The components of a refrigeration unit include a compressor, condenser, expansion valve, evaporator, and control system.

1. The function of refrigeration compressor

The refrigeration compressor is the most important equipment in the refrigeration system, usually referred to as the main unit in the refrigeration system. The increase of refrigerant vapor from low pressure to high pressure, as well as the continuous flow and transportation of the vapor, are all accomplished through the work of the refrigeration compressor. In other words, the function of the refrigeration compressor is to:

1) Extract refrigerant vapor from the evaporator to ensure a certain evaporation pressure inside the evaporator.

2) Raise the pressure to compress low-pressure and low-temperature refrigerant vapor into high-pressure and high-temperature superheated vapor, creating conditions for condensation at higher temperatures (such as around 35 ℃ in summer).

3) Transport and push the refrigerant to flow within the system, completing the refrigeration cycle.

2. According to the different types of cooling media, condensers can be classified into four categories, and their functions are as follows:

⑴ Water cooled type: In this type of condenser, the heat released by the refrigerant is carried away by the cooling water. Cooling water can be used once or recycled. Water cooled condensers can be divided into various types according to their different structural types, such as vertical shell and tube, horizontal shell and tube, and sleeve type.

⑵ Air cooled type (also known as air-cooled type): In this type of condenser, the heat released by the refrigerant is carried away by the air. Air can be naturally convection or forced flow through fans. This type of condenser is used for Freon refrigeration units in places where water supply is inconvenient or difficult.

⑶ Water air cooling type: In this type of condenser, the refrigerant is cooled by both water and air, but mainly relies on the evaporation of cooling water on the surface of the heat transfer tube, absorbing a large amount of heat from the refrigerant side as the latent heat of vaporization of water. The role of air is mainly to accelerate the evaporation of water and carry away water vapor. So this type of condenser consumes very little water, and is the preferred type for areas with dry air, low water quality, low water temperature, and insufficient water volume. This type of condenser can be divided into two types based on their structural types: evaporative and shower type.

⑷ Evaporative condensing type: In this type of condenser, the cooling effect generated by the evaporation of refrigerant in another refrigeration system is used to cool the refrigerant vapor on the other side of the heat transfer partition wall, promoting the latter to condense and liquefy. The evaporator condenser in a cascade refrigeration unit is such.

3. The function of the expansion valve: The expansion valve plays a role in throttling and reducing pressure. When the high-pressure refrigerant liquid condensed by the condenser passes through the throttle valve, it is blocked and the pressure drops, causing some of the refrigerant liquid to vaporize while absorbing the latent heat of vaporization. Its temperature also decreases accordingly, becoming low-temperature and low-pressure wet vapor, which then enters the evaporator.