Water Cooled Screw Chiller: Structure and Refrigeration Principle

The water cooled screw chiller is used to provide chilled water for air conditioning systems and can be integrated with air handling units and packaged air conditioning units to form large centralized air conditioning systems. It is widely applied in hotels, hospitals, shopping malls, office buildings, entertainment venues, and other places for air conditioning, as well as for cooling industrial production processes.

Structure of the Water Cooled Screw Chiller

The water cooled screw chiller primarily consists of a semi-hermetic twin-screw compressor, a shell-and-tube condenser, a flooded evaporator, an oil separator, an expansion valve, and an electrical control system.

• Evaporator:During the operation of the chiller, the evaporator maintains a low temperature and pressure to ensure that the evaporated refrigerant gas absorbs heat from the chilled water flowing through it.

  
  

• Condenser:During operation, the condenser maintains a high temperature and pressure, allowing the cooling water passing through the condenser to absorb heat from the refrigerant, thereby cooling it down.

  
  

• Screw Compressor:The screw compressor continuously delivers the refrigerant vapor evaporated in the evaporator to the condenser, maintaining the high and low-pressure differential in the system.

  
  

• Oil Separator:The oil separator removes the refrigerant oil that is carried along with the refrigerant gas and returns it directly to the compressor to ensure the safe and reliable operation of the compressor.

  
  

• Electrical Control System:The chiller is equipped with a PLC or microcontroller-based control system that automatically adjusts the cooling output to meet the actual demand. It can control the user-side pumps, heat source, and cooling tower fans, and display parameters such as the inlet and outlet temperatures of chilled water and cooling water, evaporating and condensing pressures, and other system parameters. It also allows for the query of current and historical fault records.

  
  

Refrigeration System of the Water Cooled Screw Chiller

The water cooled screw chiller is a type of vapor-compression refrigeration system. The refrigeration principle of the chiller involves the compressor applying energy to the refrigerant vapor, which increases its pressure and temperature. The refrigerant then goes through the condensation and expansion processes, transforming into a low-pressure, low-temperature liquid refrigerant. In the evaporator, the liquid refrigerant evaporates into vapor, absorbing heat from the surrounding environment (the heat carrier, such as chilled water), which lowers the temperature of the heat carrier, thus achieving artificial cooling.

This process clearly illustrates that the vapor-compression refrigeration cycle consists of four essential processes: compression, condensation, expansion, and evaporation.