APPLICATION OF REFRIGERATION TO HANDLING OF MILK. 
43 
BRINE-CIRCULATING SYSTEM. 
In 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 
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FlG. 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 tha 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 
