Air Conditioning Margaret I n g e l s , Carrier Corp., S y r a c u s e , Ν . Υ . HEMISTS and engineers use air condi tioning as a valuable tool in more than two hundred industries. Air conditioning is a tool with many facets. In one industrial application its main function may be temperature control; in another, moisture control; and in still an other, it may maintain a constant differ ence in vapor pressures between the prod uct and the air. In these and many other functions, air conditioning has proved to be a necessity in manufacturing processes. The value of air conditioning may be measured in several lights. It is an eco nomic necessity in some fields where the product is dependent on weather, as is the case of rayon or confectionery. In other fields, the value is measured in im proved products and minimized waste, as in tobacco factories or food storage. In all fields of industry, air conditioning is a health measure with decreased num ber of absentees and higher efficiency of the personnel which comes with controlled temperatures, and humidities of cleaned air, circulated without drafts.
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Textiles The textile industry was one of the first in which air conditioning was applied. High humidities are necessary in the manufacture of cloth. The crude make shift of introducing live steam into the air of the early textile mill also produced high temperatures w*hich were detri mental to the health of workers. Air conditioning, with its positive control of temperature and humidity, is now used in many stages of cloth making. In a cotton mill, the picker room, carding, drawing, roving, combing, warping, winding, spool ing, twisting, spinning, anc weaving opera tions are each maintained at definite humidities and tempérâture. The relat ive humidities necessary in the different processes may vary over a range from 50 to 95 per cent. In silk and wool industries the control of relative humidity is essential in many of the operations. Cloth cannot be uniform in weave, unless the threads are uniform, free of kinks,
smooth, and of constant elasticity. Such thread cannot be produced except in air which is maintained at a constant relative humidity. When textiles are handled in dry air, a static charge is set up on each fiber causing the thread to become "shaggy" and to kink easily. The threads repel each other, producing an unevenness in weave. If a change in relative humidity of the air occurs during an operation, the size and strengthof the thread are affected so that an inferior product is obtained. The rayon industry is so dependent upon definite atmospheric conditions that rayon cannot be manufactured without air conditioning. Rayon is very hygroscopic and loses its strength when moist or wet. If the atmosphere in a rayon mill is allowed to become humid, the threads stretch to such an extent that weaving is impossible. In an inspection room, comfort conditions of air must be maintained to prevent ruining the product by perspiration of the workers' hands. Foods In the preparation of many foods, air conditioning is very important. Not only is the function of providing clean air sufficient to justify the wide use of air conditioning in the food industry but there are economic advantages also. These are expressed in minimized spoilage, reduction in loss of weight owing to excessive evaporation, and elimination of waste because of loss of appetizing appearance and taste. Any branch of the food industry may be used to illustrate the necessity of conditioned air for superior products, whether it be low-temperature air conditioning, as for meats, on through the range to the high-temperature air conditioning, as for macaroni. The bakery was one of the first branches of the food industry to adopt air conditioning, and offers several varieties in application, starting with the flour mill and continuing to the storage of baked goods. The baker desires not only t o have a product of highest quality but t o main-
tain a constant quality and uniformity throughout the year, regardless of variations in outdoor weather. T o do this he must control the enzymatic action of flour and the fermentation of yeast, both affected by temperature and moisture content of the surrounding air. With conditioned air in the dough room he controls not only the amount of fermentation action but also its rate so that a definite schedule of production can be maintained. A standardized mix is used through all seasons of the year without the necessity of adding more yeast when the weather is cold. Crusting of the dough in the fermentation troughs will not occur when the air in the dough room is properly humidified, nor will bread in the shipping room go stale and dry when the temperature and moisture content of the air is controlled. Chemicals and Pharmaceuticals During the World War, air conditioning played an important role in the crystallization of a chemical in the manufacture of explosives, and in peace times a similar role is played in the crystallization of medical compounds where constant temperature and moisture content of air is necessary for maximum yield. Air conditioning is employed extensively in the pharmaceutical industry. Many of the materials used in medicines are very hygroscopic and cannot easily be handled with the accuracy required for mixing compounds. In granulation, drying temperatures of air may be from 135° t o 175° F. and the relative humidity not more than 30 per cent. Effervescent salts should not be exposed to air over 35 or 40 per cent relative humidity with 75° F. or 80° F. temperature. Lozenge drying is performed in air a t 20 per cent relative humidity and 110° F. dry bulb. As all formulas demand exact measurements of the ingredients, each ingredient must have a known and constant moisture content so that the exactness of weights of each required in the finished product will b e assured.
