COOLING HOT-BOTTLED PASTEURIZED MILK. 25 
B. T. U. extracted from wood, 198X0.5 (79.0-43.3) = 2,534 
B. T. U. extracted from iron, 198X0.113 (79.0-43.3) = 799 
75, 261 
B. T. U. through walls of box, 296X4(70-58)2,47 = _, 462 
24 
73, 799 
The foregoing figures indicate that 12 per cent more heat was taken 
out than the material gave up, which, of course, is impossible; hence 
it is believed that the Pitot-tube readings were wrong, as the weight 
and temperature of the material were carefully determined and are 
believed to be correct. On the other hand, if the anemometer read- 
ings of air velocities are taken and calculations made with them as 
a basis, the two sets of calculations balance within 2 per cent. In 
other words, 98 per cent of the heat given up in cooling the liquid, 
glassware, and crates is accounted for in the heat balance, showing 
that all our observations were practically correct. With this, then, 
73 790 
as a basis, the total amount of refrigeration performed was ' = 
2oo ,000 
0.26 ton, or at the rate of 0.106 ton an hour. The horsepower input 
qo y on 
to the motor = 7ztfi =2.6. The efficiency of the motor, how- 
ever, was not determined, but in view of the fact that it was designed 
for a voltage of 120 and was operated at a voltage of only 98, its 
efficiency was necessarily low. Under the operating conditions, and 
assuming a cost of 6 cents a kilowatt hour for electric energy, the 
cost of power per ton of refrigeration was $1.11. When the air supply 
is colder, the time required to cool the milk is, of course, shorter; 
hence the cost of power is decreased. The over-all efficiency of a 
direct-connected blower set of this size and type when operated under 
normal service conditions should be about 40 per cent, but under our 
conditions it was only about 22 per cent; hence the cost of power for 
cooling in these experiments is considerably greater than it should 
be in a commercial plant. If the over-all efficiency of the blower 
set is assumed to be 40 per cent, then the total cost of electric energy, 
under the conditions mentioned above, and at a cost of 6 cents a 
kilowatt hour, would be only about 66 cents a ton of refrigeration. 
As the blower set used in these experiments was operated very 
inefficiently, the cost of cooling is not typical of this method. The 
figures obtained do serve, however, to show that the cost of cool- 
ing by means of circulating cold outside air is very small. Of course, 
this can not be done throughout the year, but in a great many locali- 
ties cooling may be accomplished by circulating cold outside air 
through the refrigerating rooms during several months of the year. 
In summer the air would have to be cooled artificially. This, how- 
ever, is being done in a large number of milk plants which cool the 
air in a separate coil room and circulate it through the milk-storage 
