6-10
October 2012
Equation 6-3. Cooling Tower Make-UpWater (gallons)
= Evaporation + Drift + Blowdown + Leaks and Overflows
Where:
••
Evaporation (gallons)
••
Drift (gallons)
••
Blowdown (gallons)
••
Leaks and Overflows (gallons)
See Figure 6-2 for an illustration of the water being recirculated, added to, or lost
from a cooling tower.
Figure 6-2. Cooling Tower System
A key parameter used to evaluate cooling tower operation is cycles of concentration
(
sometimes referred to as “cycles” or “concentration ratio”). The concentration ratio
is the ratio of the concentration of TDS (i.e., conductivity) in the blowdown water
divided by the conductivity of the make-up water. Since TDS enter the system in the
make-up water and exit the system in the blowdown water, the cycles of concentra-
tion are also approximately equal to the ratio of volume of make-up water to blow-
down water. See Equations 6-4 and 6-5.
6.3
Cooling Towers
Cooling Tower
EvaporatedWater
Drift Loss
Make-UpWater
Supply
Blowdown
Circulated CoolingWater
Chiller
