CAT 85 Unit 1: Fundamentals of Air Conditioning
What is the boiling point of R-134a?
-15 Deg F.(warmer than R-12)
What is the boiling point of R-12?
-22 Deg F.
Two containers of water are boiling, one at 212 Deg F and one at 71 Deg F, Which has more latent heat?
Both have the same quantity of latent heat.
Where is oil reintroduced into circulation ?
Bottom of the accumulator.
What is the term used for the measurement of latent heat?
British Thermal Unit(BTU)
What does a reciever-dryer do?
Catches moisture and allows for vapor to condense to liquid.
What is the cycle of the air conditioning system?
Compression, Condensation, Expansion, and Evaporation.
What components seperate the HIGH PSI side from the LOW PSI side?
Compressor and Expansion component(Orifice tube/TXV)
There is a ____ relationship between a vaccum, the ambient temperature, and the boiling point of a liquid.
Direct.
When a liquid is pressurized, the boiling point of the liquid does what?
Each 1 PSI increase causes the boiling point to rise 3 Deg F.
What is the advantage of the H-block system?
Easy to work on, no equalizer bulb.
What component of the system has a pan and drain tube to allow condersation buildup to drain out of the vehicle/machine?
Evaporator.
Basic Law of Refrigeration III -
For a liquid to change to a gas it has to take on heat. The heat is carried off in a gas vapor. If a vapor is to change into a liquid it has to give up heat.
On the Farenheit scale, what is the freezin point and what is boiling point for water?
Freezing is 32 Deg F and boiling is 212 Deg F.
What system has a reciever dryer?
H-block and Thermostatic Expansion valve system.
Basic Law of Refrigeration II -
Heat is ready to flow or pass to anything that has less heat. Nothing can stop the flow of heat; It can only be slowed down.
What is "Sensible" heat?
Heat that can be felt and measured on a thermometer.
What is "Latent" heat?
Heat that cannot be felt or recorded on a thermometer.
Define Radiation.
Heat transfer through a medium that does not get hot. Heat waves.
Define Conduction.
Heat transfer through a solid object.
Define Convection.
Heat transfer through circulation of a fluid or vapor.
All substances contain some ____.
Heat.
When charging a system with the engine running, be sure the ____ PSI gauge valve is closed.
High.
What is the measurement used to describe the moisture content in the air?
Humidity - 0-100 scale.
What is the unit of measurement used when PSI drop below 0 and becomes a vacuum?
Inches of Mercury(Hg).
What strokes do the pistons make during one cycle?
Intake and compression.
If an air conditioning system only has 1 sensor on it what is that sensor taking readings of?
It is dual purpose and reads the low PSI and high PSI readings.
Where is the TXV located?
On the inlet side of the evaporator.
What are the two kinds of accumulators that a system may have?
One has desiccant and one does not.
What air conditioning system contains an accumulator?
Orifice tube system.
What air conditioning system contains an in-line dryer?
Orifice tube system.
What is PSIA?
PSIA is a measurement taken to find atmospheric pressure, but does not compensate for the 14.7 PSI at sea level.
What is PSIG?
PSIG is a type of measurement that can be taken and it compensates for the 14.7 PSI that is at sea level(At sea level the guage would be 0).
What does PSIA stand for?
Pounds per Square Inch Absolute.
What does PSIG stand for?
Pounds per Square Inch Gage.
What kind of refrigerant was used until 1996?
R-12.
What is the current refrigerant used in air conditioning systems?
R-134a.
What piston arrangements can be found in the compressor on an air conditioning system?
Radial, axial, in-line, and V-type.
What component often has a moisture indicator and sight glass?
Reciever-dryer.
What are the valves on the compressor referred to as?
Reed vavles.
What does the compressor do?
Refrigerant coes in as a LOW PSI VAPOR, is compressed, and moves back into the system as a HIGH PSI VAPOR.
What does the accumulator do?
Refrigerant enters as a LOW PSI LIQUID/VAPOR, liquid sttels in the bottom of the accumulator to evaporate while vapor continues throught the system as LOW PIS VAPOR.
What does the evaporator do?
Refrigerant enters the evaporator as a LOW PSI LIQUID, the cabin air flowing through the evaporator removes latent heat from the refrigerant causing it to boil, the refrigerant continue out of it as a LOW PIS LIQUID/VAPOR.
What does and In-line dryer/orifice tube do?
