空气源热泵冬季制热运行存在结霜问题，严重影响其制热效率与可靠性。翅片表面超疏水改性可实现抑制结霜和强化融霜双高效，为解决热泵结霜问题提供了有效途径。然而，超疏水翅片竖直放置引发的接触角滞后效应对其结霜/融霜特性的影响及微观作用机理尚未明确，制约了其抑霜/融霜性能的优化提升及实际应用。项目通过理论与实验研究相结合，由宏观层面深入微观层面，可视化获取竖直超疏水翅片结霜/融霜的动态行为及热力学特性，阐明结霜初期凝结液滴生长—冻结过程、霜层融化以及融霜水运动的演化规律；运用表面物理化学与传热传质理论，构建接触角滞后效应对结霜/融霜过程影响的理论模型；基于微观表征及表面能理论，明确不同润湿模式下翅片表面微结构的几何特征与滞后效应的数学关联，揭示滞后效应对结霜/融霜的微观作用机理，指导高效抑霜/融霜型超疏水翅片表面微结构的优化设计，为通过翅片表面改性实现空气源热泵稳定、高效运行提供理论基础与技术支持。

Frost formation is unavoidable when an air source heat pump is used for heating in winter, which seriously affects its heating efficiency and running reliability. Superhydrophobic fin is effective in both against frosting and defrosting improvement, which provides a promising way to solve the frosting problem of air source heat pump. However, the influence of contact angle hysteresis caused by vertical placement of superhydrophobic fin on its frosting/defrosting characteristics and the microscopic mechanism have not yet been clarified, which limits the optimization of anti-frosting/defrosting performances and the practical application. Therefore, the effects of contact angle hysteresis on frosting/defrosting characteristics of vertical superhydrophobic fin and its microscopic mechanism are studied in this project from macro level to micro level, by combining theoretical and experimental researches. In this project, the dynamic behavior and thermodynamic properties of frosting and defrosting on vertical superhydrophobic fin are obtained experimentally. Then, the theoretical models, including the parameter of contact angle hysteresis, are developed to achieve the influence rules of hysteresis on frosting/defrosting processes of superhydrophobic fin. Based on microscopic characterization and surface energy theory, the mathematical relationship between the geometric characteristics of the surface microstructures and the contact angle hysteresis is clarified, and the microscopic action mechanisms of the hysteresis on frosting/defrosting characteristics of superhydrophobic fin are revealed, which is finally used to guide the optimize design of the surface geometric characteristics of superhydrophobic fin. The study can provide theoretical foundation for using surface modification of fin to achieve efficient and stable operation of air source heat pump.