Q1: Channelling is most severe

ANS:A - in towers packed with stacked packing.

Channelling, a phenomenon where the liquid or gas flow preferentially follows certain paths through the packing material, is most severe in towers packed with stacked packing. Stacked packing consists of layers of structured packing elements stacked on top of each other in a column. The regular arrangement of these packing elements can create preferential flow channels, leading to uneven distribution of the liquid or gas across the column cross-section. This uneven distribution can result in reduced mass transfer efficiency, lower separation performance, and decreased column efficiency. In contrast, towers packed with randomly packed crushed solids or dumped packing of regular units typically exhibit more chaotic flow patterns, which can help mitigate the occurrence of channelling. Randomly packed or dumped packing creates a more tortuous path for the fluid flow, preventing the formation of well-defined flow channels. While high liquid flow rates can exacerbate channelling in packed columns by increasing the likelihood of channel formation, the type of packing material and its arrangement play a more significant role in determining the severity of channelling. Therefore, towers packed with stacked packing are most prone to severe channelling compared to other packing configurations.