Document NNej46daYjDz9RnnJbapadyDV

American Society 0/ Heating and Ventilating Engineers Guide, 1935 PROPERTIES OF STEAM Steam is water vapor which exists in the vaporous condition because sufficient heat has been added to the water to supply the latent heat of evaporation and change the liquid into vapor. This change in state takes place at a definite and constant temperature which is determined solely by the pressure of the steam. The volume of a pound of steam is the specific volume which decreases as the pressure increases. The reciprocal of this, or the weight of steam per cubic foot, is the density. (See Table 7.) Steani which is in contact with the water from which it was generated is known as saturated steam. If it contains no actual water in the form of mist or priming, it is called dry saturated steam.'If this be heated and the pressure maintained the same as when it was vaporized, its temperature will increase and it will become superheated, that is, its temperature will be higher than that of saturated steam af the same pressure. PROPERTIES OF WATER Composition of Water. Water is a chemical compound (H20) formed by the union of two volumes of hydrogen and one volume of oxygen, or two parts by weight of hydrogen and 16 parts by weight of oxygen. Density of Water. Water has its greatest density at 39.2 F, and it' expands when heated or cooled from this temperature. At 62 F a U. S. gallon of 231 cu in. of water weighs approximately 8J/3 lb, and a cubic foot ^ of water is equal to 7.48 gal. The specific volume of water depends on the temperature and it is always the reciprocal of its density. (See Table 8.) Water Pressures. Pressures are often stated in feet or inches of water column. At 62 F, with h equal to the head in feet, the pressure of a column of water is 62.383ft lb per square foot, or 0.433ft lb per square inch. A column of water 2.309 ft (27.71 in.) high exerts a pressure of one pound per square inch at 62 F. Boiling Point of Water. The boiling point of "water varies with the: pressure; it is lower at higher altitudes. A change in pressure will always be accompanied by a change in the boiling point, and there will be a cor responding change in the latent heat of evaporation. These values are given in Table 7. Specific Heat. The specific heat of water, or the amount of heat (Btu) required to raise the temperature of one pound of water one degree Fahren heit, varies with the temperature, but it is commonly assumed to be unity at all temperatures. Steam tables are based on exact values, however. The specific heat of ice at 32 F is 0.492 Btu per pound. The ` amount of heat required to raise one pound of water at 32 F through a known temperature interval depends on the average specific heat for the temperature range. Sensible and Latent Heat. The heat necessary to raise the temperatureof one pound of water from 32 F to the boiling point is known as the heat of the liquid or sensible heat. When more heat is added, the water begins to evaporate and expand at constant temperature until the water, is entirely changed into steam. The heat thus added is known as the latent heat of evaporation. 