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730 CHAPTER 32 1954 Guide h0 = friction loss under actual (operating) conditions, any consistent units. .' = pressure loss due to sudden contraction, feet of fluid flowing. h, = 'pressure loss due to sudden enlargement, feet of fluid flowing. h, = friction loss, feet of fluid flowing. h, = regain in static pressure, feet of fluid flowing. h, = friction loss under standard conditions, any consistent units. h, = total dynamic pressure loss, feet of fluid flowing. k = conductivity, Btu per (hour) (sq ft) (Fahrenheit degree per inch). L = additional equivalent length of duct for loss in elbows, feet. L/W and L/D = additional equivalent length in terms of width and diameter, dimensionless. J = length of straight duct, feet. P = perimeter of duct, feet. Q = air quantity, cubic feet per minute. Qw = heat loss through duet walls, Btu per hour. R -- centerline radius of elbow, or vane radius as noted, feet. R/W and R/D = radius ratio, dimensionless. r = loss through specified duct sections, inches of water. Ij =a temperature of air entering duct, Fahrenheit degrees. 1, = temperature of air leaving duct, Fahrenheit degrees. (i = temperature of air surrounding duct, Fahrenheit degrees. . U - thermal transmittance coefficient, Btu per (hour) (square foot), (Fahrenheit degree). _ V = mean velocity of standard air, feet per minute. Fm " mean velocity of air or fluid, feet per minute. Fj = mean velocity of standard air in inlet duct section, feet per minuter' * jr, = mean velocity of standard air in outlet duct section, feet per minute,; v = mean fluid or air velocity, feet per second. Vi = mean velocity in inlet duct section, feet per second. Vt = mean velocity in outlet duct section, feet per second. W -- duct dimension in plane of bend, feet. w = weight rate of air flow through duct, pounds per hour. x -- thickness, inches.' REFERENCES 1 A.S.H.V.E. Research Paper No. 1280--A New Friction Chart for Round Ducts, by D. K. Wright, Jr. (A.S.H.V.E. Transactions, Vol. 51, 1945, p. 303). 2 Friction Factors for Pipe Flow, by L. F. Moody (A.S.M.E. Transactions, Vol. 66, 1944, p. 671). 3 See Chapter 1 for definition of standard air. 4 Friction Charts for Gases Including Correction for Temperature, Viscosity and Pipe Roughness, by R. D. Madison and W. R. Elliot (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, October, 1946). 2 Friction Equivalents for Round, Square and Rectangular Ducts,_ by R. G: Huebscher (A.S.H.V.E. Journal Section, Heating, Piping and Air Conditioning, Decem ber, 1947). Winter Air Conditioning, by S. Konzo (National Warm Air Healing and Air Con ditioning Association, 1939, p. 363). " 7 Modem Air Conditioning, Heating and Ventilating, by W. H. Carrier, R- E. Cherne and W. A. Grant, 1940, p. 234 (Pitman Publishing Corp.). 3 Heating, Ventilating and Air Conditioning, by L. A. Harding and A. C. Willard, 1932, p. 673 (John Wiley and Sons). 9 A.S-H.V.E. Research Report No. 1405--Energy Losses in 90-Depee Duct Elbows: A Survey and Analysis of Available Information, by D. W. Lockhn (A.S.H.VE. Transactions, Vol. 56,1950, p. 479). 10 Pressure Loss in Ducts with Compound Elbows, by J. R- Weske {National A. visory Committee-for Aeronautics, Advance Restricted Report W-39, February 1943). 11 Pressure Losses in Rectangular Elbows, by R. D. Madison and J. R- Barker (Heating, Piping and Air Conditioning, July, p. 365, August, p. 427, Septembe , p. 483, 1936). 12 Fittings Losses for Extended-Plenum Forced Air Systems, by H. H. Korst, A. Buckley, S. Konzo, and R. W. Roose (A.S.H.V.E. Journal Section, Heating, Pip ing and Air Conditioning, February 1950, pp. 111-118. Air Duct Design 731 13 A.S.H.V.E. Research Report No. 216--Effect or Vanes in Reducing Loss in Elbows in Seven-Inch Square Ventilating Duct, by M. C. Stuart, C. F. Warner, and W. C. Roberts (A.S.H.V.E. Transactions, Vol. 48, 1942, pp. 409-424). 14 Pressure Losses Due to Bends and Area Changes in Mine Airways, by G. E. McElroy (U. S. Bureau of Mines, Information Circular I.C. 6663, p. 4). 13 Pressure Losses Resulting from Changes in Cross-Sectional Area in Air Ducts, by A. P. Kratz and J. R. Fellows (University of Illinois Engineering Experiment Station, Bulletin No. 300). 13 Fan Engineering, (R. D. Madison, Editor) 5th ed., 1948, pp. 124-128 (Buffalo Forge Company). 17 Design of Power Plant Installations: Pressure-Loss Characteristics of Duct Components, by J. R. Henry (National Advisory Committee for Aeronautics, Advance Restricted Report L4F26, June 1944, L-208). 13 Air Conditioning Principles, by C. O. Mackey, 1941, p. 158 (International Text book Company). - 19 Fluid Mechanics, by R. C. Binder, 1943, p. 152 (Prentice-Hall). 29 Modern Diffuser Design, by G. N. Patterson (Aircraft Engineering, Sept., 1938 P- 267) and The Design of Airplane Ducts, by G. N. Patterson (Aircraft Engineering, July, 1939, p.263). 21 Duct Sizing with Partial Static Regain, by R. H. Anderegg and F. W. Hutchin son (Healing, Piping and Air Conditioning, August, 1946, p. 97). 22 Power Sayings Through Static Pressure Regain in Air Ducts, by J. R. Fellows (Heating, Piping and Air Conditioning, April, 1939, p. 219). 23 Standards of the National Board of Fire Underwriters (N.B.F.U. Pamphlet No. 90, p. 21). . 24 Design of Air Conditioning Systems for Low Maintenance, by M..G. Kershaw (Refrigerating Engineering, October, 1946, p. 315). 23 Clean Your Ducts, by G. L. Candler (Heating, Piping arid Air Conditioning, July, 1947, p. 83). 23 Duct'Leakage and Job Revision, by E. L. Schulz (Healing and Ventilating, October, 1944,.p. 83). . ' BIBLIOGRAPHY * r L/vrr y&ee soapier 4; 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.). i'Tnv of Liquids, by W. H. McAdams (Refrigerating Engineering, February, 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 (A.S.M.E. 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 ~.e"veen the Smooth and Rough Pipe Laws, by C. F. Colebrook (Journal, Institute OJ Civil Engineers, Vol. II, 1938-39, p. 133). Evaluation of Boundary Roughness, by H. Rouse (Proceedings Second Hydraulics Conference, University of Iowa, Bulletin 27, 1943). PLOW OF AIR IN DUCTS I Rr*o^0na*^ ftesistance to the Flow of Air in Straight Ducts, by F. C. Houghten, ,- t. Schmieler, J. A. Zalovcik, and N. Ivanovic (A.S.H.V.E. Transactions, Vol. 45> 1939, p. 35). 1 Factors Affecting Duct Friction, by J. B. Schmieler, F. C. Houghten, d H. T. Olson (A.S.H.V.E. Transactions, Vol. 46, 1940, p. 193).