MECHANICAL REFRIGERATION 8l 



I 1/2 gallons at 60° F. per minute per ton of refrigeration. The 

 amount of ammonia used should not exceed one twentieth of a 

 pound per ton of ice manufactured in an economically operated 

 plant. 



Cost of Making Ice. — The cost per ton for manufacturing 

 ice is nearly double that for refrigeration per ton. This is due 

 to the fact that, in ice making, the water must first be cooled to 

 freezing point, and, after being frozen, the ice must be cooled 

 still lower until it reaches the temperature of the surrounding 

 brine. 



It is often claimed that natural ice will yield a greater amount 

 of refrigeration than artificial ice. There should be absolutely 

 no difference if both are properly frozen. In artificial ice made 

 from raw water, the cake of ice often has a reddish or, in some 

 cases, a milky or cloudy core through the center. The former 

 is due to iron; the latter is due to carbonates and sulphates of 

 calcium and magnesia. The discoloration may be overcome to 

 some extent by agitating the water with air during the freezing 

 process. 



ABSORPTION SYSTEM 



General Principles. — This system of refrigeration is based 

 on the fact that water has the power of absorbing various 

 vapors having a low boiling point, and that such vapors are 

 again readily separated from the water by heating the liquid. 



In reality, there is much similarity between the compression 

 system and the absorption system. Common to both are the 

 condenser and the expansion coils, including the brine tank and 

 the entire circulating system. In the absorption system there 

 is a pump, but no compressor. The generator, the ammonia 

 receiver, and the absorber are also important parts. In addi- 

 tion, we have the analyzer, the exchanger, the dehydrator, and 

 other parts of less importance which are added primarily to 

 make the system more complete in its operation. 



Operation. — This system may be operated without any 

 great amount of steam, the only steam required being that used 

 for the pump and the exhaust steam for the generator. 



