Refrigeration And Ventilation Flashcards
What are freezers and fridges used for
The storage of food to prevent spoilage
What are domestic refrigerators used for
Kept in the sickbay to keep medical supplies cool
Also fitted in mess decks to cool drinks
What are ice making machines used for
Make ice cubes for medical purposes and also for drinks
Explain the effects of pressure on the boiling point of water
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
What is the definition of conduction
Energy is transferred by direct contact
What is the definition of convection
Energy is transferred by the mass motion of molecules
What is the definition of radiation
Energy is transferred by electromagnetic radiation
Define heat transfer
Heat will always transfer from a hot body to a cold one
What does the cold room store and at what temperature
Frozen meat, fish etc
At -18 to -22 degrees C
What does the cool room dairy, store and at what temperature
Butter, milk, and other dairy product
At +4 to +6 degrees C
What temperature is the fruit and vegetable store kept at
+4 and +6 degrees C
What temperature is the galley ready use cupboard kept at
+5 to +7 degrees C
What does the compressor do
Pumps the refrigerant around the system
What does the condenser do
Uses sea water to cool the refrigerant changing its state from a gas to a liquid
What does the TEV (Thermal Expansion Valve) do
Controls the flow rate of refrigerant through the system.
Increasing and decreasing the flow depending on the temperature of the refrigerant leaving the evaporator
What does the evaporator do
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
What is the condition of the refrigerant from compressor to condenser
Hot
High pressure
Gas
What is the condition of the refrigerant from condenser to TEV
Warm
High pressure
Liquid
What is the condition of the refrigerant from TEV to evaporator
Very cold
Low pressure
Liquid
What is the condition of the liquid from evaporator to compressor
Cool
Low pressure
Gas
What does the LP cut out do
Stops the compressor if the pressure drops too low
What does the HP cut out do
Stops the compressor if the pressure gets too high
What does the oil separator do
Separates oil from the refrigerant
What does the liquid receiver do
Stores refrigerant during maintenance
What does the drier do
Removes moisture from refrigerant
What does the sight glass do and what do the different colours mean
Indicates moisture in the refrigerant
Yellow - there is moisture
Green - there isn’t moisture
What are the different refrigeration procedures
Defrosting
Leak detection
Lubrication
When is defrosting required and what are the different methods
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
What are different methods for leak detection
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)
What liquid does the compressor require for lubricating
OM70 and SW68
They are Hygroscopic lubricants (absorb moisture from the atmosphere)
What are the Methods for adding the unopened cans of oil
Via sump filler plug
By a hand pump
Through the use of a dosing pot
What is the Montreal protocol
Agreement to phase out harmful ozone depleting substances/refrigerants such as:
CFC’s
HCFC
Halons
What is the Kyoto summit
Agreement to reduce all greenhouse gases such as:
CO2
HFC
PFC
What are some refrigerant hazards
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
What is the procedure for entering the refrigeration compartments
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
What is chilled water used to cool
Weapon systems
Radars
Ships computer systems
Air treatment units (ATU)