Definitions of
psychrometric qualities
The humidity ratio is
the mass of water per mass of dry air, (for example, kg H20 per kg dry air).
This is sometimes expressed as grains of water per pound of dry air. There are 7000 grains
per pound.
The specific humidity is the ratio of the
water vapor to the total mass of the moist air sample.
The relative humidity is the ratio of the
mole fraction of water vapor in a given moist air sample to the mole fraction in an air
sample at saturation at the same temperature and pressure.
The dew point temperature is the temperature
at saturation for a given humidity ratio and a given pressure.
The wet bulb temperature is the temperature
caused by the adiabatic evaporation of water at a given pressure.
The enthalpy of the moist air is the sum of
the enthalpies of the air and the water vapor.