196 DAIRY TECHNOLOGY 



the compressor to the expansion valve; the expansion 

 side from the expansion valve to the suction side of the 

 compressor, inclusive. 



Transferring the Cold. — The methods of transferring 

 the cold to the different places in the building vary. There 

 are two systems: 



1. Direct Expansion. 



2. Brine System. 



1. By the direct-expansion system the condensing 

 pipes of the system are extended to the room or place 

 at which the cooling is to be done. An extended set of 

 expansion coils then conveys the gas which absorbs the 

 heat. A lower temperature can be produced by this 

 method than with the brine system. 



2. In the brine system a large brine tank is placed 

 somewhere in the creamery or ice-cream plant at a place 

 most convenient with respect to cooling. This tank con- 

 tains a strong solution of brine. The chief reason why 

 brinC' is used in preference to water is that brine has a 

 very low freezing-point. This varies with different de- 

 grees of saturation. 



Either sodium chloride (common salt) or calcium chlo- 

 ride may be used for brine. The latter is considered best 

 chiefly because it is not so hard on the pipes, and it keeps 

 the brine pipes cleaner than does a salt brine. The follow- 

 ing tables give properties of brine made from these two 

 substances. 



The expansion coils pass through the brine tank and 

 cool the brine. Special pumps force the cold brine through 

 pipes to the cooling room, cream vat, cooling coils, ice- 

 cream freezer, etc. 



