Water evaporation phenomena on micro and nanostructured surfaces

Augmentation of a microevaporator performance has been investigated experimentally to provide high quality vapor flow. Silicon, Silicon dioxide (SiO2), Silicon nanowires (SiNW), silicon pillars (P-Si), silicon pillars covered by silicon dioxide (P-SiO2) and silicon pillars with nanowires etched on the top (P-SiNW) are considered as evaporation surfaces. These surfaces are fabricated based on deep reactive ion etching (DRIE) as well as electrochemically etched nanowires. Two regimes (no flooded evaporation regime and flooded evaporation regime) are called for evaporation based on different applications. Experiments are repeated three times to ensure repeatability of the observations. Results show that in the case of no flooded regime, evaporation rate are significantly affected by three mechanisms; water spreading between micro and nanostructures, shape and thickness of water droplets on the surface and dynamic behavior of evaporation. In this regime, the P-SiO2 surface has the highest performance among the other surfaces. However, in the case of the flooded regime, the nucleation sites of boiling are very important to achieve maximum rate of evaporation. In this regime the P-SiNW surface is the most efficient surface.