Page:The New International Encyclopædia 1st ed. v. 18.djvu/606

* STEAM. 520 STEAM. is formed. This temperature will depend upon the pressure or the load on the piston. If this pressure is the normal atmospheric pressure of 14.7 pounds per square inch, steam begins to form at a temperature of 212° F. As soon as 212° F. is reached, steam will begin to form and the piston will steadil}' rise, but no matter how hot the fire may be, the temperature of both water and steam will remain at 212° F. until all the water is evaporated. We had one pound of water at 32° F. and at 14.7 pounds ab- solute pressure, and found that steam formed at a temperature of 212° F. and remained at that temperature. We added 180.9 B. T. U. (British Thermal Units), the lieat of the liquid, to bring the water from 32° to the boiling point. To convert water at 212° into steam at 212°. we added 005.7 B. T. U. more. This quantity, known as the latent heat, or heat of vaporization, makes the total heat 114G.6 B. T. U. If we should measure the volume carefully after all the water was evaporated, we should find that there was just 26.36 cubic feet of dry saturated steam. We had one pound of water, and therefore must have one pound of steam, for none of it could escape; hence one cubic foot will weigh 1 = 0.03794 pound, which is known as the density of steam at 14.7 pounds absolute pressure or 212° F. In the table of properties of satu- lated steam all these quantities are found in the order given and at the piessure of 14.7 pounds above vacuum. Suppose now we place a weight of 85.3 pounds on the piston. Tlie pressure is 85.3 pounds plus 14.7 pounds, or 100 pounds absolute. We sliall now find that no steam will form until a tem- perature of 327.58° is reached. Starting with water at 32°, it will be necessary to add 297.9 B. T. U. before a temperature ' of 327.58° is reached, and also we nmst add 884 B. T. U. more to vaporize it. making a total heat of 1181.9 B. T. U. Under this greater pressure the steam occupies a volume of only 4.403 cubic feet, or one cubic foot of it weighs j.jji;, ^ 0.2271 pound. We have already seen that any change in the temperature of saturated steam produces a change of pressure, and that every change of pressure corresponds to a certain change in tem- perature. There are several properties of sat- urated steam that depend upon tlie temperature and pressure; and the values of all these differ- ent properties when arranged for all tempera- tures and pressures are called steam tables. The Table of- Pbopebtieb of Saturated Steam PREK8UBE Total heat Heat of Density or Volume Factor of Total pres- sure above vacuum IN POUNDB FEB SQUARE INCH ABOVE VACUUM Temperature in degrees. Fahrenheit in heat-units from water at 32° Heat in liquid from 32° in units vaporiza- tion, or latent heat in heat-units weight of cubic foot in pounds of 1 pound in cubic feet equivalent evapora- tion at 212<= 1 1 101.99 1113.1 70,0 1043.0 0,(10299 334,5 ,9661 1 2 126.27 1120.6 94,4 1026,1 0.II0S76 173,6 .9738 2 3 141.62 1126.1 109.8 1016.3 o,ons44 118.5 ,9786 3 4 153.09 1128. 6 121.4 1007,2 0,01107 90.33 ,9822 4 5 162.34 1131.5 130,7 1000, 8 0,01360 73,21 .9862 5 6 170.14 1133.8 138,6 996,2 0,01622 61. (» ,9876 6 7 176.90 1135.9 146,4 990,6 0,01874 63,39 .9897 7 8 182.92 1137.7 151,6 986,2 0,02125 47.06 ,9916 S 9 188.33 1139.4 166.9 982,5 0,02374 42,12 ,9934 9 10 193.25 1140.9 161,9 979,0 II (12621 38,15 .9949 10 15 213.03 1146.9 181,8 965,1 n,ii;ts26 26,14 1,0003 15 20 227.95 1161.5 196,9 954,6 (1.1)51)23 19,91 1.0061 20 25 240.04 1156.1 209,1 946,0 0,06199 16,13 1,0099 25 30 260.27 1158.3 219,4 938,9 0,07360- 13,69 1,0129 30 35 259.19 1161.0 228,4 932,6 0.08508 11,75 1,0167 35 40 267.13 1163.4 236,4 927,0 0.09644 10,37 1.0182 40 46 274.29 1165.6 243,6 922,0 0.1077 9,265 1.0206 45 60 280.85 1167.6 250,2 917,4 0,1188 8,418 1.0225 50 56 286.89 1169.4 266.3 913,1 0,1299 7,698 1.0246 56 60 292.61 1171.2 261,9 909,3 0,1409 7,097 1.0263 60 66 297.77 1172.7 267,2 905,6 0,1619 6,583 1.0280 65 70 302.71 1174.3 272,2 902,1 0,1628 6.143 1.0296 70 75 307.38 1175.7 276,9 898.8 0,1736 5,760 1,0309 75 80 311.80 1177.0 281.4 895,6 0,1843 6.426 1,0323 80 85 316.02 1178.3 286,8 892,6 0.1961 6.126 1,0337 85 90 320.04 1179.6 290,0 889.6 0,2068 4.859 1,0350 90 96 323.89 1180.7 294,0 886,7 0,2165 4,619 1,0362 95 100 327 . 58 1181.9 297.9 884,0 0,2271 4,403 1,0374 100 106 331.13 1182.9 301,6 881.3 0,2378 4,205 1,0385 106 110 334.56 1174.0 306,2 878,8 0,2484 4,026 1,0396 110 116 337.86 1186.0 308,7 876,3 0,2689 3,862 1,0406 116 120 341.06 1186,0 312,0 874.0 0,2695 3.711 1.0416 120 126 344.13 1186,9 316,2 871,7 0,2800 3,571 1,0426 125 130 347 . 12 1187.8 318,4 869.4 0,2904 3,444 1,0436 130 140 362.85 1189,5 324,4 865.1 0,3113 3,212 1,0453 140 160 368.26 1191.2 330.0 861,2 0.3321 3,011 1.0470 150 160 363.40 1192,8 335,4 857,4 0.3530 2,833 1,0486 160 170 368.29 1194.3 340,5 863, S 0,3737 2,676 1,0502 170 180 372.97 1195.7 345.4 i 850,3 0,3945 2,535 1,0517 180 190 377.44 1197.1 350.1 1 847.0 0,4153 2,408 1,0631 190 200 381,73 1198.4 354,6 843,8 0,4359 2,294 1,0546 200 226 391.79 1201.4 365,1 836,3 0,4876 2.061 1,0676 226 260 400.99 1204,2 374.7 829,6 0.5393 1,854 1.0605 260 275 409.50 1206,8 383.6 823,2 0,,5913 1,691 1.0632 275 300 417.42 1209,3 391.9 817.4 0,644 1,553 1,0657 300 326 424.82 1211,5 399.6 811.9 0,696 1,437 1,0680 326 360 431.90 1213,7 406.9 800,8 0,748 l.,<137 1,0703 360 376 438.40 1215,7 414.2 801.5 0,800 1,2.50 1,0724 375 400 445.16 1217,7 421.4 7K,3 0,863 1,172 1.0745 400 BOO 466.57 1224.2 444,3 779,9 1 1.065 .939 1,0812 500