Deposition of nanosized particles in cylindrical tubes under laminar and turbulent flow conditions

There are few studies of deposition of nanoparticles due to difficulties in their generation and size measurement. These difficulties can be overcome by the use of radioactive nanoparticles (Po-218). This aerosol is obtained with a constant production rate from radon decay, and its concentration is determined using nuclear measurement techniques. We present an experimental and numerical study of Po-218 deposition in laminar and turbulent tube flo ws, in order to validate the appropriated theories. For laminar flows, we o bserve a better correlation between our experimental and numerical results, as these rake into account, unlike analytical theories, ail the phenomena occurring. For turbulent flows, the theories which are the most suitable ar e those of Wells and Chamberlain (1967, Brit. J. Appl. Phys. 18, 1793-1799) and Friedlander (1977, Smoke, Dust and Haze, Wiley, New York). Our experim ental results show that an unexpected surface effect on nanoparticles depos ition can be observed, even for a hydraulically smooth surface. We also ass essed the influence of surface roughness on nanoparticle deposition experim entally. Unexpectedly, an influence of surface texture on the deposition ra te was observed, although all tube surfaces were hydraulically smooth. This could be explained by a diffusion process. (C) 2000 Elsevier Science Ltd. All rights reserved.