APPLICATION OP REFRIGERATION TO HANDLING OF MILK. 49 



Considering the moisture in the air, the moisture content at 70° F. 

 and 70 per cent relative humidity would be 5.596 grains per cubic 

 foot, and at 20° F. for saturation there would be 1.235 grains. There- 

 fore, there is eliminated per cubic foot 5.596 — 1.235 = 4.361 grains, 

 or for the 1,000 cubic feet, 1,000 X 4.361 =4,361 grains or 0.623 pound. 

 Consequently the refrigeration required is : 



Latent heat of liquefaction, 0.623X970.4 605 



Cooling from 70° to 32° F., 0.623X(70-32) 24 



Freezing, 0.623X144 90 



Cooling ice from 32° to 20° F., 0.623X0.5(32-20) 4 



723 



The total heat, therefore, that must be removed in cooling the 

 1,000 cubic feet of air under the above conditions is 885 + 723 = 1,608 

 B. T. U. In the case of cold storage the total amount of refrigeration 

 required for air cooling depends, of course, on the number of times the 

 air in the room is renewed in a given time. With the indirect-air 

 system usually employed in the dairy industry the same air is kept in 

 circulation to a great extent. 



In all cold-storage work the air in the rooms must, of course, be 

 cooled, but as the refrigeration required is generally small compared 

 with that necessary for cooling the goods and in taking care of the 

 heat that comes through the walls, floors, and ceiling, it is usually 

 ignored and a liberal allowance made to cover this as well as lighting, 

 presence of workman, poor workmanship, and other factors. 



INSULATION. 



The word "insulate" is derived from the Latin word "insula," 

 meaning "island." Therefore the significance of the definition of 

 insulate is: To place alone or in a detached situation; separated by 

 a nonconductor from other conducting bodies; having no communi- 

 cation with surrounding objects. Hence insulation in a cold-storage 

 room is applied on the interior surface of the outside walls, under the 

 roof, and under the lowest floor, to prevent, as far as possible, the 

 transfer of heat from exterior heat-conducting bodies like the air and 

 the ground. 



With the increased application of refrigeration the problem of 

 properly insulating the walls, floors, and ceilings of the cold-storage 

 rooms is of the greatest importance and should be considered in the 

 light of a permanent investment along with the building and equip- 

 ment, the returns on which should be based on the saving effected by 

 the lower operating cost. 



It is evident that after the goods in storage have once been cooled 

 to the desired temperature, it is then merely a question of supplying 

 40083°— Bull. 98—14 4 



