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780 CHAPTER 30 1957 Guide ASHVE Research Report No. 1204--Entrainment and Jet-Pump Action of Air Streams, bv G T Tuve, G. B. Priester, and D. K. Wright, Jr. (ASHVE Transactions, VoI. 48,1942, p. 241). ASHVE Research Report No. 1248--Control of Air Streams in Large Spaces, by G. L. Tuve and n B. Priester (ASHVE Transactions, Vol. 50, 1944, p. 153). ASHVE Research Report No. 1328--The Discharge of Air-from a Long Slot, by Alfred Koestel and O L. Tuve (ASHVE Transactions, Vol. 54, 1948, p. 87). - ASHVE Research Report No. 1366--Air Streams from Perforated Panels, by Alfred Koestel. Phflin Hermann and G. L. Tuve (ASHVE Transactions, Vol. 55, 1949, p. 283). ASHVE Research Report No. 1404--Comparative Study of Ventilating Jets from Various Typ* of Outlets, by Alfred Koestel, Philip Hermann, and G. L. Tuve (ASHVE Transactions, Vol. 56, 1950 d 459). . ASHVE Research Report No. 1429--The Control of Air Streams from a long Slot, by Alfred Koeetd and C. Y. Young (ASHVE i ransactions, Vol. 57, 1951, p. 407). ASHVE -Research Report No. 1476--Air Velocities in Ventilating Jets, by G. L. Tuve (ASHVE Transactions, Vol. 59, 1953, p. 261). ASHAE Cooperative Research at Kansas State College ASHVE Research Report No. 1327--Downward Projection of Heated Air, by Linn Helander and G. V. Jakowatz (ASHVE Transactions, Vol. 54,1948, p. 71). ASHVE Research Report No. 1475 (In Cooperation with the Industrial Unit Heater Association}-- Maximum Downward Travel of Heated Jets from Standard Long Radius ASMS Nozzles, by linn Helander. S. M. Yen, and R. E. Crank (ASHVE Transactions, Vol. 59, 1953, p. 241). ASHAE Cooperative Research--General ASHVE Research Reports No. 857,911 and 966--Measurement of the Flow of Air Through Registers and Grilles, by E. L. Davies (ASHVE Transactions, VoL 36, 1930, p. 201; Vol. 37, 1931, p. 619 and Vol 39, 1933, p. 373). ASHVE Research Report No. 1076--Air Distribution from Side Wall Outlets, by D. W. Nelson and D. J. Stewart (ASHVE Transactions, Vol, 44,1938, p. 77). ASHVE Research Report No. 1092--The Flow of Air Through Exhaust Grilles, by A. M. Greene, Jr. and M. H. Dean (ASHVE Transactions, Vol. 44,1938, p. 387). ASHVE Research Report No. 1155--ThePerformanceof Stack Heads, by D.W. Nelson, D. H. Krans, and A. F, Tuthill (ASHVE Transactions, Vol. 46,1940, p. 206). ASHVE Research Report No. 1165--Development of Instruments few the Study of Air Distribution in Rooms, by A. P. Kratz, A. E. Hershey, and R. B. Engdahl (ASHVE Transactions, Vol. 46, 1940, p. 351)* ASHVE Research Report No. 1206--Performance of Stack Heads Equipped with Grilles, by D. W. Nelson, D. H. Lamb and G. E. Smedberg (ASHVE Transactions, Vol. 48, 1942, p. 279). ASHVE Research Report No. 1226--Performance of Side Outlets on Horizontal Ducts, by D.W. Nelson and G. E. Smedberg (ASHVE Transactions, Vol. 49, 1943, p. 68). Other Papers Presented at ASHAE Meetings ASHVE Research Report No. 1051--The Noise' Characteristics of Air Supply Outlets, by D. J. Stewart and G. F. Drake (ASHVE Transactions, Vol. 43,1937, p. 81). ASHVE Research Report No. 1158--Dirt Patterns on Walls, by R. A. Nielsen (ASHVE Transac tions, Vol. 46, 1940, p. 247). ASHVE Research Report No. 1361--Balancing Air Delivery of a System of'Manifold Air Diffusers, by G. S. Dauphinee and Peter Argentieri (ASHVE Transactions, Vol. 55, 1949, p. 213). ASHVE Research Report No. 1362--Air Distribution and Draft, by John Rydberg and Per NorbSck (ASHVE Transactions, Vol. 55, 1949, p. 225). ASHVE Research Report No. 1471--Room Air Distribution Research for Year *Round Air Condition* ing. Part I--Supply Outlets at One High Sidewall Location, by 8. F. Gilman, H. E. Straub, A. E. Herscef. and R. B. Engdahl (ASHVE Tranbactxonb, VoL 59, 1953, p. 151). ASHVE Research Report--Room Air Distribution Research for Year 'Round Air Conditioning Part H--Supply Outlets at Three Floor Locations, by H. E. Straub and 8. F. Gilman (ASHVE Trans actions, VoL 60, 1954, p. 249). Miscellaneous Articles Measuring Air Distribution and Grille Performance in Air Conditioning, by G. L. Tuve (ASHVB Journal Section, Heating, Piping A Air Conditioning, November 1937, p. 700). Air Discharge from Narrow Slots, by F. F. Stevenson {Healing, Piping A Air Conditioning, May iWL ft 308, and June 1941, p. 368. Discussed by J. R. Fellows and D. W. Nelson, loc. cit., September 1941, P-050 andV5e5r9t)ic. al Air Distribution in Tall Buildings, by Sturm {Heating, Piping A Air Conditioning, June l^L P* 69 and September 1947, p. 93). Efficient Air Distribution in Theatre- {Heating, Piping and Air Conditioning, Question of the Mon August 3947, p. 107; September 1947, p. 313; November 1947, p. 103). Test Every Air Conditioning System, by L. T. Avery and J. Black. {Heating and Ventilating, June 1 P- 9B6a).lancing an Air Conditioning System, by L. R. Phillips. {Refrigerating Engineering, July 195* P' What is a Draft? {Heating, Piping A Air Conditioning, Open for Discussion. May 1951, p. 67, July 1951P 71, Sept. 1951, p. 69, January 1952, p. 113, March 1952, p. 73). Seven Questionson Ducts and Grilles. {Heating, Piping A Air Conditioning, Question of the Month* 1952, p. 106 and July 1952. p, 111). ^ Air Distribution Studies, by R. V. Martelli and H. O. Scarlett (Hearing, Piping A Air Conditioning vember 1952, p. 77. Discussed by W. O. Huebner, loc. cit. Jan. 1953, p. 119 and by the Authors, Mare** P- 85). CHAPTER 31 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 Ducts 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 of the air flow rate from 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 Hv . Thus, H = P + H, (1) Pressures are considered in units of inches of water. The velocity.pres sure is then given by - ~ (m)' where V is defined by the equation (2) V = (3) where V mean velocity of flow, feet per minute. Q -- air flow rate, cubic feet per minute. A =--* c- ross-sectional area of duct, square feet. The total pressure H is a measure of the total mechanical energy at a crss section. In any duct system, the total pressure always decreases in 781