APPLICATION OF REFRIGERATION TO HANDLING OF MILK. 
27 
of the liquid is absorbed from the brine, which in turn is absorbed 
from the air by the brine. In this case there is a double transfer 
of heat, viz, from the air to the brine and from the brine to the 
evaporating liquid in the test tube. The cooling effect is assisted 
by the circulation within the brine itself, due to the difference in 
weight of the colder liquid in contact with the surface of the test 
tube, and that at a distance from it. The colder brine sinks to the 
bottom of the vessel and its place is taken by the warmer brine, 
thus producing a circulation as indicated by the arrows, whereas 
in the preceding case the heat from the surrounding air was absorbed 
directly by the re- 
frigerant . In view of 
the fact that it is im- 
practicable to lower 
the temperature of 
the brine to that of 
the refrigerant, the 
absorption of heat 
from the surround- 
ing air by the brine 
is not so rapid as 
when the air is in 
direct contact with 
the walls of the ves- 
sel as in the preced- 
ing case. Figure 11 
embodies the prin- 
ciples of the commer- 
cial brine-storage 
system of refrigera- 
tion, which will be 
discussed later. 
Going one step f ur- 
ther toward the 
practical application of artificial refrigeration, imagine an arrange- 
ment as shown in figure 12, where the test tube in the foregoing- 
illustration is replaced by a steel cask or drum, such as is commonly 
used for shipping ammonia, carbon dioxid, and other liquid gases, the 
tank corresponding to the beaker containing the brine. The liquid in 
the drum is underpressure, and if allowed to escape in a small stream 
through the throttling or expansion valve against atmospheric pres- 
sure it will evaporate in the coils located in the brine tank and the 
heat required for vaporization will be taken from the brine. If a 
pump were attached to the free end of the pipe the suction of the 
pump would tend to produce a vacuum, which action would accelerate 
Fig. 11. 
