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How Does a Compression Refrigeration System Work?

Vapor compression refrigeration systems are commonly used in industrial facilities to create environments conducive to the perseveration and safe storage of products. In this guide, we will go over how a compression refrigeration system works, and the four main components used to create the refrigeration cycle.

The Vapor Compression Refrigeration Cycle

The compression refrigeration cycle consists of circulating a liquid refrigerant through four stages of a closed system. As the refrigerant circulates through the system, it is alternately compressed and expanded, changing its state from a liquid to a vapor. As the refrigerant changes state, heat is absorbed and expelled by the system, lowering the temperature of the conditioned space.

Stage 1: Compression

In the first stage of the refrigeration cycle, refrigerant enters a compressor as a low-pressure vapor. The compressor compresses the refrigerant to a high-pressure vapor, causing it to become superheated. Once the refrigerant is compressed and heated, it leaves the compressor and enters the next stage of the cycle.


There are several styles of compressors that can be used in the refrigeration cycle, including scroll, screw, centrifugal, or reciprocating compressors.

Stage 2: Condensation

After leaving the compressor, the hot vapor refrigerant enters the next stage of the cycle, condensation. During the condensation stage, the refrigerant enters a condenser and flows through a series of S-shaped tubes. As the hot vapor flows through the condenser, cool air is blown across the tubes by a fan.

Because the air being blown across the tubes is cooler than the refrigerant, heat transfers from the tubing to the cooler air. This heat transfer causes the hot vapor refrigerant to reach its saturated temperature, which then changes its state to a high-pressure liquid. Once the refrigerant is in a high-pressure liquid state, it is ready to leave the condenser and move on to the metering and expansion stage of the cycle.

Stage 3: Metering and Expansion

The third stage of how compression refrigeration systems work consists of the high-pressure liquid refrigerant entering a metering device or expansion valve. The metering device works to maintain high-pressure on the inlet side, while also expanding the liquid refrigerant and lowering the pressure on the outlet side. During the process of expansion, the temperature of the liquid refrigerant is also reduced.

Stage 4: Evaporation

In a cool, low-pressure liquid state, the refrigerant is now ready to enter the evaporation stage, which is where the heat is finally removed from the space being conditioned.

In the evaporation stage, the cool liquid refrigerant leaves the metering device and enters coiled tubes in an evaporator. Fans are then used to blow warm air from the conditioned space across the evaporator coils. The cooler refrigerant in the evaporator coils begins absorbing the heat out of the warmer air, reducing the temperature in the conditioned space

Meanwhile, as the refrigerant absorbs heat from the air, it begins to boil and changes to a low-pressure vapor. The low-pressure vapor is then pulled back into the compressor, and the cycle starts over.

About Process Solutions, Inc.

Located near Seattle, Washington, Process Solutions has over 30 years of experience providing high quality and reliable control systems. With over 100 engineers and technicians on staff and an output of over 3,000 industrial control panels per year, Process Solutions is the Northwest largest control systems integrator. In addition to custom control panel design, build and commissioning, Process Solutions’ control systems services include PLC and HMI programming, robot system integration, energy management and industrial refrigeration control systems, SCADA software, and DAQuery machine monitoring software.