• computed tomography
• fluid dynamics
• liquid hold-up
• mass-transfer area
• random packing
• wetted area

The qualitative investigation of the flow behavior and the quantitative evaluation of widespread fluid dynamic parameters like liquid hold-up, wetted area and mass-transfer area in a randomly packed column are carried out using Computed Tomography CT, a totally non-invasive measuring technique. Despite the huge effort of different researchers, a lack of comprehension about the flow field within the packed bed still prevents the development of completely satisfying models, that are precisely able to predict these fluid dynamic parameters in order to achieve an economically optimized design of the column.
In the present work, three commercial random packings (Raflux Ring, RMSR and RSR), belonging to different generations, are scanned in a 0.1 m diameter column in presence of two different systems: water / air and isopropanol /air. The latter is used for the first time in CT investigations despite the common industrial applications of these organic compounds. An algorithm, previously developed by Schug and Arlt, is applied to compute the profile and the integral values of fluid dynamic parameters along the packed bed, highlighting the effect of the liquid load (ranged between 2 m3 / m2 h and 70 m3 / m2 h), the gas load (ranged between 0 Pa^0.5 and 2 Pa^0.5), the packing type.
The main aims of the present work are summarized in two points: firstly, the investigation of the effect of the column’s re-packing and on the variance of the fluid dynamic parameters. The results show an extremely weak effect of the re-packing of the column, with deviation less than 4 % in terms of coefficient of variation for each fluid dynamic parameter. Secondly, these parameters are evaluated with an organic liquid (isopropanol) to assess the combined influence of significantly different physical properties like viscosity and surface tension. A better wettability of the packing and a higher mass-transfer area is recorded. Furthermore, a graphical qualitative evaluation of the liquid flow morphology and a successive classification of the present liquid structures (films and rivulets) are conducted.