APPLICATION OF REFRIGERATION TO HANDLING OF MILK. 47 
CONGEALING-TANK SYSTEM. 
There is in use a modification of the brine-storage system known 
commercially as the " congealing-tank system." The principal 
advantage of this system is that by using a weak solution of brine 
a greater amount of refrigeration per cubic foot of brine is obtained 
by freezing a portion of the brine on the direct-expansion coils. 
This method, however, is not so efficient as the brine-storage system, 
due to the fact that the ice formed around the coils acts as an insula- 
tion. But the advantage gained in being able to store a greater 
amount of refrigeration in a small space often makes it advisable to 
install this system. In the operation of the conge aling- tank system 
care should be taken not to let the volume of brine in the tanks 
freeze solid, for during the hold-over period some of the brine ice will 
melt, leaving a space between the ice and the sides and bottom of the 
tanks, and when starting up the refrigerating machine the smaller 
space between the ice and sides of the tanks will freeze first; con- 
sequently when the larger volume of brine at the bottom freezes the 
sides of the tank will be bulged out, due to the expansive force of the 
freezing brine. Therefore, ample space between the coils and sides 
of the tanks should be provided in order to allow the requisite amount 
of brine ice to form around the pipe coils at a safe distance from the 
sides. When a part of the brine solution is to be frozen, the volume 
of brine required is necessarily less than that required for a brine- 
storage tank system of the same capacity. In practice about one- 
half the volume of the brine storage is allowed for the congealing- 
tank system. Therefore the case under consideration will require 
two tanks 8 feet long, 2\ feet deep, and 6 inches wide. The effective 
surface of the two tanks is 93 square feet. The heat absorbed by 
each square foot of surface per hour during shutdown period is 
^> 4QQ =23.1 B. T. U. Taking the coefficient of heat transmission 
C70 X 10 
in B. T. U. per degree difference in temperature as 1.5 per square foot 
per hour, the temperature difference necessary between the brine and 
air is -r-=- = 15.4 . 
1.0 
With a 15 per cent solution, by weight, of common salt the freezing 
point is 12.2° F. Then the temperature of brine at the time the plant 
is shut down will be 12.2°, and at the time of starting up 27.6°. One 
cubic foot of the brine will absorb 59.2 B. T. U. per degree rise in 
temperature, and for a 15.4° rise 59.2 X 15.4 = 91 1 B. T. U. The vol- 
ume of the two tanks is 20 cubic feet, consequently the heat absorbed 
by the brine will be 911X20 = 18,220 B. T. U., leaving 34,400- 
18,220 = 16,180 B. T. U., to be absorbed by brine ice. Taking the 
latent heat of the brine ice as 122, the amount of brine to be frozen 
on the coils will be ^j^ = 132 pounds. With 117 feet of submerged 
