Refrigeration And Ventilation

Question 1

What are freezers and fridges used for

Answer 1

The storage of food to prevent spoilage

Question 2

What are domestic refrigerators used for

Answer 2

Kept in the sickbay to keep medical supplies cool

Also fitted in mess decks to cool drinks

Question 3

What are ice making machines used for

Answer 3

Make ice cubes for medical purposes and also for drinks

Question 4

Explain the effects of pressure on the boiling point of water

Answer 4

High above sea level, a kettle will boil much sooner than 100 degrees C due to reduced pressure
At sea level a kettle will boil at 100 degrees C
Below sea level the boiling point will be much more than 100 degrees C due to the air pressure being much more dense and the volume will be even less

Question 5

What is the definition of conduction

Answer 5

Energy is transferred by direct contact

Question 6

What is the definition of convection

Answer 6

Energy is transferred by the mass motion of molecules

Question 7

What is the definition of radiation

Answer 7

Energy is transferred by electromagnetic radiation

Question 8

Define heat transfer

Answer 8

Heat will always transfer from a hot body to a cold one

Question 9

What does the cold room store and at what temperature

Answer 9

Frozen meat, fish etc

At -18 to -22 degrees C

Question 10

What does the cool room dairy, store and at what temperature

Answer 10

Butter, milk, and other dairy product

At +4 to +6 degrees C

Question 11

What temperature is the fruit and vegetable store kept at

Answer 11

+4 and +6 degrees C

Question 12

What temperature is the galley ready use cupboard kept at

Answer 12

+5 to +7 degrees C

Question 13

What does the compressor do

Answer 13

Pumps the refrigerant around the system

Question 14

What does the condenser do

Answer 14

Uses sea water to cool the refrigerant changing its state from a gas to a liquid

Question 15

What does the TEV (Thermal Expansion Valve) do

Answer 15

Controls the flow rate of refrigerant through the system.

Increasing and decreasing the flow depending on the temperature of the refrigerant leaving the evaporator

Question 16

What does the evaporator do

Answer 16

The refrigerant that flows through the evaporator removes heat from the refrigerator/cold room.
Changes the state of the refrigerant from a liquid into gas

Question 17

What is the condition of the refrigerant from compressor to condenser

Answer 17

Hot
High pressure
Gas

Question 18

What is the condition of the refrigerant from condenser to TEV

Answer 18

Warm
High pressure
Liquid

Question 19

What is the condition of the refrigerant from TEV to evaporator

Answer 19

Very cold
Low pressure
Liquid

Question 20

What is the condition of the liquid from evaporator to compressor

Answer 20

Cool
Low pressure
Gas

Question 21

What does the LP cut out do

Answer 21

Stops the compressor if the pressure drops too low

Question 22

What does the HP cut out do

Answer 22

Stops the compressor if the pressure gets too high

Question 23

What does the oil separator do

Answer 23

Separates oil from the refrigerant

Question 24

What does the liquid receiver do

Answer 24

Stores refrigerant during maintenance

Question 25

What does the drier do

Answer 25

Removes moisture from refrigerant

Question 26

What does the sight glass do and what do the different colours mean

Answer 26

Indicates moisture in the refrigerant
Yellow - there is moisture
Green - there isn’t moisture

Question 27

What are the different refrigeration procedures

Answer 27

Defrosting
Leak detection
Lubrication

Question 28

When is defrosting required and what are the different methods

Answer 28

When ice builds up on the evaporator coils
The methods:
Natural defrost - every 3-6 months
Hot gas defrosting - maximum of 1 hour in 24 in 15 minute slots
Electrical heating coils - maximum of 1 hour in 24

Question 29

What are different methods for leak detection

Answer 29

Oil slicks - where oil is leaking there will also be refrigerant leaking
Infra-Red Leak Detection System (IRLDS)
Spectrolyne Dye and UV Lamp
Snoop (similar to soapy water)
Halogen Leak Detector (hand held electronic device)

Question 30

What liquid does the compressor require for lubricating

Answer 30

OM70 and SW68

They are Hygroscopic lubricants (absorb moisture from the atmosphere)

Question 31

What are the Methods for adding the unopened cans of oil

Answer 31

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

Question 32

What is the Montreal protocol

Answer 32

Agreement to phase out harmful ozone depleting substances/refrigerants such as:
CFC’s
HCFC
Halons

Question 33

What is the Kyoto summit

Answer 33

Agreement to reduce all greenhouse gases such as:
CO2
HFC
PFC

Question 34

What are some refrigerant hazards

Answer 34

If exposed to high temperatures they can produce phosgene gas
Can produced cold burns on exposed skin (frost bite)
Decomposing fruit and veg can produce CO2

Question 35

What is the procedure for entering the refrigeration compartments

Answer 35

The rating in charge of the watch is to be informed of entering and leaving of the compartment
Use the breathing apparatus available at the machinery space access
Ensure the exhaust fans are running
No smoking
Any hot work is to be very tightly controlled
The IRLDS is working correctly and indicating safe
The personnel trapped warning lamps are in working order
Anyone entering is to be accompanied by another who remains outside as a safety number
The internal door opening mechanism is in correct order

Question 36

What is chilled water used to cool

Answer 36

Weapon systems
Radars
Ships computer systems
Air treatment units (ATU)