空气源热泵冬季制热运行一般是基于蒸发器表面霜层充分生长后中断制热进行除霜，由此导致其存在制热性能随霜层生长而衰减和因进行除霜引起供热不连续等问题。为此，本项目基于翅片表面结霜初期所形成的凝结液滴是霜层生长的基础，创新性地提出超疏水翅片结霜初期表面特性与热气流综合作用的除霜新方法，以期达到在凝结液滴冻结前将其去除，从而阻断霜层生长的目的。采用理论与实验研究相结合，研究表面特性与热气流综合作用下超疏水翅片表面凝结液滴脱除的瞬态行为特征及综合作用机制，探索尚滞留翅片表面的微尺度凝结液滴蒸发的非稳态传热传质特性，揭示超疏水翅片表面特性与热气流综合作用除霜机理，构建实现综合作用除霜并以制冷剂过冷为热气流加热热源的空气源热泵系统，揭示综合作用除霜特性与系统性能的耦合机制，为探索出可实现制热性能不衰减和除霜供热不中断的除霜方法及其系统实现提供理论基础和关键技术支撑，有望丰富和发展空气源热泵除霜理论。

The current defrosting methods for air source heat pumps all implement defrosting at the frost layer fully growth period. As a result, the heating performance decays because of the frost layer growth. Moreover, the heating cycle of the air source heat pump is interrupted when defrosting starts, which leads to the discontinuous heating and decrease in efficiency. The frost layer grows on the surfaces of the condensate droplets which form at the initial stage of the frosting process. If the condensate droplets are removed before they are frozen, the process of the frost layer growth will be cut off. Thus, a comprehensive defrosting method, combining the effects of surface characteristics of superhydrophobic fin and hot air, was proposed in this project. Firstly, the space and size distribution of condensate droplets on superhydrophobic fin surface will be investigated by methods of theoretical analysis, experiment and simulation. Secondly, the transient behavior characteristics of condensate droplets (including rolling, merging and shedding) under the effect of fin surface characteristics and high speed flow will be explored, and the comprehensive effect of fin surface characteristics and hot air on shedding droplets with big sizes will be revealed. Then, the unsteady heat and mass transfer mechanism of residual micro-scale condensate droplets under the mulriple effect of hot air and cold fin surface will be investigated, and the unsteady heat and mass transfer model will be built. Furthermore, an air source heat pump system and its model, which use the supercooling refrigerant as the heat source for heating air, will be established based on the comprehensive defrosting, and the system efficiency of comprehensive defrosting will be evaluate and optimized. Finally, the mechanism of the comprehensive defrosting method will be revealed to provide theoretical technological foundation for efficient and stable operation of air source heat pumps. All research achievements will enrich and improve the defrosting theory for air source heat pumps.