摘要
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。
Self-assembled monolayers （SAMs） of 1-octadecanethiol [CHa（CH2）lTSHI were applied to promote dropwise condensation on copper substrate. At low pressure, the temperature distribution of droplet surface and the temperature variation of condensation surface during droplet falling off were measured using ThermoVisionA40. Major conclusions drawn in this study are as follows： The temperature distribution on the condensing surface is nonuniform while the temperature distribution of droplet surface is convex. The temperature of droplet surface is higher for larger condensate droplet. However, the temperature of droplet surface decreases with an increase in subcooling at given vapor pressure. The temperature of droplet surface rises gradually due to the falling behavior of the droplet. Consequently the temperature of the renewed location decreases with the surface subcooling increasing and then rises back. As the vapor pressure decreases, an increase in the critical surface subcooling for condensation results in a higher activated nucleation site density in the center of the renewed location where the temperature is lower and eventually lead to the nonuniformity of the temperature distribution.
出处
《工程热物理学报》
EI
CAS
CSCD
北大核心
2012年第6期1027-1031,共5页
Journal of Engineering Thermophysics
基金
国家自然科学基金青年基金(No.50906006)
关键词
低压蒸汽
滴状冷凝
红外热像
表面温度
low-pressure steam
dropwise condensation
infrared thermal image
surface temperature
