许津萍,贾依丛,季旭,范全海,张海麟.铜基超疏水表面改性强化冷凝传热[J].表面技术,2023,52(7):306-314.
XU Jin-ping,JIA Yi-cong,JI Xu,FAN Quan-hai,ZHANG Hai-lin.Condensation Heat Transfer Enhancement by Copper-based Superhydrophobic Surface Modification[J].Surface Technology,2023,52(7):306-314 |
| 铜基超疏水表面改性强化冷凝传热 |
| Condensation Heat Transfer Enhancement by Copper-based Superhydrophobic Surface Modification |
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| DOI：10.16490/j.cnki.issn.1001-3660.2023.07.028 |
| 中文关键词: 超疏水涂层 接触角 膜状凝结 珠状凝结 传热系数 |
| 英文关键词:superhydrophobic coating contact angle filmwise condensation dropwise condensation heat transfer coefficient |
| 基金项目: |
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| Author | Institution |
| XU Jin-ping | School of Energy and Environmental Science, Yunnan Normal University, Kunming 650500, China |
| JIA Yi-cong | School of Energy and Environmental Science, Yunnan Normal University, Kunming 650500, China |
| JI Xu | School of Energy and Environmental Science, Yunnan Normal University, Kunming 650500, China |
| FAN Quan-hai | School of Energy and Environmental Science, Yunnan Normal University, Kunming 650500, China |
| ZHANG Hai-lin | School of Energy and Environmental Science, Yunnan Normal University, Kunming 650500, China |
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| 中文摘要: |
| 目的 提高超疏水铜管的传热系数，产生并长久维持珠状凝结，在冷凝过程中实现从膜状冷凝到珠状冷凝的转变。方法 首先以硬脂酸铜和环氧树脂为原料，设计并制备超疏水材料，通过静电喷涂法在铜基换热器表面制备超疏水涂层，通过喷枪将配制好的硬脂酸铜悬浮液加压，将所制备的硬脂酸铜悬浮液通过喷枪的作用分散为微米级以及纳米级的小颗粒，然后将这些小颗粒叠加涂覆到铜基底上，最终会形成具有微纳米级复合阶层粗糙结构的均匀涂层。在此基础上，搭建冷凝传热试验系统，探究水蒸气在超疏水表面冷凝传热性能。结果 试验发现，在静电压90 kV的条件下，所制备的超疏水材料和热固性粉末比例为1∶5时性能最好，接触角达到154.3°，涂层机械稳定性最佳。经喷涂处理后的换热器在高温水蒸气气流下仍保持超疏水性，且在冷凝传热试验中，超疏水铜基换热器放热量以及传热系数大大增加，放热量比常规盘管提高23.6%，而传热系数也比常规盘管提高38%。结论 通过静电喷涂法可制备出超疏水材料，且其机械稳定性较好。超疏水膜层能够有效实现液滴跳跃和自去除，在高温气流中保持超疏水性。在稳定的蒸汽流下，超疏水换热器的放热量以及传热系数比常规换热器有了较大提高。 |
| 英文摘要: |
| Hydrophobic copper stearate powder was prepared by the reaction of anhydrous copper sulfate with sodium stearate. It was mixed with epoxy resin in the ratio of 5∶1 by mass and coated on the copper sheet uniformly by electrostatic spraying. The powder was cured in an oven at 80 ℃ for 12 h and then removed. The light blue copper stearate powder evenly covered the copper-based surface, and the film was stable and unlikely to peel off. The surface water droplets appeared as full spheres and did not appear to be spreading. SEM images and the microscopic morphology showed scale-shaped and staggered stacking arrangement, forming a micro- and nano-graded structure. Its static contact angle reached 154.3°, and the superhydrophobic film layer was successfully constructed on the copper surface. The same process conditions were used to construct a superhydrophobic film on the coil heat exchanger surface to realize the transformation of its surface filmwise condensation to dropwise condensation and to strengthen the heat and moisture transfer during water vapor condensation. The steam generation system was used to provide constant steam to the coil heat exchanger without interruption, as well as to enable high-precision temperature and flow measurement. When water vapor came into contact with the wall of the copper tube below its saturation temperature, the condensate quickly spread into a liquid film and adhered to the wall. It continuously accumulated until gravity was greater than the viscous force and slowly slides off from the wall. When the surface of the heat exchanger coil was transformed into a superhydrophobic state, the condensate could not wet the wall surface well and formed multiple small droplets and then dripped down rapidly, which could effectively achieve droplet jumping and self-removal. The heat transfer performance of the tube was studied in convective heat transfer experiments. Due to the good balance between droplet nucleation and separation, the heat transfer coefficient of the superhydrophobic tube was increased by 38% compared with that of the copper tube. The superhydrophobic film did not peel off or lose the superhydrophobic performance when the high temperature air flowed through. The variation of temperature and humidity of water vapor inlet and outlet and the variation of water temperature in the condenser inlet and outlet was recorded. Dropwise condensation was difficult to produce and maintain for a long time on conventional metals. The hydrophobic coating was prepared by electrostatic spraying on the copper-based heat exchanger surface to realize the transformation from filmwise condensation to dropwise condensation during the condensation. The prepared hydrophobic material and thermosetting powder with a ratio of 5∶1 showed the best stability performance with a contact angle of 154.3° and the best coating performance. The gas condensation experiments on the heat exchanger surface showed that the superhydrophobic filmwise could effectively achieve droplet jumping and self-removal, and the high temperature airflow did not cause the superhydrophobic filmwise to peel off or lose its superhydrophobic performance, and the heat transfer coefficient was 38% higher than that of conventional coils. |
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