COOLING HOT-BOTTLED -PASTEURIZED MILK. 



19 



TEMPERATURE VARUTIONS IN QUART BOTTLES OF MILK AND WATER 

 UNDER VARYING CONDITIONS. 



A differential thermocouple was placed in a quart bottle of milk, 

 another in one of water, and the difference in temperature at the top 

 and bottom of the bottles noted under varying air conditions and 

 directions of flow. One of the junctions of the differential couple 

 was placed about one-half inch above the bottom while the other was 

 placed in the top just beneath the surface of the liquid when the latter 

 was cooled, both being in the center line of the bottle. 



The curve in figure 14 shows graphically the difference in tempera- 

 ture between the top and bottom of a quart bottle of milk when 

 cooled by an air blast from the bottom of the stack. The average 

 temperature of the cold-air supply was 39.4° F. (4.1° C), and the 































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TiMe- MiNu-res. 



Fig. J 2. 



Cooling by forcing air from top downward.— Difference in temperature of Ijottles at different 

 positions in stack. 



velocity at which the air was blown up through the stack was 1,625 

 feet a minute. When the fan was started there was a difference of 

 about 8° F. (4.4° C.) in temperature between the top and bottom of the 

 bottle; 22 minutes later the difference had increased to about 23° F. 

 (12.8° C). Upon standing for a few minutes the bottom layers of 

 milk will naturally be the colder, and with the same source of cold 

 applied to the bottom of the bottle the difference in temperature will 

 of course b<i increased, owing to llio absence of convection currents 

 in the milk itseif. Tlx* rapidity with which the cooling go(is on tends 



