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CONDENSATION PHASE CHANGE BEHAVIORS ON A ROUGH SURFACE CHARACTERIZED BY FRACTAL CANTOR
Fractals ( IF 3.3 ) Pub Date : 2021-10-09 , DOI: 10.1142/s0218348x21502194
HE WANG 1 , ZILONG DENG 1 , FENG YAO 2 , CHENGBIN ZHANG 1
Affiliation  

Understanding the fundamental mechanisms of vapor condensation on rough surfaces is crucial to a wide range of industrial applications. A hybrid thermal lattice Boltzmann model of the condensation heat transfer process on downward-facing rough surfaces characterized by the Cantor fractal is developed and numerically analyzed to investigate the condensation phase change behaviors on rough hydrophobic and hydrophilic surfaces. The dynamic behaviors of vapor condensation, including the evolutions of vapor–liquid interface, heat flux, condensate mass, and temperature distribution, on the hydrophilic and hydrophobic rough surfaces are presented and compared with corresponding smooth surfaces. The results indicate that the rough surface preferred a filmwise condensation under hydrophilic conditions but a hybrid dropwise–filmwise condensation under hydrophobic conditions. On the rough hydrophobic surface, the liquid film can rapidly adsorb droplets, maintaining a high-efficiency dropwise condensation. The absorption of droplets accelerates the liquid film growth and detachment process on the rough hydrophobic surface, which reduces the time-averaged thermal resistance of the filmwise region. These two behaviors together enhance condensation heat transfer on the downward-facing rough hydrophobic surface. Besides, stable dropwise condensation could also be formed on smooth hydrophilic surfaces and has better heat transfer performance than corresponding hydrophobic surfaces under the same heat transfer condition.

中文翻译:

以分形康托尔为特征的粗糙表面上的凝结相变行为

了解粗糙表面上蒸汽冷凝的基本机制对于广泛的工业应用至关重要。开发了一种以康托尔分形为特征的向下粗糙表面冷凝传热过程的混合热格子玻尔兹曼模型,并对其进行了数值分析,以研究粗糙疏水和亲水表面的冷凝相变行为。介绍了亲水和疏水粗糙表面上蒸汽冷凝的动态行为,包括蒸汽-液体界面的演变、热通量、冷凝物质量和温度分布,并与相应的光滑表面进行了比较。结果表明,粗糙表面在亲水条件下更倾向于成膜缩合,而在疏水条件下则倾向于混合逐滴-成膜缩合。在粗糙的疏水表面上,液膜可以快速吸附液滴,保持高效的液滴冷凝。液滴的吸收加速了粗糙疏水表面上的液膜生长和分离过程,从而降低了成膜区域的时间平均热阻。这两种行为共同增强了面向下的粗糙疏水表面上的冷凝传热。此外,在光滑的亲水表面上也可以形成稳定的滴状冷凝,在相同的传热条件下,其传热性能优于相应的疏水表面。在粗糙的疏水表面上,液膜可以快速吸附液滴,保持高效的液滴冷凝。液滴的吸收加速了粗糙疏水表面上的液膜生长和分离过程,从而降低了成膜区域的时间平均热阻。这两种行为共同增强了面向下的粗糙疏水表面上的冷凝传热。此外,在光滑的亲水表面上也可以形成稳定的滴状冷凝,在相同的传热条件下,其传热性能优于相应的疏水表面。在粗糙的疏水表面上,液膜可以快速吸附液滴,保持高效的液滴冷凝。液滴的吸收加速了粗糙疏水表面上的液膜生长和分离过程,从而降低了成膜区域的时间平均热阻。这两种行为共同增强了面向下的粗糙疏水表面上的冷凝传热。此外,在光滑的亲水表面上也可以形成稳定的滴状冷凝,在相同的传热条件下,其传热性能优于相应的疏水表面。液滴的吸收加速了粗糙疏水表面上的液膜生长和分离过程,从而降低了成膜区域的时间平均热阻。这两种行为共同增强了面向下的粗糙疏水表面上的冷凝传热。此外,在光滑的亲水表面上也可以形成稳定的滴状冷凝,在相同的传热条件下,其传热性能优于相应的疏水表面。液滴的吸收加速了粗糙疏水表面上的液膜生长和分离过程,从而降低了成膜区域的时间平均热阻。这两种行为共同增强了面向下的粗糙疏水表面上的冷凝传热。此外,在光滑的亲水表面上也可以形成稳定的滴状冷凝,在相同的传热条件下,其传热性能优于相应的疏水表面。
更新日期:2021-10-09
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