In natural, the condensation, coalescence and growth of water droplets have crucial positive effect in the process of cloud formation, which is hard to occur under sub-saturated environment. In this paper, the growth of water droplets is detected in a 0.24 m3 sub-saturated cloud chamber with unipolar corona discharge and needle electrode configuration. The results show that the diameter of water droplets can grow up from submicron to 32 μm under -39 kV at relative humidity ~ 85 % and ambient temperature ~ 10 ℃. The growth mechanism in the evolution process is further discussed, focusing on the effect of charge on charged droplets condensation, and the synergistic effect of charges and electric field. The former is verified by the comparison of experimental average net charges of some typical diameter droplets and minimal charges needed to maintain self-growing. The latter is demonstrated by the analysis of charged droplets motion and the ionic wind recorded by camera. The analysis is in good consistent with the experimental results, which suggests its promising and potential applications in the utilization of atmospheric water resources, especially in arid regions.

中文翻译：

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电荷和电场的协同效应：亚饱和云室中的水滴凝结和聚结

在自然界中，水滴的凝结、聚结和生长在云的形成过程中具有至关重要的积极作用，这在亚饱和环境下是很难发生的。在本文中，使用单极电晕放电和针电极配置在 0.24 m3 亚饱和云室中检测到水滴的生长。结果表明，在-39 kV、相对湿度~85%、环境温度~10℃条件下，水滴直径可以从亚微米增大到32 μm。进一步讨论了演化过程中的生长机制，重点研究了电荷对带电液滴凝聚的影响，以及电荷与电场的协同效应。前者通过比较一些典型直径液滴的实验平均净电荷和维持自生长所需的最小电荷来验证。后者通过对带电液滴运动的分析和相机记录的离子风来证明。分析结果与实验结果吻合较好，表明其在大气水资源利用方面具有广阔的应用前景，尤其是在干旱地区。