First, understand the functions of these 14 key components in the operation and maintenance of screw refrigeration units

The refrigeration system is an indispensable part of modern life, widely used in equipment such as air conditioners and refrigerators. The normal operation of a refrigeration system relies on four core components: compressor, condenser, evaporator, expansion valve, and various auxiliary components. Each component plays an indispensable role in the refrigeration cycle, and the following will provide a detailed introduction to the functions, classifications, and characteristics of these components.

1. Compressor
As the heart of a refrigeration system, the compressor's main function is to compress and deliver refrigerant. Through the operation of the compressor, low-temperature and low-pressure refrigerant gas is converted into high-temperature and high-pressure gas. According to different working principles, compressors can be divided into two categories: volumetric and velocity types:

Positive displacement compressor: This type of compressor compresses refrigerant by changing the volume of the working chamber, including piston type, screw type, rolling rotor type, etc. They can be further divided into open, semi closed, and fully closed types based on their structure.
Speed type compressor: uses centrifugal force generated by high-speed rotation to compress refrigerant, the most common being centrifugal compressors. This type of compressor is mainly used in large commercial and industrial systems.
For small to medium-sized commercial refrigeration systems, reciprocating (piston) compressors are the most commonly used; In household refrigerators and air conditioners, vortex or rotary compressors are more commonly used. In addition, screw compressors are widely used in large-scale refrigeration systems due to their high efficiency and adaptability

2. Condenser
The function of the condenser is to output heat and cool the high-temperature and high-pressure gaseous refrigerant into liquid form. It can be divided into three types based on the cooling medium used: water-cooled shell and tube, air-cooled, and evaporative
Water cooled shell and tube condenser: It has high heat transfer efficiency because the internal water flow rate is fast, usually 1.8 to 3.0 meters per second, which can effectively remove heat. However, due to the high resistance of the cooling water, cleaning is more difficult. This design is suitable for situations that require efficient heat exchange and sufficient water sources.
Air cooled condenser: relying on air flow to dissipate heat, suitable for places lacking sufficient water sources. It is generally used for small units with a cooling capacity of no more than 60 kilowatts, and the face wind speed is about 2.5 to 3.5 meters per second. Compared to water cooling, its heat transfer coefficient is lower, approximately between 25 and 50 watts per square meter Kelvin.

3. Evaporator
The evaporator is the part of the refrigeration system responsible for absorbing heat and reducing the ambient temperature through the vaporization process of the refrigerant. According to the different cooling objects, evaporators can be divided into two forms: cooling liquid refrigerant (such as water or salt water) and cooling air:
Evaporator for cooling liquid refrigerant: for example, a horizontal shell and tube evaporator (dry evaporator), in which the refrigerant evaporates inside the tube while the chilled water flows outside. The characteristic of this type of evaporator is that the refrigerant mass flow rate inside the tube is relatively high, usually ranging from 180 to 200 kilograms per square meter per second, and there are many processes to ensure sufficient contact.
Cooling air evaporator: This type of evaporator is commonly used in direct evaporative air coolers, installed on split air conditioners or other similar equipment. They are equipped with fins to enhance heat transfer efficiency and have internal separators to evenly distribute refrigerant

4. Expansion valve
Expansion valve is a key valve that precisely regulates the flow of refrigerant and also serves as a throttling element. It can automatically adjust the opening according to the pressure changes of the evaporator, thereby maintaining an appropriate degree of superheat. Expansion valves not only achieve effective control of refrigerant flow, but also undertake the tasks of cooling and throttling. Proper installation and maintenance of expansion valves are crucial for ensuring the stability and energy efficiency of the entire refrigeration system.
5. Reservoir
The accumulator is located after the condenser and before the expansion valve, and its main function is to compensate for the fluctuation of the condenser liquid level caused by load changes. When the expansion valve is opened or closed, the liquid level in the condenser will change; If there is no additional refrigerant provided by the reservoir, it may lead to insufficient liquid at the front end of the expansion valve, which in turn affects the stability of the expansion valve's operation. In addition, the accumulator also serves as a separation container, helping to separate liquid refrigerant from vapor and ensuring that pure liquid refrigerant enters the expansion valve

In summary, a complete refrigeration system is not just a simple combination of the four core components, but also includes a series of carefully designed and supportive auxiliary components. Every detail of the design reflects the engineers' focus on efficiency, reliability, and user experience. Understanding the functions of these additional components and their interrelationships can help us better understand the entire refrigeration process and provide guidance for daily maintenance and upkeep. By studying these components, we can have a more comprehensive understanding of refrigeration technology, thereby enhancing our professional knowledge in related fields

Shanghai KUB Refrigeration Equipment Co., Ltd.

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