Enhancing flow boiling and antifouling with nanometer titanium dioxide coating surfaces

This article aims to develop a new heat-transfer surface on which both heat-transfer enhancement and fouling prevention can be observed. One of the potential methods is to coat a thin layer on the heat-transfer surface with nanometer material. The selection of coated nanometer material, the preparation, and characterization of nanometer coatings on heat-transfer surface, including the measurement and calculation of the coated thickness, contact angle and surface free energy, the experiments on heat transfer of flow boiling and antifouling are all investigated in this article. The results declare that heat-transfer film coefficients of flow boiling on TiO2 coating surfaces with film thickness of 1.41 X 10(-7) and 1.587 x 10(-6) m are higher than those on uncoated surface of heated tube. The fouling resistance on the surface modified with nanometer material is lower than that on the untreated heat-transfer surface and remains constant during a long operating time. Under present experimental conditions, the coated heat-transfer surface with thin film thickness of 1.41 X 10(-7) m is the best one in enhancing heat transfer of flow boiling and preventing fouling, since its surface free energy is the lowest one. (c) 2007 American Institute of Chemical Engineers.