冷凝换热表面超疏水复合涂层的制备及性能

Preparation and Properties of Superhydrophobic Composite Coating on Condensing Heat Transfer Surface

摘要:

针对目前促成滴状冷凝换热的超疏水表面造价昂贵、热导率低和综合性能差等问题，以可溶性聚四氟乙烯、改性石墨烯（C）、气相二氧化硅等为原料，通过共混法在不锈钢基材上制备了用于冷凝传热表面的高导热超疏水复合涂层，并对其耐腐蚀能力、导热系数、强度和蒸汽冷凝传热性能进行测试分析。结果表明，涂层的耐酸腐蚀性能、导热性能强于304不锈钢，当含3%的C时，导热系数为18.188W·（m·K）^-1，在20%硫酸浓度恒温30℃条件下腐蚀速率为0.201mg·（cm²·h）^-1，和基材结合强度达38MPa。SEM分析表明，涂层疏水性能与气相二氧化硅含量有关，且质量分数为10%时接触角达155°。冷凝实验表明常压蒸汽在涂层表面冷凝时传热系数达120kW·（m²·K）^-1，大于不锈钢表面近10倍，并得出其滴状冷凝不持久的原因。

Abstract:

The work aims to the problems of high cost， low thermal conductivity and weak comprehensive performance of superhydrophobic surfaces that promote drop condensation heat transfer at present， using polyfluoroalkoxy， functionalized graphene （c） and fumed silica as raw materials， a high thermal conductivity and superhydrophobic composite coating for condensation heat transfer surface was prepared on stainless steel substrate by blending method.The corrosion resistance， thermal conductivity， strength and steam condensation heat transfer performance were tested and analyzed.The results show that the acid corrosion resistance and thermal conductivity of the coating are stronger than those of 304 stainless steel.When it contains 3% of C， the thermal conductivity is 18.188W（m·K），the corrosion rate was 0.201 mg/cm²·h at a constant temperature of 30 ℃ with 20% sulfuric acid concentration， and the bonding strength to the substrate is 38MPa.SEM analysis shows that the hydrophobicity of the coating is related to the content of fumed silica， and the contact angle reaches 155° when the mass fraction is 10%.Condensation experiment demonstrates that the heat transfer coefficient of atmospheric steam reaches 120kW/（m²·K） ，nearly 10 times larger than the surface of stainless steel，when the coating surface is condensed，and clarify the reason why the dropwise condensation is not lasting.