COOLING, STORING, AND SHIPPING MILK. 



of water at an initial temperature of 37° F. The weight of the can 

 containing the milk is taken at 21 pounds and its temperature is 

 approximately that of the milk, 85° F. The weights of the water, 

 milk, and can are 250, 86, and 21 pounds, respectively, and their 

 specific heats are 1, 0.93, and 0.113, respectively. Substituting these 

 in the formula above and solving for the final temperature of the 

 whole, we have : 



. _ (250X1X37) + (86X0.93X85) + (21X0.113X85) _ 16252 = 409° F 

 (250X1) + (86X0.93) + (21X0.113) 332.4 



In practice, however, some heat is absorbed in the surrounding air 

 so that the final temperature of milk and water is higher than that 



/Zetf^O/f^ a/re/ ^7/=72?7? 



Fig. 1.- 





P^ 



-Initial and final temperature of milk and water in a concrete-insulated cool- 

 ing tank. 



given in the formula. In other words, the final temperature as 

 calculated must be divided by the per cent efficiency of the tank. The 

 efficiency of a good insulated tank of the size and construction of 

 that shown in figure 1 was found to be about 97 per cent. The final 

 temperature of the milk and water will, consequently, be 48.9 divided 

 by 0.97 or 50.4° F. 



Ice is usually necessary in order to lower the temperature of water 

 to a point at which it will cool milk quickly and efficiently. One 

 pound of ice has many times the cooling capacity of an equal weight 

 of water at an initial temperature of 37° F. To change the tempera- 

 ture of 1 pound of water 1 degree requires the addition or extraction 

 of only 1 B. t. u. To freeze 1 pound of water, however, requires the 



