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168 CHAPTER 8 1958 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^i letin No. 289, 1945). '' . Clouds and Smokes, by W. E. Gibbs (P. Blakiston's Son & Co., Philadelphia, Pa., 1924). --V^ 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). if.lW- (The) Environment and Its Effect upon Man (Harvard School of Public Health,-A Boston, 1937). Industrial Dust, by Drinker and Hatch (McGraw-Hill Book Co., New York, 1936).^-; Industrial Health Engineering by A. D. Brandt (John Wiley & Sons, Inc., New'i-- York, 1947). pfg;. Industrial Hygiene and Toxicology, edited by F. A. Patty (Interscience Publishers, Inc., New York, Vol. I, 1948 and Vol. II, 1949). -gj Journal of Industrial Hygiene and Toxicology (monthly) (Harvard School m Public Health, Boston, Mass.). See cumulative abstract and subject indexes. Manual of Industrial Hygiene, by W. M. Gafafer, et al (U. S. Public Health Sereice, \y.: W. B. Saunders Co., Philadelphia, 1943). .' Noxious Gases and the Principles of Respiration Influencing Their Action, by Hen^Ss derson and Haggard (American Chemical Society Monograph Series No. 35, Reinhola.ijij New York,-1943) r ------ -------- ............. ... Occupation and Health, two volumes (International Labor Office, Washington,1* D. C.). - ';iH Toxicology and Hygiene of Industrial Solvents, by Lehmann and Flury, trans-ip^ lated by Eleanor King and H. F. Smyth, Jr. (Williams and Wilkins, Baltimore, 1943).ij|| CHAPTER 9 HEAT TRANSMISSION COEFFICIENTS OF BUILDING MATERIALS Heat Transfer Symbols; Calculating Overall Coefficients; Conductivity of Homo geneous Materials; Soil Conductivity and Specific Heat; Surface Conductance;. Air Space Conductance; Practical Coefficients and Their Use; Computed Coefficients of Walls, Roofs, Ceilings and Floors; Effect of Insulation; Combined Ceiling, Roof, and Floor Coefficients; Glass Coefficients; 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, floors, 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 or thermal transmittance. 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 it is impracticable to test all combinations of building materials, the procedure and necessary data for calculation of the value of U are given in this chapter, together with tables of computed values for a large number of the more common constructions. HEAT TRANSFER SYMBOLS ,, Uovrall coefficient of heat transmission or thermal transmittance (air to air); e time rate of heat flow expressed in Btu per (hour) (square foot) (Fahrenheit de gree temjierature difference between air on the inside and air on the outside of a wall, 5r* ,roo!,or ceiling). The term is applied to the usual combinations of materials, j,,,,.a 30 to s*ng}e materials, such as window glass, and includes the surface contance on both sides. This term is frequently called the U value. conductivity; the time rate of heat flow through a homogeneous ma- cciiitiOIis per unit temperature gradient through unit area perthe temperature gradient. Its value is expressed in Btu per (hour) hdmnMnDn (Fahrenheit degree per inch of thickness). Materials are considered samnu JJPF "ien va^ue f * is not affected by variation in thickness or size of sample within the range normally used in construction. terial conductance; the time rate of heat flow through a unit area of a ma te ,Mr/,,-.o0neT?f lts surfaces to the other per unit temperature difference between the gree) The te S ue ls. expressed in Btu per (hour) (square foot) (Fahrenheit de- heteroeenamiof11 'A. a?P!'d 40 specific materials as used, either homogeneous or f = fil US't0r ttle clnckness or construction stated, not per inch of thickness, a surface'anH r^ace conductance; the time rate of heat flow between a unit area of foot of surfaceWir8<i,rroA!ld'ng air" Its value is expressed in Btu per (hour) (square used to different' fv.en"eit deg(ee temperature difference). Subscripts i and o are a = th , late between inside and outside surface conductances, respectively, area of ar^air conductance of an air space; the time rate of heat flow through a unit Its value is vn?ACe ?r un't temperature difference between the boundary surfaces. The conductanceSSf ln per (kur) (square foot of area) (Fahrenheit degree), height, the deDth ti?n alr- s.Pace is dependent on the temperature difference, the faces. ' Since the if- poMon> character, and temperature of the boundary siir. test and not relat1onships are not linear, accurate values must be obtained by ' computation. 169