Air Conditioning Packs
True or false - ram air mixes with the pack air and eventually goes into the cabin.
False - ram air bypasses the pack air via the heat exchangers, but doesn't actually mix.
What is ram air used for on a combustion heater?
Carries heat to the places where needed.
The outlet of the compressor.
True or false - it's possible to control the temp in different cabin zones on a large aircraft.
True - each zone has its own sub trim air valve to trim the temp of the pack air.
What is a BTU?
It is the amount of heat required to increase the temperature of 1 pound of water 1 degree F.
What is the purpose of a trim valve in a compressor bleed air air conditioning system?
Control the supply of hot air to be mixed with cold pack air.
The operation of an aircraft combustion heater is usually controlled by a thermostat circuit. what does the thermostat do?
alternately turns the fuel on and off, a process known as cycling.
What is the condition of the refrigerant as it leaves the evaporator of a vapor-cycle cooling system?
Low-pressure vapor.
What is the name of the parent valve that controls the cabin temperature?
The trim air valve or trim air pressure regulating valve.
What is a calorie?
It is the amount of heat required to increase the temperature of a gram of water 1 degree C.
The basic air-cycle pack system consists of
A source of compressed (bleed, usually) air, an aircycle machine, heat exchangers, a water separator.
What is a danger of an exhaust shroud or combustion heater? How is it prevented?
Carbon monoxide. Leak check the system.
What is the condition of the refrigerant as it enters the condenser of a vapor-cycle cooling system?
High-pressure vapor.
What is the name of the parent valve of the pack system?
Pack valve or pack flow control and shutoff valve.
What are: Latent heat, specific heat, sensible heat?
Latent heat: heat added to a liquid that changes its state but not its temperature.
Specific heat: the amount of BTUs required to raise the temperature of a substance by 1 degree F.
Sensible heat: heat that is added to a liquid that increases its temperature.
Which section of a turbine engine provides high pressure bleed air to an air cycle machine for pressurization and air conditioning?
Low or high pressure compressor.
When an aircraft has a combustion heating system how does it operate on the ground?
It has a fan to replace the flow of ram air it would have in the air.
The point at which freon flowing through a vapor-cycle cooling system gives up heat and changes from a gas to a liquid is the
condenser
What do the two parts of an aircycle machine do?
The first part, the compressor, compresses the air and heats it up. The second part, the expansion turbine, expands the air, which cools it. It is also cooled from the energy it takes to spin the turbine. This is on the same shaft as the compressor, so it also spins the compressor.
How do you convert C to F and back again?
Multiply C by 1.8 and add 32.
Subtract 32 from F and then divide by 1.8.
Where does the last stage of cooling before the water separator in an air-cycle air conditioning system occur?
Expansion turbine.
Which is considered a good practice concerning the inspection of heating and exhaust systems of aircraft utilizing a jacket around the engine exhaust as a heat source?
Supplement physical inspections with periodic operational carbon monoxide detection tests.
What component might possibly be damaged if liquid refrigerant is introduced into the low side of a vapor-cycle cooling system when the pressure is too high or the outside air temperature is too low?
Compressor.
Where does bleed air go before it enters the pack system? What other source of air is involved?
It goes through the precooler to drop the temp to the correct temp for the first heat exchanger; it is cooled by bypass fan air, via a heat exchanger.
What are the three ways heat can move? Does it move hot to cold or cold to hot?
1.Conduction – heat transfer by touching
2.Radiation – heat through the air by electromagnetic waves
3.Convection – currents in a liquid or gas move the heat
Hot to cold.