COOLIISTG HOT-BOTTLED PASTEUEIZED MILK. 33 



the addition of the bunker and heating coUs. The crates were stacked 

 in the box as shown, and the air was' forced by the fan from the 

 heating-con bunker into the top of the box, down through the stack 

 of crates, and out at the bottom. The floor of the box was made 

 practically air-tight around the crates, so that the hot air necessarily 

 had to flow through the crates and around the bottles in its passage 

 from the box. 



In figm-e 17 it wiU be noted that the galvanized piping for air was 

 so arranged r^t by manipulating dampers a closed hot-air circuit 

 would be maintained for heating, or cold air from the outside could 

 be admitted to the box for the purpose of cooling. By closing the 

 dampers in uilet pipe G and outlet pipe B and opening the damper in. 

 pipe E a closed hot-air circuit would be maintained in which the 

 fan A would draw the hot air from the bottom of the box and force 

 it upward around the heating coils and into the top of the box 

 through the opening H, thence downward through the crates. 



After heating the liquid to the desired point, the steam supply was 

 cut off, the dampers were reversed, and cold outside air admitted to 

 the box for cooling; that is, the dampers in pipes G and .B were 

 opened, and the one in pipe E closed. Then cold air from the out- 

 side was drawn in by the fan A, forced up through the heating coils 

 and into the box through the opening H, thence downward through 

 the crates, and outside through the pipe B. The heating coils were so 

 arranged that the number of coils could be varied, thus making it 

 possible to regulate the amount of heat in the box. The steam pres- 

 sure and the amount of condensed steam from the coils were recorded 

 during the experiments. 



RESULTS OF HEATING FROM BOTTOM UPWARD. 



Before the equipment was arranged as shown in figure 17, the 

 heating coils were placed in the bottom of the box, under the plat- 

 form, and the air was forced by the fan around the coils and upward 

 througli the stack of crates, leaving the box near the top. After the 

 liquid was heated to the desired point, cold air for cooUng was blown 

 downward tlirougli the crates. The results obtained under these 

 conditions are shown by the curves in figure 18. It will be seen that 

 there was a wide variation in the temperatures of bottles at different 

 parts of the stack. 



After heating there was an average difference of 16° F. (8.9° C.) 

 between the top and bottom quarts of milk, and a maximum differ- 

 ence of about 30° F. (10.7° C.). This variation in temperature is 

 considered too great for satisfactory pasteurization, as certain bottles 

 will be overheated while others will not be heated to the required 

 point; furthermore, there is a variation in temperature of from 10° 



