Preparation Of Nanometer TiO₂ Coating Surface By Liquid Phase Deposition And Anti-Fouling Characteristic On The Surface In Pool Boiling

There are many fouling problems in heat exchange equipments that use water as the carrier in industry. Expensive cost and pollution exist in the traditional way of fouling removal by machine or chemic cleanout. Some researchers found that treating the heat transfer surface with surface treatment technology can reduce the surface energy and will reduce the formation of the fouling on the heat transfer surface.Because of the potential of the method of liquid phase deposition (LPD) in industrialization, study of preparation of TiO2 film by LPD was carried out in this paper. Systemic study on effect of [TiF6]2- concentration, [TiF6]2-/H3BO3 molar ratio, deposition time and the surface condition of the substrate on the deposited thin films is made. The surface energy, contact angle and thin film thickness of the treated heat surface were measured and characterized to find the relationship between the thin film thickness and the surface energy. It is showed that surface energy of the TiO2-coated copperplate obviously was lower than that of the untreated copperplate and the polished copperplate. The result showed that the surface energy almost could be reduced to 45 mJ·m-2 when the thickness of the TiO2 thin films is less than 100nm.The investigations of heat transfer and fouling formation on the different heat surfaces were studied by pool boiling device with the system of automatic data acquisition. In the distilled water experiment, it is showed that compared with the untreated surface, the pool boiling heat transfer coefficients of the surfaces deposited TiO2 thin film were much higher. The experiment results showed when thickness of the TiO2 thin film was 46.7nm, its pool boiling heat transfer coefficient was 30% higher than that of the untreated surface, when the thickness of the TiO2 thin film was 76.8nm, its heat transfer coefficient was 50% higher than that of the untreated surface and when the thickness of the TiO2 thin film was 108nm, its heat transfer coefficient was 13% higher .In the fouling experiment, the heat transfer coefficients of the untreated and polished surface dropped quickly within a short time. For the untreated surface and polished surface, the time of fouling formation was 400 min and 700min, respectively. When thickness of the TiO2 thin film was 46.7nm and 76.8nm, their fouling time was 4000min and 3500min respectively. So we can come to the conclusion that the surfaces deposited the TiO2 thin film had anti–fouling characteristic.