Working principle of explosion-proof screw chiller

In industrial production and some special environments, reliable refrigeration equipment is needed to meet the needs of process cooling or environmental regulation. As an efficient and safe refrigeration device, explosion-proof screw chillers play a key role in dangerous places where flammable and explosive gases, steam or dust exist. Understanding their working principles is essential for the correct selection, operation and maintenance of equipment.

Refrigeration cycle basics

The refrigeration principle of the explosion-proof screw chiller is based on the reverse Carnot cycle, which mainly consists of four basic processes: compression, condensation, throttling and evaporation. These four processes are carried out in sequence in different components of the unit to achieve the transfer of heat from the low temperature environment to the high temperature environment, thereby achieving the cooling effect.

Compression process

The compressor is one of the core components of the chiller. In explosion-proof screw chillers, screw compressors are usually used. The screw compressor works through a pair of intermeshing spiral rotors. When the motor drives the active rotor to rotate, the driven rotor also rotates synchronously. A closed working chamber is formed between the teeth of the rotor. As the rotor rotates, the volume of the working chamber gradually increases, the pressure decreases, and the low-temperature and low-pressure refrigerant vapor is sucked into the working chamber from the suction port. When the working chamber is isolated from the suction port, the rotor continues to rotate, the volume of the working chamber gradually decreases, the refrigerant vapor is compressed, and the pressure and temperature continue to rise. When the working chamber is connected to the exhaust port, the high-temperature and high-pressure refrigerant vapor is discharged from the compressor, completing the compression process. In explosion-proof screw compressors, special explosion-proof treatment is performed on motors, electrical components, etc. to ensure the safety of operation in hazardous environments.

Condensation process

The high-temperature and high-pressure refrigerant vapor discharged from the compressor enters the condenser. The condenser is generally water-cooled or air-cooled. In a water-cooled condenser, the refrigerant vapor exchanges heat with the cooling water. The refrigerant vapor transfers heat to the cooling water, lowers its own temperature and gradually condenses into a liquid. After the cooling water absorbs the heat, its temperature rises, and the heat is dissipated into the environment through a cooling tower or other cooling methods. In an air-cooled condenser, the refrigerant vapor exchanges heat with the air, and the air takes away the heat of the refrigerant vapor to condense it. Because it is in an explosion-proof environment, the structural design and material selection of the condenser also need to meet explosion-proof requirements to prevent the risk of explosion caused by heat accumulation or sparks.

Throttling process

After the high-pressure refrigerant liquid is condensed by the condenser, it enters the evaporator through the throttling device (such as the expansion valve). The function of the throttling device is to reduce the pressure of the refrigerant, so that it changes from a high-pressure liquid to a low-pressure liquid. In this process, the temperature of the refrigerant is also reduced accordingly. The throttling device controls the flow of the refrigerant to ensure the appropriate refrigerant evaporation pressure and temperature in the evaporator to meet the cooling capacity requirements. For explosion-proof screw chillers, the installation and protection of the throttling device must also comply with explosion-proof standards to avoid danger during the throttling process.

Evaporation process

After the low-pressure and low-temperature refrigerant liquid enters the evaporator, it absorbs the heat of the cooled medium (such as water or air) in the evaporator, boils and evaporates, and changes from liquid to gas. The temperature of the cooled medium is reduced, achieving the purpose of refrigeration. In the chiller, water is usually used as the cooled medium, and heat is exchanged with the refrigerant through the heat exchange tubes in the evaporator. The structural design of the evaporator must ensure a good heat exchange effect between the refrigerant and the cooled medium, and also meet the explosion-proof requirements to prevent safety problems caused by refrigerant leakage.

Combination of explosion-proof characteristics and working principles

In addition to the conventional refrigeration cycle principle mentioned above, the unique explosion-proof design is also the key to the safe operation of explosion-proof screw chillers in hazardous areas. In terms of electrical systems, explosion-proof motors, explosion-proof electrical components, and special explosion-proof junction boxes are used. These explosion-proof devices can effectively prevent sparks, arcs, or high temperatures that may be generated inside from being transmitted to the external flammable and explosive environment through special structural designs, such as increasing the strength of the casing and using flameproof surfaces.

In terms of mechanical structure, special treatment is given to parts that may generate friction and collision sparks. For example, the rotor of the compressor and other parts are made of special materials and processing technology to reduce the possibility of sparks generated by friction. At the same time, the unit is also equipped with complete safety protection devices, such as pressure protection, temperature protection, leakage detection, etc. When the system has abnormal conditions, such as excessive pressure or temperature, the safety protection device will immediately act to cut off the power supply or take other measures to prevent accidents.

In summary, explosion-proof screw chillers achieve refrigeration through reverse Carnot cycle, and the working principles of each link cooperate with each other to ensure efficient refrigeration effect. At the same time, the special design for explosion-proof environment enables it to operate safely and stably in dangerous places, providing a reliable solution for the refrigeration needs of industrial production and special environments. Whether in the chemical, petroleum, natural gas and other industries, or in other places with flammable and explosive risks, explosion-proof screw chillers play an indispensable role.