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首页> 外文期刊>International Journal of Heat and Mass Transfer >Evaporation and condensation of water mist/cloud droplets with thermal radiation
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Evaporation and condensation of water mist/cloud droplets with thermal radiation

机译：带有热辐射的水雾/云滴的蒸发和冷凝

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摘要

The role of thermal radiation in water droplet evaporation and condensation is investigated theoretically. The primary droplet size regime considered is that between non-continuum gas effects and gas-liquid velocity-slip effects, nominally 10~(-1)-10~2 μm, with mist or clouds (nominally 20-μm diameter) being the primary application of interest. Principles for extending the results to larger droplets are also discussed, even to the radiative-evaporative balance of the oceans. The importance of distributed (volumetric, in-depth) absorption in the droplet, conduction, and advection induced by surface regression are analyzed. It is found that advection within the liquid phase induced by surface regression can be neglected for most conditions and that conduction usually establishes a spatially isothermal droplet. Comparison with experimental results for a laser-irradiated droplet suggests that, due to the isothermal condition, these assumptions are reasonable for predicting evaporation rate. Moreover, it is shown that infrared absorption and emission can be treated as surface phenomena; in-depth effects can be neglected. Extending the analysis to cloud droplets shows that radiation, whether with colder upper layers of the atmosphere, wanner lower layers/ground, or solar radiation, can have a significant influence on cloud droplet growth and stability. For typical ambient conditions the thermal radiation effect near the edge of a cloud can be as strong as the effect of a 0.1% super- or sub-saturation, enough to modify significantly the Kohler curves governing equilibrium droplet size distribution and enough to provide the missing mechanism of warm rain droplet growth between the upper limit of non-radiating, diffusional condensation growth (～30 μm) and the lower limit of turbulent-inertial coalescence growth (～80 μm), the so-called condensation-coalescence "bottleneck".
机译：理论上研究了热辐射在水滴蒸发和凝结中的作用。考虑的主要液滴尺寸范围是在非连续气体效应和气-液速度滑移效应之间，名义上为10〜（-1）-10〜2μm，其中雾或云（标称直径为20μm）是主要的应用兴趣。还讨论了将结果扩展到较大液滴的原理，甚至扩展到海洋的辐射-蒸发平衡。分析了液滴在液滴中的分布（体积，深度）吸收，表面回归引起的对流和对流的重要性。已经发现，在大多数情况下，由表面回归引起的液相内的对流可以忽略不计，并且传导通常会建立空间等温的液滴。与激光照射液滴的实验结果进行比较表明，由于等温条件，这些假设对于预测蒸发速率是合理的。而且，表明红外吸收和发射可以看作是表面现象。深度效应可以忽略。将分析扩展到云滴表明，无论是大气上层较冷，下层/地面下降还是太阳辐射，辐射都会对云滴的生长和稳定性产生重大影响。对于典型的环境条件，云边缘附近的热辐射效果可能与0.1％的过饱和或次饱和状态一样强，足以显着修改控制平衡液滴尺寸分布的科勒曲线，并且足以弥补缺失在非辐射扩散扩散上限（〜30μm）和湍流惯性聚结增长下限（〜80μm）之间的暖雨滴生长机理，即所谓的凝结凝聚“瓶颈”。

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