25
100
90
80
70
60
1
2
3
4
5
100
105
110
115
120
125
A
B
C
D
For example, if 0.6 mm of scale clings to the tubes, the cooling
capacity drops to 76%, the chilled-water temperature rises by
2°C and fuel consumption rises by 23%.
A For constant cooling capacity
(ratio at rated fuel consumption)
B Increase in fuel consumption
C Decrease in cooling capacity
(for constant chilled water temperature)
D Increase in chilled water temperature
(for constant cooling capacity)
4.4 - Water treatment
Water treatment is very important for the chiller. As this
requires specialised technical knowledge, please consult your
Carrier service agent.
4.4.1 - Water treatment for chilled water and cooling water
The cooling water temperature in an open-type recycling
cooling tower is decreased using vaporized latent heat, and the
cooling water is reused. At this time, the water is evaporated,
and the concentration of the remaining dissolved salts
increases. This means that the water quality will gradually
deteriorate.
As the water and air are always in contact with each other in
the cooling tower, the sulfurous acid gas, dust, sand, etc. in
the atmosphere will mix with the water, further degrading the
water quality.
These factors cause problems in the cooling water system, such
as corrosion, scale and slime.
Water quality standard
The water quality standard is shown in the example in Figure
27. This is an extract from JRA-GL 02-1994.
NOTES:
1. If any item deviates from the standard values it may
cause failure due to corrosion or scale. Therefore the
water quality should be checked periodically.
2. As the water quality range differs depending on the
chemicals used, it is not given here. The appropriate
water quality values should be set together with a water
processing specialist and be checked periodically.
Typical water treatment
Even if the make-up water for the cooling water complies
with water standards, the water quality will deteriorate due to
its concentration. Therefore the following water treatment is
necessary. Depending on the degree of deterioration, chilled/
hot water also requires this treatment.
If a concrete heat storage tank is used, special attention should
be paid to water treatment.
•
Regular manual blow-down of the tower sump water
•
Automatic blow-down by measuring electric conductance
•
Addition of the anti-corrosion inhibitor
•
Slime control
•
Periodic water analysis
Service the water header periodically, check the heat
transfer tube and clean it as necessary.
Rise in chilled water temperatur
e (°C)
Fuel composition (%)
1
2
3
4
5
6
7
8
9
10
Fouling factor (m
2
h °C/kcal) x 10
-4
1
2
3
4
5
6
7
8
9
Fouling factor (m
2
K/kW) x 10
-4
0.2
0.4
0.6
0.8
1.0
1.2
Scale/slime (mm)
Fig. 25 - Example of the effect of tube fouling
Decr
ease in cooling capacity (%)
