APPLICATION OF BEFBIGEEATION TO HANDLING OF MILK. 



43 



BRINE-CIRCULATING SYSTEM. 



Iii this system the coils of pipe in which the refrigerant is expanded 

 are located in a tank or specially designed brine cooler containing a 

 solution of common salt, or calcium chlorid, of sufficient density to 

 insure a low freezing point. After the brine has been reduced to a 

 low temperature by the transfer of its heat to the expanding refriger- 

 ant, it is pumped through coils of pipe located in the room to be cooled, 

 absorbing from the atmosphere a good part of its heat. It is then 

 returned to the brine tank, or brine cooler, where it is recooled and 

 again circulated through the rooms. 



While the direct-expansion system is simple to operate, less expen- 

 sive to install, and more efficient from the standpoint of heat transfer, 

 nevertheless in the operation of small plants, applicable to the dairy 

 industry where the plant proper is operated perhaps six or eight 

 hours per day, it is more economical to install a brine system, in order 



*-©W f*f?£SZURF H/aH PRFSSuRt 



Ft£ffHOt£f?ATOii 



Fig. 20. — Elementary diagram of brine circulating system. 



that some work of refrigeration may go on after the plant is shut 

 down for the day, or in case of accident to the machinery. It is only 

 necessary in the brine-circulating system to operate the brine pump 

 for forcing the brine through the coils. The principles of this system 

 are illustrated in figure 20. In addition to the usual members 

 shown in the direct-expansion system, this system employs a brine 

 tank, a series of brine coils, and a brine pump for circulating the 

 brine through the coils. The cooling effect of. the evaporating 

 refrigerant is expended in the brine in this case, instead of directly in 

 the cooling room, as indicated in the direct-expansion system, and 

 the brine is circulated by the pump through the brine coils located in 

 the cooling room. It should be borne in mind, however, that there 

 is a double transfer of heat which cuts down the efficiency of the 

 system to a certain extent, namely, from the air in the cooling room 

 to the brine and from the brine to the expansion coils. The initial 



