非平衡定态下气固界面吸附相变及热量传递耦合机理研究

Adsorption at solid-vapor interface can be found practically in nature and in industrial technologies. In non-equilibrium steady state, the adsorption and phase change at solid-vapor interface are coupled with interfacial heat transfer process, and the coupling mechanisms are still unknown up to now. Focused on the key scientific problem of coupled mechanism among adsorption phase change, interfacial temperature jump and heat transfer, this project studies the adsorption phase change and heat transfer through the solid-vapor interface in non-equilibrium steady state, by means of experimental observation, theoretical analysis and molecular dynamic simulation. First, the characteristics of non-equilibrium adsorption process are examined, the cluster distribution and its evolution are captured. The conditions for adsorption phase change are determined and the stabilities of liquid-like film are analyzed. Then, the unified theoretical model for non-equilibrium adsorption and phase change is proposed. Furthermore, the temperature jump and the major influence factors are explored. The interrelations between adsorption phase change and heat transfer are determined. Finally, the interfacial heat flux calculation model is established and the physical mechanism for the coupling effect among adsorption phase change, interfacial temperature jump and heat transfer is revealed. This project could lead to the discovery of new non-equilibrium interfacial phenomenon and underlying mechanism. Therefore, this project has high scientific and academic importance in advancing interfacial heat and mass transfer and non-equilibrium thermodynamics, as well as practical value in improving the interfacial heat transfer enhancement and thermal management technologies.

气固界面吸附广泛存在于工业生产和日常生活中，非平衡定态下气固界面吸附相变与热量传递相互耦合，相关机理尚不清楚。本项目以非平衡定态下气固界面吸附及相变过程为研究对象，紧紧抓住“吸附相变-温度跳跃-热量传递耦合机制”关键科学问题，采用实验测量、理论分析和分子动力学模拟相结合的方法，认知非平衡定态下气固界面吸附特征，捕获吸附团簇的形成及演变规律，分析类液膜的形成机制及其结构稳定性，提出能完整描述界面吸附及相变过程的理论模型，获取界面温度跳跃规律及其主要影响因素，探讨非平衡吸附特性与界面热量传递之间的相互影响规律，揭示界面吸附相变、温度跳跃以及热量传递耦合的物理本质。本研究有望发现新的界面非平衡现象，从而进一步丰富和发展非平衡热动力学理论，并在非平衡定态下气固吸附相变机制及其与界面传热耦合机理方面取得创新性成果，为界面传热传质理论研究做出科学贡献，为传热强化及热管理技术的研发提供理论支撑。

项目以气固界面吸附相变过程为研究对象，结合实验观测、理论分析和分子动力学模拟相结合的方法，研究了非平衡定态下界面吸附相变及其能量传递耦合机制。主要结论如下：（1）明确了吸附质以团簇的形式吸附在固体表面，小压比下，小分子团簇和零吸附单元占据主导地位，随着压比的增加，吸附团簇类型增多；临界条件下，吸附熵达到极值，界面发生吸附相变，随着压比的进一步增大，性质均一的大分子团簇聚集，形成类液膜润湿界面；团簇吸附模型能很好的描述吸附热力学过程。(2)确定了界面吸附相变动力学特性，当吸附开始发生时，均方位移分布呈现弹道输运特征，随着吸附的进行，转变为三维随机漫步状态；明确了团簇形成及其演变规律，结合团簇模型和统计速率理论，提出了能完整描述界面吸附相变的热动力学理论模型。（3）确定了吸附相变发生的临界条件，绘制了吸附界面随气固相互作用强度以及温差变化的相图，采用团簇模型理论预测了吸附相变以及润湿转变临界条件，理论预测结果与模拟结果吻合很好。（4）构建了不同气相压力和过冷度下从吸附到冷凝转变的时空演化模型，在空间上，整个转变过程分为三个区域：稳态吸附区，吸附层的厚度保持不变；亚稳区，吸附层厚度缓慢增加；冷凝区，吸附层快速增厚，远离壁面处达到了液相饱和密度，形成液相。时间尺度上，初始阶段为近吸附过程，基于团簇演化模式和统计速率理论提出了能有效预测吸附相变全过程界面传质速率的理论模型。（5）综合分析了气固界面能量传递物理机制，得到了吸附团簇、振动特性和界面热阻的耦合关系，小压比时，零吸附单元逐渐被气体分子占据，界面热阻降低。随着吸附量的增加，小分子团簇合并，吸附相声子类型增加，与固壁声子耦合程度增强，界面热阻降低。对于硅-水体系，水分子的振动频谱较高，随着压比增大，团簇的振动频率类型增加，增强气固界面的声子耦合，强化界面能量传输。研究结果进一步丰富和发展了非平衡热动力学理论，为界面传热传质理论研究做出了科学贡献，为传热强化及热管理技术的研发提供了理论支撑。