Humidity Ratio Psychrometric - Chart

[ W = \fracm_vm_a ]

[ W = 0.62198 \cdot \fracP_vP - P_v ]

Among these, the (W, often expressed in kg water/kg dry air or grains of moisture/lb dry air) is arguably the most direct measure of actual moisture content. While relative humidity is widely used in weather forecasts and comfort discussions, it fails to indicate the absolute quantity of water vapor. The humidity ratio fills this gap, making it indispensable for engineering calculations involving mass balance, humidification, dehumidification, and drying. humidity ratio psychrometric chart

where ( h_fg ) ≈ 2501 kJ/kg (latent heat of vaporization). Without W, latent loads cannot be separated from sensible loads. Given mass flow rates ( \dotm a1 ) and ( \dotm a2 ), the mixed humidity ratio: [ W = \fracm_vm_a ] [ W = 0

[ \dotQ latent = \dotm a \cdot h fg \cdot (W in - W_out) ] where ( h_fg ) ≈ 2501 kJ/kg (latent heat of vaporization)

Understanding the Humidity Ratio: A Critical Analysis of Moisture Representation on the Psychrometric Chart

[ W_mix = \frac\dotm a1 W_1 + \dotm a2 W_2\dotm a1 + \dotm a2 ]