Gas / liquid contact apparatuses are widely used in chemical, biochemical or pharmaceutical industry to provide and transfer gas species as reactant from the gaseous phase to pre-dissolved reactants in the liquid phase enabling a preferred reaction. The global and local transport are complex interlinked processes and therefore in practice in reactor design industry, mostly empirically correlated. For a secure control of the overall process and a more efficient reactor design, the local transport processes at gas / liquid interfaces need to be investigated in complexity reduced systems to be understood. Elongated bubbles, Taylor bubbles, in vertical channels 5.5