电场下含带电Janus纳米颗粒流体的湿润及相变特性研究

Boiling is widely involved in many energy utilization and conversion systems. Due to its complex phenomena and chaotic bubble kinetics, the studies of boiling still encounter great challenges. Among various affecting facts, the solid surface wettability plays significant roles in the boiling process. During the nucleate boiling stage, hydrophobic surfaces are energetically favourable for bubble nucleation, which can enhance the heat transfer coefficient. However, during transition boiling stage, hydrophilic surfaces can suspend the film boiling and hence, increase the critical heat flux (CHF). In this project, we proposed a novel method to manipulate the bubble kinetics by switching the surface wettability for different boiling stages or according to the inputting heat flux. The wettability of fluids on solid surfaces can be tuned by controlling the self-assembly of charged Janus nanoparticles (with hydrophobic head and hydrophilic tail) on the solid surface or on the bubble interface with external electronic field. Therefore, both the heat transfer coefficient and the CHF can be enhanced. Sophisticated experimental and multi-scale simulation techniques will be used to investigate the roles of Janus nanoparticles microscopic motions in the macroscopic wetting kinetics. The bubble dynamic behaviors and their tunable methods can be revealed by exploring the effects of Janus nanoparticle kinetics on the fluid dynamic wetting. The deliveries of this project lie in the mechanisms of nanoparticle kinetics with external fields, as well as the tunable methods of enhancing boiling heat transfer and manipulating bubble kinetics according to the inputting heat flux, which will provide a smart thermal management in microscopic energy utilization and conversion devices.

沸腾相变广泛应用于各种能量转换和利用系统中。影响因素的多样性和气泡行为的随机性，使得沸腾相变及其精确调控的研究目前仍极具挑战。固体表面湿润特性是影响沸腾换热的关键因素之一：疏水表面能促进气泡核化，提高核态沸腾换热系数；亲水表面能促进气泡脱离，抑制膜态沸腾，提高临界热流密度。本项目通过电场调控带电Janus纳米颗粒（一端疏水一端亲水）在固液/汽液界面的自组装，在不同的沸腾阶段或根据输入热流密度大小切换固体表面的湿润性质，调控气泡动力学行为，提高沸腾换热系数和临界热流密度。拟采用实验和跨尺度（微观-介观）模拟，揭示电场下带电Janus纳米颗粒微观输运机理及其对流体宏观动态湿润特性的影响规律。通过研究动态湿润这一连接气泡动力学行为和沸腾相变的纽带，探析在纳米尺度精确调控沸腾相变换热特性的原理和方法。本课题的研究成果有望为提升沸腾相变换热性能以及微小器件智能化热管理提供全新的解决思路和理论支撑。

沸腾相变广泛应用于各种能量转换和利用系统中。影响因素的多样性和气泡行为的随机性，使得沸腾相变及其精确调控的研究目前仍极具挑战。本项目通过湿润调控，在不同的沸腾阶段或根据输入热流密度大小切换固体表面的湿润性质，调控气泡动力学行为，提高沸腾换热系数和临界热流密度，探析在纳米尺度精确调控沸腾相变换热特性的原理和方法。. 项目主要成果和发现为：揭示含Janus纳米颗粒流体在复杂外场下的动态湿润规律；在纳米尺度揭示湿润特性对气泡核化影响的微观机制，构建湿润特性与气泡核化的构效关系，亲疏水特性对纳米尺度液膜爆沸核化的影响特性研究，澄清“经典核化理论在纳米尺度是否失效”问题；在微米-毫米尺度揭示湿润特性对汽泡动力学的影响机制，构建包含“微液层蒸发-气泡生长模型-流固耦合”的完整气泡动力学耦合模型，从微液层和汽液界面相变传热量角度阐释湿润特性对气泡动力学行为的影响机制；揭示多种相变模式对动态湿润的影响，实验发现微小液滴内部受限气泡新现象；提出可规模化低成本加工微纳/亲疏水双复合强化换热表面新方法，实现沸腾气泡动力学行为的精细调控。研究成果有望为提升沸腾相变换热性能以及微小器件智能化热管理提供全新的解决思路和理论支撑。. 在项目资助下，利用电场调控颗粒运动的研究成果，申请发明专利1项，实用新型1项，应用于静电除尘器的颗粒改性和调控上，形成均流式静电除尘器技术，在8家钢厂得到应用，产业化项目合同额七千多万。相关成果已申报钟南山科技创新（成果转化）奖（第二完成人）。共发表论文19 篇，其中国际期刊论文14 篇，SCI 收录14 篇。工程热物理学会年会优秀论文1篇。在项目执行期间，项目负责人获得了华北电力大学优青培育计划资助1项；学术会议特邀报告3次。项目执行期间，共有4名研究生和3名本科生参与了本项目的研究工作，已毕业3名本科生。指导研究生获工程热力学学会年会优秀论文二等奖1 项。项目执行期间负责人SCI他引次数新增400余次。