Psychrometric Chart

B hPa

Mode

Mix Ratio 60%

Parameters

t₁ ℃

φ₁ 68.5%

t₂ ℃

φ₂ 34.5%

φ_m 19%

h_a

h_b

h_c

h_d

P1: t=32.0℃ d=20.1g/kg h=83.6kJ/kg
P2: t=17.0℃ d=4.2g/kg h=27.8kJ/kg
Mix: t=26.0℃ d=13.7g/kg h=61.3kJ/kg

Moist Air Properties

B = 1100 hPa — Humidity ratio & enthalpy at various relative humidity levels

t ℃	ρ_sat kg/m³	P_sat hPa	Ps(φ=0.685) hPa	d(φ=0.685) g/kg	h(φ=0.685) kJ/kg	Ps(φ=0.345) hPa	d(φ=0.345) g/kg	h(φ=0.345) kJ/kg	Ps(φ=0.19) hPa	d(φ=0.19) g/kg	h(φ=0.19) kJ/kg	d_sat g/kg	h_sat kJ/kg	d(h_a=69.5) g/kg	d(h_b=72.9) g/kg	d(h_c=106.4) g/kg	d(h_d=138) g/kg

Air Enthalpy
h = 1.01·t + 0.001·d·(2500 + 1.84·t)

h — enthalpy (kJ/kg_da) | t — temperature (℃) | d — humidity ratio (g/kg_da)
Humidity Ratio
d = 622·P_s/(B − P_s) = 622·φ·P_sat/(B − φ·P_sat)

d — humidity ratio (g/kg_da) | P_s — vapor pressure (hPa) | B — barometric pressure (hPa)
Humidity Ratio from Enthalpy
d = (h − 1.01·t) / (2.5 + 0.00184·t)
Relative Humidity
φ = P_s / P_sat × 100%
Temperature from h & d
t = (h − 2.5·d) / (1.01 + 0.00184·d)
Sensible Heat Ratio
ε = 3.6·Q/S = 1000·Δh/Δd = 1000·(h₂−h₁)/(d₂−d₁)

Q — total heat (W) | S — moisture gain (kg/h)
Mixed Air Temperature
t_mix = (h_mix − 2.5·d_mix) / (1.01 + 0.00184·d_mix)
Wet-Bulb Temperature
The wet-bulb temperature equals the temperature at which air reaches saturation when humidified adiabatically (constant enthalpy). "Apparatus dew point" φ ≈ 90%~95%.

ln(P_sat) = C₁/T + C₂ + C₃·T + C₄·T² + C₅·T³ + C₆·ln(T)

T = t + 273.15 K, valid for −20℃ ~ 50℃
C₁ = −5800.2206, C₂ = 1.3914993, C₃ = −0.048640239, C₄ = 4.1764768×10⁻⁵, C₅ = −1.4452093×10⁻⁸, C₆ = 6.5459673