STORAGE 



3249 



The cold brine passes through the secondary coils, and, 

 as it absorbs the heat from the rooms or chambers, its 

 density is decreased and it flows upward and is returned 

 to the top or primary coils, where it is cooled and the 

 process repeated. Fig. 3700 is a diagram illustrating 

 the principle upon which the Cooper gravity-brine 

 system depends. At the top of the illustration the 

 primary coils are shown and the methods of placing 

 the pipe systems or coils is indicated. 



The cooling effects secured from the Cooper brine 

 system are indirect in that the refrigeration obtained 

 from the ice-and-salt mixture is first exerted upon the 

 brine solution and this solution is the means of carry- 

 ing the refrigeration to the place where it is needed. 

 There is an inevitable loss in the indirect method 

 because of the loss of refrigeration in the conduct- 

 ing pipes. 



In the second system of securing refrigeration from 

 ice and salt, the air is passed directly through the 

 mixture and, consequently, the refrigerating effect is 

 obtained directly from the mixture. Experiments 



3700. Diagram of Cooper gravity-brine system. 



have shown that very low temperatures can be obtained 

 by passing a current of air through an ice-and-salt 

 mixture, the temperature depending on the propor- 

 tion of salt used in the mixture. The higher the per- 

 centage of salt the lower the temperature obtainable. 

 The device for obtaining refrigeration in this way is 

 simple. It consists of a tank for holding the crushed 

 ice and salt. At the bottom of this tank openings are 

 provided through which a current of air can be forced. 

 The particular working out of the design for obtaining 

 refrigeration in this way has been accomplished by 

 S. J. Dennis, of the United States Department of 

 Agriculture. Dennis' apparatus has been used suc- 

 cessfully in several plants on the Pacific coast, and 

 owing to the fact that it was developed as a part of 

 the Departmental investigations, its use by the citi- 

 zens of the country is free. It is essentially an ice-and- 

 salt tank of "magazine" type. As the ice is melted at 

 the bottom the supply from above drops down. From 

 7 to 10 per cent salt has been found to yield satisfactory 

 temperatures. The apparatus can be constructed by 

 almost any ordinary mechanic who can follow detailed 



drawings or instructions. A fan is used to draw the 

 air through the ice-and-salt mixture and to force the 

 refrigerated air into the storage chambers. Ducts are 

 provided for the return of the air, and in this way the 

 same air is used continuously. 



There is another method of securing refrigeration 

 from ice and salt which may be designated as the 

 "tube system." In this system the mixture of ice and 

 salt is contained in tubes located at the sides of the 

 room. The tubes are filled with the mixture from the 

 top and the refrigeration is obtained by the cooling of 

 the air in contact with the tubes. The number of tubes 

 necessary to cool a given quantity of goods depends 

 upon the character, size, and insulation of the room. 

 The tubes are constructed of galvanized iron and are 

 about 8 or 10 inches in diameter. The tops of the tubes 

 open above the storage room, so that the filling can be 

 done without opening the room itself. A proper arrange- 

 ment of pipes at the bottom to carry off the meltage is 

 necessary, and in arranging for this meltage outlet, a 

 proper trap must be provided in order to prevent the 

 wastage of the cold air. This system has found con- 

 siderable application in the Hudson River Valley of 

 New York state, and is very effective for a short season 

 of storage. 



Systems of applying refrigeration. 



Refrigeration may be denned as the cold obtained 

 from a refrigerating medium or directly from mechanical 

 appliances. The temperature-reducing properties of the 

 ice-and-salt mixture and those of the liquid ammonia 

 are the refrigerating qualities of these agencies. Re- 

 frigeration is ordinarily measured in terms of ice- 

 melting capacity in a day of twenty-four hours. For 

 example, a machine which is rated as yielding a capac- 

 ity of ten tons a day is based upon the meltage of 

 ten tons of ice in that time. Ordinarily, it is not 

 >the quantity of ice which can actually be produced 

 by the machine, except when ice manufacture is the 

 primary object. 



There are three systems of applying the refrigeration 

 secured by mechanical means: (a) direct expansion; 

 (6) brine circulation; (c) air circulation. 



In the direct-expansion system, the expansion pipes 

 in which the gas is allowed to expand, and thereby 

 produce the refrigeration, are located in the storage 

 rooms. The claims for this system are that the work is 

 direct; therefore there is no loss in conducting the 

 refrigeration obtained from the pipe surface. The 

 greatest objection to this system, especially with 

 ammonia or sulfur dioxide plants, is the danger of 

 leaks. Small leaks may allow a sufficient quantity of 

 gas to escape to damage the goods stored in the rooms; 

 there is also great danger to the workmen, which has 

 already" been referred to. The greatest care is necessary 

 in constructing the direct-expansion system. With the 

 perfection of mechanical devices for welding and fas- 

 tening pipes, the danger from lealcs has been reduced 

 to a minimum, and there are many direct-expansion 

 systems in operation in which no injuries have ever 

 been recorded. One disadvantage is the fact that 

 there is no reserve power except that which is contained 

 in the liquid receivers. Should it be necessary to shut 

 down the machinery for repairs for any considerable 

 length of tune, there would not be sufficient reserve to 

 continue the refrigerating effects and the temperature 

 of the storage rooms would be likely to rise to a con- 

 siderable extent. 



In the brine-circulation system, the expansion coils 

 are surrounded by a non-congealable brine such as a 

 solution of calcium chloride, which has a very low 

 freezing-point. The brine is cooled in the pipes and this 

 cold brine is circulated through coils in the rooms 

 by means of pumps. In applying this method, there is, 

 firstj what is known as a brine-cooler in which the actual 

 cooling of the brine takes place; the cold brine is then 



