CHAPTER XIX. 



MECHANICAL REFRIGERATION. 



In warm climates and in localities where ice is not 

 obtainable or only so at a high cost, cold may be produced 

 by artificial means known as mechanical refrigeration. 

 This system of refrigeration is also finding its way into 

 dairies that are able to procure ice at a moderate cost 

 but which are seeking more satisfactory means of control- 

 ling the temperature of their milk, cream and refrigerator. 

 Most of the mechanical refrigerating machines in use at 

 the present time belong to the compression type. What- 

 ever is said here, therefore, will pertain strictly to this 

 class of machines. 



Kig. 59 shows a desirable method of piping and also 

 illustrates the circulation of the ammonia. The milk and 

 cream are cooled with cold brine which is circulated by 

 means of a pump. No ice is needed. When an especially 

 low temperature of the brine is desired, as in making ice 

 cream, valves A' (Fig. 59) are shut oflf and valves B 

 opened, leaving all of the ammonia to circulate through 

 the brine tank. 



Principle of Refrigeration. The "principle employed 

 in mechanical refrigeration is the production of cold by 

 the evaporation of liquids which have a low boiling point, 

 like liquid ammonia, liquid carbonic acid, ether, etc. 



When a liquid evaporates or changes into the gaseous 

 state it absorbs a definite amount of heat called heat of 



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