For intermittent spray cooling purpose, it is essential to study the unsteady aspects of film evaporation and heat transfer characteristics. In the present study, total evaporation time and surface temperature variations are investigated for four different liquid films (water, ethanol, n-octane and n-hexane). The evaporation process is analyzed using a three-dimensional spray-wall impact with Lagrangian wall-film model. The evaporation process occurs in three stages; at the initial moments, most of the heat is used to raise the film temperature, and slight evaporation also exists. The film temperature rises until it reaches the liquid saturation point to evaporate at a constant rate. In the last stage, the evaporation rate decreases with time due to the accumulation of vapor in the bulk flow. The effect of heat flux and initial film thickness on the total evaporation time and the slope of its changes are investigated. The results show that the total evaporation time increases linearly with the initial thickness. Also, the molecular weight and saturation point of liquids are influential parameters after the enthalpy of evaporation. The surface temperature rises to a maximum value before reducing by the film evaporation. The maximum amount of the wall temperature depends on the liquid thermal conductivity and the evaporation rate. Finally, the effect of the initial value of the film temperature is investigated, and a correlation for estimating the total evaporation time is extracted.

中文翻译：

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液体性质对非稳态喷壁冲击形成的液膜传热和蒸发特性的影响

对于间歇喷雾冷却目的，有必要研究薄膜蒸发和传热特性的非稳态方面。在本研究中，研究了四种不同液膜（水、乙醇、正辛烷和正己烷）的总蒸发时间和表面温度变化。使用拉格朗日壁膜模型的三维喷壁冲击来分析蒸发过程。蒸发过程分三个阶段进行；初始时刻，大部分热量用于提高薄膜温度，也存在少量蒸发。薄膜温度升高直至达到液体饱和点以恒定速率蒸发。在最后阶段，由于整体流中蒸汽的积累，蒸发速率随着时间的推移而降低。研究了热通量和初始膜厚度对总蒸发时间及其变化斜率的影响。结果表明，总蒸发时间随初始厚度线性增加。此外，液体的分子量和饱和点也是蒸发焓之后的影响参数。表面温度先升至最大值，然后因薄膜蒸发而降低。壁温的最大值取决于液体的导热率和蒸发速率。最后，研究了薄膜温度初始值的影响，并提取了估计总蒸发时间的相关性。结果表明，总蒸发时间随初始厚度线性增加。此外，液体的分子量和饱和点也是蒸发焓之后的影响参数。表面温度先升至最大值，然后因薄膜蒸发而降低。壁温的最大值取决于液体的导热率和蒸发速率。最后，研究了薄膜温度初始值的影响，并提取了估计总蒸发时间的相关性。结果表明，总蒸发时间随初始厚度线性增加。此外，液体的分子量和饱和点也是蒸发焓之后的影响参数。表面温度先升至最大值，然后因薄膜蒸发而降低。壁温的最大值取决于液体的导热率和蒸发速率。最后，研究了薄膜温度初始值的影响，并提取了估计总蒸发时间的相关性。壁温的最大值取决于液体的导热率和蒸发速率。最后，研究了薄膜温度初始值的影响，并提取了估计总蒸发时间的相关性。壁温的最大值取决于液体的导热率和蒸发速率。最后，研究了薄膜温度初始值的影响，并提取了估计总蒸发时间的相关性。