2. Humidification

Humidification operations involve simultaneous transfer of heat and mass between a gas and a liquid when the gas is brought into contact with the liquid in which it is insoluble.

When the partial pressure of the vapor in the vapor-gas mixture is equal to the vapor pressure of the liquid at that temperature, the mixture is said to be saturated.

When the partial pressure of the vapor in the vapor-gas mixture is less than the equilibrium vapor pressure of the liquid at that temperature, the mixture is said to be unsaturated and there is scope for further vaporisation.