Experimental study on frosting characteristics of vertical fins
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摘要: 冬季放置室外的空气取水装置，其冷端竖直翅片表面容易结霜。通过可视化试验，研究不同空气条件下竖直翅片表面结霜特性，为抑制翅片表面结霜提供依据。结果表明，冷表面温度影响翅片表面霜晶的形貌。在冷表面温度降低过程中，霜晶依次呈现无规则状、扇状、羽毛状和树状。设置空气相对湿度为60%，空气温度在10～25 ℃递增，翅片表面水珠冻结时间先从273 s缩短至205 s后延长至269 s，霜层生长平均速度先快后慢。设置空气温度为20 ℃，空气相对湿度在20%～80%递增，翅片表面水珠冻结时间从345 s逐渐缩短至218 s，霜层生长平均速度变快。设置空气含湿量近似相等，空气温度在10～25 ℃递增，霜层生长平均速度变慢。Abstract: In winter, the surface of the vertical fin of the cold end of the outdoor air intake device is prone to frost. Through visualization experiments, the characteristics of frost formation on the surface of vertical fins under different air conditions were studied to provide a basis for suppressing frost formation on the surface of fins. The results show that the frost crystal morphology of fin surface is affected by the cold surface temperature, and the frost crystal show irregular shape, fan shape, feather shape and tree shape in turn when the cold surface temperature decreases. When set the relative humidity of the air to 60% and increase the air temperature within the range of 10 to 25 ℃, it was found that the freezing time of water droplets on the surface of the fin was shortened from 273 to 205 s and then extended to 269 s. The average frost growth rate was first fast and then slow. When the air temperature is setted to 20 ℃ and the relative humidity of air increases within the range of 20% ~ 80%, the freezing time of water droplets on the surface of fin is gradually shortened from 345 to 218 s, and the average growth rate of frost layer is faster. The moisture content of the air is approximately equal, the air temperature increases within the range of 10 to 25 ℃, and the average growth rate of the frost layer slows down.
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Key words:
- frost formation on fins /
- freezing time /
- frost crystal morphology /
- frost layer height
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图 2 热电制冷系统冷端竖直翅片示意图
Figure 2. Schematic diagram of vertical fin of cold end of thermoelectric refrigeration system
图 6 不同空气温度下翅片表面水珠出现时间
Figure 6. Time of water droplets appearing on fin surface at different air temperatures
图 7 不同空气温度下翅片表面水珠冻结时间
Figure 7. Freezing time of water droplets on fin surface at different air temperatures
图 8 不同空气相对湿度下翅片表面水珠出现时间
Figure 8. Time of bead occurrence on fin surface under different air relative humidity
图 9 不同空气相对湿度下翅片表面水珠冻结时间
Figure 9. Freezing time of bead on fin surface under different air relative humidity
图 11 霜层高度与空气相对湿度的关系
Figure 11. Relationship between frost height and air relative humidity
表 1 不同空气条件下的相变驱动力
Table 1. Driving forces of phase transformation under different air conditions
空气温度/℃ 空气相对湿度/% 相变驱动力 /（1023× J） 20 20 55 20 40 311 20 60 461 20 80 568 10 60 223 15 60 344 25 60 574 10 83 343 20 44 347 25 32 341 
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表 2 空气含湿量近似相等时4种试验工况
Table 2. Four experimental conditions when air moisture content is approximately equal
空气温度/℃ 空气相对湿度/% 空气含湿量/（g·kg−1） 10 83 6.32 15 60 6.35 20 44 6.38 25 32 6.29
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