疏水性辐射供冷末端结露特性及建筑渗风作用下调控方法研究

Radiant cooling is a novel air-conditioning system and has gained appreciable interest and success due to its thermal comfort and energy efficiency. The condensation risks of radiant cooling systems when applied in a hot and humid climate becomes the main obstacle for their applications in new buildings and renovations. Research on condensation characteristics of the radiant cooling system with hydrophobic treatment and control strategy dealing with air infiltration in buildings will be investigated in this project, which mainly includes three aspects as follows: (1) Theoretical and experimental analysis on the condensation characteristics of hydrophobic radiant cooling. The characteristics of dew formation, coalescence, and fall-off on hydrophobic and superhydrophobic surfaces will be clarified. The condensation rate, departure duration of condensate droplet, and size of falling droplets of the hydrophobic radiant cooling will be explored. (2) Analysis on flow pattern and indoor influencing area of air infiltration in buildings. Through onsite measurement and simulation of typical large space buildings and offices, the influencing area of air infiltration is investigated in order to optimize radiant cooling design for eliminating condensation risks, taking the air infiltration inlet position and indoor and outdoor temperature and humidity difference into account. (3) Analysis on control strategy dealing with air infiltration induced condensation. Theoretical model of condensation and evaporation dynamic process on the hydrophobic radiant cooling surface will be developed to evaluate condensation risks. A conjunctive control strategy of hydrophobic radiant cooling and air dehumidification system is proposed for preventing condensation risks and optimizing performance of an actual radiant cooling.

辐射供冷末端是一种新兴的空调末端方式，在改善舒适性、节省输送能耗等方面具有显著优势，如何有效避免结露风险是其推广应用的重要基础问题。本项目即是针对疏水性辐射末端结露特性及其在建筑渗风作用下调控方法开展的研究，具体包括：1）疏水性辐射末端结露特性研究，实验测试和理论分析疏水性辐射末端表面结露过程，揭示疏水材料表面的露珠形成、聚合及脱落规律，得到表面冷凝速率、凝露的脱落时间和脱落粒径特征；2）热湿渗风的流动扩散规律研究，实际测试与模拟分析室外热湿空气进入室内的流动路径，阐明渗风侵入位置、室内外温湿度差等因素的影响，定量刻画典型室内外参数下的渗风作用范围，优化设计辐射末端的敷设位置；3）辐射供冷系统应对热湿渗风的调控方法研究，分析实际环境中室内热湿扰动下疏水性辐射末端表面结露及再蒸发的动态过程，评估结露风险及可行的应对措施，构建疏水性辐射末端和除湿系统防结露的联合调控方法。

辐射供冷方式在改善室内舒适性、提高需求冷源温度和节省输配能耗等方面具有显著优势，如何有效避免辐射供冷方式的结露风险是其推广应用的重要基础问题。本项目主要针对辐射供冷末端的结露特性展开理论和实验研究，主要研究内容和成果包括：1) 揭示了常规金属表面重力诱导液滴脱落和超疏水表面合并诱导液滴脱落的机理，定量刻画了水平表面凝露脱落粒径与材料疏水性的关系。凝露脱落粒径随接触角的增大而减小，但现有的超疏水表面仍存在可被人体感知的重力诱导脱落的凝露，无法杜绝结露风险；2) 综合考虑材料表面特性和过冷度，定量刻画了辐射吊顶表面凝露的脱落时间。水平铝合金辐射吊顶在5 K的过冷度下凝露初次脱落时间约为10小时。因此辐射吊顶在短期的高湿环境下并不会发生表面滴水事故，为除湿系统和辐射吊顶的调控留有充足的响应时间；3) 基于计算流体力学模拟，定量刻画了室外热湿渗风在办公室、高大空间等典型建筑空间内的流动扩散特征，阐明了室外渗风在室内的影响范围，为辐射地板的敷设位置优化提供了理论支撑；4) 基于辐射供冷末端的表面“冷凝-蒸发”循环，提出了部分负荷下可提高辐射末端表面温度均匀性、降低结露风险的新型通断调节方式，有效规避了辐射供冷末端在湿热气候区应用中结露风险，为辐射供冷末端推广应用提供了技术保障。.本项目建立了辐射供冷末端表面结露特性研究的理论体系，为降低结露风险提供了有效的分析方法和理论支撑。研究过程圆满完成了各项预期目标，研究期间共发表SCI检索论文5篇，申请发明专利1项，出版中文学术专著1章，培养硕士生2人。