Cycles of Concentration Calculator
Determine actual operating Cycles of Concentration (COC) using electrical conductivity or TDS, identify mineral scaling caps, and calculate water savings.
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Cycles of Concentration & Mineral Scaling Science
Cycles of Concentration (COC) indicate how many times the dissolved minerals in raw makeup water are concentrated inside the evaporative cooling loop. Operating at higher cycles significantly reduces blowdown sewer discharge and overall water consumption, but increases the risk of irreversible mineral precipitation onto heat transfer surfaces.
Conductivity & Mineral Balance Equations
- Cycles of Concentration:
COC = Tower Conductivity / Makeup Conductivity = Chloride_basin / Chloride_makeup - Silica Scale Boundary:
Max COC_silica = Max Allowable Silica (ppm) / Makeup Silica (ppm)
Because reactive silica forms an amorphous, glass-like scale that cannot be dissolved with acid, tower water must never exceed 150 to 180 ppm SiO₂. - Blowdown Fraction:
Blowdown % = (1 / COC) × 100%
Frequently Asked Questions
Why is silica the limiting mineral in cooling tower cycles of concentration?
Silica precipitates as a tenacious glassy coating that cannot be dissolved by standard chemical acid washing without damaging metal pipes. It must be kept below 150 to 180 ppm.
How much water is saved by increasing cycles from 2 to 4?
Increasing cycles from 2 to 4 cuts cooling tower blowdown by 67% and total makeup water consumption by approximately 33%.
What is the relationship between TDS and conductivity in cooling tower water?
Total Dissolved Solids (TDS in ppm) is typically estimated as 0.65 to 0.70 times the electrical conductivity in micromhos/cm (µS/cm).