Document jmYymYXQ6Ow4m3ekJzpDJvy7R

580 CHAPTER 31 1965 Guide And-Oata Book . Table;.l 3 _. . .> .WeighfSjqnd;Thidcrestes of Steel Sheets11 Member Gafvantzed Steei Steels (Gafv. Steel Gage) Weight, Lb Per Sq Ft Appro*. Thkkncn. inches -. ttocoofed. Corbon Steei Sheets . (th_S. Standard Gage) Weight, Lb Per Sq Ft Appro*. Thickness, Mia Chrota* Nkket Sfahdea Sfeef Steel* (U. S. Standard Gage) Appro*. Weight,.. Lb Per Sq Ft Appro*. Thickness, btdtet 26 24 22 20 18 " .14'. 0.906 1.156 1.406 1.656 2.156 ; 2.656 : .3.281- ' 10, , 5.781 : 0.0217 0.0276 0.0336 , 0.0396 . . 0.0516 1 , . -!o.0635 . . 0.0785 *' 0.1084 0.1382 .. .. 0.75 1.0 1.25 1.5 2.0 / 2.5 3.125....,4.375" 5.625 0.0179 . . 0.0239 0.0299 , 0.0359 0.0478 0.0598 i " 0.0747 0.1046 . 0.1345 0.787 1.05 1.313 1-575. 2.1. ' " 2.625 3.281 4.593 . 5.906 0-0187 0.025 0.0312 0.0375 0.05 0.0625...... - 0.0781.. . 0.1093. 01406 _ P -- perimeter.ofrduct, feet. , . t.. ... .. ' , I.TM, length of duct, feet: . 1 ,, Ji temperature of air entering duet, Fahrenheit.. t% -- temperature of air leaving duct, Fahrenheit. U " temperature of air surrounding duct, Fahrenheit. To obtain the temperature drop' in warm air for a given distance of transmission, or the temperature rise if the duct curies aircooler than the room through which it passes, the following formulas can be used: - 28J&AVp for rectangular ducts or. UPl . 7.2DV, .for round ducts. Ul A *= cross-sectional area of duct, aquare'feet. p ~ density of air, pounds per cubic foot. .;T V = mean velocity of-fluid, feet per minute.. ' D diameter of round duct, feet. Table, 14 .... Weights and Thicknesses of Non-Ferrous . . Sheets ' . , :~ If Equations 18 and 19 are used, one of the duct air tempera:..tures will be tinknown'and'.can be obtained by substitution ' of the other known or assumed values. Heat loss -coefficients for insulated ducts with various coaductivities are given in-Eig;;17. The conductivities of various materials will be found in Table 4 of Chapter 24. For cases where the mean 'temperature is other than that at which the Specified Ihickness, Appro*. Weight Specified - Approximate * Weight, - thickness. inches _ Oz Per Sq Ft -- 6I62O 0.025 0.032 0:040 ' 0.050 p ' 0T063 ' 0.285 .0.356 . ' 0:456 - 0:570 0.713 0.898 16 20 24 32 36 48 0.0216 0.0270 - : - 0.0323 * 0.0431......... 0.04S6 .. -. .0.0647 Table 15 .... Weights and Properties of Steel Angles . .Sim,:,. .it_ fnche*i a',, Uacoated Steel Gaivaaized Steel ApproxJ Weight, 'Approx. Weight,' -..i; f. lb:Per ft-.-. Moment of Inertia, j . , Inches* ix ixUbil a "l0\42'"'" "' `6.44'' ". 1X1X1 0.80 0.84 ijxux* 1.01 1.06 ljxijxi ' 1.23 i . . V- 1.29 lfxiixA ; - i,-8p` - - ; | 1.89' 1o:oi'1. 0.02 0.04 0.08 0.11 2X2X1 2X2XA 2X2Xf 2IX2JXA;' 1.65 2.44 3.19 " 3.07 1 1.73 2.56 - . .3.35., , . 0.19 0.28 . 0.35 , :' 0:55 : 1j :. - ri ^5*0- ' V - . X.r....... ...... . TTr-nJ] ""a .'CtstKCvr mows . . CCtFTH . MAUI OOCT DUCT ' THM MUaCH - tvmcaa mutch TWEprrs'ujoa vcuctrr) Fig. 16 .... Duct Arrangement Air- Duct Design 581 Substituting in Equation;17: .-0.X10X70[(^f^)-40] -- 28400 Btu per hr. * for round doct* fee* (ban SO In. dknnoter, feeroot* hoaf trmaaistiati 1 Thfatness of /ntipfa'lion (imdiet) 2 ;H i : AH 12- to 21rin.-Duct Diameter................ 13% 5% 7%. '9%' 21- to 30-in.-Duct Diameter..-. ........ 