Hydrodynamics and heat transfer during droplet impingement on nanostructured surfaces

In this study we analysed the droplet shape and heat transfer during impact on three different surfaces of 6J.1m thick copper foil: two coated with superhydrophobic and hydrophilic materials and one uncoated surface. The droplet temperature and the shape were measured simultaneously with high speed and thermal imaging cameras. Simulations using computational fluid dynamics (CFD) were then carried out to investigate the droplet shape and they were validated with the experimental results. Both the experimental and the simulation results of water droplet on a superhydrophobic surface show the complete droplet shapes (spreading, retracting, bouncing and oscillating) compared to the two other surfaces. The temperature distribution of the experiment result shows that the hydrophilic surface cools faster compared to the superhydrophobic surface, because of the larger contact area.