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WorksheetsAir Conditioning Systems Quiz
Total questions: 17
Worksheet time: 21mins
What is the difference between a single split AC system and a multi-split system?
Single split uses a compressor, while multi-split uses a condenser
Single split operates in a similar way to refrigerators, while multi-split operates in a similar way to freezers
Single split is for a single room, while multi-split is for multiple rooms
Single split has an internal and external unit, while multi-split only has an internal unit
What is the purpose of an Air handling unit (AHU)?
To remove heat from the refrigerant gas
To draw room air across the heat exchanger
To compress gas and give off heat
To condition and distribute air within a building
State 3 types of ducted air conditioning system.
VRV, VAV, Dual duct
Split system, Central plant, Dual duct
CAV, VAV, split system
Single split, Multi-split, VRV
Briefly explain how a simple air conditioning system works.
It takes fresh ambient air, cleans it, heats or cools it, and forces it through a wind tunnel around a building
It conditions individual rooms as stand-alone units using an internal and external unit
It uses a compressor, condenser, expansion valve, and evaporator in a refrigeration process
It compresses water to give off heat, then expands gas to have a cooling effect
What does VRF stand for and how does it work? How is it different to ducted systems?
Variable Refrigerant Flow, it connects to one or more air handlers and incurs minimal energy loss compared with forced air systems
Variable Refrigerant Volume, it uses a three-pipe distribution system and requires a backup heat source, unlike ducted systems
Variable Refrigerant Fluid, it uses a main refrigeration unit to feed a single storey of a building, and it saves space by not using air ducts
Variable Refrigerant Volume, it has a drainage system to remove condensate when cooling and requires ductwork, unlike ducted systems
What is the function of a condenser in an air conditioning system?
To compress the refrigerant gas
To distribute conditioned air within a building
To remove heat from the refrigerant gas
To draw room air across the heat exchanger
What is the role of an expansion valve in an air conditioning system?
To compress the refrigerant gas
To remove heat from the refrigerant gas
To distribute conditioned air within a building
To reduce the pressure of the refrigerant gas
What is the difference between a VRV and a VAV air conditioning system?
VRV is a type of ducted system, while VAV is a type of split system
VRV stands for Variable Refrigerant Volume, while VAV stands for Variable Air Volume
VRV uses a three-pipe distribution system, while VAV uses a two-pipe system
VRV is for multiple rooms, while VAV is for a single room
What is the function of a compressor in an air conditioning system?
To distribute conditioned air within a building
To remove heat from the refrigerant gas
To compress the refrigerant gas
To draw room air across the heat exchanger
What is the difference between a CAV and a VAV air conditioning system?
CAV stands for Constant Air Volume, while VAV stands for Variable Air Volume
CAV is a type of split system, while VAV is a type of ducted system
CAV uses a two-pipe distribution system, while VAV uses a three-pipe system
CAV is for a single room, while VAV is for multiple rooms
What is the function of an evaporator in an air conditioning system?
To compress the refrigerant gas
To distribute conditioned air within a building
To remove heat from the refrigerant gas
To absorb heat from the room air
What is the difference between a ducted and a split air conditioning system?
Ducted system uses a compressor, while split system uses a condenser
Ducted system operates in a similar way to refrigerators, while split system operates in a similar way to freezers
Ducted system is for multiple rooms, while split system is for a single room
Ducted system has an internal and external unit, while split system only has an internal unit
What is the role of a filter in an air conditioning system?
To compress the refrigerant gas
To remove dust and particles from the air
To distribute conditioned air within a building
To reduce the pressure of the refrigerant gas
Compressor
To cool a room down, you need to collect the heat and dump it somewhere else. The air in this “somewhere else” must be a lower temperature than the refrigerant for you to be able to dump the heat. To make sure this is possible, the refrigerant is compressed so that the temperature increases. That way when the refrigerant reaches the condenser, the refrigerant within the pipe will be hotter than the air on the outside of the pipe, so it will be able to dump the heat. If the pipe was the same temperature as the air then you wouldn’t be able to reject any heat and you wouldn’t cool the room down.
The refrigerant enters the compressor as a warm, saturated low pressure gas, it is then compressed within the compressor (hence the name). During compression, the quantity of fluid remains the same but the volume decreases, this increases the pressure and temperature. The refrigerant leaves the compressor as a superheated (hot) high pressure gas.
What state does the refrigerant leave the compressor in?
