How structure-induced resonance waves intensify mass transfer in a falling film absorber for CO$_2$ capture

Efficient solvent utilization is critical in energy-intensive processes such as solvent-based carbon capture. This study adopts a combined experimental and numerical approach to investigate how surface structure modification can intensify liquid-side mass transfer in a falling film CO2 absorber. Structure-induced resonance waves, which are found to evolve in the flow for specifically tailored structure configurations, offer significant potential in this context. The associated flow destabilization is directly reflected in the mass transfer characteristics. Compared to a smooth reference plate, a structure-induced increase in the volumetric mass transfer coefficient by up to a factor of 4.1 is achieved. Complementary numerical simulations provide new insights into the underlying mass transfer enhancement mechanisms. The wave-related increase in interfacial area plays a minor role, while changes in internal flow conditions are the dominant contributor. Most importantly, convective mixing patterns in steep wave humps transport clusters of saturated liquid from near the interface toward the less saturated bulk liquid. In contrast to solitary waves on smooth surfaces, the wave humps do not remain spatially isolated but merge back into less distorted interface regions after passing a few structure elements. ... mehrThis highly dynamic reconfiguration of the gas-liquid interface, along with the interplay of large-and small-scale internal mixing patterns, continuously perturbs the concentration boundary layer and promotes homogenization of the CO2 concentration across the falling film, enabling a substantially larger fraction of the liquid phase to participate in the absorption process compared to smooth surfaces.