22 Properties of Saturated Steam: Pressure Table* Table 7. Ab<< Pr*u< Temp. Lb./Sq. In. Per. F. P W'Bg 3A" Hg i"Hg lW'Bg 58.83 70.44 79.06 9.1...7.5 2"Hg 101.17 3W'Kg 108.73 3"Hg 115.08 1.0 101.76 2.0 126.10 8.0 141.49 Specific Volume Set Uquid Vf E*PVfg Set. V*Pr Vg 0.01603 1256.9 0.01605 856.5 0.01607 652.7 0.01610 445-2 0.01613 339.5 0.01616 275.2 0.01618 231.8 1256.9 856.5 652.7 4453 339.5 275.2 231.8 0.01614 0.01623 0.01630 0.01636 3333 333.9 173.94 173.96 118.84 118.86 90.72 90.74 Total Heat SatLiquid Evap. Set. Vapor hi hi, *hg 26.SS38.47 47.06 59.72 69.10 76.63 82.96 1058.8 10S2.5 1047.8 1040.8 1035.7 1031.5 1027.9 108S.7 1091.0 1094.9 1100.6 1104.8 1108.1 1110.8 69.69 93.97 10933 120.83 103S3 110S.0 1021.6 1115.6 1012.7 1122.0 100S.9 11263 Entropy Sat. Liquid Eap. Sat. Abe. Praea. Vapor Lb./Sq. In. Sf Sfg 8e P 0.0533 0.0754 0.0914 0.1147 0.1316 0.1450 0.1561 2.0422 1.9856 1.9451 1.8877 1.8468 1.8148 1.7885 2.0955 2.0609 2.0365 2.0024 1_._9_7__8_4 1.9598 1.9446 %" %"gg l"Hg lW'Hg 2"Hg 2Vfc"Hg 3"Hg 0.1326 0.1750 0.2009 0.2198 1.8442 1.7442 1.6847 1.6420 1.9769 1.9192 1.8856 1.8618 1.0 2.0 3.0 4.0 4.0 152.99 6.0 162.25 6.0 170.07 7.0 176.85 8.0 182.87 9.0 188.28 10.0 11.0 12.0 13.0 14.0 14.696 193.21 197.75 201.96 205.88 209.56 212.00 16.0 18.0 ' 20.0 22.0 24.0 26.0 28.0 21632 222.40 227.96 233.07 237.82 242.25 246.41 30.0 32.0 34.0 36.0 38.0 25034 254.05 257.58 260.94 264.16 40.0 42.0 44.0 46.0 48.0 26734 270.21 273.06 27S.81 278.45 60.0 62.0 64.0 66.0 68.0 281.01 283.49 28S.90 288.23 290.50 60.0 62.0 64.0 66.0 68.0 292.71 294.8$ 296.94 298.98 300.98 70.0 72.0 74.0 76.0 78.0 302.92 304.82 306.68 308.50 31038 80.0 312.03 62.0 313.74 84.0 , 315.42 86.0 317.06 88.0 ' 318.68 90.0 92.0 94.0 96.0 98.0 32037 321.83 32337 32438 32637 0.01641 ~73;59 0.01645 0.01649 0.01652 62.03 53.68 4738 0.01656 42.42 73;61---- -130.10-1000.4 .1230.6 62.05 137.92 9953 1133.7 S3.70 144.71 991.7 1136.4 4739 150.75 988.1 1138.9 42.44 156.19 9843 1141.0 0.01658 0.01661 0.01664' 0.01666 0.01669 0.01670 38.44 35.15 32.40 30.06 28.05 26.80 38.45 35.17 32.42 30.08 28.06 26.82 161.13 165.68 169.91 173.8S 177.55 180.00 9813 979.1 976.5 974.1 9713 970.2 1143.0 11443 1146.4 1147.9 11493 1150.2 0.01673 0.01678 0.01682 0.02685 0.01689 0.01692 0.01695 24.75 22.16 20.078 18363 16.924 15.701 14.647 24.76 22.18 20.095 18380 16.941 15.718 14.664 18435 .190.48 196.09 20135 206.05 210.54 214.75 967.4 963.5 959.9 956.6 953.4 950.4 947.7 11513 1154.0 1156.0 11573 1159.5 1161.0 1162.4 0.01698 0.01701 0.01704 0.01707 0.01710 13.728 