EKS-HUM-030 / Dehumidification technology and performance

Desiccant Dehumidification

吸附式除湿

Desiccant dehumidification removes water vapour from air by transferring it to a solid or liquid sorbent with a lower water-vapour pressure.

Aliases: sorption dehumidification

QUANTITY, SYMBOL AND UNIT

Quantity / objectDesiccant dehumidification process

UnitNot applicable

Definition

Desiccant dehumidification removes water vapour from air by transferring it to a solid or liquid sorbent with a lower water-vapour pressure.

Solid desiccants adsorb water on their internal surface, while liquid systems commonly absorb it into solution. Regenerative equipment restores sorption capacity and carries the released moisture away in a separate regeneration process.

Relations and distinctions

Adsorption and absorption

Adsorption concentrates water at a solid surface; absorption incorporates water into a liquid phase. Both can be desiccant processes.

Desiccant and refrigerant methods

Desiccants use a vapour-pressure-driven sorption process; refrigerant equipment first cools air below dew point and condenses liquid water.

Engineering meaning

Consider desiccant processes when low outlet moisture or operation outside favourable condensing conditions is required.
Include regeneration energy, process-air temperature rise, leakage, cooling and air-stream pressure in the system review.

Common misconceptions

MisconceptionDesiccant dehumidification always means a rotating silica-gel wheel.

Accurate explanationThe category also includes other solid beds and liquid-desiccant systems with different regeneration arrangements.

Application boundaries

Desiccant type alone does not determine delivered dew point, capacity or energy use.
Some systems require postcooling or downstream filtration depending on the process and equipment design.

Supporting sources

ASHRAE / SRC-ASHRAE-S20-CH24

ASHRAE Handbook - HVAC Systems and Equipment, Chapter 24: Desiccant Dehumidification and Pressure-Drying Equipment ↗

2020 IP edition / Chapter 24, Sections 1 and 2, desiccant methods and equipment
Supports: Desiccant dehumidification removes water vapour through adsorption or absorption; The vapour-pressure difference between air and desiccant drives transfer; Regenerative systems restore capacity and reject moisture to another stream

Maintenance record