3250 



STORAGE 



STORAGE 



collected in a brine tank of sufficient capacity to oper- 

 ate the plant for a considerable length of time. This 

 really acts as a reservoir of cold, and from this reser- 

 voir the cold brine is circulated throughout the entire 

 cold-storage plant, the temperature and quantity of 

 the brine circulated being governed by the results 

 desired. 



The coils of pipes in the rooms are commonly referred 

 to as the "piping." These coils or racks of pipes are 

 the room's equipment for refrigeration, and the number 

 of coils or length of piping depends upon the size of 

 the room and the temperature desired. Low-tempera- 

 ture rooms or freezers have a large number of coils and 

 a great length of pipes. Pre-cooling rooms should also 

 have heavy piping and many pipes. The advantages 

 of the brine-circulation system are that there is no 

 danger from leakage of ammonia or other irritating 

 gas. The statement is also made that there is a more 

 uniform temperature, the flow of the brine being under 

 constant and easy control. The temperature of the 

 brine is also under definite control. Perhaps the 

 greatest advantage is that the supply of cold {brine 

 acts as a reservoir of refrigeration and a reserve supply 

 can be drawn upon in case of necessary shutting down 

 of the machinery. 



In placing the pipes in cold-storage chambers, it is 

 important to have them located at the upper part of 

 the room. Ordinarily, the dependence for the circula- 

 tion of refrigeration throughout the room is on the 

 natural circulation of the air within the room. The air 

 in contact with the pipes is cooled and, being rendered 

 more dense, flows to the floor, the warmer air from other 

 parts of the room taking its place. In this way, a con- 

 stant circulation throughout the room is maintained. 

 It is easy to see, therefore, that the placing of the pipes 

 in the upper part of the rooms is essential; otherwise, 

 there is danger that the parts of the room above the 

 pipes may be beyond the refrigerating effects. The air 

 is, therefore, the medium of applying the refrigeration. 

 It is due to convection currents that the transfer from 

 the refrigerating pipes is effected, and it is very difficult 

 to obtain a uniform cooling in all parts of the room 

 unless the pipes are carefully placed. 



In the air-circulation system of applying refrigera- 

 tion, there is a forced air circulation. The air is forced 

 through conduits or ducts by means of fans. In this 

 system the expansion coils of pipes are in groups or 

 batteries in what are known as bunker rooms, or more 

 correctly, coil rooms. The refrigerating capacity of 

 the plant is, therefore, concentrated in one place. In 

 arranging the coil pipes, baffles are placed in such a 

 way that the air passing through the coil rooms must 

 come in contact with all of the pipes. If all of the pipe 

 surfaces are not reached by the air, the full refrigerat- 

 ing effect of the plant is not obtained. The coils may 

 be direct-expansion coils or brine-circulating coils, 

 that is, have the brine circulating through them. The 

 Cooper gravity-brine system may also be used. For 

 this purpose, the secondary coils are located in coil 

 rooms where the air to be cooled can be forced through. 



In placing the fans for such a plant, the arrangement 

 must be such that the air is drawn from the coil room 

 and forced through ducts to the storage chambers. 

 With this arrangement there is a constant pressure in 

 the rooms which is preferable to the exhaustion of the 

 air. Any leakage which occurs, therefore, is outward 

 from the room instead of inward. Return ducts are 

 provided which conduct the air back to the coil rooms, 

 the same air being used continuously. Impurities from 

 the storage rooms are absorbed by the air and deposited 

 in the moisture which freezes on the cold pipes. The 

 impurities, therefore, are very largely absorbed by the 

 frost, and the circulation of the current of air through 

 the coil rooms acts largely as a purifier of the air of the 

 storage rooms. Some ventilation, however, is frequently 

 desirable. The problem of ventilating a cold-storage 



chamber is a difficult one and special appliances must 

 be provided for this purpose. The outer air cannot be 

 admitted directly into the storage chamber unless it 

 is at the same temperature as the air of the storage 

 room. In warm weather, therefore, the admitted air 

 must be cooled and in extremely cold weather it must 

 be warmed. There are special mechanical devices for 

 accomplishing both of these purposes. 



Shape of storage plants. 



Many storage plants are planned without considera- 

 tion of the factor of the most economic shape; that is, 

 the most efficient as well as the most economical size 

 of plant to be constructed. The first consideration is 

 that the plant should be planned to supply the required 

 floor space and cubical capacity. In figuring the size of 

 storage rooms to accommodate packages of fruits, the 

 size of the fruit packages must be taken into consider- 

 ation and enough space must be made to allow the au- 

 to circulate between the stacks or bales of packages. 

 A barrel of apples, for example, requires 8 to 10 cubic 

 feet. Another factor which must be considered is the 

 economical handling of the packages in the storage 

 rooms. Where the storage season is comparatively 

 short, the extra expense of piling in high stacks must 

 be considered. Where, however, the storage season is 

 to be long, higher stacks may be made and, conse_- 

 quently, rooms of greater height will be most economi- 

 cal. After the size and the cubical contents of the 

 chamber are determined, the next consideration is the 

 shape of the plant or room. 



The most economical shape for a storage plant is 

 the cube. This is due to the fact that the ratio between 

 cubical contents and exposed outside surface is smaller 

 for the cube than for any other shape. It is important 

 to take this into consideration because of the fact that 

 there is no perfect insulating material and, consequently, 

 when the ratio of exposed outside surface is very high, 

 the rate of heat leakage into the room is increased 

 considerably when the shape of the room differs 

 materially from the cube. Such a room must have either 

 much heavier insulation or considerably more power 

 must be supplied to offset the greater heat leakage. 

 Sometimes limitations of space, as for example, utiliz- 

 ing parts of buildings, require that the rooms be of odd 

 shapes. When this is necessary, it will require con- 

 siderably more insulation or power, as suggested. The 

 capacity of the plant must be determined by the nature 

 of the commodity to be stored. Large rooms are easier 

 to maintain at a desired temperature after the entire 

 load of the room is reduced to the required tempera- 

 ture. In large rooms, however, it is more difficult to 

 cool uniformly unless some special attention is given 

 to the placing of the pipes, or the duct openings where 

 forced air circulation is used. For periods of short 

 storage, such, for example, as the more perishable fruits 

 like berries, rooms of smaller capacity are more desir- 

 able than very large rooms. 



Insulation. 



There are three ways in which heat may be trans- 

 ferred: radiation, conduction, and convection. Radia- 

 tion is the transference of heat from one body to 

 another through a third medium without perceptibly 

 affecting the medium. The heat which one feels when 

 standing before a fire is radiant heat. The conduction 

 of heat is accomplished by the passing of heat from one 

 body to another by contact with the heated body. The 

 heat that one feels when the hand is placed on a warm 

 pipe is conducted heat. Heat is transferred by convec- 

 tion by means of a third medium, usually air. In 

 attempting the construction of storage houses, all 

 three methods of heat transference must be taken into 

 consideration. The heat actually radiated is compara- 

 tively small in storage buildings. The quantity of 

 heat transferred by conduction is greater, but the most 



