Air Conditioning Circuit Columbia Basin College Automotive Technology.
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Transcript of Air Conditioning Circuit Columbia Basin College Automotive Technology.
Air Conditioning CircuitAir Conditioning Circuit
Columbia Basin College
Automotive Technology
The Basic Cycle The Basic Cycle
Heat is picked up by the Evaporator Fins Heat picked up by the liquid refrigerant as it
evaporates. Heat-laden refrigerant vapor is pumped by
compressor into the condenser The refrigerant in the condenser is given up to
the less-hot air passing across the condenser coils as it condenses back to a liquid
Transfer of Heat Relies on Transfer of Heat Relies on Pressure ChangePressure Change
Low Pressure of 21-35 lbs - Temp of 21-28 degrees F
High Pressure of 180-220 lbs - Temp of 88-100 degrees F
Anytime there is a pressure change there is a temperature change
Anytime pressure & temp changes there is a change of state
Pressure’s Effect on Gases Pressure’s Effect on Gases and Vaporsand Vapors
Pressure affects the temperature of gases and vapors by raising it’s boiling point.
Compressing a gas or vapor increases its temperature because the same amount of heat is concentrated into a smaller space.
The temperature of the gas or vapor can be raised without adding extra heat.
Refrigerant Changes State Refrigerant Changes State
Low Pressure side - Liquid to a Vapor– Low side tubing is often cool enough to collect
frost or water droplets on high humidity days. High Pressure side - Vapor to a Liquid
– Tubing diameter is often smaller than on the low side
– Hotter than the low side tubing
Temperature - Pressure Temperature - Pressure RelationshipRelationship
Heating refrigerant causes it to expand. Different refrigerants have different expansion rates.
When confined in a enclosed place, a increase temperature is always accompanied by an increase in pressure.
For a given temperature, a corresponding pressure will exist in a container of R-12 or R134a
Basic A/C SystemBasic A/C System
Two copper coils– one coil is evaporator– one coil is condenser
Between coils is a compressor Fans
page 68C
CompressorCompressor
Pulls in low-pressure vapor Pumps out high-pressure vapor Provides a endless cycle of cooling Condenses, Evaporating and heating Raises pressure and temperature of
refrigerant entering condenser to a point where it can transfer heat to outside air through the condenser
SERVICE VALVESSERVICE VALVES
A/C Service ConnectorsA/C Service Connectors
CondenserCondenser
Located in front of radiator Compressor pumps high pressure vapor into
condenser where ram air passing over coils carries off heat
The heat loss causes the refrigerant to become a high-pressure liquid.
Expansion Valve or Expansion Valve or Fixed Orifice TubeFixed Orifice Tube
Provides a restriction in refrigerant flow which the compressor can build up a pressure in the condenser.
Compressor suction lowers pressure in the evaporator
Regulates pressure differential between the high and low sides.
Keeps evaporation and expansion of refrigerant and most efficient level.
EvaporatorEvaporator
Function is opposite of condenser Evaporator coils remove heat and humidity
from the air being circulated in passenger compartment.
When liquid refrigerant absorbs heat, it again becomes a vapor under low pressure
Has a tray to collect moisture from fins
FansFans
One fan to circulate air through evaporator fins
One fan to circulate air through condenser fins
High Pressure SideHigh Pressure Side
High side includes – Discharge side of Compressor– High Pressure vapor lines to condenser– Condenser– High Pressure liquid lines to orifice valve– Inlet side of orifice Valve
Low Pressure SideLow Pressure Side
Includes:– Orifice– Low Pressure Liquid lines– Evaporator– Low Pressure Vapor Lines– Suction side of Compressor– Outlet side of orifice valve