Document 44MYEXOaB7B7ZRG98dJboX69V

302 CHAPTER 21 1959 Guide 17 R. D. Tutt: Modem trends in air distribution (Refrigerating Engineering, May 1953, p. 509). "W. W. Kennedy: Design factors in high velocity air dis tribution (Heating and Ventilating, January 1954, p. 83). uJ. W. Kreuttner: Can air conditioning be simplified in large buildings? {Heating, Piping and Air Conditioning, August 1954, p. 94). "Gardner Savage: Air conditioning an operating hotel {Heating and Ventdating, September 1954, p. 100). "C. M. Wilson: Handbook on high velocity air distribution (Heating, Piping and Air Conditioning, November 1954, p. 94). Discussions {Heating, Piping and Air Conditioning, December 1954, p. 73; February 1955, p. 69; March 1955, p. 99; June 1955, p. 82). **R. W. Waterfill: Air conditioning of multi-room buildings (ASHAE Transactions, VoL 61,1955, p. 233). B P. B. Gordon: Air conditioning multi-story buildings {Heating, Piping and Air Conditioning, April 1955, p. 112). Discusion {Heating, Piping and Ad Conditioning, May 1955, p. 103). " N. S. Shataloff: Elements of dual duct design and per formance (ASHAE Transactions, Vol. 62, 1956, p. 257). N. J. Janisse: How to control high velocity double duct air systems (Heating, Piping and Ad Conditioning, November 1955, p. 122 and'December 1955, p. 100). "E. F. Snyder, Jr.: Self-actuated room control from high speed air (ASHAE Transactions, Vol. 62, 1956, p. 295). " High-velocity Ad Distribution (collected papers read at Symposium at ASHAE 62nd Annual Meeting, January 25,1956). "C. M. Ashley, S. F. Gilman, and R. A. Church: Branch fitting performance at high velocity (ASHAE Transactions, Vol. 62, 1956, p. 279). " National Board of Pde Underwriters Standards {NBFU Pamphlet No. 90, p. 21). BIBLIOGRAPHY Hurd Row (Sm Chapter 4) Hunter Rouse: Elementary Mechanist of Fluids (John Wiley A Sons, Inc., New York, 1946). J. C. Hunsakcr and B. G. Righttniie: Engineering Applica tions of Fluid Mechanics (McGraw-Hill Book Co., New York, 1947). Clifford'McClain: Fluid Flow in Pipes (The Industrial Press, New York, 1952). H. C. Berry: Flow and Fan-Principles of Moving Ad Through Ducts (Hie Industrial Press, New York, 1954). R. J. S. Pigott: Hie Sow of fluids in closed conduits (Me chanical Engineering, Vol. 55, 1933, p. 497). E. Kemler: A study of the data on the flow of fluids in pipes {ASMS Transactions, Vol. 55, 1933, p. 7). Row of Afr tn Owcfr F. C. Houghten, J. B. Schmieler, j. A. Zalovrik, and N. Ivaaovic: ASHVE Research Report No. 1105--Frictional re sistance to the flow of air in straight ducts (ASHVE Trans actions, Vol. 45, 1939, p. 35). J. B. Schmieler, F. C. Houghten, and H. T. Olson: ASHVE Research Report No. 1154--Analysis of factors affecting duct friction (ASHVE Transactions, Vol: 46, 1940, p. 193). G. R. Whitn&h and J. V. Bony: Pressure loss characteristics of small diameter round duct systems (ASHVE Journal Sec-' tion, Heating, Piping and Ad Conditioning, November 1952, p. H. G. Conn, W. G. Colborne, and W. G. Brown: ASHVE Research Report No. 1470--Pressure losses in 4-inch diameter galvanized metal duct and fittings (ASHVE Transactions, VoL 59, 1953, p. 139). Prawn Low m Shows F. L. Busey: Loss of pressure due to elbows in the transmis sion of air through pipes or ducts (ASHVE Transactions, Vol. 19, 1913, p.366). Loring Wirt: New data for the design of elbows in duct sys tems {General Electric Review, Vol. 30, June 1927, p. 286). O. E. Parker: An investigation of pressure losses in air duct elbows (Northeastern University thesis. May 28, 1934). C. H. McLellan and W. A. Bartlett, Jr.: Investigation of Air Flow tn Right Angle Elbows tn a Rectangular Duct (National Advisory Committee for Aeronautics, Advanced Restricted Report L-328, October 1941). M. C. Stuart, C. F. Warner, and W. C. Roberts: ASHVE Research Report No. 1211--Pressure loss caused by elbows in eight-inch round ventilating duct (ASHVE Transactions, Vol. 48, 1942, p. 335). J. R.* Weske: Experimental Investigation of Velocity Dis tributions Downstream of Single Duct Bends {National Ad visory Committee for Aeronautics Technical Note 1471, Jan uary 1948). J. R. Weske: Investigations of the flow in curved ducts at large Reynolds numbers (Applied Mechanics Journal, Decem ber 1948, p. 344). R. K. Guthrie: How much pressure loss in round elbows? {Heating, Piping and Ad Conditioning, March 1955, p. 130). R. D. Madison and R. M. Conner: Discussion (Heating, Piping and Ad Conditioning, April 1955, p. 89). R. K. Guthrie: Discussion (Heating, Piping and Ad Con ditioning, June 1955, p. 81). Prescur* ton in OivNted-Aow FtHmgt H. H. Korst, H. A. Buckley, S. Konzo; and R. W. Roose: ASHVE Research Report No. 1392--Fitting losses for ex tended-plenum forced air systems (ASHVE Transactions, Vol. 56, 1950, p. 259). J. W. Hoil, S. F. Gilman, R. J. Martin, and S. Konzo: ASHVE Research Report No. 1430--Pressure losses of take-offs for ex tended-plenum duct systems (ASHVE Transactions, Vol. 57, 1951, p. 419). L. G. Miller, C. H. Pesterfield, and R. J. Waalkes: Resistance of rectangular divided-flow fittings (ASHAE Transactions, Vol. 62, 1956, p. 145). Duct Design L. G. Miller: ASHVE Research Repost No. 1050--A rational method of duct design (ASHVE Transactions, Vol. 43, 1937, p. 71). Kirby Walker: Modem thinking applied to duct design {Heating, Piping and Ad Conditioning, March 1949, p. 85; April 1949, p. 104; May 1949, p. 91; July 1949, p. 95; September 1949, p. 96; November 1949, p. 97; March 1950, p. 97; May 1950, p. 94). Pointers on air conditioning duct design and installation {Reference Section, Heating and Ventilating, October 1951). Peter Franck: Economical duct layouts {Heating, Piping and Ad Conditioning, December 1952, p. 100). F. W. Hutchinson: The Design of Aluminum Duct Systems (Kaiser Aluminum & Chemical Sales, Tnc. Oakland, California. 