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TRG-TRC010-EN 43
period five
Application Considerations
notes
Three types of heat-recovery chillers are commonly available:
The dual-condenser, or double-bundle, heat-recovery chiller contains a
second, full-size condenser that serves a separate hot water loop. It is capable
of more heat rejection and higher leaving-water temperatures. This type of
chiller allows the amount of heat being rejected to be controlled, although
chiller efficiency is sacrificed for higher hot water temperatures.
Similarly, an auxiliary-condenser heat-recovery chiller makes use of a
second, smaller condenser bundle. It is not capable of rejecting as much heat as
the dual-condenser chiller. Since its leaving-water temperatures are also lower,
it is typically used to preheat returning hot water before it goes to the primary
heating equipment or to preheat incoming water prior to entering a traditional
water heater. It requires no additional controls and actually improves chiller
efficiency.
A heat-pump chiller is a standard chiller (no extra shells are required) applied
where the useful heat transfer occurs in the condenser, not the evaporator. The
evaporator is connected to the chilled water loop, typically upstream of other
chillers, but it only removes enough heat from the chilled water loop to handle
the heating load served by the condenser water loop. This application is useful
in a multiple-chiller installation, where there is a base or year-round comfort or
process load, or where the quantity of heat required is significantly less than
the cooling load. Chiller efficiency is not compromised.
heat-recovery
(dual) condenser
auxiliary
condenser
◆ No extra
condenser
◆ Large base heating
loads or continuous
operation
◆ High hot water
temperatures
◆ Controlled
◆ Chiller efficiency
preserved
◆ Second, full-
size condenser
◆ Large heating
loads
◆ High hot water
temperatures
◆ Controlled
◆ Degrades
chiller efficiency
◆ Second, smaller
size condenser
◆ Preheating loads
◆ Moderate
hot water
temperatures
◆ Uncontrolled
◆ Improves chiller
efficiency
heat pump
Heat-Recovery Chiller Options
Figure 59
trgtrc010_book.book Page 43 Wednesday, September 1, 1999 10:42 AM