Appendix B: Conversion Factors; Water Vapor Pressure & Temperature; Absolute Humidity - Ametek 5000 Instrument Manual

APPENDIX B: CONVERSION FACTORS

This section provides information on the conversion of water vapor pressure values to more com-
monly used terms, such as parts per million by volume, dew point, mg/L, and lb/mmft
Water Vapor Pressure and Temperature
Most tables used to express the concentration of water vapor are based on vapor pressure data of
liquid water and ice. The concentration of water vapor above the liquid or solid is known as the
water vapor pressure. Tables expressing the vapor pressure above ice and water at various tempera-
tures may be found in the International Critical Tables, chemical handbooks, or other engineering
handbooks.
parts per million by volume =
At saturation pressures above 301 kPa absolute (45 psia), nonideal gas corrections are required.
Table B1: Saturation Vapor Pressure of Water Vapor in Millimeters of Mercury
with Respect to Water Above 0°C and with Respect to Ice Below 0°C
Temp 0
°C
– 70 0.0019
– 60 0.0080
– 50 0.0294
– 40 0.0964
– 30 0.2878
– 20 0.7834
– 10 1.9643
– 0 4.5802
0 4.5802
10 9.210
20 17.548
30 31.860
40 55.396
50 92.639
60 149.57 156.62
70 233.91 244.21
80 355.40 370.03
90 525.97 546.26
100 760.00

Absolute Humidity

The absolute humidity of water vapor in air or other gases is defined as the pressure of water vapor
or as the weight per volume of water vapor. It is expressed in various units such as grams per liter,
grams per cubic foot, or millimeters of mercury pressure.
water partial pressure (Pv) psia @ temperature
————————————————————— x 10
(Reproduced from the Smithsonian Meteorological Tables)
1 2 3
------ ------ ------
0.0070 0.0061 0.0053
0.0260 0.0229 0.0202
0.0859 0.0765 0.0680
0.2591 0.2231 0.2094
0.7115 0.6456 0.5854
1.7979 1.6444 1.5029
4.2199 3.8868 3.5775
4.924 5.921 5.682
9.84 10.521 11.235
18.665 19.844 21.087
33.735 35.705 37.775
58.417 61.580 64.889
97.33 102.23 107.33
163.96 171.59
254.88 265.96
385.16 400.81
567.20 588.80
total pressure (Pt) psia
4 5 6
------ ------ ------
0.0046 0.0040 0.0035
0.0178 0.0156 0.137
0.0605 0.0537 0.0476
0.1880 0.1686 0.1511
0.5303 0.4800 0.4341
1.3726 1.2525 1.1421
3.2907 3.0248 2.7785
6.098 6.541 7.012
11.992 12.794 13.642
22.398 23.780 25.235
39.947 42.227 44.619
68.350 71.968 75.751
112.66 118.20 123.98
179.52 187.75 196.31
277.43 289.32 301.63
416.99 433.71 540.99
611.08 634.06 657.75
.
3
6
7 8 9
------ ------ ------
0.0030 0.0026 0.0022
.0120 0.0105 0.0092
0.0421 0.0373 0.0329
0.1352 0.1209 0.1080
0.3923 0.3541 0.3194
1.0406 0.9474 0.8618
2.5505 2.3395 2.1445
7.513 8.045 8.610
14.539 15.487 16.489
26.767 28.380 30.076
47.127 49.756 52.510
79.703 83.830 88.140
130.00 136.26 142.78
205.19 214.41 223.98
314.38 327.59 341.25
468.84 487.28 506.32
682.18 707.35 733.28
Conversion Factors B-1