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

【時 間】2024年7月1日  下午：15:00-16:30

【地 點(diǎn)】保定校區(qū) 自動化系315

【主講人】丁偉，博士，亥姆赫茲-德累斯頓-羅森道夫研究中心(HZDR)

【主講人簡介】

丁偉博士于2003年，2006年畢業(yè)于德國杜伊斯堡大學(xué)機(jī)械系獲學(xué)士和碩士學(xué)位。2012年畢業(yè)于德國杜伊斯堡大學(xué)過程與水技術(shù)專業(yè)，獲博士學(xué)位。丁偉博士現(xiàn)任職于Helmholtz Zentrum Dresden Rossendorf（HZDR）海姆赫茲德累斯頓羅森道夫研究中心，流體研究所，熱流體方向。主要研究壁面沸騰傳熱，臨界熱通量（CHF）以及三相接觸面相關(guān)的微納米機(jī)制(氣泡下微液層等)。對潤濕現(xiàn)象，沸騰傳熱中壁面和氣泡的相互作用，臨界熱通量有深刻的理解和研究。主要工作涉及并使用分子動力學(xué)模擬（MD），直接數(shù)據(jù)模擬（DNS），歐拉歐拉（EE）大尺度計算流體模型以及子模型的發(fā)展和應(yīng)用，不同的實驗手段例如光學(xué)測量，超高速倫琴射線計算成像（ROFEX）等，在多個尺度上對壁面沸騰傳熱及其相關(guān)進(jìn)行了深入的研究。丁偉博士參與發(fā)表專著1篇，在JCI（IF9.9），ICHMT（IF7），IJHMT（IF5.2），ATE（IF6.2）等相關(guān)領(lǐng)域雜志發(fā)表文章30余篇。

【講座內(nèi)容簡介】

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.