APPLICATION OF REFRIGERATION TO HANDLING OF MILK. 39 
usually by allowing low-pressure steam to flow through coils of pipe 
located in the generator, as indicated in the diagram, and the ammonia 
gas is driven off under pressure through the pipe into the condenser C, 
where it is condensed to a liquid when cooled by the condensing 
water. The ammonia, now in a liquid state, flows through the expan- 
sion valve E into the vaporizer V, where it is evaporated, the heat 
required for its evaporation being absorbed from the brine surrounding 
the coils. The vaporization of the liquid ammonia is made possible 
by the low pressure which is maintained in the evaporator due to the 
rapid absorption of the anhydrous ammonia by the weak aqua 
ammonia in the absorber. The brine is circulated about the coils 
of the vaporizer and from thence through the coolers, where it in 
turn absorbs heat from the goods in storage. The vaporizer coils 
may, however, be located directly in the compartment whose tem- 
perature it is desired to lower, in which case it is termed a direct 
expansion system. From the vaporizer the ammonia, now in the 
gaseous state, flows through the pipe P into the absorber A, which 
contains a weak solution of ammonia. The absorption of the ammo- 
nia gas by the weak solution in the absorber generates heat, which 
is carried off by the cooling water which is circulated through coils 
located in the absorber. The strong liquor thus formed in the 
absorber is delivered to the generator by a pump through the outer 
space in the regenerator coil B. The weak liquor from the generator 
is transferred to the absorber through the inner coil of the regenerator; 
consequently the liquid entering the generator is thus heated while 
that entering the absorber is cooled. The function of the regenerator 
is, therefore, to economize heat by transferring the heat from the 
weak to the strong liquor. The weak liquor coming from the gener- 
ator, where it has been subjected to heat, goes into the absorber, 
where it is cooled by means of water circulation. The reverse is 
true in the case of the strong liquor; that is, the strong liquor comes 
from the absorber, where it has been cooled by water circulation, and 
goes into the generator, where it is heated. It is obvious that any 
heat transferred from the weak to the strong liquor represents just 
so much gain in economy. 
As the only power required by the absorption system is that 
necessary to circulate the various liquids, it is inconsiderable when 
compared with that required by the compression system. Usually 
the exhaust steam from the pumps furnishes sufficient heat from the 
operation of the plant. The amount of cooling water, however, 
required by this system is greatly in excess of that required by a com- 
pression plant of the same capacity. 
In practice, however, the vapor-absorption system of refrigeration 
is more complicated than shown in the elementary diagram. Figure 
