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34 TRG-TRC012-EN
notes
period five
Application Considerations
Controlling the refrigerant pressure difference between the evaporator and
condenser of a water-cooled chiller is accomplished by varying the temperature
or flow rate of the water flowing through the condenser. The following are 5
common methods used to control condensing temperature:
1) Controlling the temperature of the water leaving the cooling tower by cycling
or varying the speed of the cooling tower fans
2) Using a cooling tower bypass pipe to mix warmer leaving-condenser water
with the colder tower water and control the temperature entering the condenser
as illustrated in the accompanying slide
3) Modulating a throttling valve to restrict the flow of water through the
condenser
4) Using a chiller bypass pipe to vary the flow rate of water through the
condenser
5) Employing a variable-speed drive on the condenser water pump to vary the
water flow rate through the condenser
Each of these strategies has its advantages and disadvantages, and selection of
the appropriate condensing temperature control scheme depends on the
specific application.
The water flow rate through the chiller’s condenser must stay between the
minimum and maximum condenser bundle flow rates as specified by the chiller
manufacturer.
condenser
condenser
bypass
bypass
cooling tower
cooling tower
condensing temperature control
Cooling Tower Bypass
55°F
55°F
[13°C]
[13°C]
40°F
40°F
[4°C]
[4°C]
65°F
65°F
[18°C]
[18°C]
diverting
diverting
valve
valve
Figure 49