热交换器表面镀层对传热性能的影响

Effect of Deposit of Heat Exchangers on Heat Transfer Properties

采用化学镀的方法对热交换器表面进行表面改性,使其换热表面沉积一层表面能不同的均匀镀层。传热实验表明,随着磷含量的增大,凝结传热系数增大。进一步可视化实验研究表明,镀层换热表面均表现为珠膜共存状态,增大镀层的磷含量,换热表面促进珠状凝结的效果更加明显。这归于镀层降低了传热表面的表面能值。

In this study, the uniform electroless Ni-P deposits with different surface free energy were fabricated on the heat transfer surface of heat exchanger by adjusting process parameters of eleetroless plating. The experimental results of heat transfer showed that the condensation heat transfer coefficient was increased with the increase of phosphorus content in the deposits. By using further visual experiments, it was found that the dropwise and the film are coexisted on deposit heat transfer surface. Furthermore, the deposit surface with higher phosphorus contents showed more evident effect in enhancing dropwise condensation, which was ascribed to surface free energy was reduced.