scholarly journals Characterizing Acoustic Fluidized Bed Hydrodynamics Using X-Ray Computed Tomography

2013 ◽  
Author(s):  
David R. Escudero ◽  
Theodore J. Heindel
Keyword(s):  
Computed Tomography ◽  
Fluidized Bed ◽  
Acoustic Field ◽  
High Heat ◽  
Industrial Applications ◽  
Fluidized Bed Reactors ◽  
Hydrodynamic Behavior ◽  
Pressure Drops ◽  
X Ray ◽  
X Ray Computed

Fluidized bed reactors are important assets of many industrial applications because they provide uniform temperature distributions, low pressure drops, and high heat/mass rates. Characterizing the hydrodynamics of a fluidized bed is important to better understand the behavior of these multiphase flow systems. The hydrodynamic behavior in a cold flow 3D fluidized bed, with and without acoustic intervention, using X-ray computed tomography is investigated in this study. Experiments are carried out in a 10.2 cm ID fluidized bed filled with glass beads, with material density of 2600 kg/m3 and particle size ranges between 212–600 μm. In this study, three different bed height-to-diameter ratios are examined: H/D = 0.5, 1 and 1.5. Moreover, the sound frequency of the loudspeaker used as the acoustic source is fixed at 150 Hz with a sound pressure level of 120 dB. Local time-average gas holdup results show that the fluidized bed under the presence of an acoustic field provides a more uniform fluidization, the bed exhibits less channeling, and the jetting phenomena produced by the distributor plate is less prominent when compared to no acoustic field. Thus, acoustic intervention affects the hydrodynamic behavior of the fluidized bed.

scholarly journals High Energy X-Ray Computed Tomography for Industrial Applications

2000 ◽  
Vol 20 (1Supplement) ◽  
pp. 361-364
Author(s):  
Shigeru IZUMI ◽  
Hiroshi KAMIMURA ◽  
Hiroshi KITAGUCHI ◽  
Eisaku MIZUFUNE
Keyword(s):  
Computed Tomography ◽  
High Energy ◽  
Industrial Applications ◽  
X Ray ◽  
X Ray Computed

High energy X-ray computed tomography for industrial applications

1993 ◽  
Vol 40 (2) ◽  
pp. 158-161 ◽  
Author(s):  
S. Izumi ◽  
S. Kamata ◽  
K. Satoh ◽  
H. Miyai
Keyword(s):  
Computed Tomography ◽  
High Energy ◽  
Industrial Applications ◽  
X Ray ◽  
X Ray Computed

scholarly journals Comparisons of Annular Hydrodynamic Structures in 3D Fluidized Beds Using X-Ray Computed Tomography Imaging

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Joshua B. Drake ◽  
Theodore J. Heindel
Keyword(s):  
Computed Tomography ◽  
Fluidized Bed ◽  
Annular Flow ◽  
Fluidized Beds ◽  
Local Scale ◽  
Gas Holdup ◽  
Ct Imaging ◽  
X Ray ◽  
X Ray Computed ◽  
Time Average

Fluidized beds are common equipment in many process industries. Knowledge of the hydrodynamics within a fluidized bed on the local scale is important for the improvement of scale-up and process efficiencies. This knowledge is lacking due to limited observational technologies at the local scale. This paper uses X-ray computed tomography (CT) imaging to describe the local time-average gas holdup differences of annular hydrodynamic structures that arise through axisymmetric annular flow in a 10.2 cm and 15.2 cm diameter cold flow fluidized bed. The aeration scheme used is similar to that provided by a porous plate and hydrodynamic results can be directly compared. Geldart type B glass bead, ground walnut shell, and crushed corncob particles were studied at various superficial gas velocities. Assuming axisymmetry, the local 3D time-average gas holdup data acquired through X-ray CT imaging was averaged over concentric annuli, resulting in a 2D annular and time-average gas holdup map. These gas holdup maps show that four different types of annular hydrodynamic structures occur in the fluidized beds of this study: zones of (1) aeration jetting, (2) bubble coalescence, (3) bubble rise, and (4) particle shear. Changes in the superficial gas velocities, bed diameters, and bed material densities display changes in these zones. The 2D gas holdup maps provide a benchmark that can be used by computational fluid dynamic (CFD) users for the direct comparisons of 2D models, assuming axisymmetric annular flow.

scholarly journals Repeatability of Gas Holdup in a Fluidized Bed Using X-Ray Computed Tomography

2009 ◽  
Author(s):  
Joshua B. Drake ◽  
Theodore J. Heindel
Keyword(s):  
Computed Tomography ◽  
Fluidized Bed ◽  
Fluidized Beds ◽  
Gas Holdup ◽  
X Ray ◽  
Calibration Methods ◽  
Multiphase Systems ◽  
X Ray Computed ◽  
Bed Material ◽  
High Degree

