Abstract:

Steam condensation can release a large amount of latent heat of phase change at a small temperature difference, and plays an important role in petrochemical, waste heat utilization, seawater desalination and other fields. Here, a capillary liquid film condensation driven by superhydrophilic porous metal structures is proposed by coupling the rapid condensate transport in capillary structures and the reduced thermal resistance of wetted porous structures. Such a capillary liquid film mode is suitable for enhancing condensation heat transfer of water and various low surface energy fluids. A heat and mass transfer model of capillary liquid film condensation is established to investigate the effect of the porosity and thickness of porous structures, the physical properties of working fluids, and the operating conditions of condensation on the heat transfer coefficient, critical heat flux, and flooding threshold of subcooling. The results show that as the thickness and porosity of porous structures increase, the heat transfer coefficient increases while the maximum surface subcooling and critical heat flux decrease. Combined with condensation heat transfer and visualization experiments, the effect of the copper foam structure on liquid condensate behaviors and heat transfer performance is further investigated. The heat transfer model of capillary liquid film condensation is also verified.

Key words: phase-change, heat transfer, interface, liquid film condensation, heat transfer enhancement

摘要：

蒸汽冷凝可以在小温差下释放大量的相变潜热，在石油化工、余热利用、海水淡化等领域发挥重要作用。提出了超亲水多孔金属结构驱动的毛细液膜冷凝传热新模式，通过耦合毛细结构对冷凝液的快速输运和多孔金属对液层热阻的降低，实现了适用于水和低表面能工质体系的冷凝传热强化。建立了毛细液膜冷凝的热质传递模型，分析了多孔结构的孔隙率与厚度、工质物性、操作条件等对冷凝传热系数、临界热通量和最大溢流过冷度的影响。结果表明，随着多孔结构厚度和孔隙率减小，冷凝传热系数显著增大，而最大溢流过冷度和临界热通量减小。结合冷凝传热与可视化实验，分析了泡沫铜结构表面对液膜冷凝形态和传热性能的影响，验证了毛细液膜冷凝传热模型的准确性。

关键词: 相变, 传热, 界面, 液膜冷凝, 强化传热