Feasibility study on improving the performance of atomization liquid desiccant dehumidifier with standing-wave ultrasound

Liquid desiccant dehumidification systems are promising to increase building energy efficiency. Furthermore, the dehumidification performance can be improved using ultrasound capable of atomizing liquid desiccant into numerous droplets. However, the droplets fall rapidly by gravity and converge into liquid films at the dehumidifier’s bottom, reducing the effective transfer time, which is another crucial factor for dehumidification, and the energy efficiency of the ultrasonic system. This study investigated a new and improved method using a standing-wave ultrasound and its levitation effects; using this method, desiccant droplets can be levitated and vibrated in humid air, and thereby, the mass transfer can be increased. The feasibility of the method was carefully verified through comparative experiments within an improved ultrasonic liquid desiccant system (ULDS), which was switched between the conventional traveling-wave and the standing-wave ultrasound. Performance criteria related to the moisture removal rate and specific energy consumption of the ultrasonic system were adopted. We found that the standing-wave ultrasound significantly improved the dehumidification performance of ULDS (by 56% on average) at a negligible additional energy cost. Moreover, low-concentration desiccant solutions become useable, and the ultrasonic device is more energy-efficient in the standing-wave ULDS. This study can aid in improving the dehumidification performance of ULDSs. •Ultrasonic levitation effect was newly introduced to liquid desiccant dehumidification.•A new SW-ULDS was built and effects of operating conditions were clarified.•Standing-wave ultrasound significantly facilitates dehumidification process.•Less-concentrated desiccant solution can be utilized in the SW-ULDS.•In ULDS, standing-wave ultrasounds are more energy-efficient for dehumidification.