Aerosol retention in the vicinity of a breach in a tube bundle: An experimental investigation

This article summarizes the main results of a bench-scale program focused on experimentally assessing the aerosol retention near the tube breach in a tube bundle. The major variables investigated were particle nature (polydispersed TiO2 agglomerates vs. solid, monodisperse SiO2 spheres) and ReD (0.8-2.7 105). In addition, comparisons to other data sets provided insights into the particle aerodynamic size effect on retention efficiency. Results showed that particle nature substantially affects aerosol retention in the tube bundle: mass retention efficiency was low for TiO 2 agglomerates (less than 30%) whereas it was much higher for SiO2 particles (around 85%). Retention efficiency is also affected by ReD: its sensitivity was found to follow a log-normal behavior with a maximum retention attained at ReD near 1 105. This evolution with ReD was similar for both types of compounds. Particle size also influences retention efficiency: the bigger the TiO2 agglomerates the lower retention efficiency (no data were available for SiO2). Among all these variables, particle nature was noted to have a prime importance for in-bundle retention, whereas ReD and particle aerodynamic size, although also affect retention efficiency, did not play such a key role. In light of the results, the presence of retention-inhibiting mechanisms such as fragmentation, resuspension or bouncing has been discussed. The data recorded will enhance the overall understanding of the governing mechanisms involved and will serve as a database against which compare model predictions. Nevertheless, further experimental data would be desirable to set up a sound database.