FRUIT STORAGE 105 
Mechanical Refrigeration.—Space and time will not 
permit going into this subject in detail, but it seems best 
to give a general idea of how cold storages are oper- 
ated under the mechanical systems. Of these there are 
two general types: the first and older one is known as 
the air compression system. This was originally installed 
on ocean steamships where large quantities of stored 
food products had to be carried. It consisted simply of 
compressing the air under pressure until the heat was re- 
moved and then discharging it direct into the storage 
room. As the air expands, heat is taken up from the 
room, thereby keeping the temperature lowered. 
This method is still in use in some places but has 
largely been discarded because of the high cost of oper- 
ation. The other method, and the one now in most 
common use, is the ammonia compression system. In 
this an ammonia solution is used because it will liquify 
under much lower pressure than air. Large costly ma- 
chinery of special make is required to operate such a 
system. 
Ammonia Compression System'.—‘‘The production 
of cold by this system is accomplished by the expansion 
or evaporation of liquid anhydrous ammonia. The sys- 
tem consists of three essential parts, the compressor, 
the condenser, and the expansion coils. 
The Compressor.— ‘The compressor is a pumping 
engine especially designed to compress the ammonia gas 
and force it through the pipes of the condenser, under a 
pressure, varying according to the temperature of the 
condensing water from 150 to 185 pounds per square 
inch, 
1 Remington Machine Company, Wilmington, Del. 
