摘要:

AbstractA fibre optic probe system was used to measure the profiles of vertical particle velocities in the spout and the fountain of a half‐column and a full‐column spouted bed. In addition, a fibre optic image probe was employed to measure vertical particle velocity profiles in the annulus of the full‐column. In the spout, radial profiles of vertical particle velocities were of near Gaussian distribution. Particle velocities along the spout axis in the half‐column were 30% lower than in the full‐column under identical operating conditions. In the half column, particle velocities adjacent to the front plate were approximately 24% lower than a few millimeters away. The fountain core expanded suddenly near the bed surface and then gradually contracted with height. The model of Grace and Mathur (1978) gave good predictions of fountain heights for the full‐column. In the annulus region, there was a 28% difference between particle velocities adjacent to the column wall and those only 2 mm away. The integrated upward solids mass flow in the spout and the downward solids flow in the annulus matched well at different

ISSN:0008-4034    

DOI:10.1002/cjce.5450720402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractExperimental data on flooding characteristics were obtained in a Turbulent Bed Contactor (TBC). The flooding conditions and the mechanism of flooding in a single stage TBC have been analyzed for light and dense particles in order to obtain useful correlations that are easier to comprehend. The proposed correlations predict all the combinations of flooding velocities over a large range of variables.

ISSN:0008-4034    

DOI:10.1002/cjce.5450720403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractNew experiments on air‐water countercurrent flow limitations in a vertical pipe are presented. The experiments were carried out to investigate the effect of test procedure on the occurrence of the two countercurrent flow limitations; namely the onset of flooding and complete carry‐up limits. The results revealed the existence of significant hysteresis effects at both limits particularly for high liquid feed rate. For low liquid feed rate, hysteresis effects were only observed at the complete carry‐up limit. Some associated visual observations are reported and the results were empirically correlated and compared with recent data obtained by o

ISSN:0008-4034    

DOI:10.1002/cjce.5450720404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe flow of glass (0.571 mm) and canola seed (1.75 mm) particles entrained by air in a 31.8 mm i.d. conduit inclined at 72° or at 90° to the horizontal was studied. With glass particles a transition between a dilute and a dense phase was found at both orientations, but no transition point was found with canola seed particles. Plots of solids volume fraction versus solids flux in the dilute regime were curved, implying interparticle interactions were significant even at very low solids volume fractions. The velocity of canola seed particles in admixture with sand particles (0.186 mm) increased as the proportion of sand in the mixture increased. Finally, it was found that the oily film imparted by the canola seed particles to the sand particles significantly affected the behaviour of the sand particles in the dense regim

ISSN:0008-4034    

DOI:10.1002/cjce.5450720405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractExtensive experimental results on the free fall of a range of non‐spherical particles such as square bars, cylinders, spheres and crushed rock chips in Newtonian, inelastic, viscoelastic and Boger fluids are presented. It is demonstrated that the use of a volume equivalent sphere diameter in addition to a shape factor provides an adequate approximation for the non‐sphericity of particles used in this study. The applicability of two rheological models, namely, the power‐law and the Carreau viscosity model has been examined in representing the drag coefficient results. Appropriate predictive expressions of the drag coefficient as a function of the particle Reynolds number and the Deborah number, encompassing wide ranges of rheological and kinematic conditions, are pres

ISSN:0008-4034    

DOI:10.1002/cjce.5450720406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractA complete model based on the wood drying mechanism and incorporating a multi‐period operation was established for wood in batch drying systems. Both energy savings and improvement of wood quality were obtained by an optimal strategy proposed in this study. Energy saving was indicated by the numerical results to be roughly 22.5% for drying of soft wood under the conditions of a given drying time and final moisture content. The gradient of moisture content within the dried wood could be minimized for the sake of enhancing the quality of wood by applying the proposed operational mode

ISSN:0008-4034    

DOI:10.1002/cjce.5450720407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe thermal conductivity and the particle‐to‐fluid heat‐transfer coefficient for peanut‐shaped polyester particles in a packed bed were determined simultaneously using the pseudo‐random binary noise sequence (PRBNS) response technique. The modified Dispersion‐Concentric (D‐C) model was applied to beds packed with the non‐spherical particles. A time domain method, using the convolution integral, was developed for removing the effects of the bed ends and the transducer time lag on the experimental responses. Parameter estimation was performed in the time domain, using a simplex method to fit the thermal response calculated from the parametric D‐C model to the experimental response curve. The particle‐to‐fluid heat transfer coefficient in the bed was determined to be 106 W/m2. K at an interstitial fluid velocity of 2.0 m/s. The thermal conductivity of polyester was

ISSN:0008-4034    

DOI:10.1002/cjce.5450720408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe mass transfer efficiencies of dualflow trays with open hole areas of 20, 28 and 37% were experimentally investigated under total reflux conditions in a 300‐mm diameter distillation column using methanol‐water and methanol‐isopropanol systems. The results indicate that the efficiency of a dualflow tray is a strong function of the open hole area, the vapor/liquid load, and liquid properties such as surface tension and density. A fundamental model was developed to predict tray efficiency. The prediction was found to agree with the measured data to within

ISSN:0008-4034    

DOI:10.1002/cjce.5450720409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractSieve tray efficiencies for the distillation of methanol/water, acetic acid/water and cyclohexane/n‐heptane mixtures were measured as a function of composition under fixed vapour and liquid rates in a 0.15 m diameter distillation column. Experimental results show that surface tension has a significant effect on tray efficiency and the number of transfer units. Further tests in a simulator column with air/water, air/methanol and air/(water + surfactant) systems having different surface tensions revealed that bubble sizes in froths are mainly determined by surface tension. The results also show that bubble break‐up and coalescence occurs in the fro

ISSN:0008-4034    

DOI:10.1002/cjce.5450720410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractReactions carried out under conditions close to the equilibrium vapour pressure of the participating species involve physisorption on the catalyst surface. Such conditions are encountered for propene metathesis over rhenium oxide/γ‐alumina catalyst at room temperature. The sorption‐diffusion effects were tested by excluding effects due to reaction. Single‐component sorption characteristics were determined by steady‐state experiments. The model equations comprising several differential and nonlinear algebraic equations were solved by orthogonal collocation within the method of lines. The model predictions were tested against transient experiments performed in a gradientless, internal recirculation

ISSN:0008-4034    

DOI:10.1002/cjce.5450720411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY