NATURAL ICE S^-STEM 369 



feet of outside walls. The building should also be high in pro- 

 portion to width and length. This will tend to preser\-e the ice, 

 as proportionately less top surface is exposed to the air. 



The size of the building will vary according to (i) amount 

 of milk handled at the creamery, (2) whether ice is sold from 

 creamery, and (3) whether ice is used for any other purposes, 

 such as ice-cream freezing, cream shipping, etc. For creamery 

 uses, the only basis on which to estimate is the amount of milk 

 received. 



For example, suppose a creamery is receiving 12,000 pounds 

 of milk daily. This milk will produce about 2000 pounds of 

 cream and about 600 pounds of butter. Suppose that the 

 cream needs to be cooled from 90° F. down to 40° F. or a range 

 of 50° F. One pound of ice will cool about 142 pounds of water 

 1° F. Calculations are made with water as basis. The results 

 will thus be a little too high, but subsequent corrections will be 

 m^ade. If i pound of ice will cool 142 pounds of cream 1° F., 

 it will require 50 pounds of ice to cool that amount of cream 50° F. 

 By calculation from these figures we find that about 0.35 of a 

 pound of ice is required to cool each pound of cream 50° F. and 

 for cooling 2000 pounds of cream it will require 700 pounds. If it 

 takes 700 pounds of ice dailj- for coohng the cream for eight 

 months of the year, which is about the time the cream would have 

 to be cooled by artificial means, it would take 1 68, 000 pounds of 

 ice per year. As the specific heat of cream is only about 0.7, 

 the final amount needed for cooling the cream would be only 

 117,600 pounds, or about 59 tons. 



The next consideration is the ice needed for cooling the butter. 

 Roughly speaking, there will be about 6co pounds of butter. 

 Suppose the butter needs to be cooled 30° F. Granting that the 

 specific heat of butter is the same as that of water, it would 

 require 30 pounds of ice to cool 142 pounds of butter 30° F. 

 There wiU therefore be needed daih' 126 pounds of ice for cooling 

 the butter. As the specific heat of butter is only about 0.4, 

 51 pounds of ice are necessary daily. For eight months 12,240 

 pounds will be needed. The amount of ice needed in a refrigerator 

 above that needed for cooling the butter cannot be calculated. 



