Document EdKrGZ586vw9B0oVvJ4yDOxpL

HEATING VENTILATINC AIR CONDITIONING GUIDE 1944 _________________ Table 1. Flow of Steam in Pipes P = loss in pressure in pounds. D = inside diameter of pipe in inches. L -- length of pipe in feet. d -- weight of 1 cu ft of steam. W = pounds of steam per hour. P = 0.0000000367 ( Pressure Loss IN Ounces Col. 1 Pips Size .... I~P~ 100 Nomina Actual Internal Diameter Pipe Sq Inches Col. 2 1* Col. 3 vBT Gage /-- IN Feet Col. 4 V-r 0.25 65.28 i 1.049 0.864 0.536 -1.0 0.187 20 2.240 0.50 92.28 1.380 1.496 1.178 -0.5, 0.190 40 1.580 1.00 2 130.5 184.6 m 1.610 2 2.067 2.036 3.356 1.828 3.710 0.0 0.193 0.3 0.195 60 1.290 80 1.120 3 226.0 2H 2.469 4.788 6.109 1.3 0.201 100 1.000 4 261.0 3 3.068 7.393 11.183 2.3 0.207 120 0.912 5 291.8 3K 3.548 9.887 16.705 5.3 0.223 140 0.841 .6 319.7 4 4.026 12.730 23.631 10.3 0.248 160 0.793 7 '345.3 4% 4.506 15.947 32.134 15.3 0.270 180 0.741 8 369.1 5 5.047 20.006 43.719 20.3 0.290 200 0.710 10 412.7 6 6.065 28.886 71.762 30.3 0.326 250 0.632 12 452.0 7 7.023 38.743 106.278 40.3 0.358 300 0.578 14 488.3 8 7.981 50.027 149.382 50.3 0.388 350. 0.538 16 522.0 9 8.941 62.786 201.833 60.3 0.415 400 0.500 20 583.6 10 10.020 78.854 272.592* 75.3 0.452 450 ,0.477 24 639.3 12 12.000 113.098 437.503 100.3 0.507 500 0.447 28 690.5 14 13.250 137.880 566.693 125.3 0.557 600 0.407 32 738.2 16 15.250 182.655 816.872 150.3 0.603 700 0.378 40 825.4 Column 1 X 2 X 3 X 4 = lb of steam 175.3 0.645 800 0.354 per hour that will flow through a straight 48 904.1 pipe for a given condition. 200.3 0.685 900 0.333 Example i: 1 oz drop -- 2 in. pipe 80 1167.2 .-- 1.3 lb press- -- 100 ft equivalent length: 1000 . 0.316 160 1650.7 130.5 X 3.710 X 0.201 Xl = 97.2 lb per hour. 97.2 X 4b = 388.8 sq ft equivalent radiation. 1200 0.289 320 2334.5 Table 1 does not allow for entrained water in low-pressure steam, condensation in covered pipe and roughness in com- 1500 0.258 mercial pipe as found in practice. 480 2859.1 2000 : 0.224 "Pounds per square inch gage -- 2.04 in. Vacuum, Mercury Column. . bThe factor 4 is the approximate equivalent in square feet of steam radiation of 1 lb of steam per hour. 280 CHAPTER 15. PIPING FOR STEAM HEATING SYSTEMS locations may be different from those which exist for appreciable periods at other locations and which under constant pressure may have conditions that are approximately the same. In designing piping it is of especial importance to arrange the system to preclude trouble caused by such pressure differences. The systems which readily release the air permit uniform pressures to be attained in much shorter time intervals than those which are sluggish. Results are given in Fig. 1 from investigations1 to determine the rate of condensate and air return from a two-pipe gravity heating system. Variations in the steam pressure during the warming up period when the rate of air elimination and condensation is high are clearly indicated in these curves. If is evident that the condensation flow during the initial warming-up Fig. 1. Relation Between Elapsed Time, Steam Pressure, Condensate and Air Elimination Rates period reaches a peak which is greater than the constant condensation rate which is eventually reached when the pressure becomes uniform. Moreover, the peak condensation rate is obtained when the system steam pressure is lower than that existing during a period of constant condensing rate. It will also be noted that the peak rate of air elimination does not coincide with the higher condensing rate. STEAM FLOW The rate of flow of dry steam or steam with a small amount of water flowing in the same direction is in accordance with the general laws of gas flow and is a function of the length and diameter of the pipe, the density of the steam, and the pressure drop through the pipe. This relationship, has been established by Babcock in the formula given at the top of Table 1. In Columns 1, 2, 3, and 4 of this table, the numerical values of the factors for different pressure losses, pipe diameters, steam densities and lengths of pipe have been worked out in convenient form so that the steam flowing in any pipe may be calculated by multiplying together the proper factors in each column as shown in the example at the bottom of the table. lA.S.H.V.E. Research Report No. 954--Condensate and Air Return in Steam Heating Systems, by F. C. Houghten and J. L. Blackshaw (A.S.H.ViE. Transactions, Vol. 39, 1933, p. 199). 281