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CIRCULAR 74 0, U. S. DEPARTMENT OF AGRICULTURE 



terns for fruit refrigeration. The arrangement of blower and enclosed 

 brine-spray compartment in a brine-spray system are illustrated in 

 figure 5. 



UNIT-COOLER SYSTEM 



A modification of the brine-spray or the dry-coil bunker is the unit 

 cooler, which contains extended surface coils and blowers for moving 

 the air through the coils and discharging it to the room, as shown in 

 figure 6. Some are defrosted by a continuous brine spray, and in some 



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Figuee 5. — Arrangement of blower and enclosed brine-spray compartment in a 

 brine-spray system. Motor and brine pump for forcing the brine spray over 

 the enclosed evaporating coils are shown at left foreground. In this plant 

 the return air ducts end in the room containing this equipment. The cold-air 

 delivery ducts extend from the farther end of the bruie-spray compartment. 



the coils are washed periodically with fresh water to remove the frost. 

 In the latter case warm water from the condenser is generally used. 



These units usually discharge air at the top, either into ducts or 

 through nozzles, and return it to the coils through openings near 

 the floor. When the return air is picked up in the lower part of the 

 room, it is difficult to get the best distribution of temperatures. A 

 unit cooler installed with air ducts for a better distribution of refrig- 

 eration is shown in figure 7. 



When defrosting is intermittent, it is important to make the cycle 

 short enough to keep the coils fairly free from frost. A thin layer 

 of frost interferes with heat transfer just as on other types of coils 

 and also reduces the quantity of air circulated on account of the 

 close spacing of the cooling surface. 



