Document mqo38yvYEkGYJBvvyqm1nnLXZ

166 CHAPTER 8 1953 Guide H .*' . 15 The Volumetric Incidence of Atmospheric Allergens', by 0. C. Durham (Journal 'ir of Allergy, Vol. 14, September, 1943, p. 455-461). , 30 The Volumetric Incidence of Atmospheric'Allergens, II: Simultaneous Measure- ments by Volumetric and Gravity Slide Methods, by O. C. Durham (Journal of v Allergy,'Vo1. 15, May, 1944, p. 226-235). '1 11 Air-Borne Fungus. Spores as Allergens, O. Cl Durham (Aerobiology, p. 32-47, .'ij Publication No. 17, American Associationfor the A dvancernent of Science, Washington ' ^ IX C., 1942). ; ' .** Sampling Devices, by H. G. DuBuy and A. Hollaender (American Journal of Medical Science, Vol. 209, February, 1945, p. 172-177): '?, ` 33 Ventilation Problems in Safe Handling of Radioactive Materials, by W. W. % McIntosh, paper presented at ASMS Spring Meeting, March 1952. BIBLIOGRAPHY - Abstracts and Bulletins.(monthly, annual and special) Industrial Hygiene Founda tion, Inc., Pittsburgh, Pa. Aerobiology, Publication No. 17 (.American Association for the Advancement of Science, Washington, D. C., 1942). Air Sanitation and Industrial Ventilation, by W. N. Witheridge (Detroit, Mich., 1945). ' ., American Industrial Hygiene Association Quarterly (4400 Fifth Ave., Pittsburgh, Pa.). , .Analytical Chemistry of Industrial Poisons, Hazards and Solvents, by M. B. Jacobs (Interscience Publishers, New York, 1941). Bibliography of Industrial Hygiene, 1900-1943 (U, S. Public Health Service Bul letin No. 289, 1945). 192C4l)o. uds and Smokes, by W. E. GibbB (P. Blakiston's Son & Co., Philadelphia, Pa., Determination and Control of Industrial Dust, by Bloomfield and DallaValle (U. S. Public Health Service.Bulletin No. 217, 1935). Dust, by S. C. Blacktin (The Sherwood Press, Cleveland, 1934). Bos(Ttohne,)1E93n7v)i.ronment and Its Effect upon Man (Harvard School of Public Health, Industrial Dust, by Drinker and Hatch (McGraw-Hill Book Co., New York, 1936). YoIrnkd, u1s94tr7ia).l Health Engineering by A. D. Brandt (John Wiley & Sons, Inc., New Industrial Hygiene and Toxicology, edited by F. A. Patty (Interscience Publishers, Inc., New York, Vol. I, 1948 and Vol. II, 1949). Journal of Industrial Hygiene and Toxicology (monthly) (Harvard School of Public Health, Boston, Mass.). See cumulative abstract and subject indexes. Manual of Industrial Hygiene, by W. M. Gafafer, et al (U. S. Public Health Service, W. B. Saunders Co., Philadelphia, 1943). Noxious Gases and the Principles of Respiration Influencing Their Action, by Hen derson and Haggard (American Chemical Society Monograph Series No. 35, Reinhold, New York; 1943). Occupation and Health, two volumes (International Labor Office, Washington, D. C.). Toxicology and Hygiene of Industrial Solvents, by Lehmann and Flury, trans lated by Eleanor King and H. F. Smyth, Jr. (Williams and Wilkins, Baltimore, 1943). -- V V " CHAPTER 9 HEAT TRANSMISSION COEFFICIENTS OF BUILDING MATERIALS Heat Transfer Symbols; Calculating Overall Coefficients; Conductivity of Homo geneous Materials; Soil Conductivity; Surface Conductance; Air Space Con ductance; Practical Coefficients and Their Use; Computed Coefficients of Walls, Roofs, Ceilings and Floors; Combined Ceiling and R.oof Co efficients; Calculating Surface Temperatures THE design of air conditioning or heating systems for buildings requires a knowledge of the thermal properties of the walls enclosing the space. (The term walls in this case, includes windows, doors, ceilings, Hoots, roofs and skylights). The rate of heat flow through the walls under steady-state conditions at design temperatures is usually the basis for calculating the heat required. For a given wall under standard conditions the rate is a specific value designated as U, the overall coefficient of heat transmission. It may be determined by test in a guarded hot box apparatus, or it may be computed from known values of the thermal conductance of the various components. Because testing of all combinations of building materials is impracticable, the procedure and necessary data for calculation of the value of U are given in this chapter, together with-tables of computed values for the more, common constructions. HEAT TRANSFER SYMBOLS U = overall coefficient of heat transmission (air to air); the time rate of heat flow expressed in Btu per (hour) (square foot) (Fahrenheit degree temperature difference between air on the inside and air on the outside of a wall, floor, roof or ceiling). The term is applied to the usual combinations of materials, and also to single materials, such as window glass, and includes the surface conductance on both sides. k = thermal conductivity; the time rate of heat Bow through a homogeneous mate rial under steady conditions through unit area per unit temperature gradient in the direction perpendicular to the area. Its value is expressed in Btu per (hour) (square foot) (Fahrenheit degree per inch of thickness). Materials are considered homogene ous when the value of k is not affected by variation in thickness or size'of sample within the range normally used in construction. C -- thermal conductance; the time rate of heat flow through a material from one of its surfaces to the other per unit temperature difference between the two surfaces. Its value is expressed in Btu per (hour) (square foot) (Fahrenheit degree): The term is applied to specific materials as used, either homogeneous or heterogeneous. / = film or surface conductance; the time rate of heat flow between a surface and the surrounding air. Its value is expressed in Btu per (hour) (square foot of surface) (Fahrenheit degree temperature difference). Subscripts i and o are used to differen tiate between inside and outside surface conductances, respectively. ... a = thermal conductance of an air space; the time rate of heat flow through an air space per unit temperature difference between the boundary surfaces. Its value is ex pressed in Btu per (hour) (square foot of area) (Fahrenheit degree). The conduct ance of an air space is dependent on the temperature difference, the height, the depth, the position and the character of the boundary surfaces. The relationships are not linear, and accurate values must be obtained by test and not by computation. R = thermal resistance. Its value is obtained from the reciprocal of heat trans fer as expressed by XJ, k, C, f or a. It is expressed in (hours) (square feet) (Fahren heit degrees) per (Btu). For example, a wall with a U value of 0.25, would,have a 167