Document nGr9ooxjmNvya6R04jk5K0G1

296 CHAPTER IS . 1948 Guide LETTER SYMBOLS USED IN CHAPTER 15 p = solar altitude, degrees. T = difference between the azimuth angle of an outdoor wall and the azimuth angle of the horizontal projection of the sun's rays, degrees. ^ = surface emissivity, the ratio of the heat emission by radiation from a surface to the radiation from a perfectly black surface, dimensionless. X = amplitude decrement factor, a variable depending.on thickness, material, and orientation of the wall or roof dimensionless. 0 = angle of incidence for sun's rays striking a surface, degrees. t = fraction of incident radiant energy transmitted through a glass section, . dimensionless. A -- area across which heat is being transferred, square feet. a = fraction of incident radiant energy absorbed within a glass section, dimension- less. ' b -- fraction of incident radiant energy absorbed by a non-transparent surface, dimensionless. e = ratio of direct solar radiation to sky radiation falling on a horizontal surface, dimensionless. fo = unit convective conductance for outdoor surface = film coefficient of heat transfer of outdoor air, Btu per (square foot) (hour) (Fahrenheit degree). Gf = fraction of total window area receiving direct solar radiation when shaded by window reveal, dimensionless. hi = enthalpy of indoor air per pound of dry air, Btu per pound; ho = enthalpy of outdoor air per pound of dry air, Btu per pound. Id -- direct solar radiation incident upon a surface at any angle of incidence, Btu per (square foot) (hour). In = direct solar radiation incident on a surface at normal incidence, Btu per (square " foot) (hour); ; Is = sky radiation incident upon a surface, Btu per (square foot) (hour). /t = Is 4- Id, Btu per (square foot) (hour). K = cosine of angle of incidence for direct solar radiation. striking .a surface,1 dimensionless. k = thermal conductivity of building material, Btu per (square foot) (hour) (Fahrenheit degree per foot). L = thickness of building material, feet. 1 = height of window, feet. Pd = partial pressure of atmospheric water vapor at earth's surface, inches of mercury. Q = rate of entry of outdoor air, cubic feet per minute. Qra = required air quantity through conditioning equipment, cubic feet per minute; q = instantaneous rate of heat transfer, Btu per hour. ge " instantaneous latent heat load, Btu per hour. qs = instantaneous sensible heat load, Btu per hour, gt = 5e + qs, Btu per hour. gw = specific enthalpy of water vapor removed (used on Mollier diagram) Btu per pound. r = fraction of incident radiation reflected from glass surface, dimensionless. T = absolute temperature, (F deg 4- 460). /e = sol-air temperature, Fahrenheit degrees. ... fe* = sol-air temperature at a time earlier than.the time for which heat gain is being found by an amount that is equal to the time lag of the wall or roof, Fahrenheit degrees.' ' !i = indoor air temperature, Fahrenheit degrees. th = temperature of outer surface of building, Fahrenheit degrees. 1 fin = 24-hr cyclic average sol-air temperature, Fahrenheit degrees. fi> = fin + Oe* -- fin), net equivalent outdoor temperature for combined periodic and mean heat flow, Fahrenheit degrees....... ; . Cooling Load 297 U = over-all coefficient of heat transfer of a structural section, Btu per (square foot) (hour) (Fahrenheit degree). v0 = volume of outdoor air per pound of dry air, cubic feet. w = width of window, feet. Wi = humidity ratio of indoor air, pounds moisture pier'pound of dry air.1 W0 = humidity ratio of outdoor air, pounds moisture per pound of dry air.' REFERENCES - . '' 1 "Application Engineering Standards for Air Conditioning for Comfort (Air Conditioning and Refrig erating Machinery Assoeiation,Inc., 1947, p. 4-7). *--Proposed Standard Solar Radiation Curves for Engineering Use, by P. Moon (Journal of the Franklin Institute, November, 1940, Vol. 230, No. 5, p. 583-617).; ` 3"Slimmer Cooling for Comfort as Affected by Solar Radiation, by G. A. Hendrickson and J; H. Walker (Heating and Ventilating, Vol. 29, No. 11, November, 1932, p. 14-21). 