How Liquid Desiccant moisture transfer works:

A packaged liquid desiccant system typically uses four elements operating in a continuous loop:

• Air contact sections: two contactors bring separate airstreams into direct contact with the liquid desiccant. One side absorbs moisture into the solution (the Absorber), while the other side releases moisture from the solution (the Regenerator).

• Solution loop: Pumps, piping, valves, and heat exchangers circulate the desiccant between the absorber and regenerator and may recover heat between the outgoing and returning solution streams.

• Thermal loop: A DX (direct expansion) heat pump or another heating and cooling source, such as hot water and chilled water, cools the solution where moisture is absorbed and heats it where moisture is released, sustaining the water vapor pressure difference that drives moisture transfer.

• Airflow and controls: Fans, dampers, sensors, and controls manage airflow, solution temperature and concentration, and any integrated heating or cooling equipment to determine whether the process airstream is dehumidified or humidified. Depending on the system design, bidirectional operation may involve redirecting airstreams, reversing or reconfiguring refrigerant flow, and adjusting solution temperature or concentration.

Dehumidification mode:

• In dehumidification mode, supply or process air passes through the moisture absorbing contactor (absorber). Water vapor moves from the air into the liquid desiccant, lowering the air dew point without requiring a cooling coil to condense the moisture.

• The diluted solution then moves to the moisture release contactor (regenerator), where heat drives the captured water vapor into a separate exhaust or scavenger airstream. This reconcentrates the solution so it can return to the absorbing side and repeat the cycle.

Humidification mode:

• In humidification mode, the airstream being conditioned passes through the moisture release contactor (regenerator). The warmed solution releases water vapor into that air, increasing its humidity without steam injection, atomized water, or an evaporative media section.

• The opposite contactor absorbs replacement moisture from another available airstream (such as building exhaust air). The exact airflow arrangement depends on the packaged system and application; not every liquid desiccant unit is designed for reversible humidification and dehumidification.

How it differs from conventional humidity control:

• Cooling based dehumidification must drive a coil surface below the air dew point, coupling moisture removal to cooling and often creating a need for reheat to maintain acceptable comfort or relative humidity (% RH). Liquid desiccant systems transfer water vapor directly based on the salt concentration, and can control dew point (humidity) separately from dry bulb temperature.

• Conventional humidifiers add water through steam, atomization, or evaporation. A bidirectional liquid desiccant system instead absorbs reclaimed moisture from another airstream into the lithium chloride solution and subsequently releases it as water vapor into the conditioned airstream. Because the lithium chloride and most nonvolatile contaminants remain in the circulating solution, the moisture undergoes a distillation like transfer process. This approach may reduce or eliminate the need for separate makeup water addition and associated water treatment processes when source air and operating conditions are suitable.

• Solid desiccant wheels also remove moisture, but they use adsorption rather than absorption and commonly require higher regeneration temperatures. Heat transferred from the regeneration side and heat released during adsorption can raise the temperature of the dried process air, often creating a need for downstream cooling.

Where liquid desiccant systems are used:

• Ice arenas, cold and dry storage, archival storage, libraries, and museums, where precise dew point control helps prevent fog, frost, condensation, corrosion, and moisture related deterioration or safety hazards.

• Food processing, bakeries, pharmaceuticals, clean rooms, laboratories, clinics, operating rooms, and ambulatory surgery centers, where humidity can affect product quality, sanitation, safety, process consistency, and environmental control.

• Manufacturing, molding, painting, printing, and indoor agriculture, where controlled humidity can improve material handling, curing, dimensional stability, production quality and consistency, and yield.

• Natatoriums, pools, supermarkets, grocery facilities, and moisture sensitive areas within water and wastewater treatment plants, where high or variable moisture loads can create comfort, condensation, safety, corrosion, or equipment reliability issues.

• Data centers and other temperature sensitive process spaces, where humidity control independent of sensible cooling or heating can support tighter environmental control and more efficient HVAC operation.

When it is not the right fit:

Liquid desiccant equipment is not a universal replacement for cooling coils or conventional humidifiers. Where latent loads are small, standard comfort humidity is easily maintained, or the available source and receiving airstreams do not support useful moisture transfer, conventional equipment may be simpler and less expensive. Liquid desiccant systems are most valuable when dew point control is demanding, latent loads are high, humidity must be controlled separately from temperature, or both drying and humidification provide value under different operating conditions.