Document wq65G2p2LxMraxDjqpYgnQb73

674 CHAPTER 31 1950 Guide ** Clean Your Ducts,- by G.L. Ce.ndler(Heaiing, Piping and Air Conditioning, July, 1947, p. 83). . Duct Leakage and Job Revision, by E. L. Schulz (Heating and Ventilating, October, 1944, p. 83). BIBLIOGRAPHY FLUID FLOW (See Chapter i) Engineering Applications of Fluid Mechanics, by J. C. Hunsaker and B. G. Rightmire, 1947 (McGraw-Hill Book Company, Inc.). Elementary Mechanics of Fluids, by Hunter Rouse 1946. (John Wiley & Sons, Inc.). The Flow of Liquids, by W. H. McAdams (Refrigerating Engineering, February, 1925, p. 279). The Flow of Fluids in Closed Conduits,by R.J.S.Pigott (Mechanical Engineering, Vol. 55,1933; p. 497). A Study of the Data on the Flow of Fluids in Pipes, by E. Kemler (AjSJf.fi. Transactions, Vol. 55,1933, Hydraulics, p. 7). Mechanical Similitude and Turbulence, by T. von Karman (translated and re printed as Technical Memorandum N.A.C.A. No. 611,1931). Turbulent Flow in Pipes, with Particular Reference to the Transition Region Between the Smooth and Rough Pipe Laws, by C. F. Colebrook (Journal, Institute of Civil Engineers, Vol. II, 1938-39, p. 133). Evaluation of Boundary Roughness, by H. Rouse (Proceedings Second Hydraulics Conference, University ofIowa, Bulletin 27,1943). 'n FLOW OF AIR IN DUCTS Frictional Resistance to the Flow of Air in Straight Ducts, by F. C. Houghten, J. B. Schmieler, J. A. Zalovcik, and N. Ivanovic (A.8.H.V.E. Transactions, Vol. 45, 1939, p. 35). Analysis of Factors Affecting Duct Friction, by J. B. Schmieler, F. C. Houghten, and H. T. Olson (A.S.H.V.E. Transactions, Vol. 46,1940, p. 193): . .. - The Flow of Air In Ducts, by E. Kemler (Heating and Ventilating, May 1936, p. 38). . . . - Total, Static and Velocity Pressure, by A. A. Berestneff (Heating, Piping and Air Conditioning, March 1932, p. 195). PRESSURE LOSS IN ELBOWS Flow of Fluids Through Valves, Fittings and Pipe (Crane Co., Technical Paper No. 409). , . '; Pressure Losses for Fluid Flow in 90 Pipe Bends, by K. H.Beij (National Bureau of Standards,Research Paper 1110, Journal of Research July 1938, p. 1): Pressure Loss in Ducts with Compound Elbows, by J. R. Weske (NIA.CJL. War time Report, Originally issued as A.R.R. Feb. 1943)1' DUCT DESIGN A Rational Method of Duct Design, by L. G. Miller. (A.S.H.V.E. Transactions: Vol. 43,1937, p. 71). -1 MISCELLANEOUS :' .: . ,. Performance Tests.of Asbestos Insulating Air Ducts, by R. Hi Heilman and R.A. McArthur (A.S.H.V.E. Transactions, Vol. 44, 1938, p. 197). Aluminum in Heating, Ventilating and Air Conditioning, Reynolds Metals Co., Louisville, Ky. CHAPTER 32 FANS Types, Fan Performance, Fan. Laws, Fan Performance Curves, System Characteristics, Fan Arrangements, Fan Control, Motive Power, Fan Selection, Fan Installation, Fan Applications IN HEATING, ventilating and air conditioning practice, the devices used to produce air flow are variously known as fans, blowers, exhausters or propellers. The AJSM.E. Test Code1 limits fans to those in which the fluid density change does not exceed 7 per cent (one psi at atmospheric pressure) and labels as compressors those devices operating; beyond that pressure range. Since air conditioning rarely requires pressures of, over J psi, all such devices will be known as fans and the air will be considered non-compressible. Types Fans are divided into two genera!classifications: (1) centrifugal or radial flow in which the air flows radially through the impeller within a scroll type housing, and (2) axial flaw in which the air flows axially through the impeller within a-cylinder or ring.............................. Centrifugal fans are further subdivided into types denoted by, the curva ture or slope of the impeller blades, the angle of which largely determines the operating characteristics. For a given output, a forward inclination of blade indicates a relatively low speed, of operation, and a backward in clination, a relatively high speed of operation. Many intermediate forms are also found. Axial flaw fans are subdivided into types differentiated mainly by. their enclosures and refinements of impellers and appurtenances. All types vary in shape, number and angles of blades; ratios of hub diameter to im peller diameter; materials and methods of fabrication, depending upon de sign and preference of manufacturer. Tubeaxial and vaneaxial fans, usu ally used against appreciable resistance, commonly have relatively large, hubs and helical blades (the angle varies, radially along the bade). The blades may be of uniform thickness, either flat or'cambered, and either cast or made of plates; or they may be of air foil sections, either cast or of double thickness sheet. Streamlining of both impeller and enclosure is common practice. Vaneaxial fans incorporate guide vanes to modify per formance and increase efficiency. Propeller fans customarily used for free delivery, or against low resistance, also are found with a variety of blade conformations, but are simple in construction. They are merely mounted within a plate or ring. The fan nomenclature in Fig. 1 has been standardized by the National Association of Fan Manufacturers.1 FAN PERFORMANCE Fan performance is a statement of volume, total pressures, static pres sures, speed, power input, mechanical and static efficiency, at a stated density. These terms are defined by the National Association of Fan Manufacturers* as follows: 1. Volume handled by a fan is the number of cubic feet of air per minute expressed at fan outlet conditions.