1954). R. W. Ruppert: Nomograph simplifies duct design {HPAC Data Sheet, Heating, Piping and Ad Conditioning, July 1955, p. 127). V. J. Turecamo: To size ducts adequately select the right pressure drop {Heating, Piping and Ad Conditioning, April 1956, p. 110). MneeHoaeov* R. H. Heilman and R. A.-McArthur: Performance tests of asbestos insulating air ducts (ASHVE Transactions, Vol. 44, 1938, p. 197). j | j i 1s t 1 1 CHAPTER 22 FANS Types, Fan Performance, Fan Laws, Fan Performance Curves, System Characteristics, Fan Arrangements, Fan Control, Motive Power, Fan Selection, Fan Installation, Fan Applications N HEATING, ventilating and air-conditioning practice, I the devices used to produce air flow are variously known as fans, Mowers, exhausters or propellers. The ASME Test Code1 limits fans to those in which the fluid density change does not exceed 7 percent (one psi at atmospheric pressure) and labels as compressors those devices operating beyond that pressure range. Since air conditioning rarely requires pressures of over Vt psi, all such devices will be known as fans and the air will be considered non-compressible. defined by the Air Moving and Conditioning Association1 as follows: 1. Volume handled by a fan is the number of cubic feet of air per minute expressed at fan outlet conditions. 2. Total pressure of a fan is the rise of pressure from fan inlet to fan outlet. 3. Velocity pressure of a fan is the pressure corresponding to the average velocity determination from the volume of air Sow at the fan outlet area. TYPES 4. Static pressure of a fan is the total pressure diminished by the fan velocity pressure. Fans are divided into two-general classifications:. (1) centrifugal or radial flow in which the air flows radially . 5. Power output of a fan is expressed in horsepower and is baaed on fan volume and the fan total pressure. through the impeller within a scroll type housing, and (2) axial flow in which the air flows axially through the impeller within a cylinder or ring. Centrifugal fans are further subdivided into types denoted by the curvature 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 inclina tion, a relatively high speed of operation. Many intermediate forms are also found. Axial-flow 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 impeller diameter; ma terials and methods of fabrication, depending upon design and preference of manufacturer. Tubeaxial and vaneaxial fans, usually used against appreciable resistance, commonly have relatively large hubs and helical blades (the angle varies radially along the blade). The blades may be of uni form 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 im peller and enclosure is common practice. Vaneaxial fans in 6. Power input to a fan is expressed in horsepower and is measured horsepower delivered to the fan shaft. 7. Mechanical efficiency of a fan is the ratio of power out put to power input. 8. Static efficiency of a fan is the mechanical efficiency multiplied by the ratio of static pressure to the total pressure. 9. Fan outlet area is the'inside area of the fan outlet. 10. Fan inlet area is the inside area of the inlet collar. While the total pressure truly represents the- actual pres sure developed by the fan, the static pressure may best represent the useful pressure for overcoming resistance. In many installations, since the outlet velocity of the Tan is greater than the duct velocity, some of the velocity pressure may be utilized by conversion to static pressure within the system. However, due to the' uncertainty of the flow at the points of velocity change, the amount of conversion is sel dom known and therefore, most fan tables list only the static pressure as available to overcome the system resist ance. According to the Standard Test Code1 the efficiencies may be determined by the formulas: - corporate guide vanes to modify performance and increase efficiency. Propeller fans customarily used for free delivery, or against low resistance, also are found with a variety of Mechanical (total) Efficiency " 0.0001573 X (cfm) X total pressure (inches water) blade conformations, but are simple in construction. They are iperely mounted within a plate or ring. horsepower input The fan nomenclature in Fig. 1 has been standardized by the .Air Moving and Conditioning Association.1 / FAN PERFORMANCE Static Efficiency - 0,0001573 x (cfm) X static pressure (inches water) horsepower input Fan performance is.a statement of volume, total pressures, static pressures, speed, power input, mechanical efficiency, and static efficiency, at a stated density. These terms are As the static pressure is often more useful than total pres sure, static efficiency is likewise many times more useful than l j: