西安建筑科技大学学报(自然科学版)

为解决空气源热泵室外换热器在低温潮湿的工况下运行时的结霜问题,从结霜影响因素及霜层生长条件出发,改善了一种抑霜表面改性方法,制备出接触角为158.3°的超疏水铝基翅片; 基于超疏水抑霜机理分析,并通过所建立的模拟低温、高湿环境的强制对流可视化实验平台,对超疏水铝基竖直翅片的抑霜/融霜效果进行理论及实验研究.结果表明,超疏水表面液滴成核位垒大、冰桥传播慢、液滴与冷表面接触面积小、液滴频繁发生合并-弹跳-滚动-滑落现象; 霜层初始生长阶段,超疏水铝基表面较常规铝基表面结霜时间延迟165 s、霜层覆盖率增速小; 强制对流下的结霜过程中,超疏水铝基翅片结霜量为常规铝基翅片的69.8%、生长速率为常规铝基翅片的65.2%; 融霜过程中,超疏水铝基翅片融霜时间为常规铝基翅片的64%、残留化霜水比例减少47.9%.超疏水表面表现出良好的抑制结霜、快速融霜的特性,初步揭示了超疏水技术应用于空气源热泵室外机换热器表面进行有效抑霜的可行性及其实际应用价值.

Based on the influencing factors and conditions of frost layer growth to suppress frost, this paper improves a surface modification method to solve the problem that the outdoor heat exchanger of air source heat pump will frost while operating under low temperature and high humidity. By this means, superhydrophobic aluminum fins with contact angle of 158.3° are prepared. To experimentally study the frost suppression / thawing effect of superhydrophobic aluminum fins, the frost suppression mechanism of superhydrophobic surface is analyzed, and a forced convection visualization experimental platform which simulates low temperature and high humidity environment is established. The results show that the superhydrophobic surface has large nucleation barrier, slow ice bridge propagation, less contact area between droplets and cold surface, and frequent merging-bouncing-rolling-sliding of droplets. In the initial growth stage of frost layer, the frosting time of superhydrophobic aluminum fin is 165 s later than that of conventional aluminum fin, and the growth rate of frost layer coverage is small. During the frosting process under forced convection, the frosting amount of superhydrophobic aluminum fin is 69.8% of that of conventional aluminum fin, and the growth rate is 65.2% of that of conventional aluminum fin. During the defrosting process, the defrosting time of superhydrophobic aluminum fin is 64% of that of conventional aluminum fin, and the proportion of residual defrosting water is reduced by 47.9%. The superhydrophobic surface shows good characteristics of inhibiting frosting and rapid defrosting. The results preliminarily reveal the feasibility and practical application value of superhydrophobic technology, which is applied to the surface of outdoor unit heat exchanger of air source heat pump.

引言
1 超疏水表面抑霜机理
2 实验部分
3 超疏水表面的抑霜/融霜性能
4 结论

图1 蒸汽冷凝成核示意图<br/>Fig.1 Schematic diagram of steam condensation nucleation

图1 蒸汽冷凝成核示意图
Fig.1 Schematic diagram of steam condensation nucleation

图2 冰桥传播现象示意图<br/>Fig.2 Schematic diagram of ice bridge propagation phenomenon

图2 冰桥传播现象示意图
Fig.2 Schematic diagram of ice bridge propagation phenomenon

图3 Cassie-Baxter理论示意图<br/>Fig.3 Schematic diagram of Cassie-Baxter theory

图3 Cassie-Baxter理论示意图
Fig.3 Schematic diagram of Cassie-Baxter theory

图4 各制备阶段液滴形态及接触角值<br/>Fig.4 Droplet morphology and contact angle at each preparation stage

图4 各制备阶段液滴形态及接触角值
Fig.4 Droplet morphology and contact angle at each preparation stage

图5 实验装置示意图<br/>Fig.5 Schematic diagram of suppression experimental apparatus

图5 实验装置示意图
Fig.5 Schematic diagram of suppression experimental apparatus

图6 表面霜层覆盖率随时间的变化<br/>Fig.6 Variation of frost coverage with time

图6 表面霜层覆盖率随时间的变化
Fig.6 Variation of frost coverage with time

图7 两种湿润性表面在-13 ℃时“冰桥”传播<br/>Fig.7 Ice bridge propagation on two kinds of wettability surfaces at -13 ℃

图7 两种湿润性表面在-13 ℃时“冰桥”传播
Fig.7 Ice bridge propagation on two kinds of wettability surfaces at -13 ℃

图8 霜层重量随时间的变化<br/>Fig.8 variation of frost weight with time

图8 霜层重量随时间的变化
Fig.8 variation of frost weight with time

图9 翅片前部、中部、尾部霜层厚度随时间的变化<br/>Fig.9 Variation of frost layer thickness at the front, middle and tail of fins with time

图9 翅片前部、中部、尾部霜层厚度随时间的变化
Fig.9 Variation of frost layer thickness at the front, middle and tail of fins with time

图10 翅片表面霜层晶体融化示意图<br/>Fig.10 Schematic diagram of frost melting on fin surface

图10 翅片表面霜层晶体融化示意图
Fig.10 Schematic diagram of frost melting on fin surface

图11 翅片霜层重量、融化后化霜水停留位置及化霜时间对比图<br/>Fig.11 Comparison of the weight of the frost surface on the fins, the location of the defrosting water and the time of defrosting

图11 翅片霜层重量、融化后化霜水停留位置及化霜时间对比图
Fig.11 Comparison of the weight of the frost surface on the fins, the location of the defrosting water and the time of defrosting

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备注

引言

1 超疏水表面抑霜机理

2 实验部分

3 超疏水表面的抑霜/融霜性能

4 结论

期刊信息