镀层微观结构对凝结换热的影响

EFFECT OF COATING MICROSTRUCTURE ON CONDENSATION HEAT TRANSFER

通过研究Ni-P化学镀层管不同微观结构对凝结传热的影响,表明用化学镀表面改性的镀管相对于普通的碳钢管,具有明显促进珠状凝结的效果,在凝结过程中表现为珠膜共存状态,可以获得较好的换热性能。同时镀层对换热性能的改善与镀层中纳米相的含量相关,随着纳米相含量的降低,镀层的表面能也随着降低,换热效率得到增强。增加镀层的非晶度可以获得更好的珠状凝结的效果。

In this study, the effect of microstructure of Ni-P coating on condensation heat transfer performance was reported. The experimental results show that the steel tube with electroless Ni-P coating can greatly improve the performance of condensation heat transfer compared to un-coated steel tubes. The condensation state on tubes with Ni-P coating is the co-existence state of both dropwise and filmwise on most working conditions. At the same time, the heat transfer efficiency of condensation is improved with the decreasing of the amounts of nanocrystalline phase in Ni-P deposit, because it can decrease the free surface energy of surface. Increasing the degree of amorphous state of Ni-P coating will provide a better dropwise condensation effect.