Liquid
Superheated gas
Saturated vapor
Subcooled liquid
What is the state of the refrigerant when it enters the compressor?
Cool, saturated low pressure gas
Warm, saturated low pressure gas
Hot, saturated high pressure gas
Cold, unsaturated high pressure gas
What happens to the pressure and temperature during compression?
Remains the same
Decreases
Increases
Fluctuates
Expansion valve
To cool a room down, the heat within that room must be collected and dumped somewhere else. The refrigeration cycle collects this heat by sending the refrigerant at a low temperature and pressure into the evaporator within that room.
To cool the refrigerant down it is passed through the expansion valve, this will reduce the pressure of the refrigerant by restricting how much can flow through the valve. This restriction means that there will be less refrigerant in the next section of pipe, so the refrigerant which is allowed to pass through can expand a little. This expansion reduces the temperature and gives it some storage room to collect the heat.
The expansion valve restricts the flow of refrigerant through use of an internal spring loaded valve which is connected to a diaphragm.
A thin tube, known as the capillary tube, runs between the expansion valve and a thermal bulb. The thermal bulb is in contact with the pipe just after the evaporator, the liquid/vapour inside the thermal bulb expands and contracts with the change in temperature of the refrigerant leaving the evaporator. This expansion and contraction causes the diaphragm to move which in turn controls the spring loaded valve that limits the flow of refrigerant into the evaporator.
The refrigerant enters the expansion valve as a regular temperature, saturated high pressure liquid. The expansion valve will limit how much refrigerant can pass through at one time, this results in the refrigerant dropping in pressure and temperature. The refrigerant leaves the expansion valve as a cold, saturated low pressure liquid.
What is the purpose of the expansion valve in a refrigeration system?
To reduce the pressure of the refrigerant
To increase the temperature of the refrigerant
To control the flow of the refrigerant
To regulate the expansion of the refrigerant
What is the state of the refrigerant as it leaves the expansion valve?
Cold, saturated low pressure liquid
Regular temperature, saturated high pressure liquid
Warm, saturated high pressure liquid
Hot, saturated low pressure liquid
What controls the expansion valve in a refrigeration system?
Internal spring loaded valve
Thermal bulb
Diaphragm
Evaporator
The final key stage of the refrigeration cycle is the component called the evaporator. This is similar to the condenser in construction, but the refrigerant behaves differently inside.
In the evaporator, the refrigerant enters as a cold, low pressure liquid but quickly begins to boil. The refrigerant has a very low boiling temperature, typically of -23ºc (minus twenty-three degrees Celsius). As the refrigerant boils it evaporates, this evaporation picks up the rooms heat and carries it away towards the compressor where the refrigeration cycle will begin again.
The refrigerant enters the evaporator as a cold, low pressure liquid, the refrigerant begins to boil and evaporate, this evaporation causes a cooling effect in the room and the heat is carried away to be dumped in the condenser after the compressor. The refrigerant leaves the evaporator as a warm, saturated low pressure gas.
What state does the refrigerant enter the evaporator in?
Cold, low pressure liquid
Hot, high pressure liquid
Cold, high pressure liquid
Hot, low pressure liquid
What state does the refrigerant leave the evaporator in?
Liquid
Solid
Warm, saturated low pressure gas
High pressure gas
What effect does the refrigerant have when it begins to boil and evaporate?
Heating effect
Cooling effect
No effect
Humidifying effect
What about humidity control? Some buildings need to control the humidity of the air they supply into the building. We’ll find a humidity sensor at the outlet of the supply in the AHU to measure the moisture in the supply air, this will also have a setpoint for how much moisture should be in the air by design.
If the airs moisture content is below this value then we need to introduce moisture into the air using a humidifier, this is usually one of the last things in the AHU. This device will usually either add steam or spray a water mist into the air. Many standard office type building in northern Europe and north America have turned off their humidity units or uninstalled them to save energy. Although they’re still crucial for places like document stores and computer rooms.
What is used to introduce moisture into the air when the air's moisture content is below the setpoint?
Dehumidifier
Fan
Air purifier
Humidifier
What does the humidity sensor at the outlet of the supply in the AHU measure?
Temperature
Moisture level
Air pressure
CO2 levels
Why is humidity control important for some buildings?
To maintain the desired moisture level in the air
To prevent mold and mildew growth
To protect sensitive equipment and materials
To regulate temperature in the building
