Droplet Dynamics And Heat Transfer Of Dropwise Condensation For Hybrid Surface With Large Contact Angle Hysteresis

Dropwise condensation has gained extensive attentions, since Schmidt introduced its high heat transfer efficiency behavior in the last century. Therefore, many researchers have explored and investigated dropwise condensation for many aspects such as heat transfer mechanism, preparation of functional materials, and industrialization applications. Although the promoting layer lifetime is main issues which hinders dropwise condensation heat transfer in industrial applications, promoting local peeling layer may form a combination surfaces with a special wetting characteristics resulting in a higher thermal performance. This dissertation present and prepare a series of novel hybrid surfaces, which display a great contact hysteresis aiming to effectively regulate the condensation droplet motion and enhance heat transfer performance. Meanwhile, this dissertation could also provide theoretical basis and experimental data for dropwise condensation in the large-scale industrial applications.The heat transfer performance of different wetting properties of super hydrophobic surfaces and hybrid surfaces during the condensation process is systematically investigated, and the impact of a large contact angle hysteresis of dropwise was especially examined. Firstly super hydrophobic surfaces was prepared and utilized in the condensation process experimental study, which show an excellent stability. According to regulation of different wetting characteristics, a serial of hybrid surfaces are also prepared to conduct condensation experiment, mainly considered the impact of the contact angle hysteresis on the droplet motion characteristics and condensation heat transfer performance for condensation system.Different etching time could realize different regulation of the super hydrophobic surfaces, accordingly regulating the average free energy for wall surfaces. A regional regulatory laws of droplet sizes are also summarized for different divided width of hybrid surfaces. Meanwhile, Based on the condensation heat transfer experiment with different wetting properties of hybrid surfaces condensation, different contact angle hysteresis for hybrid surfaces was also analyzed. The experimental and theoretical results show that a large contact angle hysteresis can promote droplet aspiration, accelerate the updating for hydrophobic region, and ultimately enhance heat transfer performance in the dropwise condensation process.