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Module 11 Sub Modules 11.1 - 11.10 > 11.4 Air Conditioning Air & Vapour Cycle Machines > Flashcards

11.4 Air Conditioning Air & Vapour Cycle Machines Flashcards

1
Q

What is the air cycle system also known as as

A

Air conditioning pack

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2
Q

What is the pressure and temperature of air that enters the ac from bleed air

A

30-40psi 150°C

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3
Q

What does a compressor do to air

A

Raises temperature and air pressure

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4
Q

What powers the air conditioning compressor

A

Air cycle machine turbine

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5
Q

What does a heat exchanger do in the AC system

A

Cools the air

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6
Q

How is moisture removed from air before being condensed

A

Water extractor duct

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7
Q

Where is water from the water extractors sent

A

Spray nozzles into ram air inlet to improve cooling efficiency in heat exchangers

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8
Q

What happens when ice builds up in the condenser or exit of the turbine

A

Bleed Air bypassed around heat exchangers and ACM (air cycle machine) to melt ice and free exit of system

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9
Q

What does the pack/flow control valve do

A

Regulates that bleed air from the pneumatic manifold into the air cycle AC system

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10
Q

Where is the switch for pack/flow valve located

A

Flight deck

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11
Q

How is the pack/flow valve powered

A

Electrically or pneumatically

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12
Q

If power to the pack/flow valve stops what happens

A

The valve is spring loaded so will automatically close

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13
Q

What happens to mass flow of AC when altitude increases

A

Mass flow decreases

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14
Q

What happens to volumetric flow as altitude increases

A

Remains constant

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15
Q

What is the difference between mass flow and volumetric flow

A

Mass flow is the weight of the aid volumetric is the volume of the air, volume remains constant but due to lower air pressure mass decreases

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16
Q

What happens to AC when an aircraft is not fully loaded

A

AC works at lower capacity to save energy (this works by pack valve partially closing, constricting air flow)

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17
Q

How does a heat exchanger work

A

Heat transfer between two fluids (eg air) cold outside Rama air cools hot bleed air. Has fin like tubes inside to achieve this

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18
Q

What is the Pack valve purpose

A

Control airflow into the cabin

19
Q

How is the flow of ram air regulated in the heat exchanger

A

Modulating inlet and exit doors which modulate in flight to provide required cooling effect

20
Q

What must happen to ram inlet doors when your on the ground

A

There is insufficient air passing through the ram inlet doors so a fan is used to induce adequate air flow to cool heat exchangers

21
Q

Are water separations needed in flight

A

Not really as air is ver dry and very cold

22
Q

What can a high cabin humidity lead to

A

Fog, water droplets, passenger discomfort and corrosion in the cabin

23
Q

Simply, how does the water separator remove water from the air

A

Humid air from ACM emerges and is forced through a fibreglass sock that condenses and combines mist into water drops. Dry air passes through and the water collects on the sides of the separator and drains out the unit

24
Q

How is the air from the ACM prevented from being too cold

A

Air is bypassed around the ACM and it then prevents air being too cold and forming ice on the exit or in the condenser

25
Q

What air trim air valances

A

Used in some systems to mix conditioned air provide accurate temperature controlled air to the cabin and flight deck.
(Mix bleed and conditioned air)

26
Q

What is the purpose of the mix chamber

A

Collect temperature controlled conditioned air from pack then distribute the warm/cool air to the flight compartments in the aircraft

27
Q

Where is the RAM air inlet located

A

Underside of an aircraft often on wing to body fairing

28
Q

How is the amount of air into the ram air inlet controlled

A

Using a modulating door controlled by actuators on the inlet

29
Q

What does the ram air go after entering through the ram air inlet

A

To the primary and secondary heat exchangers

30
Q

What is the purpose of ram air in the heat exchangers

A

To remove hear from bleed air in the heat exchangers

31
Q

What is used to increase ram air recovery

A

Modulating vanes on the ram air exhaust

32
Q

What provides flow of air across the heat exchangers

A

A ram air fan, runs off a common shaft with the ACM powered by the ACM turbine

33
Q

What type of AC doesn’t doesn’t require bleed air

A

Vapour cycle machine air condition system

34
Q

What type of AC doesn’t doesn’t require bleed air

A

Vapour cycle machine air condition system

35
Q

How does a vapour cycle machine air conditioner system work

A

Transfers heat from inside the cabin to outside the cabin working on the principles of thermodynamics. Heat is transferred to refrigerant liquid which turns to vapour as it gains extra heat energy. Vapour then gets compressed making it even hotter. Heated vapour releases the gained heat to the outside air and returns to the cabin as a liquid, basically like a fridge.

36
Q

What are the steps of refrigeration

A

Compression, condensation, receiver-dryer, expansion, evaporation, repeat

37
Q

What refrigerant is commonly used

A

Tetrafluroethane (R134a) (Freon)

38
Q

What is the boiling point of R134a refrigerant

A

-26°C

39
Q

What refrigerant is no longer used due to ozone damage

A

Dichlorodiflouromethane (R12)

40
Q

What is the reservoir of the vapour cycle system called

A

Receiver dryer, contains refrigerant and can replace any missing refrigerant

41
Q

What does water in refrigerant do

A

Can create an acid that can damage components or can form ice and block flow of refrigerant around the system

42
Q

How do you know if refrigerant is low in receiver dryer (reservoir)

A

There will be bubbles visible in the sight glass

43
Q

What does the compressor do

A

Increases pressure and temperature of low pressure low temp air

Module 11 Sub Modules 11.1 - 11.10 (82 decks)

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