THE PASTEURIZATION OF MILK 



Third: The tubular cooler is being used to a 

 considerable extent. In this form of cooler the 

 pipes through which the hot milk flow are en- 

 closed by other pipes, through which cold water 

 is forced in a direction opposite to the flow of 

 the milk. These coolers are exactly similar to 

 the tubular heaters illustrated in Figs. 7, 10, 

 and 11. 



This form of cooler is effective and rapid; it has 

 this advantage, that sterilization by steam under 

 pressure can be made complete. There is the same 

 difficulty in emptying the tubes which was noted 

 in describing the tubular heater and holder, and 

 whatever advantage there may be in exposing milk 

 to the air in order to get rid of bad odors, etc., is 

 absent from the tubular cooler. 



The regenerative principle is made use of in the 

 tubular heater and cooler, as already described, 

 and there is little danger of the milk becoming 

 contaminated by leakage of the water, since the 

 joints of the water pipes do not come in contact 

 with the joints of the milk pipes. 



One of the most efficient forms of apparatus to 

 use from the point of view of economy of heat 

 units is probably that shown in Fig. 11. The 

 162 



