The term ‘Adiabatic’ simply means without energy loss or gain. This refers mainly to the processes of evaporative cooling and desiccant dehumidification. Evaporative cooling occurs when warm air passes near water. Even at temperatures well below its boiling point, water molecules on the surface will absorb sufficient energy from the passing air to change phase into a gas and become moisture vapour. As the moisture vapour then becomes part of the air, the energy is transferred from sensible heat into latent heat of vaporization. Thus the temperature of the air falls, but the absolute humidity rises, meaning that the overall energy content (or enthalpy) remains the same.
Desiccant dehumidification occurs when the air comes into contact with a substance such as Condi’s Crystals or silica gel. Such substances simply absorb moisture directly from the air. In the process, the latent heat of vaporization is released back into the air, raising its temperature and reducing the absolute humidity. Once again, the net overall enthalpy remains the same.
