Refrigeration Cycle - Carrier AquaEdge 19XR 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 cooler, the remaining refrigerant boils at a fairly low tem-
perature (typically 38 to 42°F [3 to 6°C]). The energy required
for boiling is obtained 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 re-
frigerant 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 flow-
ing 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 condenser water. The liquid drains into a float
valve chamber between the FLASC chamber and cooler. Here
the AccuMeter™ float valve forms a liquid seal to keep
Fig. 6 — Refrigeration Cycle — 19XR(V) Single-Stage Compressor
FLASC chamber vapor from entering 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 re-
moves heat from the remaining liquid. The refrigerant is now
at a temperature and pressure at which the cycle began. Refrig-
erant from the condenser also cools the oil and optional vari-
able speed drive.
The refrigeration cycle for a 19XRV chiller with two-stage
compressor is similar to the one described above, with the fol-
lowing exception: Liquid refrigerant from the condenser
FLASC chamber linear float valve or orifice plate flows into an
economizer at intermediate pressure (see Fig. 7). As liquid en-
ters 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 compres-
sor 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 condensing 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.
11
a19-
1550tf