped out of the system (and recycled) and purge the system is suspected of contamination and cap all the lines. Changed the par. Before servicing evacuate the system w/vacuum pup to remove all moisture and then service the system with refrigerant
