Refrigeration Flashcards
Explain pressure volume energy relationship
As pressure increases, volume decreases, and more energy is needed to boil a liquid
Heat travels from…
Hot to cold
3 methods of heat transfer
- Conduction - Solid
- Convection - Liquid
- Radiation - Air
Sensible Heat
Changes temp, NOT State
Latent Heat
Changes state, NOT Temp
Superheat
Every degree above its boiling point
e.g. 101 = 1 superheat
Sub cooling
Cools and condenses into liquid and drops below boiling point
Temperature energy graph
Temperature energy graph
Basic refrigeration system
Basic refrigeration system
Compressor
Pumps refrigerant around system
Condenser
Cools refrigerant, changing state from gas to liquid
Thermal Expansion Valve
Controls flowrate
Inc/Dec temp depending on temp of refrigerant leaving the evaporator
Evaporator
Changes state of refrigerant from liquid to gas
Condition of refrigerant as it flows from compressor to condenser
Hot, High Press Gas
Condition of refrigerant as it flows from condenser to TEV
Warm, High Press liquid (Sub Cooled)
Condition of refrigerant as it flows from TEV to evaporator
Very cold, low press liquid
Condition of refrigerant as it flows fromevaporator to compressor
Cool, low press gas (superheated)
LP Cut Out
Stops compressor if pressure drops too low
HP cut out
stops the compressor if the pressure gets too high
Oil Separator
Separates oil from the refrigerant
Liquid Receiver
Store refrigerant during maintenance
Drier
removes moisture from refrigerant
Sight Glass
indicates moisture in the refrigerant
Yellow – there is moisture
Green – there isn’t moisture
Refrigeration Procedures
- Defrosting
- Leak Detection
- Lubrication
When is defrosting required?
Ice builds up on evaporator coils
Methods of defrosting
Natural Defrost
Hot Gas Defrosting
Electrical Heating coils
How often is natural Defrost carried out?
Every 3-6 months
How often is hot gas defrosting carried out?
Max of 1hr per 24hrs
How often is electrical heating coils carried out?
Max of 1hr every 24hrs
Why is Leak Detection used?
Refrigerant leaks are harmful to the environment and reduce refrigerant plant efficiency
Methods of Leak Detection
- Oil Slicks
- IRLDS
- Spectrolyne dye
- Snoop
- Halogen Leak Detector
What is an oil Slicks?
where oil is leaking there will also be refrigerant leaking
IRLDS
Infra-red leak detection system
What kind of lubricants are needed for compressors?
Hygroscopic lubricants
What do hygroscopic lubricants do?
Absorb moisture from the atmosphere
What kinds of oils are used in refrigeration?
SUNISO 3GS
SW68
OM70
What source should oils be used
New, unopened cans
Methods of How is oil added to compressors
- Sump Filler Plug
- Hand Punp
- Dosing pot
What is the Montreal protocol?
Agreement to phase out harmful ozone depleting substances
Montreal Protocol substances
CFC
HCFC
Halons
What is the Kyoto summit
Agreement to reduce all Greenhouse gases
Greenhouse gas substances
Co2, HFC, PFC
How is phosphine gas produced?
Refrigerants are heavier than air and will displace Oxygen
If exposed to high temperatures they can produce PHOSGENE GAS
Hazards of refrigerants
Can produce Cold Burns on exposed skin (Frost Bite)
Decomposing Fruit and Veg can produce CO²
What so you do if refrigerant gets in your eyes
flushing with running water and then require medical treatment.
Procedure for entering refrigeration compartments
- Rating in charge of watch to be kept informed
- Breathing Apparatus avaliable
- High/Low exhaust fans running
- No Smoking
- IRLDS working correctl
Procedure for entering refrigeration compartments
- 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
What should happen to oil after use?
It should be disposed of in accordance with MARPOL
Chilled water provides cooling for…
Weapons Systems
Radars
Ships Computer Systems
Air Treatment Units (ATUs
Main difference between chilled water, and refrigeration
The chilled water plant has a CHILLER in place of the EVAPORATOR
What provides cooling for condenser and motors
sea water pump
