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TRG-TRC010-EN 9
period one
Components
notes
As the load decreases, less refrigerant moves through the chiller and the level
of the liquid column drops. Now, as the liquid refrigerant passes through the
orifice plates, it only undergoes a pressure drop equal to the lower head (H
2
)
before some of it flashes to vapor. This causes additional flashing at the orifice
plate which, in turn, feeds less liquid to the evaporator.
Other types of expansion devices found in centrifugal chillers include: float
valves, expansion valves (thermostatic or electronic), and variable orifices.
Economizer
An economizer can be used in conjunction with multiple expansion devices to
improve the efficiency of a multistage chiller. In a chiller with a 2-stage
compressor, the expansion process can be separated into 2 steps with an
economizer chamber between.
expansion device
Orifice Plates
H
H
2
2
to
to
evaporator
evaporator
orifice plates
orifice plates
Figure 14
2-stage chiller
Economizer
refrigerant vapor
refrigerant vapor
to second stage
to second stage
of compression
of compression
liquid refrigerant
liquid refrigerant
to evaporator
to evaporator
orifice
orifice
liquid refrigerant
liquid refrigerant
from condenser
from condenser
Figure 15
trgtrc010_book.book Page 9 Wednesday, September 1, 1999 10:39 AM