Cycles of Concentration in Cooling Water (COC)

COC is an abbreviation specifying how often fresh water added to a cooling loop can be circulated before requiring blowdown or bleed-off from the cooling tower. In open cooling water systems with cooling towers and heat exchangers, water circulates continuously. As the cooling tower cools water through evaporation, only water evaporates; minerals remain and concentrate over time, causing scaling or fouling. To manage mineral buildup, concentrated cooling water is periodically drained and replaced with mineral-poor feed water through blowdown or bleed-off processes. COC represents the relation between the concentration of minerals in the feed water and the cooling water. For example, if feed water contains 100 TDS (total dissolved solids) and cooling water contains 400 TDS, the COC is 4. Higher COC values require less fresh water replacement.