Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Mech Theory 4 > Refrigeration > Flashcards

Refrigeration Flashcards

1
Q

As pressure increases, volume ………….. and ……….. energy is required to boil.

A

As pressure increases, volume decreases, and more energy is required to boil.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

As pressure decreases, volume ………….. and ………. energy is required to boil.

A

As pressure decreases, volume increases, and less energy is required to boil.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain the three ways heat can be transferred.

A

Conduction - heat transfer through a solid.
Convection - heat transfer through a liquid.
Radiation - heat transfer through a space.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe Sensible Heat

A

Heat required to change temperature, without change in state.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe Latent Heat

A

Heat required to change state, without change in temperature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe Superheat

A

How high a substance is above its boiling point. For every degree above its boiling point, it gains one degree of superheat.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Describe Sub-cooling

A

When a substance drops below its boiling point and is condenses into a liquid. For every degree below its boiling point, it gains one degree of sub cooling.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the four main components of a basic refrigeration system?

A

Compressor
Condenser
Thermal Expansion Valve (TEV)
Evaporator

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the purpose of the compressor?

A

Compresses the low pressure cold gas to produce a high pressure gas. Also acts as a positive displacement pump to maintain system pressure.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What must never enter a compressor and why?

A

Liquid as it can’t be compressed.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the purpose of the condenser?

A

Uses sea water to cool the refrigerant, changing its state from a high pressure gas to a high pressure, warm liquid.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the purpose of the Thermal Expansion Valve (TEV)?

A

Controls the flow rate of refrigerant through the system, lowering its temperature and pressure by increasing the volume of the outlet. It increases or decreases the flow based on the temperature of the refrigerant leaving the evaporator.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the purpose of the Thermal Exlansion Valve (TEV)?

A

Controls the flow rate of refrigerant through the system, lowering its temperature and preby increasing . It increases or decreases the flow based on the temperature of the refrigerant leaving the evaporator.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens to refrigerant in the evaporator?

A

Refrigerant flowing through removes heat from the cold room. This changes the state of the refrigerant from a liquid to a gas.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the condition of the refrigerant between the compressor and condenser?

A

Hot, high pressure gas

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the condition of the refrigerant between the condenser and TEV?

A

Warm, high pressure liquid (sub-cooled to ensure no gas remains)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the condition of the refrigerant between the TEV and Evaporator?

A

Very cold, low pressure liquid.

18
Q

What is the condition of the refrigerant between the Evaporator and Compressor?

A

Cool, low pressure gas (superheated to ensure no liquid remains)

18
Q

What is the condition of the refrigerant between the Evaporator and Compressor?

A

Coo, low pressure gas (superheated to ensure no liquid remains)

18
Q

What is the condition of the refrigerant between the Evaporator and Compressor?

A

Coool, low pressure gas (superheated to ensure no liquid remains)

19
Q

What are the six additional components in the Applied System?

A

HP cut out
LP cut out
Oil separator
Liquid Reciever
Drier
Sight glass

20
Q

What is the purpose of the HP cut out?

A

Shuts down the refrigeration plant if the pressure gets too high.

21
Q

What is the purpose of the LP cut out?

A

Shuts down the refrigeration plant if the pressure drops too low.

22
Q

What is the purpose of the Oil Separator?

A

Separates any oil from the refrigerant and directs it back to the compressor sump.

23
Q

What is the purpose of the Liquid Reciever?

A

Acts as a resevoir for the refrigerant and stores it during maintenance.

24
Q

What is the purpose of the Drier?

A

Removes any moisture from the refrigerant.

25
Q

What is the purpose of the sight glass, and what colours are the indicators?

A

Indicates moisture in refrigerant. Indicators are yellow (moisture) and green (no moisture).

26
Q

What are the three methods of defrosting and how often are they carried out?

A

Natural Defrost - carried out every 3 to 6 months.

Hot Gas Defrost - Max of 1 hour per 24 hours, done in 15 minute intervals.

Electrical heating coils - Max of 1 hour in 24 hours.

27
Q

Why are refrigerant leaks bad?

A

Harmful to the environment and reduces plant efficiency.

28
Q

What are the 5 methods of leak detection?

A

1) Oil Slicks
2) Infra-Red Leak Detection System
3) Spectrolyne dye and UV lamp
4) Snoop
5) Halogen Leak Detector

29
Q

What type of lubricants are used on compressors, and what are the names of the three main lubricants used?

A

Hygroscopic lubricants (absorb moisture from the atmosphere):
1) OM70
2) SUNISO 3GS
3) SW 68

30
Q

What are the three methods of adding oil to compressors?

A

Via sump filler plug
By a hand pump
Through the use of a dosing pot

31
Q

What harmful substances are covered by the Montreal Protocol?

A

CFC’s
HCFC’s
Halons

32
Q

What harmful substances are covered by the Kyoto Summit?

A

CO2
HFC
PFC

33
Q

What are the 4 hazards associated with Refrigerants?

A

1) They are heavier than air and will displace oxygen.

2) If exposed to high temperatures they can produce Phosgene gas.

3) Can produce cold burns on exposed skin (frost bite)

4) Decomposing fruit and veg can produces CO2

34
Q

What should you do if refrigerant gets in your eyes? What if it gets on your skin?

A

If in eyes, they need flushing with water and then require medical treatment.
If on skin, wash off immediately.

35
Q

What is the procedure for entering refrigerant compartments?

A

1) Rating on watch is informed that personnel are entering the compartment and informed when the compartment is vacated.

2) Breathing apparatus is available at machinery space access.

3) High and Low exhaust fans are running.

4) No smoking at any time. Hot work is tightly controlled.

5) The IRLDS is working correctly and indicating safe.

6) The personnel trapped warning lights are in order.

7) Any rating entering the room should be accompanied by another rating who waits outside the room as a safety number.

8) Internal door opening mechanism is in correct working order.

36
Q

From what source should oil be used and what should happen to any unused oil?

A

An unopened/uncontaminated can. Unused oil is responsibly discarded as it is now contaminated.

37
Q

What systems are supplied with chilled water?

A

Weapon systems
Radars
Ships computer systems
Air Treatment Units (ATU’s)

38
Q

What is the main difference between refrigeration and chilled water systems?

A

The chilled water plant has a chiller in place of an evaporator.

39
Q

What provides cooling for the condenser and motors?

A

Seawater pump.

Mech Theory 4 (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions