APPLICATION OP REFRIGERATION TO HANDLING OF MILK. 77 



Bra = temperature range of milk. 



(7= capacity of compressor used for cooling milk. 



Hm = hours required for cooling milk. 



Kb = temperature range of brine. 

 Taking the values in the case under consideration and substituting 

 in the above formula and solving for the number of cubic feet of 

 brine, we have : 



rp (8,600X43) -(12,000X7.5X2) 011 ,. , 



1 = — ,»» w-i r = 211 cubic leet 



bO X 15 



During the 16-hour shutdown period the heat that will come 



through the walls, floor, and ceiling will be '—^ =84,224 



B. T. U., then 219.6 cubic- feet of brine will absorb in rising 1 degree 



219.6x52 = 11,419 B. T. U., or the temperature of the brine will 



rise during the 16-hour shutdown period, disregarding the milk in 



84,224 „ , , 

 storage, .,,' ,, =7.4 degrees. 

 & ' 11,419 to 



A cubic foot of milk in rising 1 degree will absorb about 61 B. T. U. 



Therefore the milk in storage, disregarding the brine, would rise 



. 84,224 in K , 

 only 8052 = 10 - 5 Agrees. 



Considering both the brine and milk, a cubic foot will absorb 

 132X61+219.6X52 



132 + 219.6 



55.4 B. T. U., and the rise in temperature will 



84 224 

 be „_-. ' — =£-. =4.3 degrees during the 16-hour shutdown period. 



Had the refrigerating machine been of sufficient capacity to have 



cooled the milk through the required range of temperature in the 



two hours it took to pasteurize, the size of the machine necessary 



351 310 X 24 

 would have been — — ' =14.6 tons. A machine of this size 



Z X 2oo,(J(J(J 



would, therefore, be idle most of the time, and as the initial cost of the 

 larger machine and equipment would be a great deal more than the 

 smaller one, it would be poor economy to install the larger machine. 

 When either the "flash" or " holder" process of pasteurization is 

 employed, the temperature of the milk is generally first lowered to 

 approximately 75° F. by water from the city mains or from wells; con- 

 sequently the refrigerating machine has only to lower the tempera- 

 ture of the milk from the temperature at which it leaves the water 

 section of the cooler to the temperature attained in the storage room. 



RAW-MILK PLANTS. 



In raw-milk plants it is only necessary to cool the milk from the 

 temperature at which it is received, say 60° F., to a final tempera- 

 ture of approximately 32° F. It is usually pumped directly from the 



