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Technology Reviews

A Review of X-Ray Flow Visualization With Applications to Multiphase Flows

[+] Author and Article Information
Theodore J. Heindel

Bergles Professor of Thermal Science, Department of Mechanical Engineering,  Iowa State University, Ames, IA 50011 e-mail: theindel@iastate.edu

J. Fluids Eng 133(7), 074001 (Jul 22, 2011) (16 pages) doi:10.1115/1.4004367 History: Received January 06, 2011; Revised May 21, 2011; Published July 22, 2011; Online July 22, 2011

Flow visualization and characterization of multiphase flows have been the quest of many fluid mechanicians. The process is fairly straight forward only when there is good optical access (i.e., the vessel is not opaque or there are appropriate viewing ports) and the flow is transparent, implying a very low volume fraction of the dispersed phase; however, when optical access is not good or the fluid is opaque, alternative methods must be developed. Several different noninvasive visualization tools have been developed to provide high-quality qualitative and quantitative data of various multiphase flow characteristics, and overviews of these methods have appeared in the literature. X-ray imaging is one family of noninvasive measurement techniques used extensively for product testing and evaluation of static objects with complex structures. X-rays can also be used to visualize and characterize multiphase flows. This paper provides a review of the current status of X-ray flow visualization and details various X-ray flow visualization methods that can provide qualitative and quantitative information about the characteristics of complex multiphase flows.

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Copyright © 2011 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic of Radiographic Imaging

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Figure 2

Single FXR images of air bubbles in various 1% by mass Rayon fiber suspensions contained in a 20 cm × 2 cm bubble column with a superficial gas velocity of 0.8 cm/s [119]. The dark amoeba-like structures in each image represent air bubbles and the bubbles appear as dark objects because the images are from the actual 25.2 cm × 20 cm negatives – the color is inverted.

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Figure 3

Schematic representation of X-ray stereographic imaging

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Figure 4

Five sequential frames of an intruder particle in a granular bed of almonds vibrated at 10 Hz [141]. The left and right images are perpendicular X-ray radiographic projections taken at the same instant in time, and each successive frame is separated by about 55 ms.

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Figure 5

Schematic representation of X-ray computed tomography (CT) imaging

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Figure 6

Sample X-ray CT imaging planes

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Figure 7

Sample X-ray CT imaging results of the time-averaged gas holdup in a 10.2 cm diameter fluidized bed filled with 500-600 μ m glass beads and operated at 3Umf with side air injection rates (Qside ) of 0, 0.1, and 0.2Qmf , where Qmf is the minimum fluidization flow rate. Local values can be extracted along any ray at a given horizontal location.

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Figure 8

Fast X-ray CT system of Hori [180]. The diameter of the measured object is 300 mm.

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Figure 9

Fast X-ray CT system of Mudde [81]. The fluidized bed had a 23 cm ID with a 5 mm wall thickness.

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