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

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.

Key words:high thermal conductivity;superhydrophobic;dropwise condensation heat transfer coefficient;graphene;corrosion resistant coating