1%. :2% :3% 4% Rg. 1 % . Heat-Loss Coefficients for- Insulated'Duds*' `-;t test was conducted, a correction should be However, in most cases, the.effect of thU factor, will be small ahtl may.be neglected. ' v ........... . ExampU 8: Determine the entering air temperature and heat i8*! duct.24 X 36 in. croes-eoction and 70 ft in Imgth irjH-m. of a material'having a conductivity of 0.35 ui at 86 F mean temperature, carrying air at a velocity of 1200 -P measured at 70 F, to deliver air at 120 F with air surround ing the duct at 40 F. Solution: Referring to Fig. 17, the overall h*t. transmission weffioeot is found to be 0.49 Btu. From Table 1, Chapter 3, the " at 1 ? "4 29.921 in. Hg is found to be 1/13.348 - .P1 6,1 ft- Substituting these and the other given values us aquation 19, y and k will be aa follows: 28.3 X 6 X 1200 X 0.0749 0.49 X 10 X 70 452 120(453 4-1) - 80 k 463-1 123.7 F REFERENCES 1D. K. Wright,-Jr.: ASHVE Research Retort No. 1280--A' new friction chart for round ducts (ASHVE TBANSAcnorts, VoL' 51,1945, p. 303). 5 L. F. Moody: Friction factors for pipe flow [ASMS Tresis^1 actions, Vol. 66, 1944, p. 671). R. D. Madison and W. R. Elliot: Friction charts for gases'.' including correction for temperature, viscosity and pipe rough-* ti<* (ASHVE Journal Section, Healing, Piping and Air Cor* ditiomng, October 1946, p. 107). *F. W. Hutchinson: ASHVE Research Report No. 1469--, Friction losses in round aluminum ducts (ASHVE Tuns-;., actions, VoL 59, 1953, p. 127). 1R. G. Huebscher: Friction equivalents for round, square and; rectangular ducts (ASHVE Transactions, VoL 54,1948, p.101). *D. W. Loddin: ASHVE Research Report No. 1405-- Energy losses in 90-degree duct elbows: A survey and analysis of available information (ASHVB Transactions, VoL 56, 1950, p- 479). * J. R. Weske: Pressure Loss m Duels'with Compound Elbows __ (National Advisory Committee for Aeronautics, Advance Re-' tlricltd Report W-39, February 1943). * R. D. Madison and J. R. Parker: Prewire losses in reo^' elbows (Heating, Piping and Air Conditioning,' July, p. 365; August, p. 427; September, p. 483; 1936). - . W. H. Carrier, R. E. Cberne, W. A. Grant and W. H. Roberts;' Modern Air Conditioning, Heating and Ventilating (Pitman Pub lishing Corp., New York, 1959, 3rd ed., p. 256). ,- /. ** M. C. Stuart, C. F. Warner, and W. C. Roberts: ASHVE Research Report No. 1216--Effect of vanes in reducing loss in elbows in seven-inch square ventilating duct (ASHVE Trans-' actions, Vol. 48,1942, p. 409). n S. F. Gilman: Pressure losses of divided-flow fittings (ASHAE Transactions, Vol. 61, 1955, p. 281). **G. E. McEiroy: Pressure Losses Due to Bends and Area Changes in Mine Airways {U. S. Bureau af Mines Information Circular I.C. 6663, p. 4). "A. P. Kjats and J. R. Fellows: Pressure Losses Resulting from Changes tn Cross-Sectional Area in Air Ducts (University of Illinois, Engineering Experiment Station Bulletin No. 300).'. 11R. D. Madison (ed.): Fan Engineering (Buffalo Forge' Company, Buffalo, New York, 1948, 5th ed., p. 124). " J. R. Henry: Design of Power Plant Installations: Pressure-. Loss Characteristics of Duct Components (National Advisoiy Committee for Aeronautics, Advance Restricted Report' L4F2S, June 1944, L-20S). "L.O. Paul: Installing ducts for higher prespires, and Why higher duct velocities? (Heating, Piping and Air Conditioning, April 1953, p. 98 and February 1954, p. 109). l] R. D. Tutt: Modem trends in air distribution (Reprigeb- atino Engineering, May 1953, p. 509). ' -t u W. W. Kennedy: Design factors in high velocity air dis tribution (Heating and Ventilating, January 1954, p.'S3). * "J. 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 Ventilating, 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. WaterfUl: Air conditioning of multi-room buildings (ASHAE Transactions, VoL 61, 1955, p. 233). "p. B. Gordon: Air conditioning multi-story buildings (Heating, Piping and Air Conditioning, April 1955, p. 112). Discusion (Heating, Piping and Air Conditioning, May 1955, p. 103).