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318 CHAPTER 13 1954 Guide tef LETTER SYMBOLS USED IN CHAPTER 13 = fraction of incident solar radiation absorbed, dimensionless; subscripts D, d, andt refer to direct, diffuse and total, respectively. P =' solar altitude, degrees. y wall solar azimuth, degrees. -- emissivity, dimensionless. B = incident angle, degrees. A *= amplitude decrement factor, dimensionless, r == fraction of incident solar radiation transmitted, dimensionless. . Subscripts D, d and t refer to direct, diffuse and total, respectively. 4> = solar azimuth, degrees. ip = wall azimuth, degrees. A = area across which heat is being transferred, square feet. b = fraction of air. passing through coil which does not contact surfaces, coil .. by-pass factor. . / = unit surface conductance, Btu per (hour) (square foot) (Fahrenheit degree). Subscripts c, r, o, and i refer to convection, radiation, outdoor, and indoor, ir respectively. y Gj = fraction of total window area receiving direct solar radiation when shaded by window reveal, dimensionless. h -- enthalpy of air per pound of dry air, Btu per pound. y/: Subscripts i, o, and s refer to indoor, outdoor, and supply air, respectively. 1 -- incident solar radiation, Btu per (hour) (square foot). -/ Subscripts D, d, Dn, and t refer to direct, diffuse, direct normal and total. solar radiation, respectively. 1 K = cosine of angle of incidence for direct solar radiation striking a surface, dimen-/fj sionless. k = thermal conductivity of building material, Btu per (square foot) (hour)^f (Fahrenheit degree per inch). I -- height of window, feet. ^ M = the permeance of the specimen in 'perms or grains per (square foot) (hour)^. (inch of mercury vapor pressure difference). & Q * rate of entry of outdoor air, cubic feet per minute. Qra -- required air quantity through conditioning equipment, cubic feet per min**s ute. q -- instantaneous rate of heat transfer, Btu per hour. = instantaneous latent heat load, Btu per hour. qc\ = instantaneous space latent ventilation load, Btu per hour. qa = instantaneous latent ventilation load which does not become a part of& space load, Btuh. qm == latent heat load due to moisture transmission through materials, (hour)(square foot). q, = instantaneous sensible heat load, Btu per hour. q\ *= instantaneous space sensible ventilation load, Btu per hour. ,T, qa -- instantaneous sensible ventilation load which does not become a part^of^ space load, Btu per hour. Qt = Qc 4- qat also q*-, + qax -f q*i + tfcx, Btu per hour. Rt = low temperature radiant energy received from outdoor surroundings not include solar radiation), Btu per (hour) (square foot of receiving surface)^ R = radiant energy emitted by a black body, Btu per (hour) (square Subscripts go and L refer to outdoor surfaces of glass and building; tively. .;J|j S = rate of heat storage within a glass section, Btu per (hour) (square foowy* L sol-air temperature, Fahrenheit. Cooling Load 319 i9* -- 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. tt-, = temperature of indoor glass surface, Fahrenheit. tgo -- temperature of outdoor glass surface, Fahrenheit. lt *= indoor air temperature, Fahrenheit. In = 24-hr cyclic average sol-air temperature, Fahrenheit. a= outdoor air temperature, Fahrenheit. i, = room supply air dry-bulb temperature, Fahrenheit. U -- overall coefficient of heat transfer of a structural section, Btu per (square foot) (hour) (Fahrenheit degree). f0 = volume of outdoor air per pound of dry air, cubic feet. id = width of window, feet. W = humidity ratio, pounds moisture per pound of dry air. Subscripts i, o, and s refer to indoor, outdoor, and supply air, respectively. REFERENCES 1 Application Engineering Standards for Air Conditioning for Comfort (Air Conditioning and Refrigerat ing Machinery Association, Inc., 1947, pp. 4-7). ` Minimal Replenishment Air Required for Living Spaces, by W. V. Consolario and L. J. Pecora (A.S.H.V.E. Transactions, Vol. 53, 1947, p. 127). 