HARVESTING AND MARKETING 179 



in the condenser coils ; third, in its evaporation to a 

 •gas in the cooHng or refrigerator coils; fourth, in its 

 absorption by the weak aqua ammonia in the absorber ; 

 and fifth, the ammonia Hquor is piped to the still and 

 redistilled. 



"There are three general methods of producing the 

 desired temperatures in cold-storage rooms, and these 

 are known as the direct-expansion, the brine- 

 circulating, and the indirect or air-circulating sys- 

 tems. All three systems may be used in a cold-storage 

 plant, and in a given room or compartment the air- 

 circulating system is sometimes used in connection 

 with the brine or the direct-expansion systems. 



"In the direct-expansion systems, the liquefied gas 

 evaporates directly in the cooling refrigerator coils or 

 pipes which are placed in the refrigerator rooms. The 

 heat used in the evaporation of the gas is absorbed 

 from the room or from its contents, and the tempera- 

 ture is thereby reduced. The gas then returns to the 

 compressor in the compression system, or to the ab- 

 sorber in the absorption system, and after being dis- 

 tilled in the latter case begins the refrigerating cycle 

 anew. 



"In the brine-circulating system, the liquefied gas, 

 instead of evaporating directly in coils in the storage 

 room, evaporates in pipes surrounded by brine, or in a 

 brine cooler. The heat used in the evaporation of the 

 gas is absorbed from the brine rather than from the 

 room and its contents, as in the direct-expansion sys- 

 tem. The cold brine is then pumped to coils in the 

 storage room and the heat of the room and its con- 

 tents is absorbed by the cold brine. The warm brine 

 is then returned to the tank or cooler from which it 

 started and is recooled. while the gas returns to the 



