Introduction to the working principle of water-cooled screw chiller

As a common and efficient refrigeration equipment, water-cooled screw chillers play a key role in industrial production, commercial buildings and some places with high temperature control requirements. A deep understanding of its working principle will help us better use this equipment to achieve efficient and stable refrigeration effects.

The working principle of the water-cooled screw chiller is based on the reverse Carnot cycle. It is mainly composed of four core components: compressor, condenser, throttling device and evaporator. The refrigerant circulates in these four components to transfer heat and achieve the purpose of cooling.

The compressor is the heart of the entire system. Its function is to compress the low-temperature and low-pressure gaseous refrigerant into a high-temperature and high-pressure gaseous refrigerant. In water-cooled screw chillers, screw compressors are widely used due to their high efficiency and stable performance. The screw compressor uses a pair of intermeshing spiral rotors. During the rotation of the rotors, the volume between the teeth and the grooves changes continuously, thereby achieving the suction, compression and discharge of the refrigerant. When the rotor rotates, the tooth grooves gradually increase, forming a low-pressure space, and the refrigerant gas is sucked into the tooth grooves; as the rotor continues to rotate, the tooth groove volume gradually decreases, the refrigerant gas is compressed, the pressure and temperature continue to rise, and then it is discharged from the compressor in the form of a high-temperature and high-pressure gas.

After high-temperature and high-pressure gaseous refrigerant is discharged from the compressor, it enters the condenser. The function of the condenser is to cool the gaseous refrigerant and condense it into liquid refrigerant. During this process, the refrigerant releases a large amount of heat. The water-cooled condenser uses water as the cooling medium, and the heat released by the refrigerant is taken away by the circulation of water. Inside the condenser, the refrigerant gas flows in the pipe, while the cooling water flows outside the pipe, and the two exchange heat through the pipe wall. The refrigerant gas gradually condenses into liquid during the cooling process and gathers at the bottom of the condenser.

After the liquid refrigerant is condensed by the condenser, the pressure is still high and needs to be reduced by a throttling device. The throttling device usually adopts an expansion valve or a capillary tube, and its function is to reduce the pressure and expand the high-pressure liquid refrigerant in a short time, turning it into a low-temperature and low-pressure liquid refrigerant. When the high-pressure liquid refrigerant passes through the throttling device, due to the small aperture of the throttling device, the flow rate of the refrigerant increases sharply, the pressure drops rapidly, and the temperature of the refrigerant also decreases. After the low-temperature and low-pressure liquid refrigerant enters the evaporator, it begins to absorb the heat of the surrounding medium (usually water or air), thereby achieving a cooling effect.

The evaporator is the place where the refrigerant and the cooled medium exchange heat. Inside the evaporator, the low-temperature and low-pressure liquid refrigerant flows in the pipe, while the cooled medium (such as water or air) flows outside the pipe. After the refrigerant absorbs the heat of the cooled medium, it gradually evaporates into a gaseous state, and the temperature of the cooled medium decreases. In a water-cooled screw chiller, the evaporator usually adopts a shell and tube structure, where the refrigerant evaporates in the tube and the cooled water flows outside the tube. Through the heat exchange of the evaporator, the temperature of the water is reduced and becomes low-temperature chilled water, which is transported to places that need refrigeration, such as the terminal equipment of the air-conditioning system or the cooling process equipment in industrial production.

After the refrigerant evaporates into gas in the evaporator, it returns to the compressor and starts a new cycle. In this way, the water-cooled screw chiller continuously transfers heat from the cooled medium to achieve a continuous refrigeration process.

In addition to the above four core components, the water-cooled screw chiller is also equipped with some auxiliary equipment to ensure the normal operation and efficient performance of the unit. For example, the control system is used to monitor and adjust the operating parameters of the unit, such as temperature, pressure, flow, etc., to achieve automatic control; the water pump is used to drive the circulation of cooling water and chilled water; the cooling tower is used to cool the hot water discharged from the condenser and recycle it; the filter is used to filter impurities in the refrigerant and water to protect the equipment from damage.

In summary, the water-cooled screw chiller achieves an efficient refrigeration process based on the reverse Carnot cycle principle through the coordinated work of components such as the compressor, condenser, throttling device and evaporator. Understanding its working principle is of great significance for the selection, installation, commissioning, maintenance and optimized operation of the equipment, which helps us give full play to the performance advantages of the equipment and meet the refrigeration needs of different places.