Carrier Transicold X4 7300, Руководство по эксплуатации и обслуживанию

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2.3.9 Condenser Coil
The condenser coil is a microchannel type and acts as
a heat exchanger in which the compressed refrigerant
gas is lowered in temperature and condensed into a
liquid. A portion of the condenser coil is occupied by
the subcooler, which removes heat from the refrigerant
liquid leaving the receiver. Air movement over the con-
denser/ subcooler/radiator is provided by a belt driven
fan mounted in the condensing section.
2.3.10 Heat Exchanger
The heat exchanger is the compact braze plate type
and is installed in the main suction line and liquid line.
The suction gas is used to cool the warm liquid refriger-
ant within the heat exchanger. This results in greater
system efficiency. The heat exchanger is locates below
the condenser coil on the curb side.
2.3.11 Ambient Air Temperature Sensor (AAT)
The AAT is a thermistor type sensor that provides con-
trol system with condenser entering air temperature
information to be displayed, recorded in the DataLink
data recorder and used to control the refrigeration sys-
tem. The sensor is located behind the front grill.
2.3.12 Solenoid Valves
Flow of refrigerant though the refrigeration system (refer
to
Section 2.12 and Section 2.13 ) is controlled by sole-
noid valves. Solenoid valves are electronic valves that
may be opened and closed (energized and de-ener-
gized) by the control system as required by the operat-
ing conditions. The solenoid valves include the
Condenser Pressure Control Solenoid Valve (SV1, item
4
Figure 2.1 ), Liquid Line solenoid Valve (SV2, item 12)
and the Hot Gas Solenoid Valve (SV4 item 11).
2.3.13 Filter-Drier
The filter-drier is a cylindrical shell containing a drying
agent and filter screen. It is installed in the liquid line
and functions to keep the system clean and remove
moisture from the refrigerant.
2.3.14 Receiver
Liquid refrigerant from the condenser flows into the
receiver. The receiver serves as a liquid reservoir when
there are surges due to load changes in the system; as
a storage space when pumping down the system and
as a liquid seal against the entrance of refrigerant gas
into the liquid line.
The receiver is provided with two bull’s-eye sight
glasses, for the observation of liquid level & moisture
content, and a fusible plug.
2.3.15 AutoFresh Air Exchange
As perishable products respire, they consume oxygen
(O
2
) and give off carbon dioxide (CO
2
). This will even-
tually cause the atmosphere within a refrigerated com-
partment to have higher levels of CO
2
and lower levels
of O2. This may adversely affect the shelf life of some
sensitive perishable products. When transporting these
products, it may be desirable to maintain normal atmo-
spheric conditions (prevent the build up of CO
2
and the
depletion of O
2
) by using fresh air exchange, in addi-
tion to accurate temperature control. The AutoFresh Air
Exchange (item 32,
Figure 2.2 ) controls the amount of
fresh air entering the refrigerated compartment without
the need for manual intervention while in transit. AutoF-
resh Air Exchange can also be used to lower the
humidity level within a refrigerated compartment if the
ambient air has a lower humidity level.
AutoFresh Air Exchange is a factory-installed option,
as it requires a modified evaporator pod. It is located at
the upper curb side door. When air is being exchanged,
two air ports open. The upper port allows fresh ambient
air to enter while stale air exits through the lower port.
2.4 EVAPORATOR SECTION
The evaporator (See Figure 2.3 ) fits into a rectangular
opening in the upper portion of the front wall of the
refrigerated compartment. When installed, the evapo-
rator section is located inside the compartment, and
the condensing section is outside.
The evaporator assembly consists of an evaporator
coil, evaporator fan, evaporator expansion valve, evap-
orator outlet pressure transducer, evaporator outlet
temperature sensor, defrost termination temperature
sensor, supply temperature sensor and return air tem-
perature sensor.
2.4.1 Evaporator Coil
The evaporator is a tube in fin type. The operation of
the compressor maintains a reduced pressure within
the coil. At this reduced pressure, the liquid refrigerant
evaporates at a temperature sufficiently low enough to
absorb heat from the air.
Heating is accomplished by circulating hot gas directly
from the compressor discharge to the evaporator coil.
Solenoid valves control the refrigerant flow to operate
the heating/cooling system.
Automatic evaporator coil defrosting is initiated by
either a defrost air switch (DAS − which senses the
pressure drop across the coil) or by the control system
defrost timer. During defrost the system is in the Heat
Mode, and the clutch is de-energized to stop the evap-
orator fan.
2.4.2 Evaporator Expansion Valve (EVXV)
The EVXV is an automatic device which controls the
flow of liquid to the evaporator according to changes in
superheat of the refrigerant leaving the evaporator. The
expansion valve maintains a relatively constant degree
of superheat in the gas leaving the evaporator regard-
less of suction pressure. The valve has a dual function
- automatic expansion control and prevention of liquid
return to the compressor. The valve is located in the liq-
uid line at the entrance to the distributor.