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730 CHAPTER 31 1956 Guide A.S.H.V.E. Research Report No. 1304--Entrainment and Jet-Pump Action of Air Streams, by G. L. T.uve, G. B. Priester, and D. K. Wright, Jr. (A.S.H.V.E. Transactions, VoL 48; 1942, p. 241). A.S.H.V.E. Research Report.No; 1248--Control of Air Streams in Large Spaces, by G. L. Tuve and G. B. Priester (A.S.H.V.E. Transactions, Vol. 50, 1944,-p. 153). ' A.S.H.YE. Research Report No.,1328--The Discharge of Air from a.Lorig Slot, by Alfred Koestel and G. L. Tuve (AiS.H.V.E. Transactions, Vol. 54, 1948, p. 87).` ' A.S.H.V.E. Research Report No. 1366--Air Streams from'Perforated Panels, by Alfred Koestel, Philip Hermann and G. L. Tuve (A.S.H.-V.E. Transactions, Vol. 55, 1949,p. 283). A.S.H.V.E. Research Report No. 1404--Comparative Study of Ventilating Jets from Various Types of Outlets, by Alfred Koestel,. Philip Hermann, and G. L. Tuve (A.S.H.V.E. Transactions, Vol. 56, 1950, - A.S.H.V.E. Research Report No.-1429--The Control of Air. Streams from a Long Slot, by Alfred Koeste, and C. Y. Young (A.S.H.V.E. Transactions, Vol. 57,1951, p. 407). . A S.HrVJS. Research Report No. 1476--Air Velocities in Ventilating Jets, by G. L. Tuve (A.S.H.VJ2. Transactions, Vol. 59,1953, p. 261)., ., A.S.H.A.E. Cooperative Research at Kansas State College A.S.H.V.E. Research Report No. 1327--Downward Projection of Heated Air, by Linn Helander and C. V. Jakowate (A.S.H.V.E. TRANBAcnoNs, Vol. 54; 1948, p. 71); \ A.S.H.V.E. Research Report No. 1475 (In Cooperation with the Industrial Unit Healer Association}-- Maximum Downward Travel.of Heated Jets from Standard Long Radius ASMS Norales, by Linn Helander, S," M. Yen, and R. E. Crank (A.S.HV-E. Transactions, Vol. 59, 1953, p. 241). A..SS..Hn../Ai..OE.. Ccuouoppcetraautivvec RAwesoebaur.cvh~--Gv e--n--e- -r--a--l A.S.H.V.E. Research Reports No. 857, 911 and 965--Measurement of the Flow of Air Through Registers and Grilles, by E. L. Davies (A.S-H.V.E. Transactions, VoL 36, 1930, p. 201: Vol. 37, 1931, p. 619 and Vol. 39, 1A9.3S3.,Hp..V3.7E3.).Research Report No. 1076--Air Distribution from Side Wall Outlets, by D. W. Nelson and D. J. Stewart (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 77). : A.S.H.V.E. Research Report'No. 1092--The-Flow of Air Through Exhaust Grilles, by A. M. Greene, Jr.and M. H. Dean (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 387). A.S.H.V.E. Research Report No. 1155--The Performance of Stack Heads,'by D. W. Nelson, D. H. Kraus, and A. F. Tuthill (A.S.H.V.E. Transactions, Vol. 46,1940, p. 206). A.S.H.V.E. Research Report No. 1165--Development of Instruments for the Study of Air Distribution in Rooms, by A. P. Kratz, A. E. HersKey; and R. B. Engdahl (A.S:H.V.E. Transactions, Vol. 46, 1940, p. 351)A. .S.H.V.E. Research Report No. 1206--Performance of Stack Heads Equipped with Grilles, by D. W. Nelson, D. H. Lamb and G. E. Smedberg (A.S.H.V.E. Transactions, Vol. 48, 1942, p. 279). A.S.H.V.E. Research Report No. 1226--Performance of Side Outlets on Horizontal Ducts, by D. W. Nelson and G. E. Smedberg (A.S.H.V.E. Transactions, Vol. 49, 1943, p. 58). Other Papers Presented at A.S.H.A.E. Meetings A.S.H.V.E. Research Report No. 1051--The Noise Characteristics of Air Supply Outlets, by D. J. Stewart and G. F. Drake (A.S.H.V.E. Transactions, Vol. 43, 1937, p. 81). A.S.H.V.E. Research Report No. 1158--Dirt Patterns on Walls, by R. A. Nielsen (A.S.H.V.E. Trans actAio.Sns.H, V.Vo.lE. .46R, e1s9e40a,rpc.h 247). Report No. 1381--Ba_ lancing Air Delivery, of a System of Manifold Air Diffusers, by G. S. Dauphinee and Peter Argentieri (A.S.H.V.E. Transactions, Vol. 55, 1949, p. 213). A.S.H.V.E. Research Report No. 1362--Air Distribution and Draft, by John Rydberg and Per Norbfick (A.8A..HS..VH..EV,.ET.rRanesseaacrtciohnRs,eVpoolr. t55N, 1o9. 4I94,?pl--. 