COOLING HOT-BOTTLED PASTEURIZED MILK. 
9 
too slow for satisfactory operation on a commercial scale, and that 
with forced-air circulation it is necessary to have small containers, 
such as quart or pint bottles. In these experiments only a few bot- 
tles were cooled by natural circulation; if a large number had been 
stacked in piles the cooling process would have been even slower. 
RESULTS OF COOLING BY MEANS OF FORCED AIR. 
BY FORCING THE AIR FROM BOTTOM UPWARD. 
The experiments previously described were of a preliminary nature, 
and we shall now take up the cooling experiments performed on a 
30-crate basis. 
The cooling effect of cold air when forced through stacks of crates 
from the bottom is shown by the curves in figures 6 to 9, inclusive. 
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Fig. 5.— Cooling in still air compared with forced air.— Relative rate of cooling of 10-gallon cans of milk 
when placed in still and in moving air. Velocity of moving air 1,250 feet per minue. 
The results, shown graphically by the curves, have been selected on 
account of some special feature, the discussion of which follows 
immediately after each set of curves. 
All the experiments made with air entering at the bottom and flowing 
upward and around the bottles show a wide difference in temperature 
between pint and quart bottles occupying upper and lower positions 
in the stack, this temperature varying with the height of the par- 
ticular bottle from the bottom of the stack. The lower bottles, Over 
which the cold air first passed, of course cooled faster than the upper 
ones, and the rate of cooling decreased rapidly as the distance from 
the cold-air inlet increased. The temperatures were very accurately 
determined by means of thermocouples, which have already been 
55377°— Bull. 420—16 2 
