The capacity of today's gas‐liquid contacting equipment such as tray or packed columns is limited by the gravitational‐driven liquid flow. Intensified equipment applying centrifugal force offers great potential for enhancing the mass transfer and for reducing equipment size. Yet, detailed knowledge about the liquid flow inside rotating packings is scarce due to limited accessibility with conventional measurement systems. In this study, a gamma‐ray computed tomography is employed to quantify the liquid hold‐up and its distribution in the moving packing.

We report on the development of a high resolution gamma ray tomography scanner that is operated with a Cs-137 isotopic source at 662 keV gamma photon energy and achieves a spatial image resolution of 0.2 line pairs/ mm at 10% modulation transfer function for noncollimated detectors. It is primarily intended for the scientific study of flow regimes and phase fraction distributions in fuel element assemblies, chemical reactors, pipelines, and hydrodynamic machines. Furthermore, it is applicable to nondestructive testing of larger radiologically dense objects. The radiation detector is based on advanced avalanche photodiode technology in conjunction with lutetium yttrium orthosilicate scintillation crystals. The detector arc comprises 320 single detector elements which are operated in pulse counting mode. For measurements at fixed vessels or plant components, we built a computed tomography scanner gantry that comprises rotational and translational stages, power supply via slip rings, and data communication to the measurement personal computer via wireless local area network.

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The paper compares two different imaging techniques for the investigation of the hydrodynamics in a laboratory packed bed reactor operating at different stationary states and with two different particle packings. The wire-mesh sensor offers cross-sectional liquid holdup distribution imaging at an ultra high speed of 10000 frames/s and good spatial resolution of 6 mm. It is therefore a very useful imaging tool for transient and periodic flow conditions. Up to now its influence on the flow in a packed bed was never analyzed. γ-ray computed tomography uses 662 keV γ photons to obtain cross-sectional phase distribution images. It offers as well a good spatial resolution of 2 mm and does not influence the flow but needs rather long scanning times. As a noninvasive technique γ-ray tomography has been used as a reference modality to evaluate the wire-mesh sensor measurements. Data from both imaging modalities are compared utilizing different analyzing models and showed good agreement. For the wire-mesh sensor only marginal intrusive effects for the specific situation were found.

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