Refrigeration

Question 1

What are the three methods of heat transfer?

Answer 1

Convection - solid and gas/liquid
Conduction - solid and solid
Radiation - through air

Question 2

What is sensible and latent heat?

Answer 2

Sensible heat - When the temperature is changing but the state is the same.
Latent heat - When the temperature stays the same but the state is changing.

Question 3

What is superheat?

Answer 3

Every degree above boiling point.

Question 4

What is sub-cooling?

Answer 4

Every degree under boiling point.

Question 5

What happens to the pressure, volume, and energy required to boil a substance when altitude is increased or decreased?

Answer 5

Increased - pressure decreases, volume increases, less energy required to boil.
Decreased - pressure increases, volume decreases, more energy required to boil.

Question 6

What happens to pressure when a substance is cooled and heated?

Answer 6

Cooled - pressure decreases

Heated - pressure increases

Question 7

What are the four components of a basic refrigeration system?

Answer 7

Compressor
Condenser
TEV Thermal expansion valve
Evaporator

Question 8

What is the purpose of a compressor?

Answer 8

Pumps refrigerant around the system.

Question 9

What is the purpose of the condenser?

Answer 9

Uses sea water to cool the refrigerant and turn it from gas into liquid.

Question 10

What is the purpose of a TEV (thermal expansion valve)?

Answer 10

Control the flow of refrigerant around through the system. Slows flow of refrigerant, reducing the temperature to very cold.

Question 11

What is the purpose of the evaporator?

Answer 11

The refrigerant flows through the evaporator and absorbs heat from the refrigerator/cold room, turning the refrigerant from liquid back into gas.

Question 12

What is the condition of the refrigerant from compressor to condenser?

Answer 12

Hot
High pressure
Gas

Question 13

What is the condition of the refrigerant from condenser to TEV?

Answer 13

Warm
High pressure
Liquid (sub cooled)

Question 14

What is the condition of the refrigerant from the TEV to evaporator?

Answer 14

Very cold
Low pressure
Liquid

Question 15

What is the condition of the refrigerant from evaporator to compressor?

Answer 15

Cool
Low pressure
Gas (super heated)

Question 16

What are the additional components of a refrigeration system and what do they do?

Answer 16

LP cut out - stops the compressor if the pressure is too low
HP cut out - stops the compressor if the pressure is too high
Oil separator - separates oil from refrigerant and return it to the compressor
Liquid receiver - stores refrigerant during maintenance
Drier - removes moisture from the refrigerant
Sight glass - indicates moisture in the refrigerant (green = no moisture, yellow = moisture)

Question 17

What are the 3 procedures associated with refrigeration machiney?

Answer 17

Defrosting
Leak detection
Lubrication

Question 18

When is defrosting required?

Answer 18

When there is a build up of ice.

Question 19

What are the 3 methods of defrosting?

Answer 19

Natural defrost - every 3-6 months
Hot gas defrost - automatically done 4 times in a day in 15 minute intervals
Electrical heating coils - automatically done 4 times in a day in 6 hour intervals

Question 20

What is the Montreal Protocol?

Answer 20

An agreement between countries to phase out the production, use and emissions of ozone depleting substances ODS.

Question 21

What are three ozone depleting substances (ODS)?

Answer 21

CFCs
HCFC
HALONS

Question 22

What is the Kyoto Summit?

Answer 22

Agreement to reduce all greenhouse gasses.

Question 23

What are examples of greenhouse gasses?

Answer 23

CO2
HFC
PFC

Question 24

What are the methods of leak detection?

Answer 24

Oil slicks 
IRLDS (infared leak detection system)
Spectrolyne dye and uv lamp 
Snoop (soapy water)
Halogen leak detection

Question 25

Why is it important to check for leaks?

Answer 25

Because refrigerants can be ozone depleting and/or greenhouse gasses. Also to maintain good engineering standards and efficient running of machinery and to avoid safety hazards.

Question 26

Which lubricants are used on the compressor?

Answer 26

OM70
SW68
Suniso 3GS

Question 27

What does hygroscopic mean?

Answer 27

Absorbs moisture from the atmosphere.

Question 28

What three methods are there to add lub oil to the compressor?

Answer 28

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

Question 29

What are the hazards associated with refrigerants?

Answer 29

They are heavier than air and will displace oxygen.
If exposed to high temperatures, they can produce phosgene gas (mustard gas).
Can produce cold burns on exposed skin.
Decomposing fruit and veg can produce CO2.

Question 30

What would you do if you got refrigerant in your eye?

Answer 30

Wash out immediately and go to med bay.

Question 31

What would you do if you got refrigerant on your skin?

Answer 31

Wash off immediately.

Question 32

What are the precautions for entering a refrigerated compartment?

Answer 32

Check the high and low level exhaust fans are running.
Check that the IRLDS is working correctly.
No smoking at any time.
Inform senior rating of watch that personnel are entering and inform them when vacated.
The internal door opening mechanism is in correct working order.
One personnel to remain outside compartment as a safety number.

Question 33

What does chilled water provide cooling for?

Answer 33

Weapons systems
Radars
Ships computer systems
Air treatment units

Question 34

What does a chilled water plant have instead of an evaporator?

Answer 34

A chiller.