Refrigeration 



151 



57. The manufacture of ice. This method is impracti- 

 cable in refrigerating on a large scale, as in cold storage. Other 

 methods have been devised and are now generally utilized for 

 this purpose and for the manufacture of ice. 



A study of an ice-making machine will explain also the im- 

 portant facts involved in current refrigerating machines. The 

 diagram (Fig. 42) presents the essential features of one type 



Tanks of fresh water to be frozen 



FIG. 42. A diagrammatic representation of an ice machine, 

 step from the compressor to the product. 



Explain each 



of ice-making machine. The machine comprises a compressing 

 pump, a coil of pipe immersed in running water for condensing 

 the compressed ammonia gas, and a cooling or evaporating coil 

 of pipe immersed in a reservoir of brine. The metal boxes or 

 tanks of distilled 'water are placed in the tank of brine, where 

 they are frozen. 



The compressor, driven by an engine or dynamo, compresses 

 the ammonia gas, and pumps it into the pipe leading to the 

 condenser. The pressure employed in any particular plant 

 is determined by the temperature of the water for the condenser, 

 and by the temperature needed in the cooling or refrigerating 



