Overall Cooling Tower Mass Balance

What enters the tower must equal what leaves. Makeup replaces evaporation, blowdown, drift, and leaks. Drift and leaks are small, so the field simplification is M = E + B.

$$M=E+B+D+L\approx E+B$$

Variables

Symbol	Meaning	Unit
M	Makeup water added	gpm
E	Evaporation	gpm
B	Blowdown	gpm
D	Drift (fine droplets carried off in exhaust air, about 0.001 to 0.006 percent of recirculation)	gpm
L	Leaks	gpm

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Part of The Blueprint of Water