Refrigeration Cycle - Carrier AquaEdge 19XR Series Start-Up, Operation And Maintenance Instructions Manual

REFRIGERATION CYCLE

The compressor continuously draws refrigerant vapor from the
cooler at a rate set by the amount of guide vane opening and motor
speed. As the compressor suction reduces the pressure in the cool-
er, the remaining refrigerant boils at a fairly low temperature (typ-
ically 38 to 42°F [3 to 6°C]). The energy required for boiling is ob-
tained from the water flowing through the cooler tubes. With heat
energy removed, the water becomes cold enough to use in an air
conditioning circuit or for process liquid cooling.
After taking heat from the water, the refrigerant vapor is com-
pressed. Compression adds still more heat energy, and the refriger-
ant is quite warm (typically 98 to 102°F [37 to 40°C]) when it is
discharged from the compressor into the condenser.
Relatively cool (typically 65 to 90°F [18 to 32°C]) water flowing
into the condenser tubes removes heat from the refrigerant and the
vapor condenses to liquid.
The liquid refrigerant passes through orifices into the FLASC
(Flash Subcooler) chamber (Fig. 6 and 7). Since the FLASC
chamber is at a lower pressure, part of the liquid refrigerant flashes
to vapor, thereby cooling the remaining liquid. The FLASC vapor
is re-condensed on the tubes which are cooled by entering con-
denser water. The liquid drains into a float valve chamber between
the FLASC chamber and cooler. Here the AccuMeter™ float
Fig. 6 — Refrigeration Cycle — 19XR(V) Single-Stage Compressor
valve forms a liquid seal to keep FLASC chamber vapor from en-
tering the cooler. When liquid refrigerant passes through the valve,
some of it flashes to vapor in the reduced pressure on the cooler
side. In flashing, it removes heat from the remaining liquid. The
refrigerant is now at a temperature and pressure at which the cycle
began. Refrigerant from the condenser also cools the oil and op-
tional variable speed drive.
The refrigeration cycle for a 19XRV chiller with two-stage com-
pressor is similar to the one described above, with the following
exception: Liquid refrigerant from the condenser FLASC chamber
linear float valve or orifice plate flows into an economizer at inter-
mediate pressure (see Fig. 7). As liquid enters the chamber, due to
the lower pressure in the economizer, some liquid flashes into a
vapor and cools the remaining liquid. The separated vapor flows
to the second stage of the compressor for greater cycle efficiency.
A damper valve located on the economizer line to the compressor
acts as a pressure regulating device to stabilize low load, low con-
densing pressure operating conditions. The damper will back up
gas flow and thereby raise the economizer pressure to permit
proper refrigerant flow through the economizer valve during those
conditions. The damper also is closed during start-up conditions to
allow the second stage impeller to start unloaded.
The subcooled liquid remaining in the economizer flows through a
float valve and then into the cooler.
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