Summary " Mass transfer operations -Humidification "

Mass Transfer Operations-I

Humidification

, Introduction

• Humidification and dehumidification are operations in which
a pure liquid is in contact with an inert gas phase which is
insoluble in the liquid.
• In humidification, the liquid vaporises and the vapors are
transferred to the gas phase, whereas in dehumidification, the
vapors are condensed and transferred from the gas phase to
the liquid phase.
• In majority of these operations, the liquid phase is pure water
and the gas phase is air.
• The mass transfer is confined to the gas phase as there is no
concentration gradient in liquid phase.

, Applications
• Liquid cooling: Cooling towers

• Gas cooling:

• Adiabatic humidification

• Dehumidification: Solvent recovery, Gas drying, Air-conditioning

• Evaporative cooling

• Water desalination

, Humidity

• Humidification involves contact between a pure liquid (A) and
a gas phase consisting of an insoluble gas (B) and the vapors
of the liquid (A).
• “Humidity” – the concentration of the vapor in a gas-vapor
mixture – the amount of vapor present per unit quantity of
vapor-free gas.
• Eg: For air-water vapor system, humidity refers to the amount
of water vapor present per unit quantity of dry air.