We introduce a new wire-mesh sensor based on capacitance (permittivity) measurements. The sensor can be used to measure transient phase fraction distributions in a flow cross-section, such as in a pipe or other vessel, and is able to discriminate fluids having different relative permittivity (dielectric constant) values in a multiphase flow. We designed and manufactured a prototype sensor which comprises two planes of 16 wires each. The wires are evenly distributed across the measuring cross-section, and measurement is performed at the wire crossings. Time resolution of the prototype sensor is 625 frames per second. Sensor and measuring electronics were evaluated showing good stability and accuracy in the capacitance measurement. The wire-mesh sensor was tested in a silicone oil/water two-phase bubbly flow.

Bubble characteristics in a three-dimension gas-fluidized bed (FB) have been measured using noninvasive ultrafast electron beam X-ray tomography. The measurements are compared with predictions by a two-fluid model (TFM) based on kinetic theory of granular flow. The effect of bed material (glass, alumina, and low linear density polyethylene (LLDPE), d p $1 mm), inlet gas velocity, and initial particle bed height on the bubble behavior is investigated in a cylindrical column of 0.1-m diameter. The bubble rise velocity is determined by cross correlation of images from dual horizontal planes. The bubble characteristics depend highly upon the particle collisional properties. The bubble sizes obtained from experiments and simulations show good agreement. The LLDPE particles show high gas hold-up and higher bubble rise velocity than predicted on basis of literature correlations. The bed expansion is relatively high for LLDPE particles. The X-ray tomography and TFM results provide in-depth understanding of bubble behavior in FBs containing different granular material types.

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This paper introduces the design of an ultra fast x-ray tomography scanner based on electron beam technology. The scanner has been developed for two-phase flow studies where frame rates of 1 kHz and higher are required. Its functional principle is similar to that of the electron beam x-ray CT scanners used in cardiac imaging. Thus, the scanner comprises an electron beam generator with a fast beam deflection unit, a semicircular x-ray production target made of tungsten alloy and a circular x-ray detector consisting of 240 CZT elements with 1.5 mm × 1.5 mm × 1.5 mm size each. The design is optimized with respect to ultra fast imaging of smaller flow vessels, such as pipes or laboratory-scale chemical reactors. In that way, the scanner is capable of scanning flow cross-sections at a speed of a few thousand frames per second which is sufficient to capture flows of a few meters per second velocity.

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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