Refrigerant vapor leaves the evaporator and flows into the compressor, where it is compressed to a higher pressure / temperature. High-pressure refrigerant vapor then goes to the condenser, where it rejects heat to the water, and then leaves the condenser as saturated liquid. The pressure drop created by the first expansion device causes some of the refrigerant to vaporize and the resulting mixture of liquid and vapor to enter the economizer. In the economizer, steam is separated from the mixture and directed to the suction of the second stage. Saturated liquid refrigerant then enters the second expansion device.
The pressure drop created by the second expansion device reduces refrigerant pressure and temperature to evaporator conditions, causing some of the refrigerant to evaporate. The resulting mixture of liquid and vapor enters the evaporator. In the evaporator, the coolant evaporates as it absorbs heat from the chilled water, and the resulting vapor is sucked back into the compressor as the cycle repeats.
