Document MJzyoY9vxD3e9b65V3q3REeN7

American Society of Heating and Ventilating Engineers Guide, 1932 Table 5. Friction Heads (in Milinches) of Central Circular Diaphragm Orifices in Unions Diameter or Orifices (Inches) 2| 3 Velocity of Water in Pipe in Inches pee Second 4| 6 8 10 12 18 | 24 %-in. Pipe 36 0.25 0.30 0.35 0.40 0.45 0.50 0.55 1300 650 330 170 2900 1450 740 380 185 5000 2500 1300 660 330 155 75 11,300 5700 2900 1500 740 350 170 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 47,000 13,000 24,000 53,000 6500 12,000 27,000 3200 5700 13,000 1600 2800 6400 0.35 0.40 0.45 0.50 0.55 0.60 0.65 900. 460 270 160 2000 1000 570 330 190 3500 1800 1000 580 330 200 120 1-in. Pipe 7800 4000 2300 1400 750 440 260 14,000 7200 4100 2300 1300 800 460 22,000 12,000 6400 3700 2200 1300 720 32,000 17,000 9300 5400 3000 1800 -1100 37,000 21,000 12,000 7000 4200 2400 65,000 37,000 22,000 50,000 13,000 28,000 7400 17,000 4300 10,000 0.45 0.50 0.55 0.60 0.65 6.70 0.75 1000 660 430 280 190 2250 1450 950 630 420 285 190 4000 2600 1700 1100 750 510 330 1 ff-in. Pipe 8900 5800 3800 2500 1700 1150 750 16,000 10,400 6800 4400 . 3000 2000 1300 25,000 16,400 10,500 6900 4700 3100 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 60,000 18,000 40,000 12,000 26,000 0.55 0.60 0.65 0.70 0.75 0.80 0.85 850 1900 3300 600 1300 2300 400 850 1500 260 600 1100 180 400 760 300 540 200 380 li^-in. Pipe 7400 5400 3600 2600 1800 1200 860 13,000 8600 7200 4400 3000 2200 1600 21,000 16,800 10,400 7000 5000 3200 2300 30,000 21,000 14,000 10,000 7000 5000 3000 50,000 30,000 21,000 14,000 10,200 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 2-in. Pipe 1600 1000 650 420 220 3700 2200 1400 830 520 350 200 6100 4000 2550 1500 900 600 400 13,800 26,000 '9800 16,000 5800 9800 3600 6200 2200 3800 1300 . 2400 600 1600 39,000 56,000 25,000 36,000 16,000 23,000 10,000 .14,000 6000 9000 3800 5600 2300 3300 59,000 29l,000 19,000 11,000 7800 52,000 34,000 22,000 52,000 13,500 31,000 Note.--The losses of head for the orifices in the and 2-in. pipe were calculated from those in the smaller pipes, the calculations being based on the assumption that, for any: given velocity, the loss of head 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 t-in., and IK-in. pipe, con ducted by the Texas Engineering Experiment Station, and also in the tests to determine the losses of head. 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). ' 120 Chapter 8--Hot Water Heating Systems and Pipe Sizes If the design of the system of Fig. 5 is to be extremely refined, the gravity pressure heads produced by the riser should be taken into con sideration. With water at 220 F and 210 F, respectively, in the risers, the gravity head is 50 milinches per foot of water column or 25 milinches per foot of pipe, flow and return. The pump pressure head in this case is 240 milinches per foot of pipe, and the gravity head, being only one tenth as large as the pump head, may be neglected without serious error. This is generally done. Temperatures of 220 F and 210 F would be used only during the coldest weather for which the system is designed. At other times the tempera tures would be lower, the temperature drop smaller, and the gravity heads smaller. The pump pressure head remains constant -throughout the 50 (fl IZOOOBTU 50 + 10% *55 (fa IZOOO 8TU Fig. 6. A One-Pipe Gravity Circulation System season if the pump is operated at a constant speed, and consequently, the gravity head is generally less than one tenth of the pump head. Permissible Variations in Pipe Sizes The pipe sizes for the several parts of the system selected from the tables are only approximately correct but the resulting error should be negligible as may be seen from the following study: Assume, as an extreme case, that the error in pipe size is so large that the water flows twice as fast through one of the radiators as through the others. This would make the friction head through this radiator almost four times as large as those through the other radiators. The result would be that the water, in flowing through the radiator, would cool 5 deg instead of 10 deg. The mean water temperature in the radiator would then be 217)^ F in stead of 215 F, and the mean temperature difference, water to air, would be 147)4 deg instead of 145 deg. The heat dissipated by the radiator would therefore be about 2 per cent more than calculated. It is evident that this difference in heat dissipation is smaller than the difference 121