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Theory 4 > Refrigeration > Flashcards

Refrigeration Flashcards

1
Q

Explain pressure volume energy relationship

A

As pressure increases, volume decreases, and more energy is needed to boil a liquid

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2
Q

Heat travels from…

A

Hot to cold

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3
Q

3 methods of heat transfer

A
  1. Conduction - Solid
  2. Convection - Liquid
  3. Radiation - Air
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4
Q

Sensible Heat

A

Changes temp, NOT State

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5
Q

Latent Heat

A

Changes state, NOT Temp

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6
Q

Superheat

A

Every degree above its boiling point
e.g. 101 = 1 superheat

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7
Q

Sub cooling

A

Cools and condenses into liquid and drops below boiling point

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8
Q

Temperature energy graph

A

Temperature energy graph

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9
Q

Basic refrigeration system

A

Basic refrigeration system

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10
Q

Compressor

A

Pumps refrigerant around system

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11
Q

Condenser

A

Cools refrigerant, changing state from gas to liquid

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12
Q

Thermal Expansion Valve

A

Controls flowrate
Inc/Dec temp depending on temp of refrigerant leaving the evaporator

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13
Q

Evaporator

A

Changes state of refrigerant from liquid to gas

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14
Q

Condition of refrigerant as it flows from compressor to condenser

A

Hot, High Press Gas

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15
Q

Condition of refrigerant as it flows from condenser to TEV

A

Warm, High Press liquid (Sub Cooled)

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16
Q

Condition of refrigerant as it flows from TEV to evaporator

A

Very cold, low press liquid

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17
Q

Condition of refrigerant as it flows fromevaporator to compressor

A

Cool, low press gas (superheated)

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18
Q

LP Cut Out

A

Stops compressor if pressure drops too low

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19
Q

HP cut out

A

stops the compressor if the pressure gets too high

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20
Q

Oil Separator

A

Separates oil from the refrigerant

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21
Q

Liquid Receiver

A

Store refrigerant during maintenance

22
Q

Drier

A

removes moisture from refrigerant

23
Q

Sight Glass

A

indicates moisture in the refrigerant

Yellow – there is moisture
Green – there isn’t moisture

24
Q

Refrigeration Procedures

A
  1. Defrosting
  2. Leak Detection
  3. Lubrication
25
Q

When is defrosting required?

A

Ice builds up on evaporator coils

26
Q

Methods of defrosting

A

Natural Defrost
Hot Gas Defrosting
Electrical Heating coils

27
Q

How often is natural Defrost carried out?

A

Every 3-6 months

28
Q

How often is hot gas defrosting carried out?

A

Max of 1hr per 24hrs

29
Q

How often is electrical heating coils carried out?

A

Max of 1hr every 24hrs

30
Q

Why is Leak Detection used?

A

Refrigerant leaks are harmful to the environment and reduce refrigerant plant efficiency

31
Q

Methods of Leak Detection

A
  1. Oil Slicks
  2. IRLDS
  3. Spectrolyne dye
  4. Snoop
  5. Halogen Leak Detector
32
Q

What is an oil Slicks?

A

where oil is leaking there will also be refrigerant leaking

33
Q

IRLDS

A

Infra-red leak detection system

34
Q

What kind of lubricants are needed for compressors?

A

Hygroscopic lubricants

35
Q

What do hygroscopic lubricants do?

A

Absorb moisture from the atmosphere

36
Q

What kinds of oils are used in refrigeration?

A

SUNISO 3GS
SW68
OM70

37
Q

What source should oils be used

A

New, unopened cans

38
Q

Methods of How is oil added to compressors

A
  1. Sump Filler Plug
  2. Hand Punp
  3. Dosing pot
39
Q

What is the Montreal protocol?

A

Agreement to phase out harmful ozone depleting substances

40
Q

Montreal Protocol substances

A

CFC
HCFC
Halons

41
Q

What is the Kyoto summit

A

Agreement to reduce all Greenhouse gases

42
Q

Greenhouse gas substances

A

Co2, HFC, PFC

43
Q

How is phosphine gas produced?

A

Refrigerants are heavier than air and will displace Oxygen
If exposed to high temperatures they can produce PHOSGENE GAS

44
Q

Hazards of refrigerants

A

Can produce Cold Burns on exposed skin (Frost Bite)

Decomposing Fruit and Veg can produce CO²

45
Q

What so you do if refrigerant gets in your eyes

A

flushing with running water and then require medical treatment.

46
Q

Procedure for entering refrigeration compartments

A
  • Rating in charge of watch to be kept informed
  • Breathing Apparatus avaliable
  • High/Low exhaust fans running
  • No Smoking
  • IRLDS working correctl
46
Q

Procedure for entering refrigeration compartments

A
  • Rating in charge of watch to be kept informed
  • Breathing Apparatus avaliable
  • High/Low exhaust fans running
  • No Smoking
  • IRLDS working correctly
  • personnel trapped warning lights working
  • sentry
  • internal door mechanism working
47
Q

What should happen to oil after use?

A

It should be disposed of in accordance with MARPOL

48
Q

Chilled water provides cooling for…

A

Weapons Systems

Radars

Ships Computer Systems

Air Treatment Units (ATUs

49
Q

Main difference between chilled water, and refrigeration

A

The chilled water plant has a CHILLER in place of the EVAPORATOR

50
Q

What provides cooling for condenser and motors

A

sea water pump

Theory 4 (4 decks)

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