​​​I. Main System Components​​

• ​​Screw Compressor:​​ The heart of the system. Compresses low-temperature, low-pressure refrigerant gas into high-temperature, high-pressure gas.

• ​​Condenser:​​ The high-pressure, high-temperature refrigerant gas releases heat here, condensing into a liquid.

• ​​Throttling Device (Expansion Valve/Capillary Tube):​​ Reduces the pressure and temperature of the high-pressure liquid refrigerant, transforming it into a low-temperature, low-pressure gas-liquid mixture.

• ​​Evaporator:​​ The liquid refrigerant evaporates here, absorbing heat, thereby lowering the temperature of the cooled medium (air or water).

• ​​Liquid Receiver / Oil Separator (for oil-injected types):​​ Separates lubricating oil and stores excess refrigerant.

​​II. Working Cycle Steps (Using an Oil-Injected Screw Compressor as an Example)​​

1. ​​(1) Compression Process​​

   • Low-temperature, low-pressure refrigerant vapor (e.g., R134a, Ammonia, R22) enters the compressor suction port from the evaporator.

   • Through the meshing rotation of the male and female rotors, the gas is progressively compressed within the inter-lobe volume:

     • Volume continuously decreases (typical volumetric ratio 2.5–5.0).

     • Pressure and temperature rise sharply (discharge temperature can reach 70–100°C).

   • ​​Oil Injection Role:​​ Oil is simultaneously injected for sealing, cooling, and lubrication.

2. ​​(2) Discharge & Oil Separation​​

   • The high-temperature, high-pressure mixture of refrigerant gas and oil enters the ​​Oil Separator​​:

     • Lubricating oil is separated (separation efficiency >99.9%) and returns to the compressor.

     • Pure high-pressure refrigerant gas flows to the condenser.

3. ​​(3) Condensation Process​​

   • High-temperature, high-pressure gaseous refrigerant in the condenser:

     • Releases heat via air or water cooling.

     • Gradually condenses into ​​high-pressure liquid refrigerant​​ (e.g., R134a condensing temperature approx. 40–50°C).

4. ​​(4) Throttling Expansion​​

   • High-pressure liquid refrigerant flows through the ​​Expansion Valve​​ (Thermal Expansion Valve / Electronic Expansion Valve):

     • Pressure drops sharply (e.g., from 15 bar to 4 bar).

     • Temperature falls to the evaporation temperature (e.g., -10°C).

     • Becomes a ​​low-temperature, low-pressure two-phase gas-liquid mixture​​.

5. ​​(5) Evaporation & Heat Absorption​​

   • The two-phase mixture enters the evaporator:

     • Refrigerant absorbs heat from the surrounding medium (chilled water or air) and evaporates.

     • Outputs cold water (e.g., 7°C) or cold air.

     • Finally becomes ​​low-temperature, low-pressure saturated gas​​, re-entering the compressor to complete the cycle.

✅ ​​Essential Principle:​​ Heat absorption in the Evaporator → Heat rejection in the Condenser, achieving heat transfer from the low-temperature zone (Evaporator) to the high-temperature zone (Condenser).

​​III. Core Advantages of Screw Compression Refrigeration​​

• ​​Continuous Compression Capability:​​

  • No suction/discharge valves ensures smooth, non-pulsating gas flow.

  • Ideal for high-capacity cooling applications (typical capacity range ​​100–3000 kW​​).

• ​​Highly Efficient Variable Load Operation:​​

  • ​​Sliding Valve Capacity Control:​​ Enables stepless cooling capacity modulation (10–100%), perfectly adapting to varying loads.

  • ​​Variable Speed Drive (VFD) Control:​​ Further optimizes efficiency under partial load conditions.

• ​​Tolerance to Liquid Slugging & Wet Compression:​​

  • Rotor clearance design allows small amounts of liquid refrigerant to enter without causing damage (unlike reciprocating compressors which suffer from liquid slugging).

• ​​Low Vibration & High Reliability:​​

  • Excellent rotor dynamic balancing results in significantly lower vibration than piston compressors, eliminating the need for complex foundations.

  • Suitable for sensitive environments (hospitals, laboratories).