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4.4 - exhibit Le (cont.)
4.4.5 - Cooling water blow-down method
Prevent concentration and replace cooling water by blow-down.
Calculate the blow-down volume as follows.
N: Concentration factor (N = 3 is normal condition)
M: Volume of make-up water
E: Evaporation loss = 860 x 2.43 (exhaust heat factor) divided by 575 (latent heat of water at 40°C) = 3.63 l/h/kW
W: Splash loss (0.2% of circulation water volume)
B: Blow-down volume
M = E + W + B
N =
1
B =
x E - W
M =
N - 1
1
overflow
(Overflow at cooling tower via
manual valve)
Constant blow-down
2
(Constant blow-down via
solenoid valve)
Pressure switch and solenoid
3
valve
(Blow-down via solenoid valve
at pressure switch)
4
Conductivity meter and/or pH
meter
(Blow-down by conductivity or
pH)
E + W + B
W + B
N
x E
N - 1
example
blow-down
adjustment valve
Control panel
Cooling water flow rate =
E = 3.63 l/h/kW
N = 3
W = 0.46 l/h
1
B =
x 3.63 - 0.46
3 - 1
B = 1.36 l/h/kW
Chiller
P
overflow
Chiller
P
Higher than cooling tower
water level
Solenoid
valve
Chiller
Pressure
switch
P
Chiller
Sensor
P
overflow
230 l/h/kW
(chiller cooling capacity)
Manual valve
Make-up water
Make-up water
Make-up water
Solenoid
valve
Make-up water
1
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