ANIMAL PRODUCTS 



Artificial refrigerating machines — A 

 great variety of machinery has been de- 

 vised for artificial refrigeration on a 

 commercial scale, but many of the de- 

 tails of these matters are of interest 

 chiefly to technicians and builders. For 

 the refrigeration of animal products two 

 systems are in most extensive use, viz.: 

 cold air or expansion machines and cold 

 vapor or compression machines. The 

 first system is based on the fact that 

 compressed air becomes much colder and 

 absorbs heat in expanding. Air under 

 the pressure of two, three or four atmos- 



temperature of —40 to —58° F. The 

 greatest defect of this system has been 

 the formation of snow in the pipes by the 

 freezing of the moisture in the air. 

 Many improvements have been made in 

 the way of drying the air, particularly 

 in the Arctic cold-air machine. In this 

 machine the air is cooled to a tempera- 

 ture of 32° F. before reaching the ex- 

 pansion cylinder. The low temperature 

 thus deprives the air of all excess of 

 moisture. 



Compression machines make use of 

 rapidly vaporizing substances, such as 



Fig. 191 — THE GALLOWAY SKIN MAKES AN EXCELLENT RUG 



pheres and at a temperature of 86° F., 

 acquires temperatures of — 13° F., — 63° 

 F. and — 94° F. respectively, on expand- 

 ing. 



The Bell-Coleman cold air machine 

 — In this machine the air is taken from 

 the cooling room and subjected to a pres- 

 sure of two to three atmospheres in a 

 compression cylinder. The air thus 

 heated by compression is cooled by a 

 water spray, dried by passing through 

 a series of sieve structures and finally 

 cooled in tubes to a temperature of 41° 

 F. From the expansion cylinders, the 

 air escapes into the cooling rooms at a 



methyl ether, sulphuric ether, sul- 

 phurous acid and ammonia, but princi- 

 pally ammonia. The principle on which 

 these machines are based is that fluids 

 when vaporized extract heat from sur- 

 rounding substances. The ammonia is 

 kept in circulation in a system of pipes 

 and, after being vaporized, is brought 

 back in a fluid form and the heat ab- 

 sorbed by water. 



Importance of refrigeration — The im- 

 portance of cold storage can scarcely be 

 overestimated. Cold is the best method 

 for preserving animal products. It pro- 

 duces no unfavorable change, either ic 



