Comparative assessment of different image processing methods to determine the gas–liquid interfacial area in froth regimes of sandwich packings from ultrafast X-ray tomography image data

Sandwich packings consist of alternatingly stacked structured packing layers of different specific surface area. In such packings froth two-phase flow appears when the packing is operated between the loading limits of the layers. For this highly agitated flow regime, there is a lack of hydrodynamic data, in particular on gas-liquid interfacial area. Ultrafast X-ray tomography, a cross-sectional imaging technique with a frame rate of more than 1000 cross-sectional images per second, is applied to visualize the gas-liquid flow and to extract the gas–liquid interfacial area data via image post-processing methods. For that, we assessed different segmentation methods, that are, level set and gray level contour techniques.