July 1-6, 2007
Molecular modelling approach was utilized to describe detailed fouling mechanism caused by crystallization. The interest was on the heat transfer surfaces, which were manufactured from titanium and stainless steel. With ab initio calculations, the role of the surface oxide layer structure of titanium and stainless steel on fouling was investigated. The surface structure of titanium and stainless steel were assumed to consist of rutile (TiO2) and dichromium trioxide (Cr2O3), respectively. It was found that the inorganic fouling depends strongly on the oxide layer structure and the existence of hydroxyl groups on the surface. Based on the results, two mechanistically different fouling categories were found. When the surface hydroxyl groups exist, the fouling can take place via condensation reactions with species containing hydroxyl groups. On surfaces without the surface hydroxyl groups, fouling takes place preferably via adsorption of ions.
E. Puhakka, M. Riihimäki, and R.L. Keiski, "FOULING MECHANISMS BY AB INITIO CALCULATIONS CONDENSATION REACTIONS ON THE RUTILE (101) SURFACE AND ADSORPTION OF IONS ON THE Cr2O3 SURFACES" in "Heat Exchanger Fouling and Cleaning VII", Hans Müller-Steinhagen, Institute of Technical Thermodynamics, German Aerospace Centre (DLR) and Institute for Thermodynamics and Thermal Engineering, University of Stuttgart, Germany; M. Reza Malayeri, University of Stuttgart, Germany; A. Paul Watkinson, The University of British Columbia, Canada Eds, ECI Symposium Series, (2007). http://dc.engconfintl.org/heatexchanger2007/39