13.745 12.923 12.940 12.209 12.226 11.570 11.587 10.998 11.015 218.73 222.50 226.09 229.51 232.79 945.0 942.5 940.0 937.7 935.5 1163.7 1165,0 1166.1 11673 11683 0.01712 0.01715 0.01717 0.01719 0.01722 10.480 10.010 9.582 9.189 8.829 10.497 10.027 9.599 9307 8.846 235.93 238.95 24136 244.67 24737 9333 9313 9293 9273 925.4 11693 11703 1171.1 1171.9 1172.7 0.01724 0.01726 0.01728 0.01730 0.01732 8.496 8.189 7.902 7.636 7388 8.514 8.206 7.919 7.653 7.405 249.98 252.52 254.99 25738 259.71 923.5 1173.5 921.7 11743 920.0 ` 1175.0 9183 1175.7 916.6 1176.4 0.01735 0.01737 0.01739 0.01741 o!oi743 7.155 6.937 6.732 6.539 6357 7.172 6.95S 6.749 6.556 6375 261.98 264.18 26633 268.43 270.49 915.0 913.4 911.9 910.4 908.9 1177.0 1177.6 11783 1178.8 1179.4 0.01744 0.01746 0.01748 0.01750 ol017S2 6.186 6.024 5370 5.723 5.584 6303 6.041 S.887 5.741 5.602 272.49 274.45 27637 27Z2S 280.09 907.4 906.0 904.6 9033 901.9 1179.9 1180.5 1181.0 1181.5 1182.0 0.017S4 0.01756 0.01757 0.01759 0.01761 0.01763 0.01764 0.01766 0.01768 0.01769 5.452 5325 5304 5.089 4.979 4374 4.773 4.676 4.584 4.494 5.470 5343 5322 5.107 4.997 4.892 4.791 4.694 4.602 4.512 281.90 283.67 285.42 287.13 288.80 290.45 292.07 293.67 `29535 396.80 900.5 8993 897.9 896.7 895.4 1182.4 1182.9 1183.4 1183.8 11843 8943 893.0 891.8 890.6 889.4 1184.6 1185.0 1185.4 1185.8 11863 03348 1.6088 1.8435 0.2473' 1.5814- -1.82870.2580 1.5582 1.8162 03674 1.5379 1.8053 0.2758 1.S20Q 1.7958 6.0 6.0-- 7.0 8.0 9.0 03834 0.2903 03968 03027 03082 03119 1.5040 1.4894 1.4760 1.4636 1.4521 1.4446 1.7874 1.7797 1.7727 1.7663 1.7604 1.7S64 10.0 11.0 12.0 13.0 14.0 14.696 03184 03274 03356 03431 03500 03564 03624 1.4312 1.4127 13960 13809 13670 13542 13422 1.7496 1.7402 1.7317 1.7240 . 1.7170 1.7106 1.7046 16.0 18.0 20.0 22.0 24.0 26.0 28.0 03680 03732 03783 03830 03876 13310 13206 13107 13014 13925 1.6990 1.6938 1.6890 1.6844 1.6800 30.0 32.0 34.0 36.0 38.0 03919 03961 0.4000 0.4039 0.4076 1.2840 1.2759 1.2682 1.2608 1.2537 1.6759 1.6720 1.6683 1.6647 1.6613 40.0 42.0 44.0 46.0 48.0 0.4111 0.414S 0.4178 0.4210 0.4241 1.2469 1.2404 1.2340 1.2279 13220 1.6580 1.6549 1.6518 1.6489 1.6461 60-0 62.0 64.0 66.0 68.0 0.4271 0.4300 0.4329 0.43S6 0.4384 1.2162 . 1.6434 1.2107 1.6407 1.2053 1.6382 13001 1.6357 1.1950 1.6333 60.0 62.0 64.0* 66.0 68.0 0.4410 0.4435 0.4460 0.4485 0.4509 1.1900 1.18S2 1.1805 1.1759 1.1714 1.6310 1.6287 1.6265 1.6244 1.6223 70.0 72.0 74.0 76.0 78.0 0.4532 0.4555 0.4578 0.4599 0.4621 1.1670 1.1627 1.1586 1.154S 1.1505 1.6202 1.6182 1.6163 1.6144 1.6126 80.0 82.0 84.0 86.0 68.0 0.4642 0.4663 0.4683 0.4703 0.4723 1.1465 1.1427 1.1389 1.1352 1.1316 1.6107 1.6090 1.6072 1.6055 1.6038 90.0 92.0 94.0 96.0 98.0 .Abstracted from Steam Tables and Mollier Diagram by Prof. J. H. Keenan. 1930 edition, by Per ot the publisher. The American Society af Mechanical Engineers. 23