Enhancing Packed Column Design through Local Hydrodynamic Data: A Liquid Film Thickness Sensor Approach in Miniaturized Measuring Cells

Abstract The design of structured packed columns relies on hydrodynamic and mass-transfer models that require reliable experimental input parameters. However, established measurement techniques mainly provide global quantities such as pressure drop, liquid holdup, or HTU/NTU values and therefore do not resolve local flow phenomena such as channel-wise liquid distribution, wall flow, or incomplete wetting. As a result, important hydrodynamic effects are incorporated only indirectly into existing correlations, limiting model parametrization and increasing the uncertainty when transferring results to different operating conditions or column geometries. In this work, an advanced conductivity-based liquid film thickness sensor (LFS) is developed and integrated into a miniaturized measuring cell to generate spatially and temporally resolved hydrodynamic data in structured packings. Building on previous conductivity-based sensor concepts, the present work combines conductivity compensation, flexible sensor integration, and channel-resolved evaluation under countercurrent gas−liquid operation. This enables the investigation of local liquid distribution, wall-flow effects, sensor-based wetting degree, and temporal film-thickness fluctuations in a realistic structured-packing geometry. After calibration and proof-of-concept on a flat reference plate, the sensor is integrated into a miniaturized measuring cell equipped with Montzpak B1-250 structured packing. The measurements reveal channel-resolved film-thickness distributions, wall-flow effects, and local wetting patterns under varying gas and liquid loads. Increasing gas load leads to higher mean film thicknesses, higher sensor-based wetting degrees, and stronger temporal film-thickness fluctuations, indicating enhanced gas−liquid interaction and lateral liquid redistribution. The derived quantities provide local hydrodynamic information that is not accessible through conventional integral measurement techniques and can support future validation of hydrodynamic models for structured packed columns.