Applications of Refrigeration

APPLICATIONS OF REFRIGERATION Refrigeration has developed from its application in the brewery industry and more or less academic uses in other directions to a very important economic position. The ice-making industry in 1932 was ninth in the amount of invested capital in the United States. Without refrigeration natural ice would be a luxury in all except those localities exposed to severe winter conditions, and modern meat packing, the supply of fresh fruit and vegetables out of season, marine refrigeration and modern industry, where a de pressed temperature and air conditioning are required, would each be an impossibility. Some details of a few of these applications are described below.

Cold Storage.

Cold storage is one of the essential uses of mechanical refrigeration. By its means the season for fruits and vegetables is increased from a few weeks to from four to six months. Eggs may be kept from the period of great plenty in the early spring until fall if necessary, whereas the modern meat packer could not exist without refrigeration. In the latter case the animals are slaughtered under hygienic conditions and the meat is promptly chilled or frozen. Conditions of handling and holding the carcasses are as ideal as possible and shipment may be made in refrigerator cars to the retail trade. The space in the United States cooled mechanically to 4o° F or lower for all kinds of cold storage work, exclusive of the packing house, is esti mated at 700,000,000 cu.ft., with an estimated invested capital of $200,000,000.

Some indication as to how this may affect the modern city may be obtained from the statistics for New York city, where the following car loads of perishables are consumed each week: Dairy products 200; milk 2,200; meat 75o; live stock 600; poul try Soo; fruit 85o; vegetables 1,750; sea food 5o; totalling 6,700 car loads. The usual practice in regard to the temperatures, spe cific heats and tolerances will be seen by consulting the following table.

The Packing Plant.

The total refrigerated space in the

packing plants of the United States in 1921 amounted to 000 cu.ft., which included 443 plants, of which 15,400,000 cu.ft. were held at io° F or lower, 28,300,000 cu.ft. held at temperatures ranging from 11° to 29° F and 200,000,000 cu.ft. held at tem peratures ranging from 3o° to 44°. According to the U.S. Gov ernment reports 63,415,000 animals were slaughtered in 1920 under Government inspection including 7,600,000 cattle, 3,800,000 calves, 13,000,000 sheep and lambs and 39,000,000 hogs. Not less than 8o% of these require refrigeration for a short time at least although the average time is between one and two months, and the average time between slaughtering and the consumption of the meat is less than two months. A very small amount (5%) of the meat is frozen and is held in freezer storage.

Method of Cooling.—The method of chilling meats just re ceived from the killing floor is not standard. As a rule the loft system is used, this upper portion being separated from the storage room below by means of a false ceiling. When brine is used it may be passed through pipe coils, or it may be made to come into actual contact with the air in the form of a finely divided spray, using a nozzle similar to that used in the washing and conditioning of air. By this means an intimate mixture of air and brine is obtained inasmuch as the air has to pass through a curtain of finely divided brine. The air in the room is kept in constant circulation by the flow of the brine and the temperatures of the air in the different parts of the room are almost uniform. Where head room does not permit the use of a sprat' loft, the brine tube or brine box system may be used to advantage. In these cases the brine spray is confined to a limited space and the air has a forced circulation on account of the action of the sprays. Table VI. shows some statistics in regard to existing plants. Storage space may be piped in the usual manner.