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2006
Journal Article
Titel
Foulingminderung durch Grenzflächenmodifikationen in Wärmeübertragern
Alternative
Fouling reduction by interfacial modifications in heat exchangers
Abstract
A study was made to identify the optimal coating parameters and characteristics to maximize the induction time in heat exchangers and thereby minimize fouling-related costs. Modifications to the surface on molecular scale are needed. Plasma assisted chemical vapor deposition (PA-CVD) coatings can achieve this with silicon or oxygen doping the surface to change the water contact angle/surface energy. Equivalent modification possibilities were offered by sol-gel prepared nano composite coatings. This lengthened the induction time by a factor of 4 in tests with low flow loads. This desired influence of surface composition was characterized by surface energy measurements on drops lying on the surface, roughness measurements, and fouling tests and was visualized by Atomic Force Microscopy (AFM) and scanning electron microscopy (REM). The contact angle of water was about 93° on stainless steel, on copper 94°, on SICON 95°, and on sol-gel 106°. After a certain length of use he at exchangers are subject to fouling, reducing heat exchange effectiveness. The fouling can be in the form of crystallization, sedimentation, corrosion, chemical reactions, and microbial vegetation (biofouling). This leads to high investment and maintenance costs. Graph.