Potential energy savings of the central air-conditioning systems can be induced by the indirect evaporative cooler (IEC) through energy recovery from exhaust air to the fresh air. However, the condensation in the dry channels can pose significant influences on cooling performance, especially for the IEC used in hot and humid areas. In this paper, a novel IEC heat exchanger was fabricated by depositing the hydrophobic nanoparticles on the surfaces of primary air channels, and experiments were conducted to compare its performance with the traditional uncoated IEC. The droplet behaviors on the plate surfaces with and without hydrophobic coating were compared under both dynamic and steady states. Results show that, the hydrophobic coating produces a higher contact angle for the plate surface, causing a reduced size of falling-off droplets and frequent droplets removal. The dropwise condensation on the hydrophobic surface has less deterioration effect on the convective heat transfer of primary air flowing over the heat exchange plates. Under dehumidifying conditions, the hydrophobic coating treatment on the primary air channel surfaces of the IEC could enhance the heat and mass transfer and improve the energy-saving rate by 8.5-17.2%, promising a great application potential for upgrading the evaporative cooling technologies in humid regions.
Keywords Indirect evaporative cooler, Condensation flow, Heat transfer, Hydrophobic surface