Refrigerant enters the in-line dryer as a HIGH PSI LIQUID, the in-line dryer removes any moisture from the refrigerant, the orifice tube restricts the flow until it passes through the orifice tube, where it becomes a LOW PSI LIQUID and cold.
Basic Law of Refrigeration I -
Refrigerate=remove heat. Absence of heat=cold. Heat is ever present.
What does the Condenser do?
Refrigerent comes in as a HIGH PSI VAPOR, the hot refrigerant passes through the condenser coils, and latent heat is removed by air passing through, causing the vapor to change state to a HIGH PSI LIQUID.
What component does the compessor or reciever-dryer have to protect the system?
Relief valve(opens at 500PSI).
What are the two types of compressor clutches?
Stationary coil and rotating coil.
What are the two openings on the compressor called and how can they be differentiated?
Suction/Discharge. Suction(inlet) is larger that discharge(outlet).
Air conditioning systems automatically control what enviromental factors?
Temperature(cools air), Humidity(removes moisture), Purity(Cabin air fiilter), and circulation(takes heat out and removes it).
Define "Specific Heat".
The ability to accept or emit heat and undergo a change of temperature of 1 Deg F.
"Cold" is actually what?
The absence of heat.
1 BTU =
The amount of heat it takes to rais one pound of water 1 Deg F.
What component tells the TXV to open or close?
The capillary tube/ thermal bulb sense heat from down stream and cause the digphram to open or close the orifice.
What does the compressor clutch do?
The compressor clutch engages the pully, using electromagnets and friction to crank the compressor.
What does the H-block system do to adjust refrigerant flow?
The diagphram on the output side of the H-block expands or retracts dependant on the temperature of refrigerant coming from the evaporator.
High humidity does what to an A/C systems function?
The increase in temperature causes a decrease in efficiency of the A/C system.
What does a thermometer reading tell?
The intensity of the heat present.
What two things determine how hot something is?
The quantity and intensity of the heat.
What component controls the compressor clutch engagement?
The thermostatic switch senses evaporator temperature and the remote bulb either expands and closes the contacts or retracts and opens the circuit.
What qualities differ between R-12 and R-134a?
The two are not compatible, and the oil used with R-134a is not compatible with R-12, require different kinds of recovery equipment, and different kinds of service ports are used.
Explain "Latent Heat of Liquidization".
To change one pound of ice at 32 Deg F to one pound of water at 32 Deg F, it must take in heat equal to 144 BTU.
Explain "Latent Heat of Condensation".
To change one pound of steam at 212 Deg F to one pound of water at 212 Deg F, it must give up heat equal to 970 BTU.
Explain "Latent Heat of Vaporization".
To change one pound of water at 212 Deg F to one pound of steam at 212 Deg F, it must take in heat equal to 970 BTU.
Explain "Latent Heat of Fusion".
To change one pound of water at 32 Deg F to one pound of ice at 32 Deg F, it must give up heat equal to 144 BTU.
When is an accumulator with desiccant used in an A/c system?
When the system does not have an inline dryer.
How does a reed valve regulate the air flow through it?
the ID of the reed valve determines the amount of air flow allowed through it.
When replacing the compressor clutch why is the gap between it and the pully important?
too small of a gap can cause unwanted rubbing and too large of a gap can make it impossible for the compressor to engage.
If refrigerent comes in contact with your eye what should be done?
1.Do not rub eye. 2.Splash water in eye to bring it back to normal temperature. 3.Cover with a sterile cloth. 4.Seek medical attention.
In order for a the moisture indicator to be accurate, how long must the sytem be ran for?
2-3 hours.
Absolute zero =
459 deg F below 0
How does a thermostatic espansion valve meter flow?
A diagohram that is adjusted by a capillary tube full of refrigerant that senses temperature from down stream(evaporator coil).
What is refrigerant?
A fluid used in a refrigeration system to produce cold by removing heat.
What would be the cause for a system to need an externally equalized TXV?
A large evaporator would make temperature sensing be delayed, so two are used to help level readings.
What is "Saturated Liquid"?
A liquid that has reached 212 Deg F, but does not have enough Latent heat to change state of matter.
Low humidity air is readily able to ____ moisture.
Absorb.
How does air flow cool the intended area?
Air flow circulates the moisture in the air through the filtration system and allowing more to evaporate and helps remove it, draws heat from surfaces.
The higher the altitude, the ____ the boiling point?
Atmospheric pressure is lower, so the boiling point would also be lower.
What does a condenser do?
condenses the