1 Recommended Safe Practice of the NBFU for Hospital Operating Rooms, Pamphlet No. 56, National Board oj Fire Underwriters. ' Proposed Standard Solar Radiation Curves for Engineering Use, by P. Moon (Journal of the Franklin Institute, November 1940, Vol. 230 No. 5, pp. 583-617). 1 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). 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.VJE. Transactions, Vol. 51, 1945, p. 75). (He7aStinugmamnedr CVeonotliinlagtinfogr, CVooml. f2o9r,tNaso,A' 1ff1e,cNteodvebmy bSeorla1r93R2,apdpia.ti1o4n-,21b)y. G. A. Hendrikson and J. H. Walker Tables of Computed Altitude and Aeimuth (U. 8. Navy Dept. Hydrographic Office Bulletin No. 214, Vols. 1-9, Washington, D. C., 1940). The American Nautical Almanac (U. S. Naval Observatory. Washington, D. C., annual). * A.S.H.V.E. Research Report No. 623--Heat Transmission as Influenced by Heat Capacity and Solar Radiation, by F. C. Houghten, J. L. Blacksbaw, E. M. Pugh and Paul McDermott (A-S.H.VJS. Trans actions, 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.VJE. Transactions, Vol. 45, 1939, p. 369). Periodic Heat Flow in Building Walls Determined by Electrical An alogy Method, by Victor Paschkis (A.S.H.V.E. Transactions, Vol. 48, 1942. p. 75).--Periodic Heat Flow-- Homogeneous Walls or Roofs, by C. 0. Mackey and L. T. Wright, Jr. (A.S.H.V.E. Transactions, Vol. 50 293). Periodic Heat Flow--Composite Walls or Roofs, by C. O. Mackey and L. T. Weight, Jr. (A.S.H.VJB. Transactions, Vol. 52, 1946, No. 1269). Periodic Heat Transfer at the Inner Surface of a Homogeneous Wall, by H. A. Johnson (A.S.H.V.E. Transactions, Vo). 54, 1948, p. 143). " TheEffeetof Solar Radiation on the HeatTransmissionThrough Walls, byP. C. Houghten, Carl Gutberlet m. > , A. Rosenburg (American Society of Testing Materials Symposium on Thermal Insulating Materials, rtuiadelpbia, 1939). (AJJ fj'v^L^c^ua^ vs- Predicted C--o--o-l-i-n-g- LoaaduoanmAoneArtiJr.CWoanhdlit(iAo.nSin.Hg.SV__y.Esuti.eTamrm,abonydRseaJercanstmeiOoaefrnsficscN,heV.RLoielv.p4eo1rm,rS1t9po3rrNi5en,ok.le1d15a7n--dSWuamtemreCroCveoroelidngRoLoofas,dbays FA. transactions, Vol. 46, 1940). Transactions, Vol. 49, 1943, p. 287). PadiatiiL^w^'S' JI^earch Report No. 1195--Heat Gain Through Walls and Roofs as Affected by Solar n,*S.H-V.E. Research Report Vol. 4g 1942 pgjJ* Houghten, E. C, Hach, S. I. Taimuty and Car) Gutberlet (A.SP.H5.3V) .E. TbryaFn-saacthioungsh, ten. Cari Gutberlet. and Albert J. W {Trans*^**61 Through Walls and Roofs for Cooling Load Calculations, by J. P. Stewart (A.S.H.V.E- Vol. 54,1948, P. 381). CA.S.H Enersy Emission of Atmosphere and Ground, by G. V. Parmelee and W. W. Aubele . 1 jubnal Section, Heating, Piping dt Air Conditioning, Nov. 1951, p. 120). Qtcloviin,i1 ,0-n 'n'the Atmcepbere, by D. Brunt (Supplement to the Quarterly Journal of the Boyal Vrif "A S^V' L 6e' 1940)- Glass, bv ^'VT^EaEAKCH Report No. 1333--Meanureznenta of Solar Heat Transmission Through Mat b- 165). ' V' ^ar*nelee. W. W. Aubele and R. G. Huebecher (A.S.H.V.E. TraatSactions, Vol. 54, 19^8. hy G. Research Report No. 1348--Solar and Total Heat Gain Through Double Flat Glass, "As J, Ir * ^ &nd W* W` Aubc)e {A.S.H.V.E. Transactions, Vol. 54, 1948. p. 407). ^lock, bv f; ^ Rk8earch Report No. 1374--Solar Energy Transmittance of Eight-Inch Hol v. Parmelee and W W. Auhele (A.S.H.V.E. Tbansactions. Vol. 55.1949, p. 435).