TM 5-3805-291-23-1
THEORY OF OPERATION - CONTINUED
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AIR CONDITIONING SYSTEM - CONTINUED
General
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1.
The orifice tube system uses an orifice tube in place of the expansion valve. The accumulator and the inline dryer with
orifice tube replace the receiver/dryer.
2.
The orifice tube assembly is located in one end of the inline dryer. The inline dryer is located in the line that goes from
the condenser coil to the evaporator coil.
3.
The desiccant is located in the inline dryer. The accumulator is located in the line that extends from the evaporator coil
to the compressor. The orifice tube assembly is before the inlet of the evaporator coils.
N OT E
The orifice tube systems do not have a sight glass for determining whether the system is low on refrigerant.
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Orifice Tube
427-C1999
1.
The orifice tube assembly has a plastic body, two screens, and a small brass tube located in the center of the body. The
O-ring seals are positioned on the body of the orifice tube to seal against leakage. The orifice tube assembly is contained
in the dryer. The orifice tube assembly is used in place of the thermostatic expansion valve.
2.
The orifice tube assembly changes the refrigerant from a high pressure and high temperature refrigerant into a low pres-
sure and low temperature liquid. The orifice tube has a restriction. The restriction in the orifice tube assembly allows the
liquid refrigerant to be reduced from a high pressure to a low pressure. The flow rate is controlled by pressure differ-
ences across the orifice. The flow rate is also controlled by the temperature of the liquid refrigerant in the bottom of the
condenser. The flow rate is sensitive to temperature and pressure differences. The flow rate is more sensitive to temper-
ature differences.
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