Blowdown Rate from Cycles
Also known as bleed rate
Worked example: 90 L/min evaporation, 30 L/min bleed → 4 cycles — press Try an example to run it live, then adjust anything.
Enter your known values, leave one input blank, and solves for the missing one. Tap a variable’s symbol to see what it means, with a typical value. Try different units for next level excitement!
Tower water balance →
UniversityFluid Mechanics, HVAC & Refrigeration
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Blowdown Rate from Cycles explained
Every mineral entering with the makeup leaves either in the blowdown or as scale on a tube. Write the salt balance — makeup in equals blowdown out, at COC times the concentration — and with makeup being evaporation plus blowdown the algebra collapses to B = E/(COC − 1). A tower evaporating 20 gpm and asked to hold 5 cycles must bleed 20/4 = 5 gpm; ask it to hold 10 cycles and the bleed drops to 2.2 gpm.
The shape of that curve is the whole economic argument for a chemical program. Going from 2 to 4 cycles cuts blowdown by two thirds; going from 8 to 10 barely moves it. Beyond about six cycles you are paying scale-inhibitor money for very little additional water saving, which is why most well-run comfort-cooling towers settle in the 4–7 range. And note what COC = 1 means physically: makeup with no concentration at all, which would require infinite bleed — the solver refuses it rather than dividing by zero.
Blowdown Rate from Cycles formula
- = Blowdown rate (L/min)
- = Evaporation rate (L/min)
- = Cycles of concentration
Missing one of these? Work it out first, then come back
- Blowdown rate — Cycles of Concentration (COC = M/B), Cooling Tower Makeup Water Rate
- Evaporation rate — Cooling Tower Evaporation Rate, Cooling Tower Makeup Water Rate
- Cycles of concentration — Cycles of Concentration (COC = M/B), Cycles of Concentration from Conductivity