Process cooling water (PCW) is a chilled water loop circulated to cool process tools and equipment in semiconductor manufacturing. Temperature: Typically 15-20 degrees C (59-68 degrees F). Precise temperature depending on process requirements. Purity: Clean but not ultra-pure. May contain corrosion inhibitors. Closed loop to maintain quality. Uses: Cool plasma chambers, RF generators, vacuum pumps, chillers, power supplies, and other heat-generating equipment. System components: Chillers, cooling towers, circulation pumps, heat exchangers, piping, valves, temperature controls. Loops: Primary loop to central chillers, secondary loops to tools. Multiple temperature zones possible. Redundancy: Critical cooling typically has N+1 redundancy. Backup chillers for continuous operation. Monitoring: Flow, temperature, pressure, water quality monitored at central plant and tool connections. Water treatment: Chemical treatment to prevent corrosion, scaling, biological growth. Regular testing. Heat rejection: Heat removed from PCW via cooling towers or air-cooled chillers to atmosphere. Energy: Major fab energy consumer. Free cooling mode when ambient temperature permits.