Electrowetting assisted shedding of droplets by a shearing airflow in dropwise condensation

Abstract

Condensation is a necessary part of most industrial processes dealing with phase change. Efficient condensate removal (shedding) increases the systems’ performance. This study investigated the influence of electrowetting on droplet shedding and heat transfer enhancement during humid air condensation on a horizontal substrate. A mini closed-looped wind tunnel was used to simulate the condensation environment and control condensation parameters. AC electric field with the frequencies of 1 and 10 kHz was applied and compared with the control case (no voltage). The transient inverse heat conduction method was used to determine the heat transfer coefficient, and heat transfer measurements were synchronized to a high-resolution camera to monitor the condensation dynamics. The results show that the area-weighted average droplet radius was increased by 61 % and 84 % for 1 kHz and 10 kHz, respectively, compared to the control case for 1 m/s airflow. At 10 kHz, the shedding time was reduced, particularly at higher airflow velocities. Additionally, the heat transfer coefficient (HTC) exhibited a significant increase at 10 kHz when shedding was present. Notably, the difference in HTC became pronounced at an airflow velocity of 15 m/s, where shedding was prominent. In this scenario, the HTC rose by an impressive 35 % compared to the control case. These findings provide a promising foundation for utilizing EW to enhance heat transfer and improve condensate shedding under shear flow conditions.