Humidifier Capacity (RH Target)
Moisture addition (lb/hr, gal/day) and latent load from supply CFM and the entering-to-target RH rise, with altitude-corrected humidity ratios. Per ASHRAE Fundamentals 2021 Ch. 1 psychrometrics.
Formula and source
Moisture addition (lb/hr) = 60 × CFM × rho × (W_target − W_entering); W = 0.621945 × Pw / (P − Pw) with Pw = RH × Pws(T_db) and P the altitude-corrected pressure. Daily water = lb/hr × 24 / 8.34. Latent load = addition × 1061 BTU/lb.
ASHRAE Fundamentals 2021 Chapter 1 (psychrometrics) by name.
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