Abstract:

Frost layer propagation is a key in the early stage of surface frosting, and it is very important in the whole surface condensation frosting process. In order to research the relationship between surface wettability and frost crystal propagation process and velocity in the process of condensation frosting, a micro-visual frosting experimental test platform was built, and three kinds of high reflectivity surfaces with different wettability were prepared according to the experimental requirements. The surface frost layer propagation process can be divided into two stages: frost crystal propagation within droplet and ice bridge propagation between droplets. It is found that the distance between the ice bridge and the droplet is the main element affecting the ice bridge propagation speed. When the distance between ice bridge and droplet decreases from 16 μm to 2 μm, the ice bridge propagation velocity increases rapidly from 2 μm/s to 12 μm/s. Besides, the distribution characteristics of condensation droplets on superhydrophobic surfaces and the obvious difference of ice bridge propagation element are the main reasons for the slow frost propagation on superhydrophobic surfaces. The key elements affecting frost transfer and inhibiting frost formation were revealed, that is, droplet size distribution characteristics of superhydrophobic surface. Present investigation may provide ideas and basis for the design and optimization of anti-frost surface.

Key words: condensation frosting, frosting propagation, ice bridge propagation, superhydrophobic, microscale

摘要：

霜层传递是表面冷凝结霜初期一个关键环节，在整个表面结霜过程中至关重要。为研究冷凝结霜过程中表面润湿性能与霜晶传播过程、速度的关系，搭建了微观可视化结霜实验测试平台，根据实验所需制备了三种不同润湿性能的高反射率表面。表面霜层传递过程大致分为两个阶段，即液滴内霜晶传播和液滴间冰桥传播。实验发现影响冰桥传播速度的主要原因是冰桥与液滴的间距L。当冰桥与液滴间距由16 μm减小为2 μm时，冰桥传播速度从2 μm/s快速地升至12 μm/s。测试了不同润湿性能表面上冷凝结霜过程和霜层的整体传递速度，研究发现，超疏水表面凝结液滴的分布特征和冰桥传播系数的明显差异是导致超疏水表面结霜过程中霜层传递缓慢的主要原因。揭示了影响霜层传递以及抑制结霜的关键因素，即超疏水表面液滴尺寸分布特性，为抑霜表面的设计和优化提供了思路和基础。

关键词: 冷凝结霜, 霜晶传播, 冰桥传播, 超疏水, 微尺度