Refrigeration Cycle - Carrier AquaEdge 23XRV Start-Up, Operation And Maintenance Instructions Manual

STANDARD
65 KAIC
CIRCUIT
BREAKER
OPTIONAL
100 KAIC
CIRCUIT BREAKER
(HANDLE SHIPPED
LOOSE INSIDE OF
CONTROL CENTER
FOR FIELD
INSTALLATION)
a23-1620
Fig. 9 — Standard and 100-KAIC Circuit Breaker Control Center (R Compressor Shown)

REFRIGERATION CYCLE

The compressor continuously draws refrigerant vapor from
the cooler. 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 liquid flowing through the
cooler tubes. With heat energy removed, the liquid becomes
cold enough for use in an air-conditioning circuit or process
liquid cooling.
After absorbing heat from the chilled liquid, the refrigerant
vapor is compressed. Compression adds still more energy, and
the refrigerant is quite warm (typically 90 to 130 F [32 to
54 C]) when it is discharged from compressor into condenser.
Relatively cool (typically 65 to 85 F [18 to 29 C]) liquid
flowing into the condenser tubes removes heat from the refrig-
erant and the vapor condenses to liquid, refrigerant.
For heat exchangers frame sizes 3-5, the liquid refrigerant in
the condenser passes through orifices into the FLASC (Flash
Subcooler) chamber (Fig. 10). 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 condens-
er liquid. The liquid then passes through a float valve assembly
which forms a liquid seal to keep FLASC chamber vapor from
entering the cooler.
Heat exchanger frame sizes A and B incorporate a sensible
subcooler instead of the FLASC, and the liquid seal and throt-
tle level control are performed by an electronic expansion
valve instead of a float valve. See Fig. 11.
An optional economizer can be installed between the
condenser and cooler. Pressure in this chamber is intermediate
between condenser and cooler pressures. At this lower pres-
sure, some of the liquid refrigerant flashes to gas, cooling the
remaining liquid. For heat exchanger frame sizes 3-5, an in-line
orifice on the economizer drain flange meters the refrigerant
liquid into the cooler. For size A and B heat exchangers, the
flash gas to the compressor is produced in a brazed plate heat
exchanger where some of the condenser liquid prior to throt-
tling is diverted through the economizer electronic expansion
valve (EXV). The EXV control logic is based on economizer
saturated temperature, superheat and compressor speed. The
flash gas, having absorbed heat, is returned directly to the com-
pressor at a point after suction cutoff (Fig. 12 and 13). Here it is
mixed with gas from the suction cut-off point to produce an in-
crease in the mass flow of refrigerant transported and com-
pressed without either an increase in suction volume or a
change in suction temperature.
13