SILK WINOIKQ ROOM, OSCAR H U H B M A N CORP., CHICAGO, I I A .
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77 heat loss or gain and the moisture loss or gain which occurs in the rooms where the processing takes place. The building construction and dimensions, exposure of wall, roof, window, and door, outdoor weather conditions, internal sources of heat, as lights, motors, steam and hot water pipes must be taken into account in the design figures. The number of people working in the processing room? and whether they are doing physical or sedentary work are also important in determining the air-conditioning equipment required. The air-conditioning engineer makes use of the psychrometric chart through the entire procedure in designing the airconditioning installation. The Carrier
UPPER VIEW. PILL COATING, HEALTH PRODUCTS, N B W A B Z ; LOWER V I E W . FOOD PACKAGING, POST PRODUCTS, BATTLE CREEK, MICH.
Of course the importance of cleaned air in the manufacture of medicine, obtained when the air is conditioned, cannot b e too strongly stressed. Great care must be taken t o prevent possible diffusion of any of the drugs, especially poisonous ones, which might occur when in powdered or granular forms. In making capsules, air conditioning is important for uniform product and constant rate of production. The thickness of the film of gelatin which is deposited on the metal form of the capsule machine is proportional to the viscosity of gelatin and t h e temperature of the form. The uniformity of the walls of the finished product depends upon the rate at which the gelatin congeals. All these variables are controlled by regulating the air in the machine where the capsules are made. Closely allied with the pharmaceutical industry is the animal assay room. B y maintaining constant conditions of air for t h e animals, experimental data may be more easily analyzed a s the variables caused by differences in climate are eliminated. Cleaned air reduces the chances for contamination from air-borne bacteria. Cardboard, Paper, and Glue Pill boxes, as well as pills, are made in conditioned air. Cardboard sheets from which boxes are to be made are stored in air held at 60 to 70 per cent relative humidity and not used until their full moisture regain corresponding to this air has been reached. T h e cardboard is then cut into desired sizes and fed into box-making machines. By maintaining the constant amount of moisture in the cardboard, the sizes of the boxes remain constant so that tops and labels fit. Glues used in making bags and boxes remain tacky in humidified air but would dry t o o quickly in the low humidity air which predominates during the heating season when the air is not conditioned. Rubber Rubber, from the time it arrives in its crude state until the finished product leaves the factory in t h e form of automobile tires or rubber gloves, is air conditioned.
Crude rubber dried at constant temperature and relative humidity not only has a fixed drying time but has a greatly increased tensile strength. Rolled or dipped operations performed in conditioned air assure even thicknesses of walls, and prevent "blisters'* from accumulation of solvent vapors. C o n d i t i o n s a n d Q u a n t i t i e s o f Air Required The air-conditioning engineer and the industrial chemist and engineer must worktogether for the best results. The scient ist will know the physical and chemical properties of his product and what they should be in each stage of the manufacturing process. The air-conditioning engineer can provide him with an air-conditioned installation which will assure the results required. In designing an air-conditioning installation there are many factors which must be taken into consideration. These may be divided into two groups—those which concern the product, and those which concern the factory and workers. The factors concerning the product deal entirely with the physical and chemical properties of the materials used in each stage of the process, the changes which take place during the processing, and the rate of production desired. The bonedry weight, density, specific heat, moisture content desired, and physical form of the material, as well as what heat is generated within the product by internal chemical reaction, and gas liberated during a process are some of the data which are required in designing an air-conditioning installation. As a rule the scientist in each industry is the only one from whom such information can be obtained. The conditions concerning the factory and workers which affect the design of the air-conditioning installations are: The
psychrometric formulas were not presented to the engineering world until 1911, but the information which is presented on the chart was used in its present form as early as 1908. The kind and volume of air to be handled, and its method of circulation are based on all the factors previously mentioned. The equipment must not only be sized to produce the desired results but to do it economically. Selection of Air-Conditioning Equipment The selection of air-conditioning equipment for economical operation requires a complete analysis of the results which must be obtained under all the variations of operating conditions. For instance, if there is a large intermittent refrigeration load it may be advisable to select a small refrigeration unit to operate continuously, storing cold water to take care of the peak requirements. If the refrigeration load is constant and the room dew-point temperature may be reduced (with a constant dry-bulb temperature) the following resizing may be advisable. Reduce the apparatus dew point with a corresponding reduction in air volume (a smaller amount of colder air will produce the same refrigerating effect as a larger volume of warmer air). If this reduction is made it will reduce the size of the fan and fan horsepower required, cooling coil surfaces will remain constant, the suction temperature of the refrigeration unit must be reduced, the compressor size either increased or run at a higher speed, and the compressor horsepower increased. The balance of these variables for maximum economy is part of the design of airconditioning installations. In installations requiring mechanical refrigeration, evaporative condensers may be used t o effect a saving in operation
