Gao Shan, Qu Jian, Liu Zhichun, Liu Wei
School of Energy and Power Engineering, Jiangsu University, Zhenjiang 212013, China.
School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China.
Langmuir. 2022 May 24;38(20):6352-6362. doi: 10.1021/acs.langmuir.2c00276. Epub 2022 May 10.
Acquiring rapid and efficient boiling processes has been the focus of industry as they have the potential to improve the energy efficiency and reduce the carbon emissions of production processes. Here, we report nanoscale thin-film boiling on different heterogeneous surfaces. Through nonequilibrium molecular dynamics simulation, we captured the triple-phase interface details, visualized the bubble nucleation, and recorded the internal fluid flow and thermal characteristics. It is found that nanoscale thin-film boiling without the occurrence of bubble nucleation shows excellent heat and mass transfer performance, which differs from macroscale boiling. In general, rough structures advance the onset time of stable boiling and improve the efficiency. The heat transfer coefficient and heat flux on a rough hydrophilic surface respectively reach to 7.43 × 10 kW/(m·K) and 1.3 × 10 kW/m at a surface temperature of 500 K, which are 100-fold higher than those of micrometer-scale thin-film boiling. However, due to the resultant vapor film trapped between the liquid and the surface, the rough hydrophobic surface leads to heat transfer deterioration instead. It is revealed that the underlying mechanism of regulatory effects resulting from surface physicochemical properties is originated from the variation of interfacial thermal resistance. It is available to reduce the overall interfacial resistance and further improve the heat and mass transfer efficiency through increasing surface roughness, enhancing surface wettability, and increasing the area proportion of the hydrophilic region. This work provides guidelines to achieve rapid and efficient thin-liquid-film boiling and serves as a reference for the optimized design of surfaces utilized for high-heat flux removal through vaporization processes.
获得快速高效的沸腾过程一直是工业界关注的焦点，因为它们有可能提高能源效率并减少生产过程的碳排放。在此，我们报告了在不同异质表面上的纳米级薄膜沸腾情况。通过非平衡分子动力学模拟，我们捕捉到了三相界面细节，可视化了气泡成核过程，并记录了内部流体流动和热特性。研究发现，不发生气泡成核的纳米级薄膜沸腾表现出优异的传热传质性能，这与宏观尺度沸腾不同。一般来说，粗糙结构会提前稳定沸腾的起始时间并提高效率。在表面温度为500 K时，粗糙亲水表面的传热系数和热通量分别达到7.43×10 kW/(m·K)和1.3×10 kW/m，比微米级薄膜沸腾的相应值高100倍。然而，由于在液体和表面之间形成了蒸汽膜，粗糙疏水表面反而导致传热恶化。研究表明，表面物理化学性质产生调节作用的潜在机制源于界面热阻的变化。通过增加表面粗糙度、提高表面润湿性和增加亲水区域的面积比例，可以降低整体界面电阻，进一步提高传热传质效率。这项工作为实现快速高效的薄液膜沸腾提供了指导方针，并为通过汽化过程去除高热通量的表面优化设计提供了参考。
