How does a refrigeration compressor work?
Three physical phenomena are essential for understanding how a compressor-based cooling system works. The first Law of physics is: gas compression increases the temperature; gas expansion decreases the temperature. The second is: the temperature of a pure liquid remains constant as it boils or condenses. Lastly, it requires a significant amount of energy for a fluid to go through phase change.
The refrigeration cycle is a constant process. Refrigerant moves from the compressor to the condenser, all the way through a metering device, to an evaporator, and then the cycle repeats.
The compressor compresses the refrigerant. It receives low pressure gas from the evaporator and converts it to high pressure gas. This raises the temperature. Hot refrigerant gas flows to the condenser. The condenser is a heat exchanger that uses a colder air to cool the refrigerant. As refrigerant flows through this heat exchanger, it condenses to a hot liquid. Liquid refrigerant leaves the condenser and flows to the system’s metering device.
The metering device is an expansion valve or a capillary tube and is used to create a pressure drop. Some refrigerant liquid vaporizes, and the temperature of the liquid-gas blend drops. Then the cool refrigerant flows to the evaporator.
The evaporator is a heat exchanger that allows the heat to move between the mechanism we wish to keep cool, called the heat source, and the refrigerant.
The refrigerant enters the evaporator as a low temperature gas-liquid blend. By design, the temperature of the heat source is always higher than the refrigerant’s boiling point. In the evaporator, the refrigerant vaporizes as it absorbs heat from the heat source. The refrigerant then leaves the evaporator as a gas, enters the compressor and the cycle starts again.