Cycles of Concentration (Conductivity Ratio)

Describes how much more concentrated cooling tower water is compared to the makeup, because pure water leaves as evaporation while dissolved solids stay behind and concentrate. Rising COC raises supersaturation and scaling pressure.

$$\text{COC}=\frac{\text{Conductivity of tower water}}{\text{Conductivity of makeup water}}$$

Variables

Symbol	Meaning	Unit
${\text{Cond}}_{tower}$	Conductivity of the recirculating tower water	µS
${\text{Cond}}_{makeup}$	Conductivity of the makeup water	µS

Worked example

Makeup conductivity = 400 µS, tower conductivity = 1,600 µS. COC = 1,600 / 400 = 4 cycles. At 4 cycles, makeup species (calcium, alkalinity, chloride, sulfate) are present at four times their makeup concentration.

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Part of The Blueprint of Water