Air Humidifying with Steam - Imperial Units

Amount of vapor (lb/h in 100 cfm) in humid air

The amount of steam needed to humidify 100 cfm (cubic feet per minute) of air is indicated below.

Vapor in 100 cfm air (lb/h)
Dry
Temperature
Humidity (%)
(oF)(oC)100858075706560555045403530
90 32.2 12.8 10.9 10.3 9.6 9.0 8.3 7.7 7.1 6.4 5.8 5.1 4.5 3.9
88 31.1 12.1 10.3 9.7 9.1 8.5 7.9 7.3 6.6 6.1 5.4 4.8 4.2 3.6
86 30.0 11.4 9.7 9.1 8.5 8.0 7.4 6.9 6.3 5.7 5.1 4.6 4.0 3.4
85 29.4 11.0 9.4 8.8 8.3 7.7 7.2 6.6 6.1 5.5 5.0 4.4 3.9 3.3
84 28.9 10.7 9.1 8.5 8.0 7.5 7.0 6.4 5.9 5.3 4.8 4.3 3.7 3.2
83 28.3 10.4 8.8 8.3 7.8 7.3 6.7 6.2 5.7 5.2 4.7 4.2 3.6 3.1
82 27.8 10.1 8.6 8.0 7.6 7.1 6.5 6.1 5.5 5.0 4.5 4.0 3.5 3.0
81 27.2 9.8 8.3 7.8 7.3 6.8 6.4 5.9 5.4 4.9 4.4 3.9 3.4 2.9
80 26.7 9.5 8.0 7.6 7.1 6.7 6.2 5.7 5.2 4.7 4.3 3.8 3.3 2.8
79 26.1 9.2 7.8 7.3 6.9 6.4 6.0 5.5 5.1 4.6 4.1 3.7 3.2 2.7
78 25.6 8.9 7.6 7.1 6.7 6.2 5.8 5.3 4.9 4.4 4.0 3.6 3.1 2.7
77 25.0 8.6 7.3 6.9 6.5 6.1 5.6 5.2 4.7 4.3 3.9 3.5 3.0 2.6
76 24.4 8.4 7.1 6.7 6.3 5.9 5.5 5.0 4.6 4.2 3.8 3.4 2.9 2.5
75 23.9 8.1 6.9 6.5 6.1 5.7 5.3 4.9 4.5 4.1 3.6 3.2 2.8 2.4
74 23.3 7.9 6.7 6.3 5.9 5.5 5.1 4.7 4.3 3.9 3.5 3.1 2.7 2.4
73 22.8 7.6 6.5 6.1 5.7 5.3 4.9 4.6 4.1 3.8 3.4 3.1 2.7 2.3
72 22.2 7.4 6.3 5.9 5.5 5.2 4.8 4.4 4.1 3.7 3.3 2.9 2.6 2.2
71 21.7 7.1 6.1 5.7 5.3 5.0 4.6 4.3 3.9 3.6 3.2 2.9 2.5 2.1
70 21.1 6.9 5.9 5.5 5.4 4.8 4.5 4.1 3.8 3.5 3.1 2.8 2.4 2.1
69 20.6 6.7 5.7 5.4 5.0 4.7 4.4 4.0 3.7 3.4 3.0 2.7 2.4 2.0
68 20.0 6.5 5.5 5.2 4.9 4.5 4.2 3.9 3.5 3.2 2.9 2.6 2.3 1.9
67 19.4 6.2 5.3 5.0 4.7 4.4 4.1 3.7 3.4 3.1 2.8 2.5 2.2 1.9
66 18.9 6.1 5.2 4.9 4.5 4.2 3.9 3.6 3.3 3.0 2.7 2.4 2.1 1.8
65 18.3 5.9 5.0 4.7 4.4 4.1 3.8 3.5 3.2 2.9 2.6 2.3 2.1 1.8
60 15.6 5.0 4.2 4.0 3.7 3.5 3.2 3.0 2.7 2.5 2.2 2.0 1.7 1.5
55 12.8 4.2 3.6 3.4 3.1 2.9 2.7 2.5 2.3 2.1 1.9 1.7 1.5 1.3
50 10.0 3.5 3.0 2.8 2.6 2.5 2.3 2.11 1.9 1.8 1.6 1.4 1.2 1.1
45 7.2 2.9 2.5 2.4 2.2 2.1 1.9 1.8 1.6 1.5 1.3 1.2 1.0 0.89
40 4.4 2.5 2.1 2.0 1.8 1.7 1.6 1.5 1.3 1.2 1.1 1.0 0.86 0.74
30 -1.1 1.7 1.4 1.3 1.2 1.2 1.1 1.0 0.92 0.83 0.75 0.67 0.58 0.50
20 -6.7 1.1 0.91 0.85 0.80 0.75 0.70 0.64 0.59 0.53 0.48 0.43 0.37 0.32
10 -12.2 0.67 0.56 0.53 0.50 0.47 0.43 0.40 0.37 0.33 0.30 0.26 0.23 0.20
0 -17.8 0.41 0.35 0.32 0.31 0.29 0.26 0.25 0.22 0.20 0.19 0.16 0.13 0.12
-10 -23.3 0.25 0.21 0.2 0.19 0.17 0.16 0.15 0.14 0.12 0.11 0.10 0.08 0.08
-20 -28.9 0.14 0.12 0.11 0.11 0.10 0.10 0.08 0.08 0.72 0.06 0.05 0.05 0.04
  • 100 cfm = 0.047 m3/s = 170 m3/h
  • 1 lb/h = 0.4536 kg/h

Example - Humidifying Air with Steam

How much steam is needed to transform air at 30oF with 100% humidity to air at 70oF with 40% humidity?

  • air at 30oF and 100% humidity - steam content 1.67 lb/h (100 cfm/h air flow)
  • air at 70oF and 40% humidity - steam content 2.76 lb/h (100 cfm/h air flow)

The difference (2.76 - 1.67) = 1.09 lb/h is the amount of steam needed for 100 cfm/h air flow.

Note!

This table neglects the sensible heat required to heat cold air to final state. In the example above the heat required to heat 100 cfm dry air from 30oF to 70oF must be added. The heat can be added as dry heat with heating panels or similar, or in general more convenient by adding more steam.

Related Topics

  • Steam and Condensate - Steam & condensate systems- properties, capacities, pipe sizing, systems configuration and more
  • Air Psychrometrics - The study of moist and humid air - psychrometric charts, Mollier diagrams, air-condition temperatures and absolute and relative humidity and moisture content

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