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UBC Theses and Dissertations

Measurement of fine particle deposition from flowing suspensions Chen, Charley Y.


A large number of investigators have taken on the task of formulating the mechanisms of the particle deposition process. Correspondingly little has been done, either theoretically or experimentally, on the process of particle attachment. Bowen and Epstein’s work (1, 16), a systematic investigation of particle deposition and release from and to aqueous suspensions in fi.illy developed laminar flow, was extended to turbulent flows in the present experimental study. The experimental investigation was carried out using uniform, spherical, silica particles (0.881 p.m diameter) and a rectangular channel (10 mm x 12 mm) constructed from plate glass cemented to a stainless steel supporting structure. The plate glass was coated with a plastic to achieve suitable surface conditions. The measurements of deposition and release of negatively charged silica spheres onto and from a positively charged plastic substrate was greatly facilitated by employing a direct microscopic technique and an image analysis system. Under the conditions of the present experiments, it was found that the rate of release from the channel surface was not observable. Thus, the declining rate of accumulation with time observed in most experimental runs could only be attributed to the declining deposition rate. The measured initial rates of deposition were found to be in good agreement with those predicted by theories of Bowen (1) and Epstein (10, 62) for laminar and turbulent flows, respectively. The initial deposition rate was observed to be influenced by the suspension flow rate and the magnitude of the positive wall zeta-potential. It was found that the concentration of deposited particles reached an asymptotic value for those runs which were performed long enough. The particle surface coverage never exceeded 3.5%.

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