Document kaEBww5R4NO0mpzGGyE4p71zb

HEATINC VENTILATING AIR CONDITIONING GUIDE 1943 REFERENCES A.S.H.V.E. 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. 1140--The Use of Air Velocity Meters, by Prof. G. L. Tuve, D. K. Wright, Jr. and L. J. Seigel (A.S.H.V.E. Transactions, Vol. 45,1939, p.645).. A.S.H.V.E. Research Report No. 1162--Air Flow Measurements at Intake and Discharge .Openings and Grilles, by G. L. Tuve and D. K. Wright, Jr. (A.S.H.V.E. Transactions, Vol. 46, 1940, p. 313). , 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. Hershey and R. B. Engdahl (A.S.H.V.E.- Transactions, Vol. 46, 1940, p. 351). A.S.H.V.E. Research Paper--Entrainment and Jet-Pump Action of Air Streams, by G..L. Tuve, G. B. Priester and D. K. Wright, Jr. (A.S.H.V.E. Journal Section, Heating; Piping and Air Conditioning, November, 1941, p. 708). Modern Air Conditioning, Heating and Ventilating, by W. H. Carrier, R. E. Cherne, and W. A. Grant (Pitman Publishing Corp., New York, N. Y., 1940). / N' ''' . 604. Chapter 32 AIR DUCT DESIGN Pressure Losses, Friction Losses, Friction Loss Chart, Elbotc Friction Losses, Proportioning the Losses, Duct Sizes, Pro cedure for Duct Design, Velocities, Main Trunk Ducts, Pro portioning the Size for Friction, Velocity Method, Equal Friction Method, Duct Construction Details THE resistance of an air handling system can be computed from the methods and data given in this chapter. The actual resistance for any given installation, however, may vary considerably from the calcu lated resistance because of variation in the smoothness of. materials, the type of joints used and the ability of the mechanics to fabricate in accor dance with the design. It is best to select fans and motors of sufficient . size to allow a factor of safety. Volume dampers should be installed iri each, branch outlet to balance the system. It is improbable that the required quantities of air will be delivered at each outlet without adjust ment of the dampers, which usually results in a total pressure exceeding that of the design, unless a liberal factor of safety is allowed. . The flow of air due to large pressure differences is most accurately stated by thermodynamic formulae for air discharge under conditions of adiabatic flow, but such formulae are complicated, arid the error occasioned by the assumption that the. gas density remains constant throughout the flow may be considered negligible when only such pressure differences are involved as occur in ordinary heating and ventilating practice. . In the development of the formulae; diagrams, and tables for the flow of air, use is made of the following basic equation for the flow of fluids: If Hv be the velocity head in feet of a fluid, and the velocity, F, he expressed in feet per minute, the fundamental equation is V = 60 ^2g Hv. The factor g is the acceleration due to gravity, or 32.16 ft per second per second. It is usual to express the head in inches of water for ventilating work and, since the . . heads are inversely'proportional to the densities of the fluids, Hv_ 62.4 hy . d' "IF or ' . 1 Hv = 5.2 if ' 605