efficiency and 10 represents very good efficiency. It has been found that the range of 5

to 7 COC represents the most cost-effective situation.

4-2.1.2.1

volumes are known, COC by volume can be calculated. The term is defined as:

EQUATION

C=MB

(20)

where

C = COC, no units

M = makeup water, kg/hr (gpm)

B = blowdown losses, kg/hr (gpm)

EXAMPLE:

M = 6.3 liters/sec (100 gpm)

B = 0.63 liters/sec (10 gpm)

C = M B = 10

4-2.1.2.2

know the mineral content of both makeup and blowdown water. For example, you must

determine both the conductivity of the recirculating cooling tower water and the

conductivity of the makeup water. (Note that the blowdown water will have the same

conductivity as the recirculating water.) Conductivity is commonly measured in

micromhos (mhos). You can also estimate COC by using other water quality

parameters such as chlorides, silica, or sulfates. The relationship is represented by this

equation:

Bmhos

BCl

EQUATION

C = ------ or ------

(21)

Mmhos

MCl

where

C

= COC, no units

Bmhos = conductivity of blowdown (recirculating water), micromhos

(mhos)

Mmhos = conductivity of makeup water, mhos

Cl

= chlorides in blowdown, ppm

Cl

= chlorides in makeup water, ppm

EXAMPLE 4-1:

The measured conductivity of the blowdown (recirculating water) is 800

micromhos and the makeup is 300 micromhos.

103

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