Combined study of evaporation from liquid surface by background oriented schlieren, infrared thermal imaging and numerical simulation
Combined study of evaporation from liquid surface by background oriented schlieren, infrared thermal imaging and numerical simulation
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背景定向纹影、红外热成像和数值模拟联合研究液体表面蒸发
DOI：
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发表时间：
2013
期刊：
影响因子：
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通讯作者：
Y. Plaksina
中科院分区：
文献类型：
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作者：
N. Vinnichenko;A. Uvarov;Y. Plaksina
采用背景定向纹影（BOS）技术和红外热成像技术同时测量了蒸发液体的温度场。两种方法的测量误差小于0.1K，符合较好.观察到两种配置的表面层：热毛细对流状态与移动的液体表面和小的热细胞，与Marangoni对流，和“冷皮肤”的表面上的速度可以忽略不计，较大的细胞和表面下的0.1 mm层内的速度急剧增加。这些配置被示出为在各种液体（具有各种纯化程度的水、乙醇、丁醇、癸烷、煤油、甘油）中形成，这取决于初始条件和环境参数而不是液体。水，这一直被认为是液体没有可观察到的马兰戈尼对流，实际上可以表现出这两种行为在同一个实验运行。蒸发也通过数值模拟进行了研究。考虑了空气和液体中的分离问题，并利用表面温度的热成像数据使分离成为可能。结果表明，在适当的边界条件下，空气侧的蒸发量可以通过数值模拟来预测。与已知的经验关系的舍伍德-瑞利关系进行了比较。水侧问题的数值模拟揭示了自由表面速度边界条件的问题，决定了表面层的结构。在第三类边界条件下，采用无滑移边界条件和表面张力边界条件相结合的方法，得到了与实验结果相似的流场。
Temperature fields in evaporating liquids are measured by simultaneous use of Background Oriented Schlieren (BOS) technique for the side view and IR thermal imaging for the surface distribution. Good agree- ment between the two methods is obtained with typical measurement error less than 0.1 K. Two configurations of surface layer are observed: thermocapillary convection state with moving liquid surface and small thermal cells, associated with Marangoni convection, and "cool skin" with negligible velocity at the surface, larger cells and dramatic increase of velocity within 0.1 mm layer beneath the surface. These configurations are shown to be formed in various liquids (water with various degrees of purification, ethanol, butanol, decane, kerosene, glyc- erine) depending rather on initial conditions and ambient parameters than on the liquid. Water, which has been considered as the liquid without observable Marangoni convection, actually can exhibit both kinds of behavior during the same experimental run. Evaporation is also studied by means of numerical simulations. Separate prob- lems in air and liquid are considered, with thermal imaging data of surface temperature making the separation possible. It is shown that evaporation rate can be predicted by numerical simulation of the air side with ap- propriate boundary conditions. Comparison is made with known empirical correlations for Sherwood-Rayleigh relationship. Numerical simulations of water-side problem reveal the issue of velocity boundary conditions at the free surface, determining the structure of surface layer. Flow field similar to observed in the experiments is obtained with special boundary conditions of third kind, presenting a combination of no-slip and surface tension boundary conditions.