HVAC Flashcards
(31 cards)
What two components in the HVAC system are used as heat exchangers?
The heater core and the evaporator.
How does dehumidifying work in the HVAC system?
As the air passes the evaporator, it is cooled and the water in the air condenses and adheres to the evaporator fins.
How is temperature controlled in a HVAC system?
An air mix damper is used, which progressively either allows or stops airflow through the heater core.
How does natural flow-through ventilation work?
Air pressure is generated by the vehicle’s forward movement, and intake and exhaust vents are placed in the car to allow air flow.
What is the purpose of the cabin filter?
It is used to purify the air that is drawn in from outside the car.
What does the air inlet damper do?
Switches between fresh and recirculated air.
What does the air flow damper do?
Directs whether air goes to feet, face, or windscreen.
What ways can a damper be controlled?
Through wire cables, or with a motor.
How does a resistor type blower work?
It uses a number of resistors in series, and the lowest speed will use all the resistors, and the highest speed will use no resistors.
How does a transistor type blower work?
It uses a transistor which has a control of many resistances on the one resistor.
What type of refrigerant does Toyota use?
R134a
What does refrigerant do to heat when condensing / evaporating?
Removes heat when evaporating and releases heat when condensing.
What three characteristics does refrigerant need to be used in vehicles?
Evaporate / condense easily, be safe to handle, and be stable and maintain quality.
What in relation to boiling point is a beneficial characteristic of refrigerant.
At low pressure, refrigerant evaporates at a low temperature, and at high pressure it has a high boiling point.
What are the main components of the refrigerant system?
Compressor, condenser, receiver/dryer, expansion valve, and evaporator.
What is the flow of refrigerant in the HVAC system?
Compressor releases high press/high temp gas -> gas flows to condenser, gas condenses to liquid (releases heat to outside air) -> liquid flows to receiver/dryer, stores/filters liquid -> filtered liquid flows to expansion valve which releases liquid/gaseous mixture to evaporator -> the refrigerant is at a much reduced pressure (boiling point lower) so it evaporates and draws in heat energy -> gas is drawn to compressor.
What is conduction?
The transmission of heat within a substance.
What is convection?
When heat is applied to a container of liquid or gas, the substance at the bottom rises to the top, as the substance is pushed to the top, the substance that was at the top is lowered to the bottom, and then also heated.
What is radiation?
The emission and transfer of heat in the form of infrared rays.
What is the difference between latent heat and sensible heat?
Sensible heat changes the temperature of an object, latent heat changes the state of an object without changing the temperature.
What is absolute pressure?
The pressure in relation to a perfect vacuum, or 0kPa.
What is gauge pressure?
Gauge pressure is 14.6psi (atmospheric pressure), and is what most gauge call 0psi.
What are the common types of AC compressors used in Toyotas?
Scroll, swash plate, variable swash plate, and electric.
How does an AC pulley work?
There is a stator in the pulley, which when current is sent through it, magnetises. This then draws the pulley’s centrepiece into the compressor shaft and spins the compresser.
