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Air Humidifying with Steam - Imperial Units

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

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The table below can be used to calculate the amount of steam needed to humidify 100 cfm (cubic feet per minute) of air.

Vapor in 100 cfm air (lb/h)
Dry
Temperature
 		 Humidity (%)
(oF) (oC) 100 85 80 75 70 65 60 55 50 45 40 35 30
90 32.2 12.84 10.92 10.26 9.6 9 8.34 7.68 7.08 6.42 5.78 5.14 4.49 3.85
88 31.1 12.06 10.26 9.66 9.06 8.46 7.87 7.26 6.66 6.06 5.41 4.82 4.22 3.62
86 30.0 11.4 9.66 9.12 8.52 7.98 7.38 6.85 6.3 5.7 5.13 4.56 3.99 3.42
85 29.4 11.04 9.36 8.82 8.28 7.74 7.2 6.6 6.06 5.52 4.97 4.42 3.86 3.31
84 28.9 10.68 9.06 8.52 7.98 7.5 6.96 6.42 5.87 5.34 4.81 4.27 3.74 3.2
83 28.3 10.38 8.82 8.34 7.8 7.26 6.72 6.24 5.71 5.19 4.67 4.15 3.63 3.11
82 27.8 10.08 8.58 8.04 7.56 7.08 6.54 6.06 5.54 5.04 4.54 4.03 3.53 3.02
81 27.2 9.78 8.34 7.8 7.32 6.84 6.36 5.87 5.38 4.89 4.4 3.91 3.42 2.93
80 26.7 9.48 8.04 7.56 7.08 6.66 6.18 5.69 5.21 4.74 4.27 3.79 3.32 2.84
79 26.1 9.18 7.8 7.32 6.9 6.42 5.96 5.51 5.05 4.59 4.13 3.67 3.21 2.75
78 25.6 8.88 7.56 7.08 6.66 6.24 5.77 5.33 4.88 4.44 3.99 3.55 3.11 2.66
77 25.0 8.64 7.32 6.9 6.48 6.06 5.62 5.18 4.75 4.32 3.89 3.46 3.02 2.59
76 24.4 8.4 7.14 6.72 6.3 5.88 5.46 5.04 4.62 4.2 3.78 3.36 2.94 2.52
75 23.9 8.1 6.9 6.48 0.06 5.67 5.26 4.86 4.48 4.05 3.64 3.24 2.83 2.43
74 23.3 7.86 6.66 6.3 5.89 5.5 5.11 4.72 4.32 3.93 3.53 3.14 2.75 2.36
73 22.8 7.62 6.48 6.12 5.71 5.33 4.95 4.57 4.12 3.81 3.43 3.05 2.66 2.29
72 22.2 7.38 6.3 5.9 5.53 5.17 4.79 4.43 4.06 3.69 3.32 2.95 2.58 2.21
71 21.7 7.14 6.06 5.71 5.35 4.99 4.64 4.29 3.93 3.57 3.21 2.86 2.5 2.14
70 21.1 6.9 5.86 5.52 5.17 4.84 4.48 4.14 3.79 3.45 3.1 2.76 2.41 2.07
69 20.6 6.72 5.71 5.38 5.04 4.7 4.37 4.03 3.7 3.36 3.02 2.67 2.35 2.02
68 20.0 6.48 5.51 5.18 4.86 4.54 4.21 3.89 3.55 3.24 2.92 2.59 2.27 1.94
67 19.4 6.24 5.3 4.99 4.68 4.37 4.06 3.74 3.43 3.12 2.81 2.5 2.18 1.87
66 18.9 6.06 5.15 4.85 4.54 4.24 3.94 3.64 3.33 3.03 2.72 2.42 2.12 1.82
65 18.3 5.87 4.99 4.7 4.4 4.11 3.82 3.52 3.23 2.93 2.65 2.35 2.06 1.76
60 15.6 4.97 4.23 3.98 3.73 3.48 3.23 2.98 2.74 2.48 2.24 1.99 1.74 1.49
55 12.8 4.19 3.56 3.35 3.14 2.93 2.72 2.51 2.31 2.09 1.89 1.68 1.47 1.26
50 10.0 3.52 2.99 2.82 2.64 2.47 2.29 2.11 1.94 1.76 1.58 1.41 1.23 1.06
45 7.2 2.95 2.51 2.36 2.21 2.06 1.92 1.77 1.62 1.47 1.33 1.18 1.03 0.89
40 4.4 2.45 2.09 1.96 1.84 1.72 1.6 1.47 1.35 1.22 1.1 0.98 0.86 0.74
30 -1.1 1.67 1.42 1.33 1.25 1.17 1.09 1 0.92 0.83 0.75 0.67 0.58 0.5
20 -6.7 1.07 0.91 0.85 0.8 0.75 0.7 0.64 0.59 0.53 0.48 0.43 0.37 0.32
10 -12.2 0.67 0.56 0.53 0.5 0.47 0.43 0.4 0.37 0.33 0.3 0.26 0.23 0.2
0 -17.8 0.41 0.35 0.32 0.31 0.29 0.26 0.25 0.22 0.2 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 0.1 0.08 0.08
-20 -28.9 0.14 0.12 0.11 0.11 0.1 0.1 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.

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Related Topics

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

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