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 (218Po). 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 218Po deposition in laminar and turbulent tube flows, in order to validate the appropriated theories. For laminar flows, we observe a better correlation between our experimental and numerical results, as these take into account, unlike analytical theories, all the phenomena occurring. For turbulent flows, the theories which are the most suitable are those of Wells and Chamberlain (1967, Brit. J. Appl. Phys. 18, 1793-1799) and Friedlander (1977, Smoke, Dust and Haze, Wiley, New York). Our experimental results show that an unexpected surface effect on nanoparticles deposition can be observed, even for a hydraulically smooth surface. We also assessed the influence of surface roughness on nanoparticle deposition experimentally. Unexpectedly, an influence of surface texture on the deposition rate was observed, although all tube surfaces were hydraulically smooth. This could be explained by a diffusion process.