Document Kaw9O0e04apJb3dpZGMYGNmN

508 CHAPTER-24 1949 Guide Fi Fi Pi. P| P P if & Fig. 4. One-Pipe System Fig. 5. A Two-Pipe Direct Return System P IFF 0; Fig. 6. A Two-Pipe Reversed Return System spectively. These figures would also illustrate forced circulation if a pump or circulator were shown in the return line at the boiler. ; One-pipe gravity systems require very precise design owing to the small circulating head available. . Also, circulation in them is slow, and tem-perature drop is large toward the end of the main, and consequently these systems are usually considered-impractical. [One-pipe forced systems compared with gravity systems provide more' rapid circulation with, consequent smaller temperature drop in. mains' and more uniform water temperature in all radiators and are therefore preferred. Special flow and return fittings are available for improving the circulation to risers. . -v ' * Two-pipe systems'have separate flow and. return mains. If the return main is direct as shown in Fig. 5 the radiator at the end of the system has Table 3. , Heat-carrying Capacity of Type L Coffer Tubing with Temperature Drop of 20 Deo* Nominal Tube Sizes 1 in. to 4 in., and Friction 60 to 70 milinche* per foot. (A = Capacity, Ubh. B = Velocity, inches per second) [One milinch equals 0.001 in.) Noxikal Tubs MiLQica Fjocxiob Loss rsa Foot of Tubs Sob, Ik. 720 600 480 360 ; 300 340 150 150 120 90. 75 ' .60 A MB A HB so: 9 27 24 3 '63. 6J 21 . 18 16* 5.4 4.6 14 * 11 20 18 ' 16 13J 12 ioi 35 30 25 21 19 17 9 15 4 ` 3.6 3 23 *2.4' 11 10 M 8 7 8 7 6 5.4 4.7 13 12 10 9 8 A H B, 36 30 '26 22.1 20 17-8- `15 13.1': 11.8 9.9 87 34 80 M 31 19 17 15 13 11 9 7.9 10 9 A HB 51 46 40 34' . 31 28 2S2 205 18.1 15.3 13.9 12.1 42 33 33 . 27 v ' 24 21 19 ' 17 14 . 12 llj 10 . 1, A B 104 94 82 70 63 56 47 - 42 37 32 28 25 48. 45. 39 84. 80 25 19 17 14.5 13 , - 12 '. A . ,185 .169 VA B 65; 51 149 125 45 . 39 112. 100 84 J5 30 25 75 66 22 ' 19 56 50 4* 17 15 * H' A IH B 300 270 235 200 ISO ICO 134 120 105 62 67: 51 43 89 35 30' 25 22 90 81 71 19 17 .15 A 625 560 495 420 375 335 280 250 200 188 170 150 .2 B -. 76.- 68 69. . 51 _47 . 42 86 . 32 .27 22 , 20 .18 > `A: 1130 1010 . 890 750 680 600 600 450 . 895 -335 2H 90- SO .69 58 49 47 r 42 37 V. 26 69A 1840 1650 1450 1210 1100 680 820 740 650 550 3 B 98 90, ' * 30;,. .-.66.. . 62 A 47 v 42 86 30 305- 270 23 . 21 490 420 27 23 A *B 27n5o0 2480 100 2170 1840 - 89- 75 1650 66 1450 1210 57 . 51 1100 45 980 40 820 740 35 . 30. 650' 26 .< A A 3900 3505 8100 2600 2350 2090 1760 1580 1390 1180' 1080 950 B . 120. . 108 96. . 83 73 63 . 55. 49 44 37 84 . .29. For other temperature drops the pipe capacities may be changed correspondingly. For example. With' temperature drop ol 30 deg the capacities shown in this table are tp be multiplied byl.$. r .. Hot Water Heating Systems and Piping 509'- - Table 4* Friction, (in Milinches) op Central Circular . '' Diaphragm Orifices in Unions (One milinch equals 0.001 in.) DO(iAIrnKicOfEaiFcTsesssa) Vilocitt of Wires hi Pits m Inches per Sxcoujd V ' 6 8 . 10 12 I! 3/rin. Pipe 36. . 0.25 0.30: 0.35 o:4o 0.45 0.50 0.55 1300 650 330 '170 2900 1450 740 380' 185' 5000 11,300 2500 5700 1300 2900 660 '330' . 1500 : 740 155 . 350 75 . 170 20,800 10,400 , 5200 2600 1300 620 300 32.000 16.000 8000 4000 2000 970 480 45.000 23.000 12.000 6800 2900 1400 700 57.000 26.000 13,000 6500 3200 1600 47.000 24.000 53.000 12.000 27.000 5700 13.000 ' . 2800 6400 1-in. Pipe 6.35 0.40 0.45 0.50 0.55 0.60 0.65 900 `2000 3500 7800 14,000 22,000 32*000' 460 1000 1800 - 4000 7200 12*000 17,000 37,000 65,000 270 570 1000 2300 4100 6400 9300 21,000 37,000 160 330 580 1400 2300 3700 5400 12,000 22,000 50,000 190 330 750 1300 2200 3000 7000 13,000 28.000 200 440 800 1300 1800 4200 7400 17,000 - 120 260 460 720 1100 2400 4300 10,000 lVrin. Pipe 1000 660 430 280 190 2250 1450 950 630 420 ;285 190 4000 2600 1700 1100 750 >510 330 . 8900 5800 3800 2500 1700 1150 750 16,000 25,000 10,400 16,400 6800 10,500 4400 6900 3000 4700 2000 . 3100 1300 2100 36,000 23,000 15,000 10,000 6700 4500 3000 53,000 34,000 22,000 15,000 10,000 6700 60,000 40,000 27,000 18,000 12,000 . 1 `/2-in. Pipe .0.55 0.60 0.65 0.70 0.75 0.80 0.85 .850 .1900 600 1300 '400 850 260 600 180 .400 300 200 3300 2300 1500 1100 760 : 540 380 7400 5400 3600 2600 1800 ' 1200 860 13,000 21,000 30,000 8600 16,800 21,000 50,000 7200 10,400 14,000 30,000 4400 7000 10,000 21,000 3000 5000 7000 14,000 ' 2200 3200 5000 .10,200 1600 . 2300 . 3000 7800 53,000 39,000 28,000 19,000 45,000 13,000 30,000 0.70 0.80 0.90 1.00 1.10 1.20 1.30 S-in. Pipe 890 1850 3500 470 975 1800 255 .560 1000 160: '340 610 "214' - 375 195 ` 7400 3900 2200 1320 850 460 275 14,000 740) 4200 2520 1600 950 525 22,300 11,700 6500 4000 2500 1360 980 33,000 17,000 9500 5800 3700 1910 1375 37,000 20,500 38,000 12,500 23,000 49,000 7900 14,000 30,000 4200. ; 8100 16,800 3100 4400 8850 Note.--The losses of head for the orifices in the IH-in. and 2-ini. pipe were calculated from those in the smaller pipes, the calculations being based on the assumption that, for any given velocity, the loss of bead is a function of the ratio of the diameter of the pipe to that of the orifice. This had been found to be practically true in the tests to determine the losses of head in orifices in K*ih.. 1-in.; and l^-im pipe, con* ducted by. the Texas Engineering Experiment Station, and also in the tests to determine the losses 01 bead in orifices in 4-in., 6-in., and 12-in. pipe, conducted by the Engineering Experiment Station of the University Of Illinois, {Bulletin 109, Table 6, p. 38. Davis and Jordan).