Abstract:

The super-hydrophobic surface structure parameters will affect the droplet condensation heat transfer performance, droplet growth and distribution. The departure radius of droplets on the vertical wall during steam condensation with non-condensable gas was determined by the force balance, and a heat transfer model for dropwise condensation with non-condensable gas was developed. The influence of the space between the micro-pillars on superhydrophobic surface on dropwise condensation heat transfer performance was conducted under various non-condensable gas concentrations and surface subcoolings. The optimum value of the micro-pillars spacing which can induce the maximum dropwise condensation heat transfer performance was developed. Furthermore, the effects of non-condensable gas concentration and surface subcooling on the optimum micro-pillars spacing were analyzed. The results illustrated that the optimum micro-pillars spacing ascended with the increase of the non-condensable gas concentration when the concentration of non-condensable gas was lower than 20%. However, the optimum micro-pillars spacing decreased with the increase of the non-condensable gas concentration when the non-condensable gas concentration was higher than 20% within the applied surface subcooling. The results supplied the primary information for optimizing the micro-nano structures of superhydrophobic surfaces which can induce the condensation heat transfer enhancement of steam in the presence of non-condensable gas.

Key words: condensation, superhydrophobic, surface, non-condensable gas, heat transfer, micro scale

摘要：

超疏水表面结构参数对滴状冷凝传热性能、液滴生长和分布均会产生影响。首先利用竖直壁面液滴的受力平衡确定了不凝气条件下蒸汽冷凝过程中液滴的脱落半径，随后建立了含不凝气蒸汽滴状冷凝的传热模型，研究了不同不凝气浓度和过冷度下超疏水表面微柱的柱间距对滴状冷凝传热性能的影响，得到了使超疏水表面冷凝传热性能达到最佳的柱间距值，并对其随不凝气浓度和过冷度的变化规律进行了分析。结果表明在所研究的过冷度范围内，当不凝气浓度较低时（<20%），最佳柱间距随不凝气浓度升高而增大；而当不凝气浓度高于20%时，最佳柱间距随不凝气浓度升高而减小。为驱动含不凝气蒸汽冷凝传热性能的超疏水微纳结构参数的优化提供了必要的基础数据。

关键词: 凝结, 超疏水, 表面, 不凝气, 传热, 微尺度