微小通道内不同润湿性表面流动冷凝传热
【摘要】利用丝网烧结和聚四氟乙烯溶液 (Teflon) 浸渍法, 在铜表面上制备了亲疏水匹配的结构, 即在疏水四氟涂层上有阵列排布的椭圆亲水点, 仅有四氟涂层的全疏水表面和不作修饰的全亲水铜表面作为对照, 考察了以这三种表面为底部换热区域的矩形微小通道 (水力直径1.5 mm) 的换热特性和流动特性。实验的通道内蒸汽质量流速为10~60 kg·m-2·s-1, 干度为0.3~1, 亲疏水匹配表面与亲水表面相比, 蒸汽冷凝传热系数 (HTC) 最高增加了454.6%, 与全疏水表面相比, 传热系数最高增加了107.3%, 利用高速相机拍摄可视化照片, 观察了通道内气液两相, 尤其是表面液滴成核、聚并、冲刷的周期运动过程, 解释了亲疏水匹配表面强化传热的机理。
【关键词】 凝结;亲疏水表面;微小通道;传热系数;
【DOI】
【基金资助】 国家自然科学基金重点项目 (51436004) ; 国家自然科学基金项目 (51676071) ;
Flow condensation heat transfer on surfaces with different wettability in mini-channel
【Abstract】The hydrophobic surface embedded with arrayed hydrophilic dots was prepared on a copper surface with mesh screen and Teflon solution. Completely hydrophilic copper surface, completely hydrophobic Teflon-coated surface and hydrophilic/hydrophobic hybrid surface are taken into consideration which serve as the bottom heat transfer area of rectangular mini-channels (1.5 mm hydraulic diameter). In this experiment, the vapor mass velocity ranges from 10 kg·m−2·s−1 to 60 kg·m−2·s−1, while the vapor quality from 0.3 to 1. According to the experimental investigation, the steam condensation heat transfer coefficient on hybrid surface is about 454.6% higher than that of the completely hydrophilic surface and 107.3% higher than the completely hydrophobic surface at most. A high-speed camera provides the photos of two-phase flow pattern, especially the periodic behavior of the droplets nucleation, coalescence and flush which can explain the mechanism of heat transfer enhancement.
【Keywords】 condensation; hydrophilic/hydrophobic surface; mini-channel; heat transfer coefficient;
【DOI】
【Funds】 Key Program of the National Natural Science Foundation of China (51436004); National Natural Science Foundation of China (51676071) ;
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ISSN:0438-1157
CN: 11-1946/TQ
Vol 69, No. 10, Pages 4156-4166+4496
October 2018
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