Refrigeration Flashcards
Complete the sentence. As pressure increases…
As pressure increases, volume decreases and more energy is required to boil a liquid.
Complete the sentence. As pressure decreases…
As pressure decreases volume increases and less energy is required to boil a liquid.
Complete the sentence. Heat always travels…
Heat always travels hot to cold.
Describe heat transfer via conduction.
Conduction is heat transfer through a solid.
Describe heat transfer via convection.
Convection is heat transfer through a fluid.
Describe heat transfer via radiation.
Radiation is heat transfer through a space. (Air)
Describe sensible heat.
This is the heat required to change temperature, but not the state of substance.
Describe latent heat.
This is the heat required to change the state of substance without any change in its temperature.
Describe superheat.
When a substance goes over its boiling point.
Describe Subcooling.
When a substance cools and condenses into liquid and then drops below its boiling point.
Describe the function of the compressor. ( What it does )
Pumps the refrigerant around the system.
Describe the function of the condenser. ( What it does )
Uses sea water to cool the refrigerant changing its state from a gas into a liquid. (Subcooling)
Describe the function of the thermal expansion valve. ( What it does )
Controls the flow rate of refrigerant through the system. Increasing or decreasing the flow depending on the temperature of the refrigerant leaving the evaporator.
Describe the function of the evaporator. ( What it does )
The refrigerant flowing through the evaporator removes heat from the refrigerator/cold room. This action changes the state of the refrigerant from a liquid into a gas. (superheating)
Describe the condition of the refrigerant as it flows from the compressor to condenser.
Hot, high pressure gas.
Describe the condition of the refrigerant as it flows from the condenser to thermal expansion valve.
Warm, high pressure liquid. (Subcooled)
Describe the condition of the refrigerant as it flows from the thermal expansion valve to the evaporator.
Very cold, low pressure liquid.
Describe the condition of the refrigerant as it flows from the evaporator to the compressor.
Cool, low pressure gas (super heated)
Describe the function of the LP cut out in a basic refrigeration system.
Stops the compressor if the pressure drops too low.
Describe the function of the HP cut out in a basic refrigeration system.
Stops the compressor if the pressure gets too high.
Describe the function of the oil separator in a basic refrigeration system.
Separates oil from the refrigerant.
Describe the function of the liquid receiver in a basic refrigeration system.
Stores refrigerant during maintenance.
Describe the function of the drier in a basic refrigeration system.
Removes moisture from the refrigerant.
Describe the function of the sight glass in a basic refrigeration system.
Indicates moisture in the refrigerant.
What colour is the sight glass if there is moisture in the refrigerant?
Yellow.
What colour is the sight glass if there is no moisture in the refrigerant?
Green.
When is a defrosting procedure required?
When Ice builds up on the evaporator coils.
How often must a natural defrost procedure be carried out?
3-6 months
How often does hot gas defrosting occur?
A maximum of one hour in 24, in 15 minute slots.
How often do electrical heating coils operate?
1 hour every 24.
Name 5 methods of leak detection
Oil slicks
Infra red leak detection system
Dye and UV lamp
Snoop
Halogen leak detector
Name 3 methods oil can be added to the compressor
Via sump filler plug
By a hand pump
Use of a dosing pot
Which three harmful substances where banned in the Montreal protocol?
CFCs
HCFC
Halons
Which three substances were banned in the Kyoto summit?
CO2
HFC
PFC
What four hazards belong with refrigerant?
It is heavier than air and will displace oxygen
If exposed to high temperature it can produce phosgene gas
Can produce cold burns on exposed skin
Decomposing fruit and veg produce co2
If refrigerant gets in the eye you must…
Flush with running water and require medical treatment
If refrigerant touches the skin it requires
Washing off immediately
Chilled water is used to provide cooling for
Weapon systems
Radars
Ships computer systems
Air treatment units
What is the major difference between components of a refrigeration and chilled water plant?
The chilled water plant has a chiller in place of the evaporator.
