APPLICATION OF REFEIGEEATION TO HANDLING OF MILK. 

 METHODS OF UTILIZING REFRIGERATION. 



41 



There are two distinct methods of utilizing refrigeration, namely, 

 the direct expansion system and the brine system. 



DIRECT-EXPANSION SYSTEM. 



The coils of pipe in which the refrigerant is evaporated or 

 expanded are placed directly in the room to be cooled; the heat 

 necessary for the evaporation of the liquid refrigerant is, therefore, 

 absorbed directly from the air, or whatever substances surround the 

 tubes. The diagrammatic arrangement in figure 19 shows, in an 

 elementary form, the commercial direct-expansion system. With a 

 system of this kind the work of refrigeration practically ceases as 

 soon as the plant is shut down; consequently it becomes necessary, in 



STEfKCI COILS 



COLO WATER COILS 





Fig. 18. — Diagrammatic arrangement showing equipment common to both the compression and 

 absorption systems of refrigeration. 



most cases, to run the plant continually or take the risk of losing the 

 goods in storage. 



For economical operation the suction pressure and evaporating 

 temperature should be as high as possible. The suction pressure is 

 governed by the temperature desired in the refrigerator. In milk 

 plants, creameries, and dairies the suction pressure with an ammonia 

 system should be about 15.67 pounds gage and a consequent gas 

 temperature of 0° F. 



Take, for example, a creamery cold-storage room 10 by 10 by 10 

 feet inside dimensions, which is of sufficient capacity to hold a week's 

 output of butter from a creamery making 2,000 pounds daily. For 

 the sake of simplicity, only the storage of butter is considered. It is 

 assumed that the average outside temperature of the room is 75° F. 

 and the inside temperature is to be maintained at 32° F. while the 



