The role of dissolved gas in boiling heat transfer on biphilic surfaces

讲座名称: The role of dissolved gas in boiling heat transfer on biphilic surfaces
讲座时间 2016-12-07
讲座地点 东三楼东汽报告厅
讲座人 Biao Shen
报告题目:The role of dissolved gas in boiling heat transfer on biphilic surfaces
报告人:Biao Shen博士
Because of the complementary effects of surface hydrophilicity and hydrophobicity on boiling characteristics—to facilitate and restrain bubble spreading, respectively—boiling heat transfer can be greatly enhanced using heterogeneous surfaces coated with a spatially alternating wettability pattern. In this work, we show experimentally that a vast majority of the improved heat transfer is actually attributable to an unusually strong gas aggregation near the hydrophobic surface. Equivalent to extremely gassy boiling, the profound impact of the persistent gas enrichment on boiling includes significant reductions of the incipient degree of superheating to levels even below the nominal saturation temperature. Moreover, by differential degassing efforts, it is revealed that bubble dynamics on the same mixed-wettability surface differ fundamentally with and without dissolved gas, which are also captured by numerical simulations of bubble evolution in a two-component system using the diffuse-interface method. Specifically, the results show that dependent on the solute gas concentrations and the strength of the solute-solvent molecular interaction (gas solubility, bubble behavior diverges between the sustained bubble growth (leading to actual pinch-off) and the eventual collapse following brief periods of dynamic equilibrium between evaporation and condensation. Interestingly, the growing bubble, while being firmly attached to the hydrophobic subsurface, is found to be surrounded by strong Marangoni flow, which is driven by pronounced surface tension stress imbalance.

报告人简介:Biao Shen博士,日本九州大学无碳能源国际研究中心机械工程和热物理工程分部博士后研究员,主要研究兴趣为相变换热,沸腾现象等。



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