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TM 9-8000
Figure 37-1. Refrigerant-12 Pressure-Temperature Relationship.
e. As the low-pressure refrigerant moves
pressures. For example, at a pressure of 30.1 psi (207.5
kPa), Refrigerant-12 boils at 32F (0C)
through the coils in the evaporator, it absorbs heat from
the airstream, therefore producing a cooling effect.
37-3.  Refrigeration Cycle. The refrigeration cycle
f. As the refrigerant nears the end of the coils in
(fig. 37-2) is a continuous closed-loop system. The
the evaporator, greater amounts of heat are absorbed.
refrigerant is pumped constantly through the components
This causes the low-pressure liquid refrigerant to boil
in the system. By changing the refrigerant pressure, and
and change to a gas as it exits the evaporator.
by removing and adding heat, the refrigeration cycle is
completed. The refrigeration cycle operates as follows:
g. The refrigerant then enters the compressor.
The pumping action of the compressor increases
a. The receiver drier collects high-pressure
refrigerant pressure, which also causes a rise in
refrigerant in a liquid form. Moisture and impurities also
are removed at this point.
h. The high-pressure, high-temperature gas
b. The refrigerant then is routed to the
then enters the condenser, where heat is removed by an
expansion valve through high-pressure lines and hoses.
outside ambient airstream moving over the coils. This
c. The expansion valve then reduces refrigerant
causes the gas to condense and return to a liquid form
pressure to the evaporator by allowing a controlled
amount of liquid refrigerant to enter it.
i. The high-pressure liquid refrigerant now
d. A stream of air is passed over the coils in the
enters the receiver again to begin another cycle. This
continuous cycle, along with the dehumidifying and
evaporator as refrigerant enters.
filtering effect, produce a comfortable atmosphere on hot


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