Documents disponibles écrits par cet auteur

Comparison of ECVT and MR measurements of voidage in a gas-fluidized bed / D. J. Holland in Industrial & engineering chemistry research, Vol. 48 N°1 (Janvier 2009) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - p. 172-181 Titre : Comparison of ECVT and MR measurements of voidage in a gas-fluidized bed Type de document : texte imprimé Auteurs : D. J. Holland, Editeur scientifique ; Q. Marashdeh, Editeur scientifique ; C. R. Müller, Editeur scientifique Année de publication : 2009 Article en page(s) : p. 172-181 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Magnetic  resonance  (MR)  Electrical  capacitance  volume  tomography  (ECVT)  Gas-fluidized Résumé : This paper reports the first quantitative comparison of magnetic resonance (MR) and electrical capacitance volume tomography (ECVT) on a 50 mm diameter gas-fluidized bed of silica−alumina catalyst support particles (dp = 58 μm). ECVT data were acquired at a temporal resolution of 12.5 ms and a nominal spatial resolution of 2.5 mm × 2.5 mm × 4.5 mm. Snapshot MR data were acquired at a temporal resolution of 26 ms and a spatial resolution of 1.9 mm × 1.9 mm in the transverse plane and 1.9 mm × 3.8 mm in the axial plane. The particles were doped with water to produce a detectable signal with MR. The two techniques are demonstrated to produce quantitatively comparable time-averaged measurements of the voidage. The bubble frequencies measured from the snapshot images using both techniques were found to be in good agreement. However, the signal intensity inside the gas bubbles was more accurate when measured with MR, and the wake structure could be more clearly resolved using MR. This was attributed to the effect of the smoothing, or point spread function, of the ECVT measurements. An initial estimate of the smoothing in the ECVT has been performed by assuming a Gaussian point spread function. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8002073 [article] Comparison of ECVT and MR measurements of voidage in a gas-fluidized bed [texte imprimé] / D. J. Holland, Editeur scientifique ; Q. Marashdeh, Editeur scientifique ; C. R. Müller, Editeur scientifique . - 2009 . - p. 172-181. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 48 N°1 (Janvier 2009) . - p. 172-181 Mots-clés : Magnetic  resonance  (MR)  Electrical  capacitance  volume  tomography  (ECVT)  Gas-fluidized Résumé : This paper reports the first quantitative comparison of magnetic resonance (MR) and electrical capacitance volume tomography (ECVT) on a 50 mm diameter gas-fluidized bed of silica−alumina catalyst support particles (dp = 58 μm). ECVT data were acquired at a temporal resolution of 12.5 ms and a nominal spatial resolution of 2.5 mm × 2.5 mm × 4.5 mm. Snapshot MR data were acquired at a temporal resolution of 26 ms and a spatial resolution of 1.9 mm × 1.9 mm in the transverse plane and 1.9 mm × 3.8 mm in the axial plane. The particles were doped with water to produce a detectable signal with MR. The two techniques are demonstrated to produce quantitatively comparable time-averaged measurements of the voidage. The bubble frequencies measured from the snapshot images using both techniques were found to be in good agreement. However, the signal intensity inside the gas bubbles was more accurate when measured with MR, and the wake structure could be more clearly resolved using MR. This was attributed to the effect of the smoothing, or point spread function, of the ECVT measurements. An initial estimate of the smoothing in the ECVT has been performed by assuming a Gaussian point spread function. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie8002073

Magnetic resonance studies of fluidization regimes / D. J. Holland in Industrial & engineering chemistry research, Vol. 49 N° 12 (Juin 2010) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 49 N° 12 (Juin 2010) . - pp. 5891–5899 Titre : Magnetic resonance studies of fluidization regimes Type de document : texte imprimé Auteurs : D. J. Holland, Auteur ; C. R. Müller, Auteur ; J. S. Dennis, Auteur Année de publication : 2010 Article en page(s) : pp. 5891–5899 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Magnetic  resonance  Gas-fluidized  bed Résumé : Measurements of the voidage and velocity distributions in a gas-fluidized bed operating in the bubbling, turbulent, and core−annular fluidization regimes were acquired using magnetic resonance imaging (MR). The bed studied was contained in a column 50 mm in diameter and was fluidized with air. The particles were silica−alumina catalyst support loaded with water doped with gadolinium (diameter 63 μm, density of the water loaded particles 1530 kg m−3). Both time-averaged and ultrafast measurements are presented and provide the first noninvasive measurements of the velocities of particles and local voidage in a fluidized bed in each of the flow regimes. Measurements of the pressure fluctuations were also recorded as a function of the superficial velocity of the fluidizing gas to compare with the MR measurements. Ultrafast measurements of the voidage were used to examine the void structures present in the different flow regimes and to provide a means of studying the dynamics. A novel MR technique was used to measure the velocities of the particles in a diametral region of 15 mm × 15 mm square cross-section through the center of the bed every 7.7 ms. These measurements confirmed that the highest particle velocities in the bubbling fluidization regime occurred in the wakes of bubbles. The distribution of particle velocities in a bubbling bed is highly skewed; however, it approaches a Gaussian distribution and appears to scale with the superficial gas velocity in the turbulent fluidization regime. Finally, a simple model to infer the slip velocity in core−annular fluidization indicates that the particles in the center of the column group together in clusters with a diameter of between 4 and 8 particles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901450q [article] Magnetic resonance studies of fluidization regimes [texte imprimé] / D. J. Holland, Auteur ; C. R. Müller, Auteur ; J. S. Dennis, Auteur . - 2010 . - pp. 5891–5899. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 49 N° 12 (Juin 2010) . - pp. 5891–5899 Mots-clés : Magnetic  resonance  Gas-fluidized  bed Résumé : Measurements of the voidage and velocity distributions in a gas-fluidized bed operating in the bubbling, turbulent, and core−annular fluidization regimes were acquired using magnetic resonance imaging (MR). The bed studied was contained in a column 50 mm in diameter and was fluidized with air. The particles were silica−alumina catalyst support loaded with water doped with gadolinium (diameter 63 μm, density of the water loaded particles 1530 kg m−3). Both time-averaged and ultrafast measurements are presented and provide the first noninvasive measurements of the velocities of particles and local voidage in a fluidized bed in each of the flow regimes. Measurements of the pressure fluctuations were also recorded as a function of the superficial velocity of the fluidizing gas to compare with the MR measurements. Ultrafast measurements of the voidage were used to examine the void structures present in the different flow regimes and to provide a means of studying the dynamics. A novel MR technique was used to measure the velocities of the particles in a diametral region of 15 mm × 15 mm square cross-section through the center of the bed every 7.7 ms. These measurements confirmed that the highest particle velocities in the bubbling fluidization regime occurred in the wakes of bubbles. The distribution of particle velocities in a bubbling bed is highly skewed; however, it approaches a Gaussian distribution and appears to scale with the superficial gas velocity in the turbulent fluidization regime. Finally, a simple model to infer the slip velocity in core−annular fluidization indicates that the particles in the center of the column group together in clusters with a diameter of between 4 and 8 particles. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie901450q