4"Dynamic Meteorology, by B. Haurwitz (McGraw-Hill Book Co.. Inc.. New York, 1941). *. 5~Summer Weather. Data and Sol-Air Temperature--Study of Data for New York City, by C. O. Mackey and-E. B. Watson (A.S.H.V.E. Transactions, Vol,..51,.1945, p. 75). ... . --A.S.H-.V.E. 'Research Report No. 1268--Summer Weather Data and*Sol-Air Temperature-- Study of Data for Lincoln, Nebr.. by C. O. Mackey (A.S.H.V.E. Transactions, Vol. 51, 1945, p. 93). 7"A.S.H.V.E. Research Report No. 923--Heat Transmission as Influenced by Heat Capacity and Solar Radiation, by F. C. Houghten, J. L. Blackshaw, E. M. Pugh and Paul McDermott (A.S.H.V.E: Transactions, Vol. 38, 1932, p. 231). Effect of Heat Storage and Variation in Outdoor Temperature and Solar Intensity on Heat Transfer Through Walls, by J. S. Alford. J. E. Ryan and F. O. Urban (A.S.H.V.E. Transactions, Vol. 45. 1939. p. 369). Periodic Heat Flow in Building Walls Determined by Electrical Analogy Method, by Victor Pascbkis (A.S.H.V.E. Transactions, Vol. 48, 1942. p. 75). Periodic Heat Flow--Homogeneous Walls or Roofs, by C. O. Mackey and L. T. Wright, Jr. (A.S.H.V.E. Transactions, Vol. 50, -1944, p.- 293). Periodic Heat Flow--Composite Walls or Roofs, by C. O. Mackey and L. T. Wright, Jr. (A.S.H.V.E. Transactions, Vol. 52, 1946. No. 1299). "A.S.H.V.E. Research Report No. 1002--Cooling Requirements of Single Rooms in a Modern Office Building, by F. C. Houghten, Carl-Gutberiet, and Albert J. Wahl (A.S.H-VJ Transactions. Vol. 41, 1935. p. 53). . . il8. |t,. "Study of Actual vs. Predicted Cooling Load on An Air Conditioning System, by James-N/Livermore (A.&H.V.E. Transactions, Vol. 49. 1943,.p. 287). , l0~A.S.H.V.E. Research Report No. 1195--Heat Gain Through Walls and Roofs as Affected by .Solar Radiation, by F. C. Houghten/E. C. Hach, S. I. Taimuty and Carl Gutberiet (A.S.H.V.E. Transactions, Vol. 48, 1942,,p. 91). , \ ,l"A.S.H.V.E.! Research -ReportNo.- 1281--The Transmisaon of Solar Radiation Through Flat Glass Under Summer Conditions, by ,G. V. Parmelee (A.S.H.V.E. Transactions, Vol. 51,1945, p. 317).- . 1 ^"A.S.H.V.E. Research Report No. 1147--Heat-Gain Through Glass Blocks by Solar Radiation and Transmittance, by F. C. Houghten; David Shore', H. T. Olson and Burt Gunst (A.S.H.V.E. Transactions, Vol. 46,. 1940. p. 83). . ,t;*. , v . . . ./ ' v. v, 13--A.S.H.V.E.' Research Report No. 975--Studies- of Solar Radiation Through Bare and Shaded Windows, by F. C. Houghten, Carl Gutberiet. and J. L. Blackshaw (A.S.H.V.E. Transactions, Vol.. 40, 1934,` p. 101). A.S.H.V.E. Research Report No. 1189--Heat Gain Through'Western Windows With and Without Shading, by F. C. Houghten, and-David Shore (A;.S.H.V.-E. Transactions, Vol. 47,;lp41, p. 251). ' ,4"Loc; cit. Note l,'p.: 8. :: C-: ,, . ' ;15~~C6oler Footcandles for Air Conditioning. by W.'G. Darley (A.S.H.V.E. Transactions, Vol. 46; 1940. r, 367). Lighting and. Air Conditioning Design Factors,; Report, of. J.ES.---A.S.H.V.E. Joint Com* mittee on Lighting,in Air Conditioning- (A.S.H.V.E.^Journal Section, Heating, Piping and Air Con ditioning, September, 1941,' p. 605)i Lighting and Air Conditioning,': by Howard M. Sharp-(Heeling and Ventilating, November, 1942, p. 35). *- ,, .. . . is--Compiled by J. P. Stewart from various sources. , 7--Moisture Condensation in Building Walls, by Harold W. Woolley (/. S. Department of. Commerce, National Bureau of Standards, Building Materials and Structures Report BMS63). Vapor Barriers with Annotated Bibliography, by Louis York; Project No. M544 for Office of Production, Research, and Develop ment, Washington, D. C., 1945. Moisture Migration: A Survey of Theory and Existing Knowledge, by P. F. McDermott (Refrigerating Engineering. August, 1941, p. 103). A Theory'Covering the Transfer of Vapor Through Materials, by F. B. Rowley (A.S.H.V.E. Transactions, Vol. 45,1939, p. .545). ; How to Estimate the Amount of Water Vapor Transmitted Through Building Walls (Heating and Ventilating, September, 1942, pi. 43).' Estimating Water Vapor Transmission Through Walls, Reference Data-Sheets 241-244 (Heating and Ventilating, February and March. 1943).