92 



APPLIED SCIENCE 



93. Manufacturing of Ice. Ice-making and cold storage de- 

 pend upon the scientific principle that ammonia evaporates readily 

 and absorbs a great deal of heat in passing from a liquid to a 

 gaseous state. Apparatus for the manufacture of artificial ice con- 



FIG. 56. General Arrangement of Refrigerating Plant. 



sists of a large cylinder containing liquid ammonia. Attached to 

 the cylinder is a vat containing brine or salt water with coils 

 of pipes passing through from the cylinder which holds the liquid 

 ammonia. The ammonia flows from the cylinder to the coils. 

 The vat is filled with galvanized iron boxes, the size of an ordi- 

 nary cake of ice, and the boxes are filled with distilled water. A 

 pump exhausts air from the coils, which in turn causes the ammo- 

 nia to evaporate quickly. As the ammonia passes through the 

 coils the latter attract the heat from the surrounding bodies to the 

 extent of freezing the water. 



94. How the Gas is Condensed. The ammonia gas is 

 taken from the refrigerating section and compressed by a pump. 

 The ammonia starts from the compressor under, a high pressure 

 and temperature and passes to a cooling coil, which is the con- 



