2-15
62-11863
d. Accumulator/Subcooler/Heat Exchanger
The accumulator is a refrigerant holding tank located in the suction line between the evaporator and compressor.
The purpose of the accumulator is to prevent entry of any liquid refrigerant into the compressor and further subcool
liquid refrigerant to TXV.
The tube-in-tank type heat exchanger is internal to the accumulator. Within the heat exchanger, the cold suction
gas is used to cool the warm liquid refrigerant. This results in greater system capacity and efficiency
Refrigerant vapor leaves the accumulator outlet pipe at a point well above any liquid level thus preventing the
entrance of liquid. The outlet pipe is equipped with an orifice that controls oil return to the compressor and prevents
accumulation of oil within the tank.
Figure 2.12 Accumulator/Subcooler/Heat Exchanger
e. Compressor Pressure Regulating Valve (CPR)
The CPR is an adjustable regulating valve that regulates the suction pressure entering the compressor. The suc-
tion pressure is controlled to avoid overloading the electric motor or engine during high refrigerated compartment
temperature operation.
f. Filter Drier
The filter drier is a cylinder shell containing a drying agent and screen. It is installed in the liquid line, and functions
to keep the system clean and remove moisture from the refrigerant.
g. Receiver
Liquid refrigerant from the condenser drains 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 equipped with two sight glasses for the observation of liquid level and a pressure relief valve.
2.5
REMOTE EVAPORATOR SECTIONS
The evaporator sections contain the evaporator coil, thermal expansion valve, heat exchanger, defrost termination
thermostat(s), electric heaters, hot gas solenoid valve, liquid solenoid valve, and electric evaporator fan motors.
2.5.1
Evaporator Coil
The evaporator coil is a tube-and-fin type. The operation of the compressor maintains a reduced pressure with the
coil. At this reduced pressure, the liquid refrigerant evaporates at a temperature low enough to absorb heat from
the air. Air movement over the evaporator coil is provided by two or three electric fans.
2.5.2
Thermal Expansion Valve (TXV)
The thermal expansion valve is an automatic device that controls the flow of liquid to the evaporator according to
changes in superheat to the refrigerant leaving the evaporator. The thermal expansion valve maintains a relatively con-
stant degree of superheat in the gas leaving the evaporator regardless of suction pressure. Thus, the valve has a dual
function
−
automatic expansion control and prevention of liquid return to the compressor.
2.5.3
Defrost Termination Temperature Sensor (DTS)
The DTS senses the temperature of the evaporator and allows defrost initiation once the temperature falls below
40°F (4.4°C)
To Compressor
To Compressor
From Condenser
From Evaporator
From Evaporator
To TXV
Summary of Contents for SUPRA 950Mt
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