Chiller plant — how it works

Animated water (and refrigerant) flow across every component, from the building to the cooling tower.

Flow speed 1.0×
Cooling tower fan rejects heat to air (condenser water cooled) Chiller Condenser gives off heat to CW Compr- essor Evaporator absorbs heat from CHW AHU coil fan Building ☀ heat from people & machines P CW pump P CHW pump CW return ~32°C CW supply ~27°C refrigerant vapor ↑ liquid ↓ CHWS 7°C CHWR 12°C ΔT = 5°C warm cool
chilled / cold water warm return water refrigerant (inside chiller) conditioned air

Follow the heat (right to left): people and machines warm the building air. The AHU fan pulls that warm air across the cooling coil; chilled water inside the coil absorbs the heat and cool air returns to the rooms. The water leaves the coil warm (CHWR ≈ 12°C) and the CHW pump sends it to the chiller's evaporator, which chills it back to CHWS ≈ 7°C. The gap between them is ΔT.

Inside the chiller, the compressor lifts the absorbed heat (carried by the refrigerant) from the evaporator up to the condenser. There, condenser water absorbs the heat and the CW pump carries it (CW return ≈ 32°C) to the cooling tower, whose fan rejects it to the outside air, returning cooler water (CW supply ≈ 27°C) to the condenser. The cycle repeats.