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本文利用自组装技术制备了铜基十八烷基硫醇疏水表面(SAM),通过红外热像仪分析了低压条件下液滴表面和换热表面的温度分布以及液滴脱落引起的温度分布演变。实验结果表明:低压蒸汽冷凝条件下,冷凝表面局部温度分布不均匀;单个液滴表面温度呈中心高边缘低的凸型分布;随着液滴半径的增加,液滴表面温度升高;相同操作压力下,随着过冷度的增加,液滴表面温度降低。在液滴脱落过程中,液滴表面温度逐渐升高,同时裸露出的换热表面局部过冷度增大,局部表面温度呈现出中心低周围高的凹型温度分布,随之恢复到液滴脱落前的温度。随着蒸汽压力降低,冷凝临界过冷度增加,导致裸露表面上具有更低温度的中心区域核化点密度高,最终加剧了整个换热表面液滴尺寸分布的非均匀程度。
In this paper, copper-based octadecyl mercaptan hydrophobic surface (SAM) was prepared by self-assembly technique. The temperature distribution of droplet surface and heat transfer surface under low pressure and the evolution of temperature distribution caused by droplet detachment were analyzed by infrared thermal imager . The experimental results show that the local temperature distribution of the condensing surface is not uniform under the condition of low pressure steam condensing. The surface temperature of a single droplet is a convex distribution with a low center and a high edge. The droplet surface temperature increases as the droplet radius increases. Under pressure, as the undercooling increases, the droplet surface temperature decreases. In the process of droplet dropping, the surface temperature of droplet gradually increases, while the local undercooling of the exposed heat exchange surface increases, the local surface temperature shows a concave temperature distribution with high center and low periphery, Before the temperature. As the steam pressure decreases, the critical undercooling increases, resulting in a high density of nucleation sites in the central region with a lower temperature on the exposed surface, eventually exacerbating the non-uniform droplet size distribution across the heat transfer surface.