Document ppaanBNap1ReKrmxjDVdQBQbX

American Society, of. Heating and Ventilating Engineers'Guide/i9jj~~' corresponding height and diameter, can then- be determined from fin tions .6 and ,7j respectively, and the economical size will then be attairiwl Equations .6, 7 and 9 may be simplified considerably for average'operatT-'' conditions in an average size steam plant, by assuming the 'following' conditions: .- ;; . ... & Average chimney gas temperature, 500 =-960' v. i . : . Mean atmospheric temperature;-62 F ....... J:...To = 522 ' ? 1 Average coefficient of friction. 0.016....................... .............../ = 0.016 Average chimney gas density, 0;09__:................................IVC = 0.09 ^ Sea level elevation with barometer of 29.92__= 29.92.. Substituting these values in Equations 9, 7 and 6, respectively, and reducing: , . Vc = 13.7W1/S, (10) D = 1.5W2,b . , dp H -- 190Dr - . (i2) Fig. 7 gives the economical chimney sizes for various amounts of gases flowing and for required draft'int.ensitie"s as computed-from Equations 10 11 and 12. ^They- are' based on the- operating factors used in reducing Equations 6, -7. and 9-to their simpler form. The sizes shown by the curves in the chart should: be used, for-general, operating conditions only, or for installations where the required data necessary for an exact deter mination are difficult or impossible to secure. Whenever it'is possible to secure accurate data', or the anticipated operating conditions are fairly well known, the required size should be'determined from Equations 6. 7 and 9. The recommended minimum inside dimensions and heights of chimneys for small and medium size, installations are given in Table 1. GENERAL EQUATION . The general draft equation for a steam "producing .plamt may be stated as follows: ............... Dt -- hi - Af + Ab + /iBd + he + hBr + hv + to + Ae + Ar (13) where , Dt ^theoretical'draft intensity created by pressure transformer; inches .of water: ' Af' = draft loss due to friction in pressure transformer, inches of water. hv = draft loss through the fuel bed, inches of water. ' ' Ab = draft loss through the boiler and setting, inches of water. hlii = draft loss through the breeching, inches of water. hv = draft loss due to velocity, inches of water. .. tiBd = draft loss due to bends, inches of water. Ac = draft loss due to contraction of opening, inches of .water. ho = draft loss due to enlargement of opening, inches of water. Ae = draft loss through the economizer, inches of water. : Ar = draft loss through recuperators! regenerators, or air heaters, inches of water. The, left hand member.of Equation 13 represents the total amount of available-draft created by the pressure transformer, that is,-the natural 432 -26--. Chapter Chimneys and Draft Calculations Table 1- Recommended Minimum - Chimney Sizes for Heating . Boilers and Furnaces8 -- VfCisBK*ACS fACfft * i-orUAO*8 PlPB Steam BotLEB Capacitt Sq Ft '.of Radi-/. ATION . . _ ' Hot .'Water'Heater .. Capacitt Sq Ft or Radi~ A1ION .. Dimen sions op : Fire Clat Lining' in Inches ' Rectangular Flub . Actual Inside Dimensions of Fire Clay . lining in Inches Actual Area ;.8q Io. Round Flub Inside nknM eter of lining - . in Inches. Actual Area Sq In. -v.,j 1000.-- . M. 590 ' 973 &i4 x13: 7" xll-H 81 .' 690 1,140 900 1,490 r 13x13: UMxllK . 127 900 .-1,490'. 8Hxl8- . 6Mx l6K 110. 1,100 . 1,820 1,700 2,800 13 x 18 iiyixitu 183 1,940 3,200 2,130 .3,520 . 18x18 15?ixl5M 248 2,480 . 4,090 20x20 17Kx'7K 298 3,150 5,200 4,300 - 7,100 - . - 4,600 . . 7,590 20x24 17x21.. 357. 5,000 8,250 24x24 21x21, 441 5,570 9,190 . 24x246 576 5,580 ;-9,200 ``V i 6,980 . 11,500. : , .u . 7,270 :12,000 24x286 672 8,700 14,400 28x286 784 9,380 15,500 - 10,150 16,750 .. i............... : .. 30 x 30b - 900 . 10,470 17,250 . I 28 x 326 . .896. 10 12 15 18 20 22' . .24 ' 27 ' 79 113' 177 254 .314 380 . -452 .573 Hbiobt in Ft Above ' Gratx ` " 35 7 .. 40 45 50 55 60 65 This table is taken from the A.S.H^V:E>,G6de of Minimum Requirements for the Heating and Venti lation of Buildings (Edition of 1929>._ ^ bOimensions are for unlined rectangular flues. . - draft chimney, Venturi chimney, or fan, and is eijudt .to-.the theoretical intensity less the internal losses incidental to.operation. ); The right hand member represents the sum of all ofthe variouslossesof draft throughout the entire boiler plant, installation outside of the ,pressure transformer itself. The left Iiand member expresses the available intensity and is analogous to the head developed by a centrifugal pump in a water works system, while the right hai^d member expresses the required draftjntensity and is analogous to^te total dynamic head iii a water works, system. For a general citculanbn of gases. where Da = Or = available draft intensity, inches of water. Dr *a required draft, inches of water. ' 4" " (14) The draft loss throughthefuel-bed (/if), or the amount of draft required to effect a given or required rate of combustion, varies between wide limits and represents the greater portion of the required draft. In coal-fired installations, the draft loss through the fuel bed is dependent upon; the following factors: (1) character and condition of the fuej, clean or dirty; (2) percentage of ash in the fuel; (3) volume of interstices in the fuel bed, 433