Document JXE8bN1pNxMgdMJ0Xp533kkX

f- Heating Ventilating Air Conditioning Guide'1938 Table 2. Regain of Hygroscopic Materials Moisture Content Expressed in Per Cent of Dry Weight of the Substance at Various Relative Humidities--Temperature, 75 F Classi fication Material Description Relative Humidrrr--Per Cent Authority 10 20 30 40 50 60 70 80 90 Cotton * Sea island--roving 23 3.7 4.6 5.5 6.6 7.9 93 115 14.1 HafhilvnfiiA Cotton American-- cloth 2.6 3.7 4.4 S3 5.9 6.8 8.1 10.0 14.3 Schloering Cotton Absorbent 4.8 9.0 115 15.7 115 20.8 22.8 243 25.8 Fuwa Natural Textile Fibres Wool Silk Tiwgn Australian merino--skein 4.7 .7.0 8.9 10.8 12.8 14.9 17.2 19.9 23.4 Hartshorns Raw chevennea--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 43 5.1 6.1 7.0 8.4. 10.2 Atkinson linen Dry spun--yarn 3.6 5.4 6.5 73 8.1 8.9 9.8 11.2 13.8 Sommer Jute Average of several grades 3.1 5.2 &9 83 10.2 12.2 14.4 17.1 20.2 5torch Hemp Manila and sisal--rope 2.7 4.7 6.0 7.2 83 9.9 11.6 13.6 15.7 Fuwa Rayons Viscose Nitrocellu lose Cupramonhun Average skein Cellulose Acetate Fibre 4.0 5.7 6.8 7.9 9.2 10.8 114 14.2 16.0 Robertson 0.8 1.1 1.4 1.9 14 3.0 3.6 43 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 O. 8. B. of S. H. M: F. Writing Wood pulp--3% ash 3.0 4.2 5.2 6.2 7.2 83 9.9 11.9 14.2 D. aB.ofS. Paper White Bond Com. Ledge Kraft Wrapping Rag--1% ash 75% rag--1% ash Coniferous 2.4 3.7 4.7 5.5 6.5 73 8.8 10.8 13.2 D.&B.ofS. 3.2 4.2 5.0 5.6 6.2 6.9 8.1 10.3 13.9 u. a B. of S. 3.2 4.6 5.7 6.6 7.6 8.9 10.5 116 14.9 u. a b. of a 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 Ghie Mine. Organic Rubber Materials Wood Hide SoEd tire Timber (average) 3.4 4.8 5.8 6.6 7.6 9.0 10.7 11.8 123 Fuwa 0.11 0.21 0.32 0.44 0.54 0.66 0.76 038 0.99 Fuwa 3.0 4.4 5.9 7.6 9.3 1U 14.0 17.5 22.0 Forest P. Lab. Soap White 1.9 3.8 5.7 7.6 10.0 119 16.1 19.8 23.8 Fuwa Tobacco Cigarette 5.4 8l6 11.0 133 16.0 19.5 25.0 33.5 50.0 Ford White Bread . <L5 1.7 3.1 43- 6.2 83 11.1 14.5 19.0 Atkinson Crackers 2.1 2.8 3.3 3.9 5.0 6.5 83 10.9 14.9 Atkinson Food stuffs 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 63 8.0 9.9 114 15.4 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 divided 0.16 0.24 0.26 0.32 0.41 0.51 0.62 0.73 0.84 Fuwa Silica Gel Mlsc. Inorganic' Domestic Coke Materials Activated Charcoal Steam activated 5.7 9.8 12.7 15.2 17.2 18.8 20.2 21.5 22.6 Fuwa 0.20 0.40 0.61 0.81 1.03 1.24 1.46 1.67 139 Selvig 7.1 14J 22.8 26.2 28.3 29.2 30.0 31.1 32.7 Fuwa Sulphuric Arid ff*S04 33.0 41.0 17.5 52.5 57.0 61.5 67.0 73.5 82.5 Mason 626 y. Chapter 33. Industrial Air Conditioning Table 2 shows the regain or hygroscopic moisture content of several organic and inorganic materials when in equilibrium at a dry-bulb tem perature of 75 F and various relative humidities. The effect of relative humidity on regain of hygroscopic substances is clearly indicated. The effect of temperature is comparatively unimportant. In the case of cotton, for instance, an increase in temperature of 10 deg has the same effect on regain as a decrease in relative humidity of one per cent. Changes in temperature do, however, affect the rate of absorption or drying. Sudden changes in temperature cause temporary fluctuations in regain even when the relative humidity remains stationary. The regain or moisture content affects the physical properties of textiles to a marked degree, changing the strength, pliability and elasticity. The fact that the regain of textiles will come into equilibrium with the conditions of the surrounding air and' vary with its temperature and relative humidity is the fundamental basis for the control of physical qualities during manufacture. During the preparation processes in a cotton mill, the cotton fibers should be in a condition to be easily carded. These preliminary processes are carried out best in a relative humidity of 50 to 55 per cent. As the cotton fiber comes to the spinning operation, more flexibility is needed and the relative humidity is increased in this department. For many years, 65 per cent relative humidity was con sidered the optimum. To offset the extra work performed on the fiber as the spindle speed is increased, many cotton mills now carry 70 per cent relative humidity in the spinning rooms.1 Winding, warping and weaving are all processes calling for great flexibility and a consequent need for higher humidity. Other textile fibers, due to their different natural characteristics, are processed under relative humidities and temperatures applicable to each. Rayons, on account of great loss of strength with the higher regains, should be processed in a relative humidity of 57 per cent. Acetate silk, another chemical fiber, with approximately 50 per cent of the regain of rayon, may be processed between 60 and 65 per cent relative humidity. All hygroscopic materials release sensible'heat equivalent to the latent heat of the moisture absorbed by the material, all of which may account for a large percentage of the total heat load. CONDITIONING AND DRYING In gerteral, the exposure of materials to desirable conditions for treat ment may be coincidental with the manufacture or processing of the materials, or they may be treated separately in special enclosures. This latter treatment may be classified as conditioning or drying. The purpose of conditioning or drying is usually to establish a desired condition of moisture content and to regulate the physical properties of the material. When the final moisture content is lower than the initial one, the term drying is applied. If the final moisture content is to be higher, the process is termed conditioning. In the case of some textile products and tobacco, *The Present Status of Textile Regain 'Data, by A. E. Stacey, Jr. (National Association of Cotton Manufacturers, 1927). 627