2R25o)o. m Air Distribution Research for Year 'Round Air Condi tioning, Part I--Supply Outlets at One High Sidewall. Location, by S.'F. Gilman, H. E. Straub, A. E. Her- shey, and R. B. Engdahl (A.S.H.V.E. Transactions, Vol. 59, 1953, p. 151). A.S.H.V.E. Research Report--R00m Air Distribution Research for Year 'Round Air Conditioning, Part II--Supply Outlets at Three-Floor Locations, by H. E. Straub and S. F. Gilman (A.S.H.V.E- Transactions, Vol. 60, 1954, p. 249). Miscellaneous Articles. Measuring Air Distribution and Grille Performance in Air Conditioning, by G. L. Tuve (A.S.H.V.E. Journal Section, Heating, Piping A Air Conditioning, November 1937, p. 700). Air Discharge from Narrow Slots, by F. F. Stevenson (Heating, Piping A Air Conditioning, May 1941, P- 308, and June 1941, p. 368. Discussed by J. R. Fellows and D. W. Nelson, joc. cit., September 1941, p. 558 andV5e5r9t)ic. al Air Distribution in Tall Buildings, by Sturm (Heating, Piping A Air Conditioning, June 1947, p. 69 aEnfdficSieepntteAmibreDr 1is94tr7i,bpu.ti9o3n). in Theatre. (Heating, Piping and Air Conditioning, Question of the Month. AugTuesstt1E94v7e, rpy. A10ir7;CSoenpdteitmiobneinrg19S4y7,spte.m11, 3b;yNLo.veTm. Abevre1ry94a7n, pd.J1.0B3)l.ack. (Heating and Ventilating, June 1948 P. 9B6)a.lancing an Air Conditioning System, by L. R. Phillips. (Refrigerating Engineering, July 1950, P- Hi)What is a Draft? (Healing. Piping A Air Conditioning, Open for Discussion. May 1951, p. 67, July 1951, P- 71, SSeevpet.n1Q95u1e,spti.o6n9s, oJnanDuuacryts1a9n5d2, Gp.ri1ll1e3s,.M(Haercahtin19g5,2P, ipp.in73g).A Air Conditioning, Question of the Month- May 1952A, ipr.D1i0s6traibnudtJiounlyS1tu95d2ie. sp,.b1y11R). . V. Martelli and H. O. Scarlett (Heating, Piping A Air Conditioning, vember 1952, p. 77. Discussed by W. 0. Huebher, loc. cit. Jan. 1953, p. 119 and by the Authors, March1W> p. 85). CHAPTER 32 AIR DUCT DESIGN Pressure Changes, Friction Losses,. Circular. Equivalents of Rectangular Ducts, Dynamic Losses, Pressure .Losses in Elbows, Pressure Losses in Divided-Flow Fittings, Losses Due to Area' Changes, Pressure Changes, Duct Design . Methods and Examples, Duct Construction Details, Heat Losses from Duets IN THE design of air duct systems, the objective is to provide a system that, within prescribed limits of noise and space available for ducts, efficiently transmits the required flow rate of air (cfm) to each space while maintaining a proper balance between investment and operating cost. When the heating,' cooling or ventilation load is established, the total flow, rate of air required can be determined by methods shown in Chapters 12 and 13. The problem is then to distribute the supply air properly among the spaces. ------- ; . PRESSURE CHANGES Ductwork imposes resistance to air flow which must be overcome by the expenditure of mechanical energy; this energy is ordinarily supplied by a fan. The portion pf the air flow rate fromi the fan that is transmitted to a particular space is governed by the law that the loss in total pressure from the fan outlet must be the same along each air path. This also holds for the return-air system except that the loss in total pressure refers to the fan inlet. In air conditioning and ventilating work, the pressure differences are ordinarily so small that the equations for incompressible flow can be applied. Additional simplicity is obtained by considering the air to be at the standard density of 0.075 lb per cu ft. At any cross section in a. duct .the total pressure H is the sum of the static pressure P and the velocity pressure //,, . Thus, . II = P + II. (1) Pressures are considered in unite of inches of water, sure is then given by The velocity pres- 4005/ where V is defined by the equation (2) where (3) V = mean velocity of flow, feet per minute. Q = air flow rate, cubic feet per minute. A -- cross-sectional area of duct, square feet. The total pressure H is a measure of the total mechanical energy at a cross section. In any duct system, the total pressure always decreases m 731