Characterizing the hydrodynamics in fluidized beds is important to many processes from producing biofuels to coating pharmaceuticals. X-ray computed tomography (CT) can quantify local time-averaged phase fractions in multiphase systems that are highly dynamic, like fluidized beds. This paper describes the calibration methods used to produced CT images of a 15.24 cm diameter fluidized bed, how in-house software used these CTs to calculate gas holdup, and how well multiple CTs of a dynamic fluidized bed produced repeatable results while varying bed material and superficial gas velocities. It was concluded there is a very high degree of repeatability using the calibration methods and in-house software developed.

scholarly journals Characterizing Jetting in an Acoustic Fluidized Bed Using X-Ray Computed Tomography

2015 ◽  
Vol 138 (4) ◽  
Author(s):  
David R. Escudero ◽  
Theodore J. Heindel
Keyword(s):  
Computed Tomography ◽  
Fluidized Bed ◽  
Local Time ◽  
Acoustic Vibration ◽  
Gas Holdup ◽  
Axial Position ◽  
Walnut Shell ◽  
X Ray ◽  
X Ray Computed ◽  
Time Average

Understanding the jetting phenomena near the gas distributor plate in a fluidized bed is important to gas–solid mixing, heat and mass transfer, and erosion to any bed internals, which can all affect the performance of the bed. Moreover, acoustic vibration in a fluidized bed can be used to enhance the fluidization quality of the particulate matter and influence the jetting behavior. Characterizing the jetting structure using X-ray computed tomography (CT) in a three-dimensional (3D) fluidized bed, with and without acoustic intervention, is the focus of this study. A 10.2 cm ID fluidized bed filled with glass beads and ground walnut shell, with material densities of 2500 kg/m3 and 1440 kg/m3, respectively, and particle sizes ranging between 212 and 600 μm, is used in these experiments. X-ray CT imaging is used to determine local time-average gas holdup. From this information, qualitative and quantitative characteristics of the hydrodynamic structure of the multiphase flow system are determined. Local time-average gas holdup images of the fluidized bed under acoustic intervention at a high superficial gas velocity show that jets produced near the aeration plate merge with other jets at a higher axial position of the bed compared to the no acoustic condition. Acoustic fluidized beds also have a fewer number of active jets than the no acoustic fluidized bed, which allowed for a more homogeneous gas holdup region deep in the bed. Hence, the acoustic presence has a significant effect on the jetting phenomena near the aeration plate in a fluidized bed.

Industrial Applications of X-Ray Computed Tomography

1987 ◽  
Vol 31 ◽  
pp. 99-105 ◽  
Author(s):  
P. K. Hunt ◽  
P. Engler ◽  
W. D. Friedman
Keyword(s):  
Computed Tomography ◽  
Industrial Applications ◽  
Axial Tomography ◽  
Cross Sectional ◽  
Attenuation Coefficients ◽  
X Ray ◽  
Minimal Sample ◽  
Computerized Axial Tomography ◽  
X Ray Computed ◽  
Non Destructive

Computed tomography (CT), commonly known as CAT scanning (computerized axial tomography), is a technology that produces an image of the internaI structure of a cross sectional slice through an object via the reconstruction of a matrix of X-ray attenuation coefficients. This non-destructive method is fast (50 ms to 7 min per image depending on the technological generation of the instrument) and requires minimal sample preparation. Images are generated from digital computations, and instruments essentially have a linear response. This allows quantitative estimations of density variations, dimensions and areas directly from console displays.

Cavitation From a Butterfly Valve: Comparing 3D Simulations to 3D X-Ray Computed Tomography Flow Visualization

2011 ◽  
Author(s):  
Graham Brett ◽  
Marc Riveland ◽  
Terrence C. Jensen ◽  
Theodore J. Heindel
Keyword(s):  
Computed Tomography ◽  
Flow Control ◽  
Control Valve ◽  
Butterfly Valve ◽  
Cfd Validation ◽  
Vapor Cavity ◽  
Pressure Drops ◽  
X Ray ◽  
Control Valves ◽  
X Ray Computed

Flow control valves may experience localized cavitation when the local static pressure drops to the liquid vapor pressure. Localized damage to the valve and surrounding area can occur when the vapor cavity collapses. Valve designs that reduce cavitation are based on empirical evidence and accumulated experience, but there are still considerable cavitation problems in industry. Valve designers may use computational fluid dynamics (CFD) to simulate cavitation in flow control valves, but model validation is challenging because there are limited data of local cavitation from the valve surface. Typically, the intensity of cavitation in a control valve is inferred from measurements of observable side effects of cavitation such as valve noise, vibration, or damage to the valve assembly. Such an indirect approach to characterizing cavitation yields little information about the location, degree, and extent of the cavitation flow field that can be used in CFD validation studies. This study uses 3D X-ray computed tomography (CT) imaging to visualize cavitation from a 5.1 cm diameter butterfly valve and compares the resulting vapor cloud to that predicted by CFD simulations. Qualitative comparisons reveal that the resulting cavitation structures are captured by the simulations when a small amount of non-condensable gas is introduced into the fluid and the simulations are completed in a transient mode.

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