Blowdown Rate from Cycles

Solves for blowdown by combining the overall mass balance (M = E + B) with the makeup-blowdown relationship (M = B x COC), giving E = B(COC - 1).

$$B=\frac{E}{\text{COC}-1}$$

Variables

Symbol	Meaning	Unit
B	Blowdown rate	gpm
E	Evaporation rate	gpm
COC	Cycles of concentration	dimensionless

Worked example

At 4 cycles with E = 10.2 gpm: B = 10.2 / (4 - 1) = 3.4 gpm.

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Part of The Blueprint of Water