1-17
1.8 REFRIGERATION
The Model 3900 utilizes a cascade refrigeration system to cool the fluid circulating in the
saturator assembly.
1.8.1
Saturator Refrigeration
Reference Drawing 95S39917
The saturator fluid system is cooled by two hermetic refrigeration systems in cascade. The
high stage refrigeration utilizes Refrigerant 134A. This refrigerant is compressed from a low-
pressure vapor into a high-pressure vapor by compressor C1. The high-pressure vapor flows
to the air-cooled condenser CON1 where it is cooled to a high-pressure liquid as heat is
removed. The condensed refrigerant passes through the filter-drier FD1 to the thermostatic
expansion valve V3. Refrigerant is metered into the interstage cooler CON2, heat is
removed, and the heat laden vapor is piped back to the compressor and the cycle is repeated.
The low stage refrigeration system utilizes Refrigerant 23, which has a boiling point of
-81.4 °C. The refrigerant is compressed from a low-pressure vapor to a high-pressure vapor
by compressor C2. The high-pressure vapor flows through the oil separator OS1 to the
interstage cooler CON2 where heat is removed as it is cooled to a high-pressure liquid. Upon
demand, refrigerant is admitted through solenoid valve SOL5 to the capillary tube where it is
metered into the saturator fluid heat exchanger/R
-23 evaporator EX1. The refrigerant
expands and changes to a low-pressure vapor as it absorbs heat from the saturator fluid
circuit. The vapor is then piped back to the suction side of the compressor and the cycle is
repeated.