摘要:

AbstractPressure measurements around the loop of a circulating fluidized bed with 152 mm ID riser and L‐valve fecuer were analysed to determine the effect of operating parameters (superficial gas velocity in the range 2.2 ‐ 4.0 m/s, solids circulation flux in the range 5 ‐ 50 kg/m2· s and solids inventory, in the range 80 ‐ 180 kg) on the components of the pressure balance. The riser pressure drop, and hence, riser solids holdup were not affected by changes in the inventory of solids in the system, provided riser superficial gas velocity and solid circulation flux were held constant. The mean suspension concentration in the riser was found to be directly proportional to the ratio of solids flux to superficial gas velocity (G / U) in t

ISSN:0008-4034    

DOI:10.1002/cjce.5450700402

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

年代:1992

数据来源: WILEY

摘要:

AbstractExperimental results obtained with 65 μm sand and 69 μm cracking catalyst showed that the smallest particles were not the most easily elutriated from fluidized beds of mixed size particles. This is in contradiction with the assumption applied to existing models for the prediction of the flux and size distribution of particles elutriated from a fluidized bed. The smallest particles cannot be removed by elutriation from a mixture of particles of various sizes.The smallest particles may be agglomerated with larger particles. Increasing the gas humidity, which would presumably reduce electrostatic effects, did not greatly affect the size distribution of the elutriated particle

ISSN:0008-4034    

DOI:10.1002/cjce.5450700403

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

年代:1992

数据来源: WILEY

摘要:

AbstractL'étude porte sur différents réacteurs triphasés du type Verlifix constitués par l'association en série d'un venturi à jet placé en amont d'une colonne remplie d'un garnissage. Les écoulements de gaz et de liquide se font à co‐courant descendant. Quatre types de garnissage ont été disposés dans la colonne, à savoir: des anneaux Raschig, des blocs de monolithe alvéolaire, des particules d'alumine microporeuses et des billes de verre. Pour les quatre supports et pour des conditions opératoires fixées, nous mesurons certaines caractéristiques hydrodynamiques du lit fixe et du réacteur et les caractéristiques de transfert gaz‐liquide du co'té liquide du réacteur dans son ensemble. Les différentes mesures permettent de mettre en évidence l'influence du type de garnissage sur les grandeurs mesurées et plus particulièrement sur le coefficient de tr

ISSN:0008-4034    

DOI:10.1002/cjce.5450700404

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

年代:1992

数据来源: WILEY

摘要:

AbstractExperiments in liquid‐liquid dispersion were performed using a circular loop reactor designed for suspension polymerization. In order to vary widely differences in physical properties such as the viscosity, density, and interfacial tension between the two liquids concerned, polystyrene pellets were dissolved into the dispersed phase which consisted of a styrene monomer liquid. The diameter distributions and mean diameters of droplets formed were measured by stepwise changes in the impeller diameter. From these results, the effect of the impeller diameter on the breakup of droplets was determined. Correlations relating the mean droplet diameter to the operational conditions were derive

ISSN:0008-4034    

DOI:10.1002/cjce.5450700405

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe steady state flow in a short‐dwell coater has been simulated by solving the two‐dimensional Navier‐Stokes equations in the primary pressure and velocity variables for substrate Reynolds numbers up to 1000. The small opening under the blade has very little effect on the flow patterns in the coating pond. However, it does have a significant effect on the pressure field in the pond. The pressure on the substrate surface, which controls liquid penetration during application, has a maximum value under the blade, near its tip. Low coating weights and high coating speeds lead to higher maximum pressure on the substrate. The operating pressure which must be applied to the blade can be predicted for a given coating weight and substrate velocity. For high substrate speeds and low coating weights, higher operating pressures are needed to keep the blade in pos

ISSN:0008-4034    

DOI:10.1002/cjce.5450700406

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

年代:1992

数据来源: WILEY

摘要:

AbstractAir bubbles were injected into the bottom of a column filled with an aqueous suspension of wood pulp fibers to permit measurement of the probability that the bubbles escape the fiber network to reach the surface. Escape probabilities were measured as functions of bubble volume, pulp consistency (weight fraction of fibers), and pulp type. For a given consistency, larger bubbles rose through the column whereas smaller bubbles were held up in the fiber network. The higher the consistency, the greater the bubble diameter required for escape. The minimum buoyancy forces required for bubble escape were correlated with estimates of the yield stress of the fiber network.

ISSN:0008-4034    

DOI:10.1002/cjce.5450700407

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

年代:1992

数据来源: WILEY

摘要:

AbstractLocal surface‐to‐suspension heat transfer coefficients in the freeboard of a fluidized bed reactor were measured by a newly designed miniature probe. Four types of plate orientations were used to test directional effects of surface on heat transfer rate.Variations of heat transfer coefficients with radial position are more significant at lower freeboard. For plate parallel both to the axial and radial directions of the column, the heat transfer coefficient (h) is higher at the center than at wall. For plate with exposed surface parallel to the axial and perpendicular to the radial directions, the plate gives nearly the same value ofhat the center and the wall. At low heights of freeboard, center‐facing surface exhibits higher heat transfer rate than wall‐facing one. The phenomena of higher solids concentration and center to wall movement of particles account for this observation.Variations of heat transfer coefficients with elevation in the freeboard are as much as an order of magnitude, decreasing to gas convection with increasing elevation. These variations are relatively insensitive to the types of plate orientation inves

ISSN:0008-4034    

DOI:10.1002/cjce.5450700408

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

年代:1992

数据来源: WILEY

摘要:

AbstractReflux condensation in a weakly fluctuating stationary mode can be classified with dissipative. pattern‐forming structures. In those states which possess a single phase region topping the two‐phase region the steady state conservation equations do not uniquely determine the length of the two‐phase column. This degeneracy can be removed in accord with the principle of maximum path probability by optimizing the rate of entropy production. Models of reflux condensers with one and several cooling jackets which possess a maximal state are presented. The model predicts the general features of the experimental data without recourse to empirical correla

ISSN:0008-4034    

DOI:10.1002/cjce.5450700409

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

年代:1992

数据来源: WILEY

摘要:

AbstractHeat and mass transfer in laminar mixed convection in the thermal entrance region of horizontal square channels is investigated by using the vorticity‐velocity formulation of the Naiver‐Stokes equations. The numerical results, including the developments of temperature and concentration contours,Nuzand friction coefficient ratios,fRe /(fRe)0, are presented for an air‐water system. The effects of bottom wall temperature and the relative humidity on the momentum, heat and mass transfer in the flow are examined in detail. Results show that the influences of the evaporation of the water vapor along the wetted wall on the heat and mass transfer and the ratiofRe /(fRe)0are rather substa

ISSN:0008-4034    

DOI:10.1002/cjce.5450700410

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe adsorption of cobalt phthalocyanine dye onto activated carbon in a continuous stirred tank adsorber was studied.The variables investigated were: adsorbent mass, adsorbent particle size and fluid flowrate.Several models based on film, pore and surface diffusion were constructed and fitted to the experimental data.Experimental results showed: (i) the increasing importance of the film mass transfer resistance for increasing adsorbent loads; (ii) the increasing importance of the surface diffusion mechanism for increasing adsorbent loads; and (iii) the better discrimination among different models for higher adsorbent loads and lower flowrate.

ISSN:0008-4034    

DOI:10.1002/cjce.5450700411

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

年代:1992

数据来源: WILEY