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costs. This t y p e of condenser consists of coils over which water is sprayed a n d air blown over the wetted surface. T h e condensing temperature is t h e wet-bulb temperature of t h e air, as the water evaporates along t h e wet-bulb tempera ture lines shown in t h e Carrier psychro metric chart. T h e heat required t o vaporize t h e water is removed from t h e refrigerant. T h e evaporative condenser requires less water t h a n t h e water-cooled shell and tube condenser; t h e savings in water may be as much as 95 per cent, with corre sponding savings in power for handling smaller water quantities. A large reduc tion in power is obtained by using t h e evaporative condenser instead of a n aircooled unit as considerably less air is handled. The balance of power, water, and steam used in manufacturing is necessary for economic production. An industry which requires large amounts of high-pressure steam for processing, or one which has a large heating load in winter, may obtain better heat balance by using a steamdriven refrigerating machine for condi tioning t h e air in t h e factory. The variables which affect t h e economic operation in an industry depend upon t h e over-all setup of each factor. Airconditioning equipment, which becomes a part of t h e over-all setup of t h e factory, is so flexible in t h e selection of equipment with reference to the power, water, and steam required, t h a t it offers an oppor tunity to improve the heat balance of t h e industry in which it is used. T h e equip ment, being completely automatically controlled, maintains a balance of power, water, and steam which it requires within itself for t h e work t h a t it must do. Any tool which has proved itself t o be so
60 65 70 Dry Bulb Temperature B a r o m e t r i c pressure, 2 9 . 9 2 inches of mercury.
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valuable t o industry will continue t o ex tend its field of application and increase its usefulness t o t h e industrial chemist.
T h e A l c h e m i s t b y N . C. W y e t h
W h i s t l e s i n t h e Air
beautiful work of a r t is from an oil paint ing especially done b y this well-known artist for the Hercules Powder Company's Silver Anniversary year. T h e original was displayed at t h e booth of t h e company a t the Chemical Exposition a n d reproduced as t h e theme of t h e 1938 calendar which has been distributed. T h e reproduction has been copyrighted and it was with t h e permission of the copyrighter only t h a t our halftone was used.
t h e engraving on page 12 IwasN PUBLISHING not made sufficiently clear t h a t this of t h e N E W S E D I T I O N of J a n u a r y 10 it
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HE butcher who used every part of t h e pig but t h e squeal h a s been outdone by Chester W. Rice, consulting engineer of the General Electric Co., Schenectady, Ν . Υ., who, in a study of the manufacture of liquid air, has shown t h a t gases like hydrogen, nitrogen, oxygen, and air can be converted into liquid form more quickly by making them whistle. Gases are liquefied by removing heat energy from them. This is done by com pressing t h e gas t o a pressure of 3000 pounds per square inch, or 200 times a t mospheric pressure, and then allowing it to expand suddenly after cooling with ice. T h e compressed gas then passes through a series of tubes into a liquefying chamber where the pressure is suddenly released through a throttle valve in t h e form of a whistle. This whistle permits a further escape of heat energy and thereby adds a marked cooling effect, increasing t h e efficiency of equipment now in use. The whistle can be set at a pitch that will convert t h e greatest amount of heat energy into sound energy. T o be effec tive, t h e sound energy must be conveyed away from t h e liquefying chamber. T h e equipment makes possible t h e liquefac tion of gas a t a faster rate t h a n can be accomplished without t h e whistle.
Synthetic Ephedrine Manufac tured i n G e r m a n y 'HREE German firms are reported t o be manufacturing synthetic ephedrine, T a chemical used widely in the manufac ture of medicinal products, according to reports reaching t h e Commerce Depart ment's Chemical Division. T h e United States is a large importer of Chinese ma huang, the source of natural ephedrine, trade in which has been disrupted by military activities in China. GERALD WENDT, editor of Chemical
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views and director of the American In stitute of t h e City of New York, has been appointed t o draw u p a plan for consolidating scientific displays a t the New York World's Fair t o be held in 1939. Dr. Wendt, with the aid of an advisory committee on science, will examine t h e possibilities of scientific displays in every industrial exhibit.
