Tech Page: Refrigeration Cycle and System Components
Two things happen during this refrigeration cycle: evaporation and condensation.
When refrigerant absorbs the unwanted heat, this raises the refrigerant’s temperature so that it changes from a liquid to a gas — it evaporates. The system then uses condensation to release the heat and change the refrigerant back into a liquid.
Seven separate components are needed in a basic system for this refrigeration cycle to work.
Refrigeration System Components
Evaporator: This device helps with the heat exchanging. The evaporator boils the liquid refrigerant at a low temperature, which causes the refrigerant to absorb heat.Suction line: This is the tube between the evaporator and the compressor. After the liquid has absorbed the heat, the suction line carries the refrigerant to the compressor. At this point, the refrigerant is a superheated gas.
Compressor: This device has two purposes, due to the fact that it separates the low-pressure side of the system from the high-pressure side. The compressor first removes vapor from the evaporator to keep the evaporator’s boiling point low. Next, the device compresses the low-temperature gas into a small volume, creating a high-temperature, high-pressure gas.
Hot gas discharge line: This tube connects the compressor with the condenser. After the compressor has discharged the high-pressure, high-temperature refrigerant gas, the hot gas discharge line carries it to the condenser.
Condenser: This device is similar to the evaporator, but its job is to expel heat, not absorb it. The condenser changes the state of the superheated refrigerant vapor back into a liquid. This is done by creating a high pressure that raises the boiling point of the refrigerant and removes enough heat to cause the refrigerant to condense back into a liquid. Liquid line: This line connects the condenser with the refrigerant control device. Only liquid
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refrigerant should be in this line. Also, the line will be somewhat warm because the refrigerant is still under high pressure.
Refrigerant control: This last control works as a metering device. It monitors the liquid refrigerant that enters the evaporator and makes sure all the liquid is boiled off before the refrigerant goes to the suction line. If liquid refrigerant enters the suction line, it will enter the compressor and cause it to fail.
Extra Components
The above components are the main components necessary for all refrigeration systems. The next set of components are added features that can enhance the refrigeration system’s operation.Liquid receiver: This can be found in the liquid line; it serves as a storage container for extra liquid refrigerant that may not have boiled off in the evaporator.
Service valves: These are not used in operating the system, but can be used by technicians for service checks and troubleshooting. The valves block off sections of the system so that a technician can use a gauge manifold to measure operating pressures. There are three types of service valves.
Suction service valve — This valve is located between the suction line and the compressor. It lets the technician control the flow of refrigerant to the compressor and read the system’s low-side pressure while the compressor continues to run.
Discharge service valve — This valve can be found on the compressor; it lets the technician restrict or stop the amount of gas leaving the compressor. It also allows the technician to read the system’s high-side pressure as the compressor continues to run.
Liquid receiver service valve — This valve can be found in the liquid line near the liquid receiver outlet. With this valve, the technician can stop or restrict the flow of refrigerant leaving the receiver. The technician can also read the system’s high-side pressure with the compressor running.
Publication date: 10/29/2001
