Water cooled screw unit is an efficient refrigeration equipment with screw compressor as the core, widely used in central air conditioning systems and industrial refrigeration fields. Its working principle is based on the vapor compression refrigeration cycle, which achieves heat transfer through four core processes (compression, condensation, throttling, evaporation). The following is a detailed analysis:

1、 Core working principle: vapor compression refrigeration cycle

The water-cooled screw unit achieves heat transfer through the phase change of refrigerant (liquid to gas conversion), and the specific process is as follows:

Compression process: Low temperature and low-pressure refrigerant gas is drawn into the cylinder of the screw compressor from the evaporator. The compressor compresses gas into high-temperature and high-pressure refrigerant gas through the mechanical work of the screw rotor, while the temperature significantly increases.

Condensation process: High temperature and high pressure gas enters the condenser (shell and tube heat exchanger) and exchanges heat with cooling water. Heat is transferred from the refrigerant to the cooling water, and the gas condenses into high-pressure liquid. After the cooling water heats up, it returns to the cooling tower for heat dissipation.

Throttling process: The high-pressure liquid is throttled and depressurized by a thermal expansion valve, becoming a low-pressure low-temperature liquid, while some of the liquid vaporizes to form a gas-liquid mixture.

Evaporation process: Low pressure and low-temperature liquid enters the evaporator (shell and tube heat exchanger), absorbs heat from the chilled water and vaporizes, cooling the chilled water to the set temperature (such as 7-12 ℃). The vaporized refrigerant gas is sucked back into the compressor to complete the cycle.

2、 Water circulation system: dual loop heat transfer

The unit achieves cooling effect through two independent water circulation systems:

Chilled water cycle: Low temperature chilled water is output from the unit evaporator and enters the indoor end devices (such as fan coil units). After absorbing indoor heat, the temperature of the chilled water increases and returns to the unit evaporator for re cooling, forming a closed loop.

Cooling water circulation: The cooling water absorbs heat from the refrigerant in the condenser, increases in temperature, flows through the cooling tower to dissipate heat and cool down, and then returns to the condenser for recycling.