AIR CONDITIONING SYSTEMS AND COMPONENTS
 | |
| Illustration 1 | g01077005 |
The standard air conditioning system contains five basic components:
Compressor - Increases pressure and temperature of refrigerant vapor.
Condenser - Removes the heat from the high pressure high temperature refrigerant vapor causing the vapor to change into high pressure liquid refrigerant
In-line dryer - Contains the desiccant and the orifice tube. Quick disconnects allow the in-line dryer to be easily changed when needed
Evaporator - Low pressure liquid refrigerant boils, collecting heat from the surrounding area.
Accumulator - Acts as a liquid/vapor separator and ensures that only vapor will reach the compressor.
On the orifice tube system, the liquid refrigerant that is leaving the evaporator can damage the compressor. Therefore, an accumulator is located in the suction line after the evaporator. The accumulator acts as a liquid/vapor separator. The accumulator ensures that only vapor will reach the compressor.
On some orifice tube systems, the orifice tube is located in the low pressure liquid line to the evaporator and the desiccant is in the accumulator.
On systems with an in-line dryer, the desiccant is in the dryer.
Compressor
 | |
| Illustration 2 | g01077006 |
The dual purpose of the compressor is listed below:
- Increase the temperature and pressure of refrigerant gas from the evaporator.
- Circulate the refrigerant throughout the system.
The compressor has reed valves that control the entrance and the exit of refrigerant gas during the pumping operation.
As the piston moves downward in the bore, the intake reed valve opens and the exhaust reed valve closes. The low-pressure, heat-laden refrigerant gas is drawn from the evaporator into the compressor. As the piston moves upward in the bore, the compressor pressurizes the gas. This increases the intensity of the heat.
Since temperature is a measurement of heat-intensity, the temperature of the gas increases. The high-pressure, high-temperature gas closes the intake reed valve and opens the exhaust reed valve. The gas is forced through a hose to the condenser.
The pressure increase is accomplished by adding a restriction in the high pressure side of the system. The restriction is caused by the orifice tube. The orifice tube is explained later in this presentation.
Condenser
The purpose of the condenser is to transfer the heat in the refrigerant gas to the atmosphere. The condenser converts the refrigerant gas into a liquid. High pressure, high temperature refrigerant gas flows from the compressor into the condenser. As the hot, high pressure gas flows through the condenser, heat flows from the hot gas to the cooler air through the condenser coils. The high pressure refrigerant gas cools and condenses into high pressure liquid. The high pressure liquid flows from the condenser to the in-line dryer.
Ram Air - Used in automotive applications.
Forced Air - Used on construction equipment.
The ram air condenser depends on machine movement in order to force large volumes of air through the condenser coils.
The forced air condenser uses fans to move large volumes of air through the condenser coils. The air is cooler than the refrigerant gas that is inside the condenser. Heat flows from the hot refrigerant gas to the cooler air.
In-line Dryer and Orifice Tube
 | |
| Illustration 3 | g01077009 |
The in-line dryer contains a desiccant bag and two quick disconnects. The disconnects allows the in-line dryer to be changed without reclaiming the refrigerant. Some in-line dryers may have a moisture indicator.
On most orifice tube systems, the orifice tube is installed in the in-line dryer. The orifice tube consists of a small tube through the center of a plastic body, two o-rings, two screens and two tabs.
The two screens (one on each end) filter the refrigerant that flows through the small tube. The two O-rings are positioned to seal against leakage past the outside of the orifice tube. The two tabs engage the tooling when the orifice tube is installed or removed.
The orifice tube separates the A/C System high side from the low side. High pressure liquid refrigerant enters the orifice tube and low pressure liquid refrigerant exits the orifice tube.
The orifice tube has a fixed diameter. The orifice tube does not have the regulating capability of the expansion valve. The refrigerant flows from the orifice tube to the evaporator. The amount of liquid refrigerant that enters the evaporator is usually more than the evaporator can boil off. Therefore, some refrigerant will leave the evaporator in the liquid form.
On some orifice tube systems, the orifice tube is installed in the evaporator inlet line.
Evaporator Unit
 | |
| Illustration 4 | g01077011 |
The evaporator unit transfers the heat in the operator's compartment to the refrigerant in the air conditioner.
A blower fan is a necessary part of the evaporator unit in the air conditioning system. The blower fan draws heat laden air from the operator's compartment, over the evaporator fins, and coils where the air surrenders heat to the refrigerant.
When the low pressure liquid refrigerant enters the evaporator, the refrigerant is cooler than the air from the blower fan. The heat in the air causes most of the low pressure liquid refrigerant to boil. The liquid refriferant changes into refrigerant gas. The heat laden low pressure refrigerant gas/liquid combination flows to the accumulator. The cooler air flows back into the operator's compartment.
Accumulator
 | |
| Illustration 5 | g01077012 |
The accumulator stores the refrigerant gas/liquid mixture. The accumulator allows only gas refrigerant to flow to the compressor. The refrigerant gas flows through the opening at the top of the vapor line.
Earlier accumulators contain a diverter cap to keep the liquid away from the opening in the vapor line. The oil bleed hole allows oil to flow back to the compressor.
Some accumulators contain a desiccant bag in order to remove moisture from the refrigerant. On systems with an in-line dryer, the desiccant is removed from the accumulator and placed in the in-line dryer.