Electric field-based enhancement and control of film and nucleate boiling heat transfer

基于电场的薄膜和核态沸腾传热的强化和控制沸腾传热影响许多工业过程的性能，如蒸汽发生、脱盐和淬火。增强的传热提高了热处理的能源效率并降低了操作温度。在高温下，由于在表面和液体之间形成绝缘蒸汽层，沸腾传热急剧减少。这种众所周知的莱顿弗罗斯特效应（薄膜沸腾）是对涉及沸腾的工业设备的性能产生不利影响的原因。施加在该蒸汽层上的电压可以促进液体表面润湿，从而消除干燥并增强热传递。类似地，电场可以控制气泡，这也影响沸腾传热。该研究为电场对多区域沸腾传热影响的基础性研究奠定了基础。将分析莱顿弗罗斯特状态的电抑制，并量化由此产生的传热增强。基于电场的控制与气泡相关的物理现象将进行分析，以量化电场增强的核态沸腾制度（其中涉及气泡）的传热。所提出的研究包括实验，分析建模和数值模拟。总的来说，该研究将在沸腾传热领域开辟一个新的研究领域。这也将为影响能源和材料加工行业的新型传热技术的发展奠定基础。这项工作的影响是特别明显的淬火（超快冷却），其中电可调冷却提供了一种新的工具，以控制金属的微观结构和机械性能。拟议的研究研究的影响，界面电场对膜和核沸腾传热，非常低（但有限）电导率的液体（如有机溶剂和去离子水）。在这样的液体中，施加的电压表示为穿过电绝缘蒸汽间隙或气泡。在电绝缘液体中，这种局部界面电场比体积电场更能影响沸腾相关现象。该研究将直接测量传热系数，并分析传热增强的基本机制。这项工作涉及一个高热流密度，高温池沸腾测试设备的发展，以测量临界热通量（CHF），这是最大的热通量，避免干涸。莱顿弗罗斯特态抑制的物理基础将通过单液滴实验和分析来捕获。电场对微流体现象的影响，如气泡的生长，振荡和分离将通过单个气泡高速可视化和分析建模来研究。将使用去离子水和异丙醇/甲醇作为工作流体进行实验。这项工作的具体成果包括电增强传热系数和CHF？的，并深入了解影响沸腾传热的微/中尺度热-流-电现象。总的来说，拟议的研究将导致沸腾传热领域的开创性贡献。这项研究可以通过使CHF极限无关和增加传热系数来重塑沸腾曲线。这项工作也奠定了电调谐沸腾传热的基础。

Electric field-based enhancement and control of film and nucleate boiling heat transferBoiling heat transfer influences the performance of many industrial processes like steam generation, desalination and quenching. Enhanced heat transfer improves the energy efficiency of thermal processes and reduces the operating temperatures. At high temperatures, boiling heat transfer is drastically reduced due to the formation of an insulating vapor layer between the surface and the liquid. This well-known Leidenfrost effect (film boiling) is responsible for adversely affecting the performance of industrial equipment which involves boiling. An electrical voltage applied across this vapor layer can promote liquid-surface wetting, thereby eliminating dryout and enhancing heat transfer. Similarly, an electric field can control bubbles, which also influences boiling heat transfer. The proposed research is a fundamental study on the influence of electric fields in multiple regimes of boiling heat transfer. Electrical suppression of the Leidenfrost state will be analyzed and the resulting heat transfer enhancement will be quantified. Electric-field-based control of physical phenomena associated with bubbles will be analyzed to quantify electric field-enhanced heat transfer in the nucleate boiling regime (which involves bubbles). The proposed research includes experimentation, analytical modeling and numerical simulations. Overall, the proposed research will develop a new area of study in the field of boiling heat transfer. This will also set the stage for the development of novel heat transfer technologies which impact the energy and materials processing sectors. The impact of this work is particularly evident in the area of quenching (ultrafast cooling), where electrically tunable cooling offers a new tool to control the microstructure and mechanical properties of metals.The proposed research studies the influence of interfacial electric fields on film and nucleate boiling heat transfer, for liquids with very low (but finite) electrical conductivity (like organic solvents and deionized water). In such liquids, the applied voltage is expressed across the electrically insulating vapor gap or bubble. This localized interfacial electric field can influence boiling-related phenomena more strongly than the volumetric electric field in electrically insulating liquids. The proposed research will directly measure the heat transfer coefficients and analyze the fundamental mechanisms underlying heat transfer enhancement. This work involves the development of a high heat flux, high temperature pool boiling test facility to measure the critical heat flux (CHF), which is the maximum heat flux that avoids dryout. The physics underlying Leidenfrost state suppression will be captured by single droplet experiments and analysis. The influence of electric fields on microfluidic phenomena like bubble growth, oscillations, and detachment will be studied by single bubble high speed visualizations and analytical modeling. Experiments will be conducted with deionized water and isopropanol/methanol as working fluids. Specific outcomes of this work include measurements of electrically enhanced heat transfer coefficients and CHF?s, and an in depth understanding of the micro/mesoscale thermal-fluid-electrical phenomena influencing boiling heat transfer. Overall, the proposed research will lead to seminal contributions in the field of boiling heat transfer. This research can potentially reshape the boiling curve by making the CHF limit irrelevant and increasing heat transfer coefficients. This work also lays the foundations for electrically tunable boiling heat transfer.