chilled water system
Chilled water systems in semiconductor fabrication facilities provide centralized cooling to process tools, HVAC systems, and facility infrastructure through a closed-loop network of chilled water distribution, maintaining the precise temperature control essential for consistent wafer processing. The central chilled water plant (CWP) typically includes multiple centrifugal or screw chillers operating in an N+1 redundant configuration, producing chilled water at specific temperature setpoints for different fab requirements. Fab chilled water typically operates at two or three temperature levels: process cooling water (PCW — typically 15-20°C/59-68°F, used directly for tool cooling where precise temperature control is required), facility chilled water (FCW — typically 5-7°C/41-45°F, used for HVAC air handling units, makeup air cooling, and dehumidification), and in some fabs, a warm chilled water loop (around 25-28°C) for heat recovery applications. System components include: chillers (electric centrifugal or screw compressor types — 500-2000+ ton capacity each, using refrigerants like R-134a, R-513A, or R-1234ze with high efficiency — 0.5-0.6 kW/ton at full load), chilled water pumps (primary and secondary pumping configurations — variable frequency drives on secondary pumps for energy-efficient flow matching to load), cooling towers (rejecting heat to atmosphere via evaporative cooling — counterflow or crossflow designs with variable speed fans), heat exchangers (plate-and-frame or shell-and-tube for isolating process loops from facility loops — preventing cross-contamination), expansion tanks and air separators (maintaining system pressure and removing dissolved air), chemical treatment systems (preventing corrosion, biological growth, and scale in piping), and building automation system (BAS) integration for monitoring and control. The chilled water system is typically the largest single energy consumer in a fab, accounting for 30-40% of total facility energy, making energy optimization critical — strategies include free cooling (bypassing chillers when outdoor wet-bulb temperature is low enough), waterside economizers, variable primary flow, and chiller plant optimization algorithms.