PRINCIPLES OF REFRIGERATION. 13 



less mature condition. If the fruit, has been bruised, or is covered 

 with rot spores, the low temperature may retard but can not prevent 

 its premature decay. If there are inherent differences in the apples 

 due to the character of the soil, the altitude, and to incidental features 

 of orchard management, or variations due to the methods of picking, 

 packing, and shipping, the low temperature must not be expected to 

 obliterate them, but rather to retard while not preventing their normal 

 development. 



In general it is the function of the cold-storage warehouse to fur- 

 nish a uniform temperature of the desired degree of cold through its 

 compartments during the storage season. The warehouse is expected 

 to be managed in other respects so that the deterioration of the fruit 

 or any other injury may not be reasonably attributed to a poorly con- 

 structed and installed plant, or to its negligent or improper manage- 

 ment. The warehouseman does not insure the fruit against natural 

 deterioration; he holds it in storage as a trustee, and in that relation 

 is bound to use only that degree of care and diligence in the manage- 

 ment of the warehouse that a man of ordinary care and prudence 

 would exercise under the circumstances in protecting the goods if 

 they were his private property. 



If the temperature of the storage rooms fluctuates unduly from the 

 point to be maintained and causes the fruit to freeze to its injury, or 

 to ripen with abnormal rapidity, or if the management of the rooms 

 or the handling of the fruit in other respects can be shown to have 

 been faulty or negligent, the warehouse has failed to perform its 

 proper function. 



PRINCIPLES OF MECHANICAL REFRIGERATION. 



Refrigeration, or cold storage, as applied to warehouses, is usually 

 produced by the evaporation of a liquefied gas, which in evaporation 

 absorbs the heat from its surroundings, thereby lowering the temper- 

 ature. The refrigerating gases generally used are anhydrous ammo- 

 nia, sulphurous acid, and carbonic acid (also known as carbon anhy- 

 drid and carbon dioxid). The cold temperature in the warehouses 

 is usually produced by either of two methods, commonly known as the 

 compression and the absorption systems. 



The compression system takes its name from the fact that the refrig- 

 erating gas — whether ammonia, carbonic acid, or sulphurous acid 

 is first compressed in a machine called a compressor. Heat is gener- 

 ated by the compression; the gas is then cooled and condensed in pipes 

 or coils called the condenser, either immersed in water or having 

 water running over them, and this converts the gas into a liquid. The 

 liquefied gas then passes an expansion valve to pipes or coils called the 

 refrigerator cooling coils or cooler, where it is evaporated by the heat 

 which is withdrawn from the surroundings. The gas formed by the 



