M.12Psychrometrics (Moist Air)

Formulas

Saturation pressure

ln p_ws = C₈/T + C₉ + C₁₀T + C₁₁T² + C₁₂T³ + C₁₃ ln T (Hyland–Wexler)

Humidity ratio

W = 0.621945 · p_w / (p − p_w)

Enthalpy

h = 1.006·t + W·(2501 + 1.86·t) [kJ/kg dry air]

Specific volume

v = 0.287042 · (t + 273.15) · (1 + 1.607858·W) / p

Use in drying

In convective dryers, the moisture air can carry is limited by the difference in humidity ratio between inlet and outlet air. Using this tool for inlet and outlet air separately gives the air needed to remove 1 kg of water (1 / ΔW) and the heating duty (enthalpy difference); combine the results with the M.03 Dryer Heat Load tool.