期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2020
卷号：117
期号：24
页码：13321-13328
DOI：10.1073/pnas.1917868117
出版社：The National Academy of Sciences of the United States of America
摘要：Above a critical temperature known as the Leidenfrost point (LFP), a heated surface can suspend a liquid droplet above a film of its own vapor. The insulating vapor film can be highly detrimental in metallurgical quenching and thermal control of electronic devices, but may also be harnessed to reduce drag and generate power. Manipulation of the LFP has occurred mostly through experiment, giving rise to a variety of semiempirical models that account for the Rayleigh–Taylor instability, nucleation rates, and superheat limits. However, formulating a truly comprehensive model has been difficult given that the LFP varies dramatically for different fluids and is affected by system pressure, surface roughness, and liquid wettability. Here, we investigate the vapor film instability for small length scales that ultimately sets the collapse condition at the Leidenfrost point. From a linear stability analysis, it is shown that the main film-stabilizing mechanisms are the liquid–vapor surface tension-driven transport of vapor mass and the evaporation at the liquid–vapor interface. Meanwhile, van der Waals interaction between the bulk liquid and the solid substrate across the vapor phase drives film collapse. This physical insight into vapor film dynamics allows us to derive an ab initio, mathematical expression for the Leidenfrost point of a fluid. The expression captures the experimental data on the LFP for different fluids under various surface wettabilities and ambient pressures. For fluids that wet the surface (small intrinsic contact angle), the expression can be simplified to a single, dimensionless number that encapsulates the wetting instability governing the LFP.
关键词：Leidenfrost point ; minimum film boiling temperature ; fluid instability ; dimensionless number
