Cooling Systems Flashcards
What are the four required mechanical parts of a cooling system?
Compressor
Condenser
Evaporator
Metering Device
What does the compressor do?
Draws suction vapour into a cylinder or chamber that reduces the volume
Increases the refrigerant pressure and temperature through compression.
What is a hermetic compressor?
Consists of a motor and a compressor sealed in a welded shell.
Not intended to be repaired
What is a semi hermetic compressor?
Consists of a motor and a compressor in a mechanically sealed case.
Sealed with bolts and gaskets.
Designed to be disassembled and repaired.
What is the main purpose of a condenser?
To transfer heat energy from refrigerant to the ambient air where it is located, typically outside.
What is an evaporator?
A heat exchanger from the air being cooled to the refrigerant.
What does the metering device do?
Delivers refrigerant to the evaporator at measured rates of flow, pressure and temperature.
What are the 3 most common metering devices for air conditioning?
Capillary tube
Fixed Orifice
Thermal expansion valve
Define Refrigerant
It is the chemical substance in a cooling system that absorbs heat from a conditioned space and releases heat outside of the conditioned space.
True or False
Refrigerant can be released to atmosphere.
FALSE
Refrigerant should never be released. Intentionally releasing refrigerants can result in fines or jail time.
What does a condenser fan do?
Draws air through the CONDENSERcoil.
Helps with the heat transfer from the refrigerant to the ambient air.
The evaporator fan is used to
draw air through the EVAPORATOR coil
What is the purpose of a high limit pressure switch?
To shut down the compressor if the pressures in the cooling system rise to a level that could present a danger and damage the equipment.
(Normally closed pressure switch)
What does the low limit pressure switch do?
Detects if the pressure in the system drops below a set pressure, which could indicate a refrigerant leak.
(Normally Open pressure switch)
The compressor contactor is used to:
Switch the compressor on and off.
A low ambient temperature limit controller interrupts the control circuit to the compressor if the outside air temperature:
Falls below the safe operating temperature of the compressor.
What is the role of the compressor crankcase heater?
Prevents refrigerant migration by keeping the compressor crankcase oil warmer than the ambient temperature.
The high temperature sensor shuts the system down if the compressor:
Operates at a higher temperature than that for which the system was intended.
How does a filter dryer work?
The filter removes small foreign particles from the refrigerant
The dryer removes moisture rom the refrigeration system
A ______ _______ can be installed for a visual verification that 100% liquid is arriving at the metering device.
Sight Glass
The term cycle indicates that the process is ________
REPEATABLE
The heat added or removed to cause state changes is called
LATENT HEAT
The heat that causes a change in temperature is called
Sensible Heat
Boiling is the change of state from
Liquid to Vapour
Condensation is the change of state from
Vapour to Liquid
The cooling cycle consists of 4 stages:
Stage 1) Evaporation
Stage 2) Compression
Stage 3) Condensing
Stage 4) Metering
Once the refrigerant’s pressure drops due to passing through the metering device’s orifice, some of the refrigerant flashes or becomes vapour. This vapour is called
Flash Gas
_________ ________ are a refrigeration system that can heat and cool through the vapour compression cycle.
Heat Pumps
Refrigerant copper piping must be secured to prevent:
Vibration
The two levels of confirmation during commissioning are
Start up
A formal commissioning process
A _______ __________ is a confirmation list that includes the measurable and operational data
COMMISSIONING REPORT
(Legal Document)
