CaCO3 fouling on microscale-nanoscale hydrophobic titania-fluoroalkylsilane films in pool boiling

Micrometer-nanometer hydrophobic titania-fluoroalkylsilane composite coatings were prepared on substrates based on liquid-phase deposition. Coatings and crystallization forms were characterized with instruments of surface analyses. Experimental facilities of pool boiling were established to evaluate heat and mass transfer on coated surfaces in deionized water and saturated calcium carbonate solution. Obvious pool boiling enhancement was observed on thinner microscale-nanoscale hydrophobic titania-fluoroalkylsilane composite films at higher heat fluxes compared to that on thicker titania-fluoroalkylsilane coatings or on titania coatings and stainless steel surfaces. Lower fouling resistance was obtained on titania-fluoroalkylsilane coatings in pool boiling of saturated calcium carbonate solution and crystal form was aragonite, which was different from calcite on titania coatings. Results of inhibition of fouling and enhancement of heat transfer on titania-fluoroalkylsilane coatings were contributed to special surface microscale-nanoscale structure and material wettability. Asymptotic model was used to fit experimental data of fouling resistance, and reasonable agreement was obtained. (c) 2013 American Institute of Chemical Engineers AIChE J, 59: 2662-2678, 2013