Trane CenTraVac Duplex CDHE, Руководство по эксплуатации и техническому обслуживанию

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CDHF-SVU01C-EN
10
General
Information
Cooling Cycle
Duplex Chillers have two refrigerant
circuits that operate as their own
independent circuits. These circuits
are discussed as individual chiller
refrigeration units in the following
discussion. The sequence of
operation of the two refrigeration
circuits is discussed in a later
section.
When in the cooling mode, liquid
refrigerant is distributed along the
length of the evaporator and sprayed
through small holes in a distributor
(i.e., running the entire length of the
shell) to uniformly coat each
evaporator tube. Here, the liquid
refrigerant absorbs enough heat from
the system water circulating through
the evaporator tubes to vaporize.
The gaseous refrigerant is then
drawn through the eliminators
(which remove droplets of liquid
refrigerant from the gas) and first-
stage variable inlet guide vanes, and
into the first stage impeller.
Note: Inlet guide vanes are designed
to modulate the flow of gaseous
refrigerant to meet system capacity
requirements; they also prerotate the
gas, allowing it to enter the impeller
at an optimal angle that maximizes
efficiency at all load conditions.
Compressor 1 or 2 (3 Stage)
Compressed gas from the first-stage
impeller flows through the fixed,
second-stage inlet vanes and into the
second-stage impeller.
Here, the refrigerant gas is again
compressed, and then discharged
through the third-stage variable guide
vanes and into the third stage
impeller.
Once the gas is compressed a third
time, it is discharged into the
condenser. Baffles within the
condenser shell distribute the
compressed refrigerant gas evenly
across the condenser tube bundle.
Cooling tower water circulated
through the condenser tubes absorbs
heat from the refrigerant, causing it to
condense. The liquid refrigerant then
passes through orifice plate ‘‘A’’ and
into the economizer.
The economizer reduces the energy
requirements of the refrigerant cycle
by eliminating the need to pass all
gaseous refrigerant through three
stages of compression. See Figure 3.
Notice that some of the liquid
refrigerant flashes to a gas because
of the pressure drop created by the
orifice plates, thus further cooling the
liquid refrigerant. This flash gas is
then drawn directly from the first
(Chamber A) and second (Chamber
B) stages of the economizer into the
third-and second-stage impellers of
the compressor, respectively.
All remaining liquid refrigerant flows
through another orifice plate ‘‘C’’ to
the evaporator.
Compressor 1 or 2 (2 Stage)
Compressed gas from the first-stage
impeller is discharged through the
second-stage variable guide vanes
and into the second-stage impeller.
Here, the refrigerant gas is again
compressed, and then discharged
into the condenser.
Baffles within the condenser shell
distribute the compressed refrigerant
gas evenly across the condenser
tube bundle. Cooling tower water,
circulated through the condenser
tubes, absorbs heat from the
refrigerant, causing it to condense.
The liquid refrigerant then flows out
of the bottom of the condenser,
passing through an orifice plate and
into the economizer.
The economizer reduces the energy
requirements of the refrigerant cycle
by eliminating the need to pass all
gaseous refrigerant through both
stages of compression. See Figure 6.
Notice that some of the liquid
refrigerant flashes to a gas because
of the pressure drop created by the
orifice plate, thus further cooling the
liquid refrigerant. This flash gas is
then drawn directly from the
economizer into the second-stage
impellers of the compressor.
All remaining liquid refrigerant flows
out of the economizer, passes
through another orifice plate and into
the evaporator.