【讲座题目】Optimization of Heat and Mass Transfer via Nano/Micro Structured Surface: Utilizing energy barriers between states and “semi-dimensional reduction”

【时 间】2024年7月1日  下午：15:00-16:30

【地 点】保定校区 自动化系315

【主讲人】丁伟，博士，亥姆赫兹-德累斯顿-罗森道夫研究中心(HZDR)

【主讲人简介】

丁伟博士于2003年，2006年毕业于德国杜伊斯堡大学机械系获学士和硕士学位。2012年毕业于德国杜伊斯堡大学过程与水技术专业，获博士学位。丁伟博士现任职于Helmholtz Zentrum Dresden Rossendorf（HZDR）海姆赫兹德累斯顿罗森道夫研究中心，流体研究所，热流体方向。主要研究壁面沸腾传热，临界热通量（CHF）以及三相接触面相关的微纳米机制(气泡下微液层等)。对润湿现象，沸腾传热中壁面和气泡的相互作用，临界热通量有深刻的理解和研究。主要工作涉及并使用分子动力学模拟（MD），直接数据模拟（DNS），欧拉欧拉（EE）大尺度计算流体模型以及子模型的发展和应用，不同的实验手段例如光学测量，超高速伦琴射线计算成像（ROFEX）等，在多个尺度上对壁面沸腾传热及其相关进行了深入的研究。丁伟博士参与发表专著1篇，在JCI（IF9.9），ICHMT（IF7），IJHMT（IF5.2），ATE（IF6.2）等相关领域杂志发表文章30余篇。

【讲座内容简介】

Energy barriers inhibit the transition of a system from one state to another. This is evident in phenomena such as bubble nucleation during boiling, droplet expansion and contraction when it impacts a heated surface, and also cavitation. In this presentation, we will elucidate our insights and understanding of the exploitation of energy barriers post-state transition to augment heat and mass transfer in various processes. Specifically, in processes like bubble nucleation in boiling, the high energy required for nucleation (attributable to the energy barrier) triggers rapid bubble expansion and results in a semi-2D microlayer, just a few micrometers thin, on the surface. This can be viewed as a typical semi-dimensional reduction effect, transitioning a part of system from 3D to 2D. As a result, this thin liquid layer brings high efficiency on heat transfer. A similar phenomenon occurs when a droplet impacts a heated surface. Following impact, the droplet’s expansion and contraction on the surface incite capillary waves that propagate along the droplet interface, inducing a semi-1D, prickle-like jet along the droplet’s axis on the top side. This jet disrupts the vapor film beneath the droplet, expelling the vapor and delaying the Leidenfrost point. As a one more thing, cavitation, one of the most typical cases of ‘dimensional reduction’, utilizes a reduction from 3D to 0D and also the large energy barrier for bubble nucleation. Following bubble collapse, the local temperature and pressure reach 5000 K and ~ Mpa, respectively. Combined with O3, this effect facilitates a highly efficient oxidation process.