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 30^oF with 100% humidity to air at 70^oF with 40% humidity?

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