Efficient liquid desiccant dehumidification system using a natural cooling source for solution regeneration

Traditional liquid-desiccant dehumidification systems use high-humidity outdoor air for regeneration, leading to low efficiencies during humid summers. Using return air for solution regeneration lowers regeneration temperatures and saves energy, but does not fully utilize natural cooling sources. This study proposes a system that uses a natural cooling source to cool circulation air for solution regeneration (not using outside air or exhaust air for regeneration) and compares its performance with both traditional and return air based regeneration systems. Numerical models of the heat exchangers, packing towers, and compressors were developed and validated. Using the climate of Beijing, China as a case study, system performance was simulated under varying outdoor environmental conditions and natural cooling source temperatures, and compared with systems utilizing outdoor air and return air for solution regeneration. Results indicate that under the summer design condition, the proposed system performs effectively when the natural cooling source is below 20 °C. The system efficiency decreases as the temperature of the natural cooling source increases. Using a 16 °C cooling source can reduce energy consumption by 3 % and 45 % compared to the return-air and outdoor-air regeneration systems, respectively. When the natural cooling source temperature remains at 16 °C, the proposed system saves energy compared to the traditional system throughout most of the summer, except during low-humidity periods. This study further proposes a hybrid system that combines natural cooling and outdoor air for solution regeneration. This configuration enables the regeneration unit to switch between natural cooling and outdoor air as needed, improving overall energy efficiency.