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SYS-APM001-EN Chiller System Design and Control 37
It quickly becomes evident that the same cooling tower and flow rate are
adequate to reject more heat—in this case, approximately 50 percent more
heat.
Figure 22. Cooling tower re-selection with different chiller capacities
Retrofit opportunities
The low-flow concepts for chilled- and condenser-water just described in
pages 33 through 37 present tremendous retrofit opportunities. Building
owners may need to increase the capacity of an existing system, for example,
in response to a building addition. In many of these buildings, the condenser
water system (piping, pump, and tower) is in good condition, but is
considered to be too small. Or, the system has expanded but the chilled water
pipes and/or coils cannot be changed. By changing from traditional design
conditions, the existing infrastructure can often be used while providing
additional capacity.
Table 11. Retrofit capacity changes
Present
Larger
chiller,
same tower
Capacity, tons
[kW refrigeration]
450 [1,580] 675 [2,370]
Cooling tower
Flow rate, gpm [L/s] 1350 [85.2] 1,350 [85.2]
Entering temperature, F [C] 94.3 [34.6] 103 [39.4]
Leaving temperature, F [C] 85 [29.4] 88 [31.1]
Ambient wet-bulb
temperature, F [C]
78 [25.6] 78 [25.6]
Y
Y
90
85
80
75
70
65
60
70 8055 65
75
Design Point (original)
Cooling Tower Water Temperature (°F)
Design Point (new)
Reselected tower for 50% more
heat rejection with 15°F [8.3°C]
range
Original design point
for tower with 10°F
[5.6°C] range
Wet-Bulb Temperature (°F)