Deposition of Corrosion Product Particles onto Heat Exchange Surfaces

Abstract

A program is continuing at UNB Nuclear to investigate the deposition of magnetite particles from suspension in water onto Alloy-800 steam generator tubes. Deposits modify the thermal hydraulic characteristics of the heat transfer surface leading to a decrease in efficiency which is often more severe when boiling or evaporation is involved. We find that the onset of boiling generally enhances the deposition rate. Experiments have been done under sub-cooled boiling conditions, in which microlayer evaporation is believed to be the dominant mechanism and local changes of the chemistry at nucleation sites may affect the particle deposition rate. A continuation of this work is to investigate the effect of bulk boiling on the deposition rate and to examine any additional mechanisms which may be involved. This entails modifying the microlayer evaporation concept to include severe local turbulence effects.