Preparation and Performance Test of Hydrophobic Coating on Heat Exchanger Surface

Abstract:

A superhydrophobic self-cleaning composite coating applied to the surface of a condensing heat exchanger was prepared by adding nano-silica and other materials to polyfluoroalkoxy（PFA）， polytetrafluoroethylene（PTFE） and epoxy resin（EP）. The composite coatings were tested for contact angle， thermal conductivity， wear resistance， bonding strength and self-cleaning properties to study its comprehensive properties. The test results show that the contact angles of the PFA coating containing 7.5 %–9.4 % nano-SiO₂ and the PTFE coating containing 1.4 %–2.3 % nano-SiO₂ are both above 150°， and its surface self-cleaning is excellent. The thermal conductivity of coatings can be increased from 0.2 W·m^-1·K^-1 to more than 2 W·m^-1·K^-1 by adding 0.8 %–1.7 % of graphite. The wear resistance of the coating increases with the increase in the SiC content. For the PFA superhydrophobic coating， the addition of SiC enables the coating to maintain good hydrophobicity after grinding. The bonding strength of the epoxy resin coating reaches ASTM （American Society of Testing Materials)grade 5B， while that of the PFA coating and PTFE coating is 4B and 3B， respectively.

Key words:nano-silica;superhydrophobic;self-cleaning;wear resistance