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/ American Society of Heating and Ventilating Engineers Guide, 1932 Table 1. Regain of Hygroscopic Materials Moisture Content Expressed in Per Cent of Dry Weight of the Substance at Various Relative Humidities--Temperature, 75 F Culssi- Material Description Relative Humiditt--Per Cent 10 20 30 40 50 60 70 80 90 Authobttt Cotton Sea Island--Roving 2.5 3.7 4.6 5.5 6:6 7.9 9.5 li.5 14.1 Hartshorne Cotton American--Cloth 2.6 3.7 4.4 5.2 5.9 6.8 8.1 10.0 14.3 Schloesing Cotton Absorbent 4.8 9.0 12.5 15.7 18.5 20.8 22.8 24.3 25.8 Fuwa Natural Textile Fibres Wool. Silk Linen Australian Merino:--Skein 4.7 7.0 8.9 10.8 12J5 14.9 17.2 19.9 23.4 Hartshorne Raw Cheyennes--Skein 3.2 5.5 6.9 8.0 8.9- 10.2 11.9 14.3 18.8 Schloesing Table Cloth 1.9 2.9 3.6 4.3 5.1 6.1 7.0 8.4 10.2 Atkinson - linen Dry Spun--Yarn 3.6 5:4 6.5 7.3 8.1 8.9' 9.8 11.2 13.8 Sommer Jute Average of Several Grades 3.1 5.2 6.9 8.5 10.2 12.2 14.4 17.1 20.2 Starch Hemp Manila and Sisal--Rope 2.7 4.7 6.0 7.2 8.5 9.9 11.6 13.6 15.7 Fuwa Rayons Viscose Nitrocellu lose Cupramonium Average Skein Cellulose Acetate Fibre 4.0 5.7 6.8 7.9 9.2 10.8 12.4 14.2 16.0 Robertson 0.8 1.1 1.4 1.9 2.4 3.0. 3.6 4J 5.3 Robertson M. F. Newsprint Wood Pulp--24% Ash 2.1 3.2 4.0 4.7 5.3 6.1 7.2 8.7 10.6 U.S: B.ofS. H. M. F. Writing Wood Pulp--3% Ash 3.0 4.2- 5.2 6.2 7.2 8.3 9.9 11.9 14.2 U. S. B. of S. Paper White Bond Rag--1% Ash 2.4 3.7 4.7 5.5 6.5 7.5 8.8 10.8 13.2 U. S. B. of s; Com. Ledger 75% Rag--1% Ash 3.2 4.2 5.0 5.6 6.2 6.9 8.1 10.3 13.9 U. S. B. of S. Kraft Wrapping Coniferous 3.2 '4.6 5.7 6.6 .7.6 8.9 10.5 12.6 14.9 U. S. B. of Sx Leather Sole Oak--Tanned 5.0 8.5 11.2 13.6 16.0. 18.3 20.6 24.0 29.2 Phelps Catgut Racquet Strings 4.6 7.2 8.6 10.2 12.0 14.3 17.3 19.8 21.7 Fuwa Glue Misc. Organic Rubber Hide Solid Tire - - 3.4 4.8. 5.8 6.6 7.6. 9.0 10.7 11.8 12.5 Fuwa 0.11 0.21 0.32 0.44 0.S4 0.66 0.76 0.88 0.99 Fuwa Wood Timber (Av.) 3.0 4.4 5.9 7.6 9*3 11.3 14.0 17.5 22.0 Forest P. Lab. Soap Ivory 1.9 3.8 5.7 7.6 10.0 12.9: 16.1 19.8 23.8 Fuwa Tobacco Cigarette 5.4 8.6 ii.o! 13.3 16.0 19.3 25.0 33.5 50.0 Ford White Bread 0.5 1.7 3.1 4.5 6.2 8.5 li.l 14.5 19.0 Atkinson Crackers 2.1 2.8 3.3 3.9 5.0. 6.5 8.3 10.9 14.9 Atkinson. Foodstuffs Macaroni Flour 5.1 7.4 8.8 10.2 11.7' 13.7 16.2, 19.0 22.1 Atkinson 2.6 4.1 5.3 6.5 8.0 9.9 12.4 ISA 19.1 Bailey Starch 2.2 3.8 5.2 6.4 7.4' 8.3 9.2 10.6 12.7 Atkinson Gelatin 0.7 1.6 2.8 3.8 4.9 6.1. 7.6 9.3 11.4 Atkinson Asbestos Fibre . . Finely Div. 0.16 0.24 0.26 0.32 0.41 0.51 0.62 0.73 0.84 Fuwa Silica GeL 5.7 9.8 12.7 15.2 17.2 18.8 20.2 21.5 22.6 Fuwa Inorganic Domestic Coke 0.20 0.40 0.61 0.81 1.03 1.24 1.46 1.67 1.89 Selvig Activated Charcoal: Jteam Activated Sulphuric Acid QtSOt - 7.1 14;3 22.8 26.2 28.3 29.2 30.0 31.1 32.7 Fuwa 33.0 | 41.0 47.5 | 52.5 | 57.0 61.S 67.0 73.5 82.5 Mason 416 ns'ix .; Chapter 29-^Air Conditioning for Industrial Processes DESIRABLE ATMOSPHERIC CONDITIONS The most desirable relative humidity during processing depends upon the product and the nature of the process. As far as the behavior of the material itself and its desired final condition are concerned, each material and process represents a different problem. The best relative humidity may range anywhere from 0 to 100 per cent. Similarly the most desirable temperature may range between wide limits for different materials and treatments. Extremes in either relative humidity or temperature require relatively expensive equipment for maintaining these conditions and con trolling them automatically. Also, in departments where people are working, their health, comfort and productive efficiency must be con sidered. A compromise often is desirable. It is generally considered that relative humidities below 40 per cent are on the dry side, conducive to low regains, a brittle condition of fibrous materials, prevalence of static electricity and a tendency toward dryness of the skin and membranes of human beings. At the other end of the scale, humidities above 80 per cent are relatively damp, conducive to high regains, extreme softness and pliability-. . . GENERAL REQUIREMENTS In general, air conditioning apparatus for industrial purposes must be capable of absorbing heat from various sources such.as machinery power, electric lamps, people, sunlight and chemical reaction; of warming or cooling to any desired degree, and of giving or permitting ample air supply at all times. Refrigeration may or may not be required, depending upon natural conditions, the required relative humidity and the maximum permissible temperature. Washing, purifying and recirculating of the air may be desirable. Accurate, sensitive and reliable automatic control of humidity or temperature, or both, is essential in most cases. The amount of moisture to be added or removed from the air is dif ferent for each industrial process. It depends upon the temperature and relative humidity to be maintained, and upon the several factors men tioned an the'previous paragraph, also upon outdoor conditions, required rate of air change, amount of material entering or leaving the room per hour and the number of employees. Weather greatly affects the im mediate requirements for air conditioning, but the advantages of a favorable climate are usually of secondary importance in modern in dustrial development. , Most industrial, processes require a constant relative humidity so that the quantity of moisture existing, naturally in the.air must be either increased or lowered. Such industries include the confectionery, rayon, printing and lithographic industries. Others require not only a constant relative humidity but also a uniform temperature. For example, plants containing full fashioned hosiery machines and automatic machines for wrapping chewing gum, food products, -confectionery and cigarettes require exact conditions of heat and moisture in order to function satis factorily without frequent adjustments. 417