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American Society of Heating and Ventilating Engineers Guide, 1935
Table 6. Properties of Saturated Water Vapor at Low Temperatures3 Barometer, 29.92 Inches of Mercury
TemfebaTURE F
Vapor Pressure
In. Ho X 10-*
-130 -129 -128 -127 -126
-125 -124 -123 -122 -121
-120 -119 -118 -117 -116
-115 ' -114 -113 -112-111
-110 -109 -108 -107 -106
-105 -104 -103 -102 -101
-100 -99 -98 -97 -96
-95 -94 -93 -92 -91
-90 -89 -88 -87 -86
0.276 .306 .338 .373 .411
.455 .499 .542 .604 .669
.735 .805 .892 .989 1.098
1.208 1.317 1.444 1.575 1.728
1.889 2.087 2.292 2.511 2.742
2.983 3.258 3.543 3.872 4.213
4.607 5.018 5.455 5.946 6.470
7.047 7.638 8.316 9.017 9.806
10.64 11.53 12.51 13.53 14.69
Weight of Saturated
Vapor per Lb ' Drt Air
X 10-*
0.005738 .006362 .007027 .007755 .008545
Btu per Lb of Vapor (32 F Datum)
1000.7 1001.2 1001.6 1002.1 1002.5
.009459 .01037
.01127
.01256 .01391
1003.0 1003.4
1003.9 1004.3 1004.8
.01528 .01674 .01854
.02056 .02283
1005.2
1005.7 1006.1 1006.6 1007.0
.02511 .02738 .03002 .03274 .03593
1007.5 1007.9 1008.4
1008.8 1009.3
.03927 .04339
.04765 .05220 .05701
1009.7 1010.2
1010.6
1011.1 1011.5
.06202 .06773 .07366 .08050 .08759
1012.0 1012.4
1012.9 1013.3
1013.8
.09578 .1043 .1134
.1236 .1345
1014.2
1014.7 1015.1 1015.6 1016.0
.1465 .1588 .1729 .1875 .2039
1016.5
1016.9 1017.4
1017.8 1018.3
.2212 .2397 .2601 .2813 .3054
1018.7 1019.2 1019.6
1020.1 1020.5
Tempera ture F
Vapor Pressure
In. Ho X I0-*
-85 -84 -83 -82 -81
-80 -79 -78 -77 -76
-75 -74 -73 -72 -71
-70 -69 -68 -67 -66
-65 -64 -63 -62 -61
-60 -59 -58 -57 -56
-55 -54 -53 -52 -51
. -50 -49 -48 -47 -46
-45 -44 -43 -42 -41
15.87
17.20 18.58 20.10 21.72
23.47 25.34 27.29 29.52
31.81
34.37 37.01 39.96 43.04 46.33
49.87 53.59 57.65
61.81 66.41
71.17 76.64
82.28 88.19 94.62
101.4 108r8
116.3 124.8 133.4
.
143.0 153.0 163.5 174.9 187.0
199.9 213.0
227.9 243.1 259.5
276.7 295.0 314.7 335.3 357.6
Weight of Saturated
Vapor per Lb Drt Air
x io*
0.3299 .3576 .3863 .4179 .4516
.4879 .5268 .5674 .6137 .6613
.7146 .7694 .8308 .8948 .9632
1.037 1.114 1.199 1.285 1.381
1.480 1.593 1.711 1.833 1.967
2.108 2.262 2.418 2.595 2,773
2.973 3.181 3.399 3.636 3.888
4.156 4.478 4.738 5.054 5.395
5.753 6.133 6.543 6.971 7.435
Btu per Lb of Vapor (32 F Datum)
1021.0 1021.4 1021.9 1022.3 1022.8
1023.2 1023.7 1024.1 1024.6 1025.0
1025.5 1025.9 1026.4 1026.8 1027.3
1027.7 1028.2 1028.6 1029.1 1029.5
1030.0 1030.4 1030.9 1031.3 1031.8
1032.2 1032.7 1033.1 1033.6 1034.0
1034.5 1034.9 1035.4 1035.8 1036.3
1036.7 1037.2 1037.6 1038.1 1038.5
1039.0 1039.4 1039.9 1040.3 1040.8
Vapor pressures converted from International Critical Tables. 16
Chapter 1--Fundamentals of Heating and Air Conditioning.
Table 6. Properties of Saturated Water Vapor at Low Temperatures3 (Con'd.) Barometer, 29.92 Inches of Mercury
Tempera* TUBE
F
Vapor Pressure
In.
Ho X 10-*
-40 -39 -38 -37
-36
380.3 405.5 431.2 459.2 488.4
-35 -34 -33 -32
-31
519.5 552.4 586.5 623.7
661.8
-30 -29 -28 -27
-26
701.0 742.2 791.2
841.0 892.1
-25 -24 -23 -22
-21
946.4 1003. 1064. 1126. 1192.
Weight of Saturated
Vapor per Lb Drt Air
X to*
7.907 8.431 8.965 9.548 10.16
10.80 11.49 12.20 12.97 13.76
14.58 15.43 16.45 17.49 18.55
19.68 20.86 22.13 23.42 24.79
Btu per Lb of Vapor
(32 F
Datum)
1041.2 1041.7 1042.1 1042.6 1043:0
1043.5 1043.9 1044.4 1044.8 1045.3
1045.7 1046.2 1046.6 1047.1 1047.5
1048.0 1048.4 1048.9 1049.3 1049.8
Tempera ture
F
Vapor
Pressure
In.
Ho X 10-*
-20
-19 -18 -17 -16
1262.0. 1337.
1416. 1496. 1584.
Weight of
Saturated Vapor
per Lb Drt Air
X 10*
26.25 27.81 29t45 31.12 32.95
-15 -14 -13 -12
-U
1675. 1772. 1874.
1980. 2093.
34.84
36.86 38.98 41.19 43.54
-10
-9 -8 --7 -6
2210. 2335. 2463. 2502.
2745.
45.98 48.58 51.25 52.06 57.12
-5 2898. -4 3055. -3 , 3222. -2 3397. -1 3580.
60.30 63.57 67.05 70.69 ' 74.50
0 3773.
78.52
Btu per Lb of Vapor
(32 F `
Datum)
1050.2 1050.7 1051.1 1051.6 i052.0
1052.5 1052.9 1053.4 1053.8 1054.3
1054.7 1055.2 1055.6 1056.1 1056.5
1057.0 1057.4 1057.9 1058.3 1058.8
.1059.2
Vapor pressures converted from International Critical Tables.
W = weight of water vapor mixed with each pound of dry air, pounds. h'tg = latent heat of vaporization at t', Btu per pound.
Since this definition holds for any mixture of dry air and water vapor, the total heat of a mixture with a relative humidity of 100 per cent and at a temperature equal to the wet-bulb temperature (/') is
. 'S' = epa (/' - 0) + Wt> h'ts
(11)
By equating Equation 10 to Equation 11, the equation for the adiabatic saturation process, Equation 9a, follows. This demonstrates that the adiabatic saturation process at constant wet-bulb temperature is also a process of constant total heat. In short, the total heat of a mixture of dry air and water vapor is the same for any two states of the mixture at the same wet-bulb temperature. This fact furnishes a convenient means of finding the total heat of an air-vapor mixture in any state.
Example 5. Find the total heat of an air-vapor mixture having a dry-bulb tempera ture of 85 F and a wet-bulb temperature of 70 F.
Solution. From Table 5, for saturation at the wet-bulb temperature Wt> = 0.01578, and from Equation 11,
S' = Cpa (70 - 0) + 0.01578 h'tg = 16.9 + 16.61 = 33.51