A membrane-based liquid desiccant system for extracting water vapor from air streams

Background

The regulation of indoor humidity is a critical component of heating, ventilation, and air conditioning (HVAC) systems across residential, commercial, and industrial sectors. Effective moisture removal is essential for maintaining human comfort and supporting specialized environments like food processing facilities, microelectronics manufacturing, and clean rooms. Because latent cooling—the extraction of water vapor from the air—accounts for a substantial portion of the total energy consumed by building climate control systems, there is a pressing need for highly efficient dehumidification strategies to reduce the overall energy footprint of modern infrastructure.

Despite this need, conventional dehumidification methods suffer from significant operational drawbacks. Traditional air conditioning relies on chilling air below its dew point to force water condensation, an energy-intensive process that frequently results in severe over-cooling. While desiccant-based alternatives exist, they present their own severe limitations. Standard solid desiccants require cumbersome physical movement to be regenerated. Conversely, conventional liquid desiccants are notoriously corrosive and toxic, making them difficult to contain safely. These harsh solutions risk contaminating the conditioned air stream through droplet entrainment, requiring expensive handling equipment and posing potential health hazards to building occupants.

Technology

The shell-and-tube dehumidification system extracts water vapor from air streams utilizing a non-corrosive, hydrophilic liquid desiccant—specifically an alkoxylated siloxane solution. The desiccant flows inside a thin, nonporous, hydrophilic membrane tube while air travels through a larger concentric outer tube. This specialized membrane selectively permits water vapor to pass from the air into the desiccant while physically blocking the desiccant molecules. By decoupling latent dehumidification from sensible cooling, the system effectively removes moisture without requiring the air to be cooled below its dew point.

This technology is highly differentiated because it overcomes the limitations of traditional dehumidification methods. Unlike conventional systems that waste energy by over-cooling air to condense water, this solution reduces chiller energy consumption by over 30%. Furthermore, traditional liquid desiccants are notoriously corrosive and risk contaminating the air stream. By utilizing a non-toxic siloxane solution paired with a nonporous membrane, this system entirely prevents droplet entrainment and air contamination. Additionally, the desiccant operates within a narrow temperature range, allowing regeneration via low-temperature renewable or waste heat. Finally, its modular design enables miniaturized, distributed units that seamlessly integrate into existing building structures.

Benefits

• Significantly reduces HVAC energy consumption by decoupling dehumidification from cooling, avoiding the need to over-cool air and cutting chiller energy use by 30% or more.
• Prevents air stream contamination and droplet entrainment by using a nonporous membrane to completely separate the air from the liquid desiccant.
• Allows for eco-friendly desiccant regeneration using low-temperature waste heat or renewable energy sources due to its narrow operating temperature range.
• Features a highly scalable, modular tube architecture that can be easily miniaturized or expanded for seamless integration into various building structures and HVAC systems.
• Utilizes a non-toxic, non-corrosive liquid desiccant that is safe for occupants and compatible with standard pumps and piping, reducing maintenance and equipment degradation.
• Adaptable for a wide range of applications, from residential and commercial air conditioning to specialized industrial drying chambers such as clean rooms and food processing facilities.

Applications

• Commercial building HVAC dehumidification
• Clean room humidity control
• Food processing drying chambers
• Microelectronics manufacturing humidity control
• Industrial painting chamber dehumidification

Additional info

This shell-and-tube system utilizes an alkoxylated siloxane liquid desiccant separated from an air stream by a nonporous, hydrophilic membrane. The desiccant flows within membrane tubes while air passes through a concentric outer shell in parallel or counter-flow. This configuration enables selective water vapor transport without droplet entrainment. By decoupling latent dehumidification from sensible cooling, the modular architecture facilitates energy-efficient moisture removal and regeneration using low-temperature waste heat.